Harnessing brewing industry effluents for microalgal bioproducts: a systematic review

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This systematic literature review explores the potential of microalgae in the treatment of brewery effluents and the production of high-value bioproducts. Several peer-reviewed studies published between 2017 and 2024 were analyzed, focusing on microalgal species, cultivation strategies, treatment efficacy, and biomass applications. Chlorella and Scenedesmus emerged as the most effective genera, achieving chemical oxygen demand (COD) removal rates of up to 88.52% and demonstrating strong biomass productivity. Co-cultivation with bacteria enhanced pollutant removal and lipid accumulation, underscoring the synergy between microalgae and native microbiota. The biomass derived from brewery effluent treatment was found to be rich in carbohydrates, lipids, and proteins, supporting its use in biofuel and biofertilizer production. Despite promising results, industrial-scale implementation remains constrained by variability in effluent composition and the need for standardized processes. The findings emphasize the dual environmental and economic benefits of integrating microalgal systems into brewery wastewater management and highlight the untapped potential for bioproduct development in line with circular bioeconomy principles. Microalgae Brewery wastewater Bioremediation Biofuels Circular bioeconomy Biofertilizer Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction Beer is the third most consumed beverage worldwide, following only water and tea, leading to a global production of approximately 1.88 billion hectoliters in 2023. Among alcoholic beverages, beer holds the top position globally, with an estimated consumption of 178.6 billion liters projected in 2024 (Jan Conway 2024). For example, Brazil is currently the third-largest beer producer in the world, with the brewing industry contributing around 2% to the country's Gross Domestic Product (GDP). This prominence is rooted in a longstanding cultural tradition of fermented beverage consumption, which has also driven the rapid expansion of the craft brewery sector (Custódio et al. 2023). However, large-scale beer production generates substantial amounts of wastewater and biological byproducts, as illustrated in Fig. 1. Depending on the brewery's size and production scale, between 3 and 10 liters of wastewater are produced for every liter of beer (Luc Fillaudeau et al. 2006). In many cases, this wastewater is discharged directly into waterways (oceans, rivers, streams, or lakes), into municipal sewer systems, or undergoes basic pretreatment before disposal. Such discharges can lead to serious environmental pollution (Simate et al. 2011). As a result, freshwater usage, wastewater generation, and its management have become critical considerations for the brewing industry. These factors significantly impact overall operational costs. Additionally, stricter regulations concerning effluent disposal and increasing concern among breweries about their environmental image have intensified research in this area (Ashraf et al. 2021). Brewing effluents are characterized by high organic loads (see Table 1), and their treatment depends on factors such as beer type, production scale, and processing stages. A typical treatment sequence includes physicochemical processing, biological treatment, sludge dewatering and management, and disinfection (Ashraf et al. 2021). Biological treatment is particularly effective in removing residual organic matter and helps breweries comply with environmental discharge standards, achieving organic matter removal efficiencies of up to 95% (MR Soluções Ambientais 2022). Table 1. Characteristics of a typical brewery wastewater (Adapted from Ashraf et al. 2021) Parameter Unit Average value pH --- 3.3-12 Temperature ºC 18-40 COD (chemical demand of oxygen) mg/L 1,250 ± 100-20,000 BOD (biological demand of oxygen) mg/L 1,200-3,600 NH 3 -N (ammonia nitrogen) mg/L 16 ± 5-46.5 Total nitrogen mg/L 0.0196-80 Phosphorus mg/L 10-50 Suspended solids mg/L 200-3,000 Heavy metals --- Very low Biological treatments often utilize microorganisms such as bacteria, algae, and fungi. These methods offer several advantages, including low capital and operating costs, reduced chemical usage, and the potential to generate valuable byproducts such as biofertilizers, biofuels, and food supplements (Umamaheswari and Shanthakumar 2016). Among these organisms, microalgae have garnered special attention due to their photosynthetic capabilities, which allow them to convert sunlight into biomass while transforming pollutants and toxic metals into nutrients. Furthermore, brewery effluents are rich in CO₂ and essential nutrients such as nitrogen, phosphorus, and potassium, which are key elements for microalgal growth (Assaf 2017). Microalgae are especially notable for their high CO₂ fixation rates and rapid biomass accumulation, often outperforming traditional plants. They can grow under autotrophic conditions (using light and CO₂), heterotrophic conditions (utilizing organic matter in the medium), or mixotrophic conditions (combining light, CO₂, and organic/inorganic nutrients) (Rossoti and Mockaitis 2011). While existing literature, such as the review by Ashraf et al. (2021), provides a broad overview of effluent treatment in the brewing industry, there remains a gap in studies specifically addressing the use of microalgae for this purpose. Given the significant volume of effluents generated by the global brewing industry and the promising potential of microalgae in bioremediation, exploring sustainable brewery effluent management through microalgal cultivation is essential. Therefore, this study aims to systematically review the most recent literature with a focus on: (i) the general characteristics of the selected studies, (ii) the effectiveness of microalgae in brewery effluent treatment, and (iii) the types of bioproducts derived from the microalgal biomass generated during treatment. Emphasis is placed on current trends and emerging practices in microalgal wastewater treatment and bioproduct development. This paper is structured as follows: the first section presents an overview of the selected articles, including 1) the number of publications per year, and 2) by country. The second section delves into the effectiveness of microalgal wastewater treatment in the brewing sector, covering 3) the types of effluents treated, 4) cultivation strategies, and 5) the efficiencies of organic matter and CO₂ removal. The third section explores the potential bioproducts derived from microalgal treatment of brewery effluents. Finally, the paper discusses 6) research limitations and future directions, followed by 7) the conclusions. 2. Methodology To understand the possibility of producing microalgae and, consequently, obtaining bioproducts using brewery effluents as a nutrient medium, a systematic literature review was performed. For this purpose, two research questions (RQA and RQB) were selected to be answered by the selected literature (Oliveira 2018): RQA: Is the effectiveness of microalgae in the treatment of brewery effluent (considering CO 2 and organic matter removal) greater than or equal to methods already applied? RQB: Is it possible to obtain high-added by-products from the microalgal biomass resulting from the treatment of brewery effluent? Once a consistent research protocol had been established, the selection and review were carried out following the flowchart shown in Fig. 2. More details regarding the eligibility criteria are described in Table 2. Table 2. Criteria for Relevance Tests 1, 2 and 3 Relevance Test 1 Criteria Yes No Was the article published between 2017 and 2023? 1 point 0 points Was the article written in English? 1 point 0 points Does the article come from a journal with an impact factor greater than or equal to 3? 1 point 0 points Relevance Test 2 Criteria Is the RQA covered? Yes No Is the RQB covered? Yes No Relevance Test 3 Criteria Yes No Does the article contain clear results on microalgae biomass growth? 1 point 0 points Does the article contain clear results on the performance of microalgae as a biological treatment agent? 1 point 0 points Does the article contain a clear analysis of the characteristics of the biomass produced? 1 point 0 points Does the article contain a clear economic analysis of the use of microalgae as a biological treatment? 1 point 0 points Does the article present a clear experimental methodology? 1 point 0 points Does the article present the use and/or feasibility using microalgal biomass in the production of bioproducts? 1 point 0 points 3. Selected articles and their general characteristics Using the protocol previously described, manual search was carried out using the proposed search terms and filtering for articles published from 2017 onwards, resulting in a total of 875 articles. Therefore, 845 articles were excluded that did not have a clear title on the use of microorganisms in the treatment of brewery effluent, 14 articles where the abstract and introduction did not demonstrate the use of microalgae in the effluent treatment process and 3 articles where the conclusion did not contain results referring to the performance of microalgae in treatment or an analysis of their biomass. Of the 13 articles approved in the pre-selection, 4 were excluded because they did not meet the requirements of relevance test 3. The number of articles excluded in each step is illustrated in Fig. 3. Fig. 4(a) illustrates the yearly distribution of publications, highlighting a substantial increase in research articles focused on using microorganisms in brewery effluent treatment, which quadrupled from 2017 to 2022. This trend reached a peak in 2022, reflecting heightened interest and investment in this area. Although there was a slight decrease in 2023, the number remained higher than in 2021, suggesting that research in this field will continue to attract attention even if publication volumes don’t surpass those of 2022. The increased research interest in microalgae can likely be attributed to the growth of cultivation facilities and the discovery of new commercial uses (Derner 2018). Fig. 5 shows that China leads with 36.4% of the relevant publications selected, followed by Portugal at 27.3%. When considering continents, Europe and Asia are tied as the top contributors to this field, with Africa ranking next in relevance. Other continents did not produce publications that met the eligibility criteria for this review. China’s leadership in this research field can be attributed to its strong national focus on the circular economy, waste management, and environmental protection. These efforts are supported by comprehensive public policies, including initiatives aimed at expanding reforestation and significantly reducing carbon emissions. As the source of 28.8% of global CO₂ emissions, China faces substantial environmental challenges driven by rapid industrialization and a large population. These include air and water pollution, soil erosion, deforestation, desertification, and biodiversity loss (Lima and Albuquerque 2021). China’s prominent role in publishing research on the use of microalgae for brewery effluent treatment may also be linked to its leading position in the global beer market, both in terms of production and consumption. Since 2002, China has surpassed the United States as the world’s largest beer producer, with an estimated output of approximately 35.21 billion liters in 2024 (USDA 2022; Xin Ou 2025). Additionally, the high volume of Chinese publications in this area can be explained by the country’s significant microalgae biomass production. Over the past 15 years, China has become one of the world’s top producers of microalgae, surpassing Japan in the cultivation of Chlorella spp. (Show 2022). China also holds one of the world’s most extensive collections of microalgae species. Institutions such as the Freshwater Algae Culture Collection at the Institute of Hydrobiology (Wuhan) and the Marine Biological Culture Collection Centre (Qingdao) have compiled over 2,000 strains (representing more than 120 genera) and around 600 marine species. Although only a fraction of these is currently exploited commercially, China’s vast microalgae resources are recognized for their potential to generate high-value bioproducts with applications in the food, pharmaceutical, and cosmetic industries (Show 2022). 4. Is the effectiveness of microalgae in the treatment of brewery effluent (considering CO2 and organic matter removal) greater than or equal to methods already applied? As Abdelfattah et al. (2023) rightly emphasize in their review, the treatment of industrial effluents using microalgae represents a highly promising technological alternative. This approach is particularly compelling given its potential to address two critical challenges simultaneously: mitigating the environmental impacts of industrial waste and contributing to the global demand for clean, potable water. As previously discussed, brewery effluents are well-suited to this strategy, both due to the significant volumes produced annually worldwide and their considerable polluting potential. Considering this, the following section will explore the current state-of-the-art in brewery effluent treatment using microalgae. We will examine the most employed microalgae species, and the strategies developed to enhance the degradation of key pollutants typically found in this type of wastewater. 4.1 Most common species used on brewery effluent treatment Fig. 6 presents the number of articles categorized by the microalgae species used in the selected studies, highlighting the prominence of the Chlorella and Scenedesmus genera. This trend may be attributed to two key factors: (i) their relevance in the global market and (ii) the relatively low cost associated with their nutritional requirements. Both genera are known for producing high-value by-products, such as lutein (Saadaoui et al. 2021). Lutein is a yellow xanthophyll carotenoid with numerous documented health benefits, including improved visual function and a reduced risk of age-related macular degeneration (Ranard et al. 2017). In 2023, the global lutein market generated USD 357.6 million in revenue and is projected to grow at a compound annual growth rate (CAGR) of 5.7%, reaching approximately USD 527.2 million by 2030 (Grand View Research 2024). Although the use of effluents in microalgae cultivation can limit the application of microalgae and their by-products for human consumption due to safety concerns—primarily related to the presence of toxic metals, this issue is generally not so relevant in the case of brewery effluents, as they contain little to no such contaminants (Show 2022). 4.2 Type of brewery effluent treated and treatment strategies The type of brewery effluent treated varied among the studies, resulting in differences in the growth media used for microalgae cultivation, as detailed in Table 3. Typically, microalgae are pre-cultured in well-established media from existing literature to achieve a suitable biomass concentration that facilitates adaptation to the effluent. Among the reviewed studies, BG-11 medium was the most commonly used—likely due to its versatility and ease of modification (Fig. 7). Notably, it was employed in studies by Su et al. (2023), Song et al. (2020), He et al. (2022), and Han et al. (2021), and has proven particularly effective for culturing microalgae of the Chlorella genus, which represented 38.9% of the microorganisms examined (Fig. 6). Other media used include Zarrouk (Dias et al. 2022), Bristol (Wang 2022; Ferreira et al. 2018), and Bold Basal Medium (BBM) (Yirgu et al. 2021). Table 3. General characteristics of brewing effluents used by articles selected in SRL Parameters Brewery effluents Dissolved oxygen (DO) (mg/L) 0.33 - 2.34 Chemical oxygen demand (COD) (mg/L) 226 - 4000 Total dissolved phosphorus (TP) (mg/L) 1.15 - 18.45 Total dissolved nitrogen (TN) (mg/L) 22.78 - 69.00 NH 3 -N (mg/L) 18.30 - 48.00 PO 4 -P (mg/L) 0.23 - 6.50 NO 3 -N (mg/L) 0.10 - 9.00 NO 2 -N (mg/L) 0.01 - 0.025 Suspended solids (mg/L) 665 - 771 Salinity (%) 1.41 - 1.60 pH 6.80 - 8.85 Na (mg/L) 160.23 - 847.68 K (mg/L) 7.63 - 20.11 Mg (mg/L) 4.11 - 17.43 Ca (mg/L) 10.06 - 36.14 Cu (mg/L) 317.88 - 348.19 Zn (mg/L) 101.07 - 114.44 As (mg/L) 0.814 - 2.57 Cd (mg/L) 0.1096 - 0.141 Mn (mg/L) 21.43 - 38.91 Fe (mg/L) 248.14 - 521.45 The types of effluents treated in these studies included sterilized brewery effluent (SBE), sterilized artificial brewery effluent (SABE), non-sterilized brewery effluent (NSBE), yeast residue (YR), and Zarrouk medium (Fig. 7). Since brewery effluents often comprise a complex mixture of discharges from various production stages, their composition is highly specific and varies significantly depending on the brewery’s location and practices. To address this variability and improve reproducibility, researchers are increasingly turning to artificial media that mimic the characteristics of specific effluents or their combinations. All selected articles involved the use of microalgae in the biological treatment of brewery effluents. However, they can be categorized into two groups based on the adopted strategy: those that employed a single microalgae species, and those that utilized co-cultivation approaches—either involving multiple microalgae species or a combination of microalgae and bacteria (Su et al. 2023). 4.2.1 Co-cultivation strategies The co-cultivation strategy enhances the treatment of brewery effluents by leveraging native bacteria to support microalgae in pollutant removal (Su et al. 2023). Studies employing this approach have investigated a range of microalgae species and culture media, as shown in Fig. 8(a) and 8(b). To isolate the effects of specific microorganism combinations and eliminate the influence of naturally occurring bacteria, many of these studies utilize synthetic and/or sterilized effluents (Abdelfattah et al. 2023). Nevertheless, a significant number still incorporate non-synthetic, unsterilized effluents to reflect more realistic conditions. Typically, synthetic effluents are used in smaller-scale setups, such as Erlenmeyer flasks (250–1000 mL), whereas studies using real, sterilized or unsterilized effluents often employ larger photobioreactors with volumes up to 14 L (He et al. 2022). In these co-cultivation experiments, the treatment period generally spans around seven days, achieving average pollutant removal efficiencies of 90.2% for Total Organic Carbon (TOC) and 73.22% for Chemical Oxygen Demand (COD), as presented in Table 4. Among the microalgae studied, Chlorella spp. were the most frequently used, and co-cultivation with bacteria consistently demonstrated superior pollutant removal performance compared to systems using multiple microalgal species alone. The highest biomass concentration recorded in co-cultivation was achieved by Tribonema aequale , reaching 6.45 g/L over an eight-day period, with biomass primarily composed of carbohydrates and lipids. In terms of the effluent treatment efficiency, Scenedesmus sp. 336 exhibited the greatest TOC removal, achieving a reduction of 85.23%. These findings highlight the effectiveness of microalgae–bacteria co-cultivation systems in treating brewery effluents, offering both high pollutant removal rates and valuable biomass production. Table 4. Characterization of effluent treatment, biomass concentration, and biochemical characterization of microalgal biomass from selected articles that used co-cultivation in their methodology Final Biomass Concentration Treatment (based on TOCᵃ or CODᵇ removal) Carbohydrate content (%w/w) Lipid content (%w/w) Protein content (%w/w) Reference 6.45 g/L of Tribonema aequale (in 8 days) SBE with bacteria but no microalgae had a 56.76% TOC reduction. With microalgae in the NSBE, 90.02% TOC was removed 56.84% using SBE, and 58.12% using NSBE 38.10% using SBE, and 35.08% using NSBE The low protein content may be related to the total nitrogen content of the effluents (SBE and NSBE), which was below average (23–69 mg/L). Su et al. (2023) 1.02 g/L of Scenedesmus sp . 336 (in 10 days) COD removal: 74.34% by Chlorella sp . UTEX1602; 77.62% by Chlorella sp . L166; 85.23% by Scenedesmus sp . 336; and 46.03% by Spirulina sp . FACHB-439 Approx. 6% of Scenedesmus sp . biomass Approx. 37.16% of Scenedesmus sp . biomass Low concentration of total nitrogen in the effluent (45 mg/L), leading to low protein levels. Song et al. (2020) 1.41 g/L of Chlorella sorokiniana (in 8 days) 77.3% COD removal 44.5% 34.9% 20.5% He et al. (2023) 821.36 mg/L of biomass, Scenedesmus sp . 336 + C. sorokiniana UTEX1602 (in 9 days) 78.83% COD removal 13.89% 9.5% 64.9% Han et al. (2021) 30.6 g/L of biomass, microalgae and yeast (in 4 days) - - 26.2% - Dias et al. (2022) ᵃ TOC = Total Organic Carbon; ᵇ COD = Chemical Oxygen Demand 4.2.2 Strategies using single microalgae species In studies utilizing single microalgae species, the genus Scenedesmus , particularly Scenedesmus obliquus , emerged as the most frequently used (Fig. 9(a)). Although Scenedesmus spp. are not as widely represented in the literature as Chlorella spp. for brewery effluent treatment, they demonstrated superior performance among the selected studies, as detailed in Section 4.1. These studies generally avoided synthetic or sterilized effluents, relying instead on the native microbial community present in brewery wastewater, which can support both microalgal growth and pollutant removal. The use of pure cultures in such cases allows for a clearer understanding of the specific role of microalgae in effluent treatment, offering valuable insights into their individual growth behavior and treatment efficacy (Fig. 9(b)). Table 5 summarizes the characteristics of studies using pure microalgal cultures, including COD removal efficiency, biomass concentration, and biochemical composition. On average, pure cultures were cultivated for 15 days, achieving COD removal rates ranging from 60.13% to 70.63%. Although the treatment period was longer than in co-cultivation systems, biomass growth in pure cultures was generally more consistent. Table 5. Characterization of effluent treatment efficiency and biomass concentration of microalgal biomass of selected articles that used pure culture in their methodology Microalgae Final biomass concentration % of COD removal Reference Chlorella sp. 2.03 g/L, in 15 d 88.52 Wang (2022) Scenedesmus obliquus 1025 (mg/(L.d)), in 12 d (the brewery effluent was the one that provided the most biomass concentration) 40-70 Ferreira et al. (2018) Scenedesmus sp. 1.05 g/L, in 18 d 62 Yirgu et al. (2021) Scenedesmus obliquus 0.95 g/L, in 17 d 50-62 Ferreira et al. (2017) Notably, Chlorella spp. demonstrated stable COD removal performance across both cultivation strategies—reaching 88.52% in co-cultivation (Dias et al. 2022) and 77.62% in pure culture (Su et al. 2023). This consistency reinforces Chlorella ’s reliability and effectiveness in brewery effluent treatment. In contrast, co-cultivation significantly enhanced the performance of Scenedesmus spp., with COD removal reaching up to 85.23% in co-culture (Su et al. 2023), compared to 62% in pure culture (Ferreira et al. 2018). Among all studies, Chlorella sp. achieved the highest biomass concentration, reaching 2.03 g/L over a 15-day period. Ferreira et al. (2018) further observed that brewery effluent produced the highest biomass yield when compared to other wastewater types (Table 6). Table 6. Microalgal biomass productivity in different effluents type, adapted from Ferreira (2018) Type of effluent Microalgal biomass productivity (mg/(L.d)) Aviary 100 Pig 300 Cattle 358 Brewery 1025 Dairy 183 Urban 440 Bristol (standard) 130 When comparing COD removal efficiencies, both pure and co-cultivation methods produced results comparable to those achieved using conventional chemical coagulants, which typically range between 53.49% and 85.6%. This suggests that microalgae-based treatments could serve as a promising alternative, especially given their potential to meet industrial discharge standards, such as the 450 mg/L COD threshold for effluent disposal (Marques 2017). In summary, all selected studies demonstrated acceptable levels of COD reduction, with the added benefit of microalgal biomass generation for use in bioproduct markets. These findings reinforce the feasibility and sustainability of microalgae-based treatment systems as effective alternatives to conventional brewery effluent treatment methods. 4.3 CO 2 fixation Among the studies reviewed, only four specifically addressed the impact of CO₂ supplementation on microalgae cultivation. These studies consistently demonstrate that CO₂ enrichment not only boosts biomass productivity but also enhances the overall efficiency of effluent treatment. This dual benefit is largely attributed to the reduction in pH levels caused by CO₂ addition, which creates a more favorable environment for nutrient uptake and removal from the effluent (Ferreira et al. 2017). Song et al. (2020) explored the integration of brewery effluent treatment with CO₂-enriched media to support optimal microalgal growth. Their results indicated that a CO₂ concentration of 15% (v/v) enabled effective wastewater treatment while simultaneously promoting high biomass yields. The study also identified Chlorella and Scenedesmus genera as particularly responsive to CO₂ enrichment. However, it was noted that excessive CO₂ levels may inhibit photosynthesis in certain microalgae strains, potentially hindering growth (Ferreira et al. 2017). Among the reviewed literature, Han et al. (2021) was the only study to provide explicit data on CO₂ fixation rates. In their experiment, Scenedesmus sp. 336 and Chlorella sorokiniana UTEX 1602 were co-cultivated in sterilized artificial brewery effluent (SABE), achieving a carbon fixation rate of 34.98 mg/L/day under a regime of 9 hours of daily aeration. These findings suggest that extended cultivation periods may further enhance CO₂ fixation, offering additional environmental benefits in conjunction with effective effluent treatment. 5. Is it possible to obtain high-added value by-products from the microalgal biomass resulting from the treatment of brewery effluent? Although it is well established that microalgae can produce a wide range of high-value by-products—including biofuels, biofertilizers, bioplastics, biopolymers, animal feed, food supplements, nutraceuticals, therapeutic proteins, pharmaceuticals, and cosmeceuticals—studies involving brewery effluents as a cultivation medium have so far focused exclusively on the production of biofertilizers and biofuels. The specific by-products identified in these studies will be discussed in detail in the following subsections. 5.1 Biofuels Despite the growing adoption of renewable fuels, driven in part by global climate concerns, fossil fuels continue to account for approximately 82% of the global energy matrix (Sapientia 2022). This underscores the urgent need for continued innovation, particularly within the biotechnology sector, to develop viable alternatives capable of eventually replacing petroleum-based fuels. This study evaluated effective microalgal cultivation strategies aimed at producing biomass rich in key biomolecules, specifically carbohydrates and lipids, which serve as essential raw materials to produce ethanol and biodiesel, respectively. As shown in Table 7, the reviewed articles, all employing co-cultivation approaches highlight the versatility of brewery effluents (real or synthetic, sterilized or non-sterilized) as culture media. These effluents, typically low in nitrogen, tend to promote lipid accumulation over protein synthesis. Moreover, the observed variation in carbohydrate and lipid content among different microalgal species emphasizes the potential to tailor cultivation conditions for the targeted production of specific biomolecules, thereby positioning microalgal biomass as a valuable and flexible resource for diverse biofuel applications. Table 7. Articles selected in the SRL that present micro-algal biomass with potential for use in the production of biofuels Microalgae Carbohydrate %(m/m) Lipids %(m/m) Reference Tribonema aequale SAG200.80 Sterilized effluent (SBE) and non-sterilized (NSBE), respectively: 56.84% and 58.12% Sterilized effluent (SBE) and non-sterilized (NSBE), respectively: 38.10% and 35.08% Su et al. (2023) Chlorella sp. L166, Chlorella sp. UTEX1602, Scenedesmus sp. 336, Spirulina sp. FACHB-439 Approximately 6% of Scenedesmus sp. 336 biomass Approximately 37.16% of Scenedesmus sp. 336 biomass Song et al. (2020) Chlorella sorokiniana CMBB276 44.5 34.9 He et al. (2022) Rhodosporidium toruloides NCYC 921, Tetradesmus obliquus (ACOI 204/07) - 26.20 Dias et al. (2022) Scenedesmus obliquus 30.2 17.9 Ferreira et al. (2018) 5.2 Biofertilizers Biofertilizers, organic fertilizers derived from natural sources, offer a sustainable alternative to synthetic fertilizers by enhancing plant and soil health without causing adverse environmental effects. Microalgal biomass is particularly well-suited for biofertilizer production due to its rich content of amino acids and plant hormones, which contribute to improved plant growth, nutrient uptake, and stress resilience (Dagnaisser et al. 2023). For optimal biofertilizer efficacy, microalgal biomass should be especially rich in carbohydrates and proteins. Recent research indicates that microalgae cultivated in brewery effluents can serve the dual purpose of effluent treatment and biofertilizer production. Among the studies reviewed, the Chlorella genus emerged as the most promising candidate. In both pure cultures and co-cultivation systems, Chlorella spp. exhibited high protein content and favorable carbohydrate levels, particularly when grown in non-sterilized brewery effluents (NSBE). The methodologies employed in these studies (see Table 8) produced biomass not only capable of enhancing plant growth but also suitable for soil rehabilitation (Dagnaisser et al. 2023). Table 8. Microalgal biomass with potential use as biofertilizer in selected articles in SRL Species of microalgae Carbohydrates (%m/m) Proteins (%m/m) Reference Chlorella sp. 7.8 63.0 (under heterotrophic conditions) Wang (2022) Scenedesmus obliquus 30.2 31.4 Ferreira et al. (2018) Chlorella sp. L166, Chlorella sorokiniana UTEX1602 and Scenedesmus sp. 336 13.9 64.9 Dias et al. (2022) These findings suggest that microalgae-based biofertilizers represent a viable and environmentally friendly alternative to synthetic fertilizers worldwide, with the potential to simultaneously enhance agricultural productivity and promote environmental sustainability. 6. Limitations and future directions The industrial application of brewery wastewater treatment using microalgae still faces several limitations. One major challenge is the high turbidity of brewery effluents, which can significantly hinder microalgal photosynthesis, thereby necessitating pre-treatment of the wastewater (Simate et al. 2011). Furthermore, the considerable variability in the physicochemical properties of brewery effluents—depending on factors such as brewery size, processes, and beer type—complicates the development of a standardized, scalable process with high replicability (Umamaheswari and Shanthakumar 2016). A promising strategy involves designing a well-defined and targeted approach that includes the selection of specific microalgae strains, a particular effluent type, an appropriate pre-treatment method, and clearly defined biomass characteristics. By narrowing the number of variables, such an approach enhances reproducibility and facilitates process optimization (Dias et al. 2022). Given the versatility of microalgae-based treatment systems, it is possible to simultaneously refine specific operational procedures and expand broader scientific understanding. This dual effort can support the wider adoption of microalgal technologies for bioproduct generation, positioning brewery effluents as a sustainable cultivation medium and contributing to the advancement of a circular bioeconomy (Ferreira et al. 2018). 7. Conclusions This literature review has demonstrated the significant potential of microalgae as a sustainable and efficient solution for brewery effluent treatment. The analysis of recent studies reveals that microalgae, particularly species from the genera Chlorella and Scenedesmus , can achieve high levels of organic pollutant removal (comparable to conventional methods) while simultaneously generating biomass suitable to produce biofuels and biofertilizers. Co-cultivation strategies, especially those involving bacteria, consistently enhanced both treatment efficiency and biomass yield, highlighting the benefits of synergistic interactions in wastewater bioremediation. Furthermore, the review underscores the relevance of microalgae in the context of a circular bioeconomy by valorizing brewery waste streams and contributing to the generation of high-value bioproducts. However, challenges remain, including the standardization of cultivation processes and the variability of effluent compositions, which complicate the scalability and replicability of these systems in industrial settings. Microalgae-based treatment systems offer a promising alternative to traditional brewery wastewater management, with the added advantage of resource recovery. With continued innovation and supportive regulatory frameworks, these systems could play a pivotal role in promoting sustainable practices and environmental stewardship across the brewing industry. Declarations Acknowledgements Pedro H. B. de Souza Silva is thankful for his doctoral fellowship provided by CAPES (Coordination for the Improvement of Higher Education Personnel). Funding: This work was supported by the São Paulo Research Foundation (FAPESP) [grant number #2022/15007-0]. Competing Interests: The authors have no relevant financial or non-financial interests to disclose. Author contributions: Pedro Henrique Barboza de Souza Silva : Writing - original Draft preparation, Data analysis; Gianluca Degli Esposti: Review & Editing; Danielle Maass: Idea for the article, Critical Review & Editing, Supervision; Noreyni Christophe Grego Ndiaye: Funding acquisition, Critical Review; Guilherme Arantes Pedro: Critical Review & Editing, Data analysis. Data availability: The data supporting the findings of this study are openly available in the UNIFESP Repository at https://repositorio.unifesp.br/. Ethical Approval: This is not applicable. Consent to Participate: This is not applicable. Consent to Publish: This is not applicable. References Assaf A (2017) Microalgae Found Growing in Effluents and Producing Biofuels. Tratamento de Água. https://tratamentodeagua.com.br/pesquisa-encontra-microalgas-que-crescem-em-efluentes-e-geram-biocombustiveis/. Accessed 8 February 2024 Ashraf A, Ramamurthy R, Rene ER (2021) Wastewater treatment and resource recovery technologies in the brewery industry: Current trends and emerging practices. Sustain Energy Technol Assess 47:101432. https://doi.org/10.1016/j.seta.2021.101432 Bone RA, Landrum JT, Fernandez L (2020) Dietary guidance for lutein: consideration for intake recommendations is scientifically supported. Am J Clin Nutr 110(6):1236–1245. https://doi.org/10.1007/s00394-017-1580-2 Conway J (2024) Global beer industry. Statista. https://www.statista.com/topics/7974/global-beer-industry/. Accessed 24 March 2025 Custódio P, Soares O, Dourado Z (2023) Beer Day: Production Grows 7.7% and Brazil Maintains Third Place Among the World’s Largest Producers. https://brasil61.com/n/dia-da-cerveja-producao-cresce-7-7-e-brasil-mantem-terceira-posicao-entre-os-maiores-produtores-do-mundo-bras239138. Accessed 18 December 2024 Dagnaisser LS, dos Santos MGB, Rita AVS, Cardoso JC, de Carvalho DF, de Mendonça HV (2022) Microalgae as Bio-fertilizer: a New Strategy for Advancing Modern Agriculture, Wastewater Bioremediation, and Atmospheric Carbon Mitigation. Water Air Soil Pollut 233:477. https://doi.org/10.1007/s11270-022-05917-x Dias C, Reis A, Santos JAL, Gouveia L, da Silva TL (2022) Primary brewery wastewater as feedstock for the yeast Rhodosporidium toruloides and the microalga Tetradesmus obliquus mixed cultures with lipid production. Process Biochem 113:71–86. https://doi.org/10.1016/j.procbio.2021.12.019 Ferreira A, Ribeiro B, Marques PASS, Ferreira AF, Dias AP, Pinheiro HM, Reis A, Gouveia L (2017) Scenedesmus obliquus mediated brewery wastewater remediation and CO 2 biofixation for green energy purposes. J Clean Prod 165:1316–1327. https://doi.org/10.1016/j.jclepro.2017.07.232 Ferreira A, Marques P, Ribeiro B, Assemany P, deMendonça HV, Barata A, Oliveira AC, Reis A, Pinheiro HM, Gouveia L (2018) Combining biotechnology with circular bioeconomy: From poultry, swine, cattle, brewery, dairy and urban wastewaters to biohydrogen. Environ Res 164:32–38. https://doi.org/10.1016/j.envres.2018.02.007 Fillaudeau L, Blanpain-Avet P, Daufin G (2006) Wastewater and waste management in brewing industries. J Clean Prod 14(5):463–471. https://doi.org/10.1016/j.jclepro.2005.01.002 Grand View Research (2024) Global lutein market size & outlook, 2023–2030. https://www.grandviewresearch.com/horizon/outlook/lutein-market-size/global. Accessed 11 February 2025 Han X, Hu X, Yin Q, Li S, Song C(2021) Intensification of brewery wastewater purification integrated with CO 2 fixation via microalgae co-cultivation. J Environ Chem Eng 9(4):105710. https://doi.org/10.1016/j.jece.2021.105710 He Y, Lian j, Wang l, Su H, Tan H, Xu Q, Wang H, Li Y, Li M, Han D, Hu Q (2022) Enhanced brewery wastewater purification and microalgal production through algal-bacterial synergy. J Clean Prod 376:134361. https://doi.org/10.1016/j.jclepro.2022.134361 Lima MC, de Albuquerque TS (2021) A brief trajectory of the recent environmental issue in China. Revista Eletrônica de Jornalismo Científico. https://www.comciencia.br/uma-breve-trajetoria-da-questao-ambiental-recente-na-china/. Accessed 11 February 2025 Marques MP, Araújo NS, Gomes PF, Ruggeri Júnior HC (2017) Evaluation of effluent treatment efficiency from a stamping industry using chemical coagulation. Rev Eletrônica Eng Civ 20(10):1-16 Oliveira C (2018) Prevention and adaptation to climate change through biotechnological resources in the construction of resilient cities: a systematic literature review. Dissertation, Federal University of Sao Paulo Ou X (2025) Beer production in China. Statista. https://www.statista.com/statistics/279239/beer-production-in-china/. Accessed 15 May 2025 Rossoti SC, Mockaitis G (2011) Brazil in the production of biofuel through microalgae: autotrophic cultivation and challenges. XXIX Congress. https://www.prp.unicamp.br/inscricao-congresso/resumos/2021P19165A36593O5277.pdf. Accessed 15 May 2025 Sapientia (2022) Pollution by synthetic fertilizers. https://www.cursosapientia.com.br/conteudo/noticias/poluicao-por-fertilizantes-sinteticos. Accessed 05 May 2025 Segura Munoz S, Takayanagui AMM, Santos CB (2002) Systematic literature review and meta-analysis: basic notions on design, interpretation, and application in the health area. Proceedings of the 8. Brazilian Nursing Communication Symposium. http://www.proceedings.scielo.br/scielo.php?script=sci_arttext&pid=MSC0000000052002000200010&lng=en&nrm=iso. Accessed 05 May 2025 Simate GS, Cluett J, Iyuke SE, Musapatika ET, Ndlovu S, Walubita LF, Alvarez AE (2011) The treatment of brewery wastewater for reuse: State of the art. Desalinisation 273(2–3):235-247. https://doi.org/10.1016/j.desal.2011.02.035 Song C, Hu X, Liu Z, Li S, Kitamura Y (2020) Combination of brewery wastewater purification and CO 2 fixation with potential value-added ingredients production via different microalgae strains cultivation. J Clean Prod 268:122332. https://doi.org/10.1016/j.jclepro.2020.122332 Su H, Wang K, Lian J, Wang L, He Y, Li M, Han D, Hu Q (2023) Advanced treatment and resource recovery of brewery wastewater by co-cultivation of filamentous microalga Tribonema aequale and autochthonous bacteria. J Environ Manage 348:119285. https://doi.org/10.1016/j.jenvman.2023.119285 Umamaheswari J, Shanthakumar S (2016) Efficacy of microalgae for industrial wastewater treatment: a review on operating conditions, treatment efficiency and biomass productivity. Rev Environ Sci Biotechnol 15:265–284. https://doi.org/10.1007/s11157-016-9397-7 United Nations (UN). Sustainable Development Goals: United Nations. https://brasil.un.org/pt-br/sdgs. Accessed 11 February 2025 USDA Foreign Agricultural Service (2022) China Beer Market Overview. GAIN Report Number CH2022-0002. United States Department of Agriculture, Foreign Agricultural Service, Beijing ATO. Wang S, Yin C, Yang Z, Hu X, Liu Z, Song W (2022) Assessing the potential of Chlorella sp. for treatment and resource utilization of brewery wastewater coupled with bioproduct production. J Clean Prod 367:132939. https://doi.org/10.1016/j.jclepro.2022.132939 Yirgu Z, Leta S, Hussen A, Khan MM, Aragaw T (2021) Optimization of microwave-assisted carbohydrate extraction from indigenous Scenedesmus sp. grown in brewery effluent using response surface methodology. Heliyon 7(5):e07115. https://doi.org/10.1016/j.heliyon.2021.e07115 Cite Share Download PDF Status: Published Journal Publication published 17 Oct, 2025 Read the published version in Environmental Science and Pollution Research → Version 1 posted Editorial decision: Major Revision 17 Jul, 2025 Reviewers agreed at journal 03 Jun, 2025 Reviewers invited by journal 03 Jun, 2025 Editor invited by journal 27 May, 2025 Editor assigned by journal 26 May, 2025 First submitted to journal 22 May, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6719777","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":465752075,"identity":"9ca4dfdf-1635-4691-8ea1-959676497d30","order_by":0,"name":"Pedro Henrique Barboza de Souza Silva","email":"","orcid":"","institution":"Federal University of Sao Paulo: Universidade Federal de Sao Paulo","correspondingAuthor":false,"prefix":"","firstName":"Pedro","middleName":"Henrique Barboza de Souza","lastName":"Silva","suffix":""},{"id":465752076,"identity":"6db1c6f2-93bd-4d4d-aff1-e3c44c3fd576","order_by":1,"name":"Gianluca Degli Esposti","email":"","orcid":"","institution":"Technische Universität Dresden: Technische Universitat Dresden","correspondingAuthor":false,"prefix":"","firstName":"Gianluca","middleName":"Degli","lastName":"Esposti","suffix":""},{"id":465752077,"identity":"d199e33f-7959-4e5a-bb4c-7a410001df69","order_by":2,"name":"Noreyni Christophe Grego Ndiaye","email":"","orcid":"","institution":"Federal University of Sao Paulo: Universidade Federal de Sao Paulo","correspondingAuthor":false,"prefix":"","firstName":"Noreyni","middleName":"Christophe Grego","lastName":"Ndiaye","suffix":""},{"id":465752078,"identity":"dc0a7f82-427a-4dd3-8e70-7b72b762fc8a","order_by":3,"name":"Guilherme Arantes Pedro","email":"","orcid":"","institution":"Federal University of Sao Paulo: Universidade Federal de Sao Paulo","correspondingAuthor":false,"prefix":"","firstName":"Guilherme","middleName":"Arantes","lastName":"Pedro","suffix":""},{"id":465752079,"identity":"03a06941-5816-4148-9329-c103b924e3df","order_by":4,"name":"Danielle Maass","email":"data:image/png;base64,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","orcid":"https://orcid.org/0000-0002-0866-2530","institution":"Universidade Federal de Sao Paulo","correspondingAuthor":true,"prefix":"","firstName":"Danielle","middleName":"","lastName":"Maass","suffix":""}],"badges":[],"createdAt":"2025-05-22 00:15:05","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6719777/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6719777/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11356-025-37057-0","type":"published","date":"2025-10-17T15:56:55+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":83943640,"identity":"0f494cfe-ee3f-4c93-b29e-3784aeafdbdd","added_by":"auto","created_at":"2025-06-04 19:44:39","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":52633,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart of the beer production process and effluents, adapted from Custódio et al. 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(2021)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/b5b93de683d084847ca5456d.png"},{"id":83943370,"identity":"1df4227e-04f7-40ef-a40a-8156b31f1ac2","added_by":"auto","created_at":"2025-06-04 19:36:39","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":102603,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart and quantity of articles obtained at each stage of the SRL\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/5d64630588bda79de2680ea8.png"},{"id":83943374,"identity":"6b84019d-393c-44a7-a4b6-579cd15016ce","added_by":"auto","created_at":"2025-06-04 19:36:39","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":55106,"visible":true,"origin":"","legend":"\u003cp\u003eYearly distribution of publications: (a) relationship between the articles and their years of publication pre-application and (b) post-application of Relevance Tests\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/f0e59244e7559d5b14083ce0.png"},{"id":83943637,"identity":"83cba8f9-1ebe-448e-8982-32d41b40d6a8","added_by":"auto","created_at":"2025-06-04 19:44:39","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":40169,"visible":true,"origin":"","legend":"\u003cp\u003eOrigin countries of selected articles\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/70ca1de205a8dd7f39691569.png"},{"id":83943381,"identity":"aa2466f1-dd89-4228-8399-7c29094ccb75","added_by":"auto","created_at":"2025-06-04 19:36:39","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":54179,"visible":true,"origin":"","legend":"\u003cp\u003eMicroalgae use and the number of selected articles\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/dd9779deeb9ae5fb6aa4b281.png"},{"id":83943639,"identity":"8272b803-b265-4ad6-93ff-c8b4e52217d6","added_by":"auto","created_at":"2025-06-04 19:44:39","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":57151,"visible":true,"origin":"","legend":"\u003cp\u003eCulture media used in the selected articles: SBE (Sterilized Brewing Effluent), SABE (Sterilized Artificial Brewing Effluent), NSBE (Non-sterilized Brewing Effluent), YR (Yeast Residue), BBM (Bold’s Basal Medium), and Zarrouk\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/bcdb927bfb21049d38a5bf95.png"},{"id":83943702,"identity":"a87d8986-8566-4eb7-af6b-6f966baa1ffe","added_by":"auto","created_at":"2025-06-04 19:52:39","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":105812,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Microalgae species, and (b) effluents and culture media used in co-cultivation strategies\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/62b6e2c88a076b9cc327cd6d.png"},{"id":83943375,"identity":"30ea137d-f83c-4ca8-af9c-c42577505374","added_by":"auto","created_at":"2025-06-04 19:36:39","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":68664,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Microalgae species, and (b) effluents and culture media used in pure culture strategy\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/430763923c148e73d194baae.png"},{"id":93955906,"identity":"a1c709b8-60ac-418a-b3cb-f8ce0653cb27","added_by":"auto","created_at":"2025-10-20 16:06:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1612341,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6719777/v1/97fa31da-827a-4e71-86cb-d376e7316686.pdf"}],"financialInterests":"","formattedTitle":"Harnessing brewing industry effluents for microalgal bioproducts: a systematic review","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eBeer is the third most consumed beverage worldwide, following only water and tea, leading to a global production of approximately 1.88 billion hectoliters in 2023. Among alcoholic beverages, beer holds the top position globally, with an estimated consumption of 178.6 billion liters projected in 2024 (Jan Conway 2024). For example, Brazil is currently the third-largest beer producer in the world, with the brewing industry contributing around 2% to the country\u0026apos;s Gross Domestic Product (GDP). This prominence is rooted in a longstanding cultural tradition of fermented beverage consumption, which has also driven the rapid expansion of the craft brewery sector (Cust\u0026oacute;dio et al. 2023).\u003c/p\u003e\n\u003cp\u003eHowever, large-scale beer production generates substantial amounts of wastewater and biological byproducts, as illustrated in Fig. 1. Depending on the brewery\u0026apos;s size and production scale, between 3 and 10 liters of wastewater are produced for every liter of beer (Luc Fillaudeau et al. 2006). In many cases, this wastewater is discharged directly into waterways (oceans, rivers, streams, or lakes), into municipal sewer systems, or undergoes basic pretreatment before disposal. Such discharges can lead to serious environmental pollution (Simate et al. 2011).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAs a result, freshwater usage, wastewater generation, and its management have become critical considerations for the brewing industry. These factors significantly impact overall operational costs. Additionally, stricter regulations concerning effluent disposal and increasing concern among breweries about their environmental image have intensified research in this area (Ashraf et al. 2021).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBrewing effluents are characterized by high organic loads (see Table 1), and their treatment depends on factors such as beer type, production scale, and processing stages. A typical treatment sequence includes physicochemical processing, biological treatment, sludge dewatering and management, and disinfection (Ashraf et al. 2021). Biological treatment is particularly effective in removing residual organic matter and helps breweries comply with environmental discharge standards, achieving organic matter removal efficiencies of up to 95% (MR Solu\u0026ccedil;\u0026otilde;es Ambientais 2022).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Characteristics of a typical brewery wastewater (Adapted from Ashraf et al. 2021)\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"588\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 43.5374%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameter\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 29.4218%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eUnit\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eAverage value\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003e---\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e3.3-12\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003eTemperature\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003e\u0026ordm;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e18-40\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003eCOD (chemical demand of oxygen)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e1,250 \u0026plusmn; 100-20,000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003eBOD (biological demand of oxygen)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e1,200-3,600\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003eNH\u003csub\u003e3\u003c/sub\u003e-N (ammonia nitrogen)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e16 \u0026plusmn; 5-46.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003eTotal nitrogen\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e0.0196-80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003ePhosphorus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e10-50\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003eSuspended solids\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003emg/L\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003e200-3,000\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" valign=\"top\" style=\"width: 43.7075%;\"\u003e\n \u003cp\u003eHeavy metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 29.2517%;\"\u003e\n \u003cp\u003e---\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 27.0408%;\"\u003e\n \u003cp\u003eVery low\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eBiological treatments often utilize microorganisms such as bacteria, algae, and fungi. These methods offer several advantages, including low capital and operating costs, reduced chemical usage, and the potential to generate valuable byproducts such as biofertilizers, biofuels, and food supplements (Umamaheswari and Shanthakumar 2016). Among these organisms, microalgae have garnered special attention due to their photosynthetic capabilities, which allow them to convert sunlight into biomass while transforming pollutants and toxic metals into nutrients. Furthermore, brewery effluents are rich in CO₂ and essential nutrients such as nitrogen, phosphorus, and potassium, which are key elements for microalgal growth (Assaf 2017).\u003c/p\u003e\n\u003cp\u003eMicroalgae are especially notable for their high CO₂ fixation rates and rapid biomass accumulation, often outperforming traditional plants. They can grow under autotrophic conditions (using light and CO₂), heterotrophic conditions (utilizing organic matter in the medium), or mixotrophic conditions (combining light, CO₂, and organic/inorganic nutrients) (Rossoti and Mockaitis 2011).\u003c/p\u003e\n\u003cp\u003eWhile existing literature, such as the review by Ashraf et al. (2021), provides a broad overview of effluent treatment in the brewing industry, there remains a gap in studies specifically addressing the use of microalgae for this purpose. Given the significant volume of effluents generated by the global brewing industry and the promising potential of microalgae in bioremediation, exploring sustainable brewery effluent management through microalgal cultivation is essential.\u003c/p\u003e\n\u003cp\u003eTherefore, this study aims to systematically review the most recent literature with a focus on: (i) the general characteristics of the selected studies, (ii) the effectiveness of microalgae in brewery effluent treatment, and (iii) the types of bioproducts derived from the microalgal biomass generated during treatment. Emphasis is placed on current trends and emerging practices in microalgal wastewater treatment and bioproduct development.\u003c/p\u003e\n\u003cp\u003eThis paper is structured as follows: the first section presents an overview of the selected articles, including 1) the number of publications per year, and 2) by country. The second section delves into the effectiveness of microalgal wastewater treatment in the brewing sector, covering 3) the types of effluents treated, 4) cultivation strategies, and 5) the efficiencies of organic matter and CO₂ removal. The third section explores the potential bioproducts derived from microalgal treatment of brewery effluents. Finally, the paper discusses 6) research limitations and future directions, followed by 7) the conclusions.\u003c/p\u003e"},{"header":"2. Methodology","content":"\u003cp\u003eTo understand the possibility of producing microalgae and, consequently, obtaining bioproducts using brewery effluents as a nutrient medium, a systematic literature review was performed. For this purpose, two research questions (RQA and RQB) were selected to be answered by the selected literature (Oliveira 2018):\u0026nbsp;\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eRQA: Is the effectiveness of microalgae in the treatment of brewery effluent (considering CO\u003csub\u003e2\u003c/sub\u003e and organic matter removal) greater than or equal to methods already applied?\u003c/li\u003e\n \u003cli\u003eRQB: Is it possible to obtain high-added by-products from the microalgal biomass resulting from the treatment of brewery effluent?\u0026nbsp;\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eOnce a consistent research protocol had been established, the selection and review were carried out following the flowchart shown in Fig. 2. More details regarding the eligibility criteria are described in Table 2.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 2.\u003c/strong\u003e Criteria for Relevance Tests 1, 2 and 3\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"606\"\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd colspan=\"3\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eRelevance Test 1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCriteria\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eWas the article published between 2017 and 2023?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eWas the article written in English?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eDoes the article come from a journal with an impact factor greater than or equal to 3?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"3\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eRelevance Test 2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCriteria\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\u003ctd valign=\"top\"\u003e\u003cbr\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eIs the RQA covered?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eIs the RQB covered?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd colspan=\"3\" valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eRelevance Test 3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCriteria\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eYes\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eDoes the article contain clear results on microalgae biomass growth?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eDoes the article contain clear results on the performance of microalgae as a biological treatment agent?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eDoes the article contain a clear analysis of the characteristics of the biomass produced?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eDoes the article contain a clear economic analysis of the use of microalgae as a biological treatment?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eDoes the article present a clear experimental methodology?\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003eDoes the article present the use and/or feasibility using microalgal biomass in the production of bioproducts?\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e1 point\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\"\u003e\n \u003cp\u003e0 points\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\n\n\n\n\n\n\n\n\n\n\n\n"},{"header":"3. Selected articles and their general characteristics","content":"\u003cp\u003eUsing the protocol previously described, manual search was carried out using the proposed search terms and filtering for articles published from 2017 onwards, resulting in a total of 875 articles. Therefore, 845 articles were excluded that did not have a clear title on the use of microorganisms in the treatment of brewery effluent, 14 articles where the abstract and introduction did not demonstrate the use of microalgae in the effluent treatment process and 3 articles where the conclusion did not contain results referring to the performance of microalgae in treatment or an analysis of their biomass. Of the 13 articles approved in the pre-selection, 4 were excluded because they did not meet the requirements of relevance test 3. The number of articles excluded in each step is illustrated in Fig. 3.\u003c/p\u003e\u003cp\u003eFig. 4(a) illustrates the yearly distribution of publications, highlighting a substantial increase in research articles focused on using microorganisms in brewery effluent treatment, which quadrupled from 2017 to 2022. This trend reached a peak in 2022, reflecting heightened interest and investment in this area. Although there was a slight decrease in 2023, the number remained higher than in 2021, suggesting that research in this field will continue to attract attention even if publication volumes don’t surpass those of 2022. The increased research interest in microalgae can likely be attributed to the growth of cultivation facilities and the discovery of new commercial uses (Derner 2018).\u003c/p\u003e\u003cp\u003eFig. 5 shows that China leads with 36.4% of the relevant publications selected, followed by Portugal at 27.3%. When considering continents, Europe and Asia are tied as the top contributors to this field, with Africa ranking next in relevance. Other continents did not produce publications that met the eligibility criteria for this review.\u003c/p\u003e\u003cp\u003eChina’s leadership in this research field can be attributed to its strong national focus on the circular economy, waste management, and environmental protection. These efforts are supported by comprehensive public policies, including initiatives aimed at expanding reforestation and significantly reducing carbon emissions. As the source of 28.8% of global CO₂ emissions, China faces substantial environmental challenges driven by rapid industrialization and a large population. These include air and water pollution, soil erosion, deforestation, desertification, and biodiversity loss (Lima and Albuquerque 2021).\u0026nbsp;\u003c/p\u003e\u003cp\u003eChina’s prominent role in publishing research on the use of microalgae for brewery effluent treatment may also be linked to its leading position in the global beer market, both in terms of production and consumption. Since 2002, China has surpassed the United States as the world’s largest beer producer, with an estimated output of approximately 35.21 billion liters in 2024 (USDA 2022;\u0026nbsp;Xin Ou\u0026nbsp;2025).\u003c/p\u003e\u003cp\u003eAdditionally, the high volume of Chinese publications in this area can be explained by the country’s significant microalgae biomass production. Over the past 15 years, China has become one of the world’s top producers of microalgae, surpassing Japan in the cultivation of \u003cem\u003eChlorella\u003c/em\u003e spp. (Show 2022).\u0026nbsp;\u003c/p\u003e\u003cp\u003eChina also holds one of the world’s most extensive collections of microalgae species. Institutions such as the Freshwater Algae Culture Collection at the Institute of Hydrobiology (Wuhan) and the Marine Biological Culture Collection Centre (Qingdao) have compiled over 2,000 strains (representing more than 120 genera) and around 600 marine species. Although only a fraction of these is currently exploited commercially, China’s vast microalgae resources are recognized for their potential to generate high-value bioproducts with applications in the food, pharmaceutical, and cosmetic industries (Show 2022).\u003c/p\u003e"},{"header":"4. Is the effectiveness of microalgae in the treatment of brewery effluent (considering CO2 and organic matter removal) greater than or equal to methods already applied?","content":"\u003cp\u003eAs Abdelfattah et al. (2023) rightly emphasize in their review, the treatment of industrial effluents using microalgae represents a highly promising technological alternative. This approach is particularly compelling given its potential to address two critical challenges simultaneously: mitigating the environmental impacts of industrial waste and contributing to the global demand for clean, potable water. As previously discussed, brewery effluents are well-suited to this strategy, both due to the significant volumes produced annually worldwide and their considerable polluting potential.\u003c/p\u003e\u003cp\u003eConsidering this, the following section will explore the current state-of-the-art in brewery effluent treatment using microalgae. We will examine the most employed microalgae species, and the strategies developed to enhance the degradation of key pollutants typically found in this type of wastewater.\u003cstrong\u003e\u003cbr\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e4.1 Most common species used on brewery effluent treatment\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eFig. 6 presents the number of articles categorized by the microalgae species used in the selected studies, highlighting the prominence of the \u003cem\u003eChlorella\u003c/em\u003e and \u003cem\u003eScenedesmus\u003c/em\u003e genera. This trend may be attributed to two key factors: (i) their relevance in the global market and (ii) the relatively low cost associated with their nutritional requirements. Both genera are known for producing high-value by-products, such as lutein (Saadaoui et al. 2021).\u003c/p\u003e\u003cp\u003eLutein is a yellow xanthophyll carotenoid with numerous documented health benefits, including improved visual function and a reduced risk of age-related macular degeneration (Ranard et al. 2017). In 2023, the global lutein market generated USD 357.6 million in revenue and is projected to grow at a compound annual growth rate (CAGR) of 5.7%, reaching approximately USD 527.2 million by 2030 (Grand View Research 2024).\u003c/p\u003e\u003cp\u003eAlthough the use of effluents in microalgae cultivation can limit the application of microalgae and their by-products for human consumption due to safety concerns—primarily related to the presence of toxic metals, this issue is generally not so relevant in the case of brewery effluents, as they contain little to no such contaminants (Show 2022).\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e4.2 Type of brewery effluent treated and treatment strategies\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eThe type of brewery effluent treated varied among the studies, resulting in differences in the growth media used for microalgae cultivation, as detailed in Table 3. Typically, microalgae are pre-cultured in well-established media from existing literature to achieve a suitable biomass concentration that facilitates adaptation to the effluent. Among the reviewed studies, BG-11 medium was the most commonly used—likely due to its versatility and ease of modification (Fig. 7). Notably, it was employed in studies by Su et al. (2023), Song et al. (2020), He et al. (2022), and Han et al. (2021), and has proven particularly effective for culturing microalgae of the \u003cem\u003eChlorella\u003c/em\u003e genus, which represented 38.9% of the microorganisms examined (Fig. 6). Other media used include Zarrouk (Dias et al. 2022), Bristol (Wang 2022; Ferreira et al. 2018), and Bold Basal Medium (BBM) (Yirgu et al. 2021).\u003cstrong\u003e\u003cbr\u003e\u003c/strong\u003e\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 3.\u003c/strong\u003e General characteristics of brewing effluents used by articles selected in SRL\u003c/p\u003e\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"605\"\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eParameters\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBrewery effluents\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eDissolved oxygen (DO) (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e0.33 - 2.34\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eChemical oxygen demand (COD) (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e226 - 4000\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eTotal dissolved phosphorus (TP) (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e1.15 - 18.45\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eTotal dissolved nitrogen (TN) (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e22.78 - 69.00\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eNH\u003csub\u003e3\u003c/sub\u003e-N (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e18.30 - 48.00\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003ePO\u003csub\u003e4\u003c/sub\u003e-P (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e0.23 - 6.50\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eNO\u003csub\u003e3\u003c/sub\u003e-N (mg/L) \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e0.10 - 9.00\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eNO\u003csub\u003e2\u003c/sub\u003e-N (mg/L) \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e0.01 - 0.025\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eSuspended solids (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e665 - 771\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eSalinity (%)\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e1.41 - 1.60\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003epH\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e6.80 - 8.85\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eNa (mg/L) \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e160.23 - 847.68\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eK (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e7.63 - 20.11\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eMg (mg/L) \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e4.11 - 17.43 \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eCa (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e10.06 - 36.14\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eCu (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e317.88 - 348.19\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eZn (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e101.07 - 114.44\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eAs (mg/L) \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e0.814 - 2.57\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eCd (mg/L) \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e0.1096 - 0.141\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eMn (mg/L) \u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e21.43 - 38.91\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 49.9174%;\"\u003e\n \u003cp\u003eFe (mg/L)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 50.0826%;\"\u003e\n \u003cp\u003e248.14 - 521.45\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003cp\u003eThe types of effluents treated in these studies included sterilized brewery effluent (SBE), sterilized artificial brewery effluent (SABE), non-sterilized brewery effluent (NSBE), yeast residue (YR), and Zarrouk medium (Fig. 7). Since brewery effluents often comprise a complex mixture of discharges from various production stages, their composition is highly specific and varies significantly depending on the brewery’s location and practices. To address this variability and improve reproducibility, researchers are increasingly turning to artificial media that mimic the characteristics of specific effluents or their combinations.\u003c/p\u003e\u003cp\u003eAll selected articles involved the use of microalgae in the biological treatment of brewery effluents. However, they can be categorized into two groups based on the adopted strategy: those that employed a single microalgae species, and those that utilized co-cultivation approaches—either involving multiple microalgae species or a combination of microalgae and bacteria (Su et al. 2023).\u0026nbsp;\u003c/p\u003e\u003cp\u003e\u003cem\u003e4.2.1 Co-cultivation strategies\u003c/em\u003e\u003c/p\u003e\u003cp\u003eThe co-cultivation strategy enhances the treatment of brewery effluents by leveraging native bacteria to support microalgae in pollutant removal (Su et al. 2023). Studies employing this approach have investigated a range of microalgae species and culture media, as shown in Fig. 8(a) and 8(b). To isolate the effects of specific microorganism combinations and eliminate the influence of naturally occurring bacteria, many of these studies utilize synthetic and/or sterilized effluents (Abdelfattah et al. 2023). Nevertheless, a significant number still incorporate non-synthetic, unsterilized effluents to reflect more realistic conditions. Typically, synthetic effluents are used in smaller-scale setups, such as Erlenmeyer flasks (250–1000 mL), whereas studies using real, sterilized or unsterilized effluents often employ larger photobioreactors with volumes up to 14 L (He et al. 2022). \u0026nbsp;\u003c/p\u003e\u003cp\u003eIn these co-cultivation experiments, the treatment period generally spans around seven days, achieving average pollutant removal efficiencies of 90.2% for Total Organic Carbon (TOC) and 73.22% for Chemical Oxygen Demand (COD), as presented in Table 4. Among the microalgae studied, \u003cem\u003eChlorella\u003c/em\u003e spp. were the most frequently used, and co-cultivation with bacteria consistently demonstrated superior pollutant removal performance compared to systems using multiple microalgal species alone.\u003c/p\u003e\u003cp\u003eThe highest biomass concentration recorded in co-cultivation was achieved by \u003cem\u003eTribonema aequale\u003c/em\u003e, reaching 6.45 g/L over an eight-day period, with biomass primarily composed of carbohydrates and lipids. In terms of the effluent treatment efficiency, \u003cem\u003eScenedesmus\u003c/em\u003e sp. 336 exhibited the greatest TOC removal, achieving a reduction of 85.23%. These findings highlight the effectiveness of microalgae–bacteria co-cultivation systems in treating brewery effluents, offering both high pollutant removal rates and valuable biomass production.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 4.\u003c/strong\u003e Characterization of effluent treatment, biomass concentration, and biochemical characterization of microalgal biomass from selected articles that used co-cultivation in their methodology\u003c/p\u003e\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd valign=\"bottom\" style=\"width: 18.2208%;\"\u003e\n \u003cp\u003eFinal Biomass Concentration\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\" style=\"width: 28.7245%;\"\u003e\n \u003cp\u003eTreatment (based on TOCᵃ or CODᵇ removal)\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\" style=\"width: 13.9335%;\"\u003e\n \u003cp\u003eCarbohydrate content (%w/w)\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\" style=\"width: 13.7192%;\"\u003e\n \u003cp\u003eLipid content (%w/w)\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\" style=\"width: 23.9014%;\"\u003e\n \u003cp\u003eProtein content (%w/w)\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\" style=\"width: 1.50054%;\"\u003e\n \u003cp\u003eReference\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 18.2208%;\"\u003e\n \u003cp\u003e6.45 g/L of \u003cem\u003eTribonema aequale\u003c/em\u003e (in 8 days)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 28.7245%;\"\u003e\n \u003cp\u003eSBE with bacteria but no microalgae had a 56.76% TOC reduction. With microalgae in the NSBE, 90.02% TOC was removed\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.9335%;\"\u003e\n \u003cp\u003e56.84% using SBE, and 58.12% using NSBE\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.7192%;\"\u003e\n \u003cp\u003e38.10% using SBE, and 35.08% using NSBE\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 23.9014%;\"\u003e\n \u003cp\u003eThe low protein content may be related to the total nitrogen content of the effluents (SBE and NSBE), which was below average (23–69\u0026nbsp;mg/L).\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 1.50054%;\"\u003e\n \u003cp\u003eSu et al. (2023)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 18.2208%;\"\u003e\n \u003cp\u003e1.02 g/L of \u003cem\u003eScenedesmus sp\u003c/em\u003e. 336 (in 10 days)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 28.7245%;\"\u003e\n \u003cp\u003eCOD removal: 74.34% by \u003cem\u003eChlorella sp\u003c/em\u003e. UTEX1602; 77.62% by \u003cem\u003eChlorella sp\u003c/em\u003e. L166; 85.23% by \u003cem\u003eScenedesmus\u003c/em\u003e \u003cem\u003esp\u003c/em\u003e. 336; and 46.03% by \u003cem\u003eSpirulina sp\u003c/em\u003e. FACHB-439\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.9335%;\"\u003e\n \u003cp\u003eApprox. 6% of \u003cem\u003eScenedesmus sp\u003c/em\u003e. biomass\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.7192%;\"\u003e\n \u003cp\u003eApprox. 37.16% of \u003cem\u003eScenedesmus sp\u003c/em\u003e. biomass\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 23.9014%;\"\u003e\n \u003cp\u003eLow concentration of total nitrogen in the effluent (45 mg/L), leading to low protein levels.\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 1.50054%;\"\u003e\n \u003cp\u003eSong et al. (2020)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 18.2208%;\"\u003e\n \u003cp\u003e1.41 g/L of \u003cem\u003eChlorella sorokiniana\u003c/em\u003e (in 8 days)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 28.7245%;\"\u003e\n \u003cp\u003e77.3% COD removal\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.9335%;\"\u003e\n \u003cp\u003e44.5%\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.7192%;\"\u003e\n \u003cp\u003e34.9%\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 23.9014%;\"\u003e\n \u003cp\u003e20.5%\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 1.50054%;\"\u003e\n \u003cp\u003eHe et al. (2023)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 18.2208%;\"\u003e\n \u003cp\u003e821.36 mg/L of biomass, \u003cem\u003eScenedesmus sp\u003c/em\u003e. 336 + \u003cem\u003eC. sorokiniana\u0026nbsp;\u003c/em\u003eUTEX1602 (in 9 days)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 28.7245%;\"\u003e\n \u003cp\u003e78.83% COD removal\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.9335%;\"\u003e\n \u003cp\u003e13.89%\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.7192%;\"\u003e\n \u003cp\u003e9.5%\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 23.9014%;\"\u003e\n \u003cp\u003e64.9%\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 1.50054%;\"\u003e\n \u003cp\u003eHan et al. (2021)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 18.2208%;\"\u003e\n \u003cp\u003e30.6 g/L of biomass, microalgae and yeast (in 4 days)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 28.7245%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.9335%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 13.7192%;\"\u003e\n \u003cp\u003e26.2%\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 23.9014%;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 1.50054%;\"\u003e\n \u003cp\u003eDias et al. (2022)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003cp\u003eᵃ TOC = Total Organic Carbon; ᵇ COD = Chemical Oxygen Demand\u003c/p\u003e\u003cp\u003e\u003cem\u003e4.2.2 Strategies using single microalgae species\u003c/em\u003e\u003c/p\u003e\u003cp\u003eIn studies utilizing single microalgae species, the genus \u003cem\u003eScenedesmus\u003c/em\u003e, particularly \u003cem\u003eScenedesmus obliquus\u003c/em\u003e, emerged as the most frequently used (Fig. 9(a)). Although \u003cem\u003eScenedesmus\u003c/em\u003e spp. are not as widely represented in the literature as \u003cem\u003eChlorella\u003c/em\u003e spp. for brewery effluent treatment, they demonstrated superior performance among the selected studies, as detailed in Section 4.1. These studies generally avoided synthetic or sterilized effluents, relying instead on the native microbial community present in brewery wastewater, which can support both microalgal growth and pollutant removal. The use of pure cultures in such cases allows for a clearer understanding of the specific role of microalgae in effluent treatment, offering valuable insights into their individual growth behavior and treatment efficacy (Fig. 9(b)).\u003c/p\u003e\u003cp\u003eTable 5 summarizes the characteristics of studies using pure microalgal cultures, including COD removal efficiency, biomass concentration, and biochemical composition. On average, pure cultures were cultivated for 15 days, achieving COD removal rates ranging from 60.13% to 70.63%. Although the treatment period was longer than in co-cultivation systems, biomass growth in pure cultures was generally more consistent.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 5.\u0026nbsp;\u003c/strong\u003eCharacterization of effluent treatment efficiency and biomass concentration of microalgal biomass of selected articles that used pure culture in their methodology\u003c/p\u003e\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eMicroalgae\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eFinal biomass concentration\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\"\u003e\n \u003cp\u003e% of COD removal\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\"\u003e\n \u003cp\u003eReference\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd\u003e\n \u003cp\u003e\u003cem\u003eChlorella\u003c/em\u003e sp.\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003e2.03 g/L, in 15 d\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003e88.52\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003eWang (2022)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd\u003e\n \u003cp\u003e\u003cem\u003eScenedesmus obliquus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003e1025 (mg/(L.d)), in 12 d (the brewery effluent was the one that provided the most biomass concentration)\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003e40-70\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003eFerreira et al. (2018)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd\u003e\n \u003cp\u003e\u003cem\u003eScenedesmus\u0026nbsp;\u003c/em\u003esp.\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003e1.05 g/L, in 18 d\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003e62\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003eYirgu et al. (2021)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd\u003e\n \u003cp\u003e\u003cem\u003eScenedesmus obliquus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003e0.95 g/L, in 17 d\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003e50-62\u003c/p\u003e\n \u003c/td\u003e\u003ctd\u003e\n \u003cp\u003eFerreira et al. (2017)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003cp\u003eNotably, \u003cem\u003eChlorella\u003c/em\u003e spp. demonstrated stable COD removal performance across both cultivation strategies—reaching 88.52% in co-cultivation (Dias et al. 2022) and 77.62% in pure culture (Su et al. 2023). This consistency reinforces \u003cem\u003eChlorella\u003c/em\u003e’s reliability and effectiveness in brewery effluent treatment. In contrast, co-cultivation significantly enhanced the performance of \u003cem\u003eScenedesmus\u003c/em\u003e spp., with COD removal reaching up to 85.23% in co-culture (Su et al. 2023), compared to 62% in pure culture (Ferreira et al. 2018).\u003c/p\u003e\u003cp\u003eAmong all studies, \u003cem\u003eChlorella\u003c/em\u003e sp. achieved the highest biomass concentration, reaching 2.03 g/L over a 15-day period. Ferreira et al. (2018) further observed that brewery effluent produced the highest biomass yield when compared to other wastewater types (Table 6).\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 6.\u003c/strong\u003e\u0026nbsp; \u0026nbsp;Microalgal biomass productivity in different effluents type, adapted from Ferreira (2018)\u003c/p\u003e\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"604\"\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003eType of effluent\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003eMicroalgal biomass productivity (mg/(L.d))\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003eAviary\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003ePig\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003eCattle\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003e358\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003eBrewery\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003e1025\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003eDairy\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003e183\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003eUrban\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003e440\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003eBristol (standard)\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"top\" style=\"width: 302px;\"\u003e\n \u003cp\u003e130\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003cp\u003eWhen comparing COD removal efficiencies, both pure and co-cultivation methods produced results comparable to those achieved using conventional chemical coagulants, which typically range between 53.49% and 85.6%. This suggests that microalgae-based treatments could serve as a promising alternative, especially given their potential to meet industrial discharge standards, such as the 450 mg/L COD threshold for effluent disposal (Marques 2017).\u003c/p\u003e\u003cp\u003eIn summary, all selected studies demonstrated acceptable levels of COD reduction, with the added benefit of microalgal biomass generation for use in bioproduct markets. These findings reinforce the feasibility and sustainability of microalgae-based treatment systems as effective alternatives to conventional brewery effluent treatment methods.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e4.3 CO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003efixation\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eAmong the studies reviewed, only four specifically addressed the impact of CO₂ supplementation on microalgae cultivation. These studies consistently demonstrate that CO₂ enrichment not only boosts biomass productivity but also enhances the overall efficiency of effluent treatment. This dual benefit is largely attributed to the reduction in pH levels caused by CO₂ addition, which creates a more favorable environment for nutrient uptake and removal from the effluent (Ferreira et al. 2017).\u003c/p\u003e\u003cp\u003eSong et al. (2020) explored the integration of brewery effluent treatment with CO₂-enriched media to support optimal microalgal growth. Their results indicated that a CO₂ concentration of 15% (v/v) enabled effective wastewater treatment while simultaneously promoting high biomass yields. The study also identified \u003cem\u003eChlorella\u003c/em\u003e and \u003cem\u003eScenedesmus\u003c/em\u003e genera as particularly responsive to CO₂ enrichment. However, it was noted that excessive CO₂ levels may inhibit photosynthesis in certain microalgae strains, potentially hindering growth (Ferreira et al. 2017).\u003c/p\u003e\u003cp\u003eAmong the reviewed literature, Han et al. (2021) was the only study to provide explicit data on CO₂ fixation rates. In their experiment, \u003cem\u003eScenedesmus\u003c/em\u003e sp. 336 and \u003cem\u003eChlorella sorokiniana\u003c/em\u003e UTEX 1602 were co-cultivated in sterilized artificial brewery effluent (SABE), achieving a carbon fixation rate of 34.98 mg/L/day under a regime of 9 hours of daily aeration. These findings suggest that extended cultivation periods may further enhance CO₂ fixation, offering additional environmental benefits in conjunction with effective effluent treatment.\u003c/p\u003e"},{"header":"5. Is it possible to obtain high-added value by-products from the microalgal biomass resulting from the treatment of brewery effluent?","content":"\u003cp\u003eAlthough it is well established that microalgae can produce a wide range of high-value by-products—including biofuels, biofertilizers, bioplastics, biopolymers, animal feed, food supplements, nutraceuticals, therapeutic proteins, pharmaceuticals, and cosmeceuticals—studies involving brewery effluents as a cultivation medium have so far focused exclusively on the production of biofertilizers and biofuels. The specific by-products identified in these studies will be discussed in detail in the following subsections.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003e5.1 Biofuels\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eDespite the growing adoption of renewable fuels, driven in part by global climate concerns, fossil fuels continue to account for approximately 82% of the global energy matrix (Sapientia 2022). This underscores the urgent need for continued innovation, particularly within the biotechnology sector, to develop viable alternatives capable of eventually replacing petroleum-based fuels.\u003c/p\u003e\u003cp\u003eThis study evaluated effective microalgal cultivation strategies aimed at producing biomass rich in key biomolecules, specifically carbohydrates and lipids, which serve as essential raw materials to produce ethanol and biodiesel, respectively. As shown in Table 7, the reviewed articles, all employing co-cultivation approaches highlight the versatility of brewery effluents (real or synthetic, sterilized or non-sterilized) as culture media. These effluents, typically low in nitrogen, tend to promote lipid accumulation over protein synthesis. Moreover, the observed variation in carbohydrate and lipid content among different microalgal species emphasizes the potential to tailor cultivation conditions for the targeted production of specific biomolecules, thereby positioning microalgal biomass as a valuable and flexible resource for diverse biofuel applications.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 7.\u003c/strong\u003e Articles selected in the SRL that present micro-algal biomass with potential for use in the production of biofuels\u003c/p\u003e\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"642\"\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd valign=\"bottom\" style=\"width: 180px;\"\u003e\n \u003cp\u003eMicroalgae\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\" style=\"width: 197px;\"\u003e\n \u003cp\u003eCarbohydrate %(m/m)\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\" style=\"width: 180px;\"\u003e\n \u003cp\u003eLipids %(m/m)\u003c/p\u003e\n \u003c/td\u003e\u003ctd valign=\"bottom\" style=\"width: 85px;\"\u003e\n \u003cp\u003eReference\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e\u003cem\u003eTribonema aequale\u003c/em\u003e SAG200.80\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 197px;\"\u003e\n \u003cp\u003eSterilized effluent (SBE) and non-sterilized (NSBE), respectively: 56.84% and 58.12%\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003eSterilized effluent (SBE) and non-sterilized (NSBE), respectively: 38.10% and 35.08%\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 85px;\"\u003e\n \u003cp\u003eSu et al. (2023)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e\u003cem\u003eChlorella\u003c/em\u003e sp. L166, \u003cem\u003eChlorella\u003c/em\u003e sp. UTEX1602, \u003cem\u003eScenedesmus\u003c/em\u003e sp. 336, \u003cem\u003eSpirulina\u003c/em\u003e sp. FACHB-439\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 197px;\"\u003e\n \u003cp\u003eApproximately 6% of \u003cem\u003eScenedesmus\u003c/em\u003e sp. 336 biomass\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003eApproximately 37.16% of \u003cem\u003eScenedesmus\u003c/em\u003e sp. 336 biomass\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 85px;\"\u003e\n \u003cp\u003eSong et al. (2020)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e\u003cem\u003eChlorella sorokiniana\u003c/em\u003e CMBB276\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 197px;\"\u003e\n \u003cp\u003e44.5\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e34.9\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 85px;\"\u003e\n \u003cp\u003eHe et al. (2022)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e\u003cem\u003eRhodosporidium toruloides\u003c/em\u003e NCYC 921, \u003cem\u003eTetradesmus obliquus\u003c/em\u003e (ACOI 204/07)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 197px;\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e26.20\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 85px;\"\u003e\n \u003cp\u003eDias et al. (2022)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e\u003cem\u003eScenedesmus obliquus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 197px;\"\u003e\n \u003cp\u003e30.2\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e17.9\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 85px;\"\u003e\n \u003cp\u003eFerreira et al. (2018)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003cp\u003e\u003cstrong\u003e5.2 Biofertilizers\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eBiofertilizers, organic fertilizers derived from natural sources, offer a sustainable alternative to synthetic fertilizers by enhancing plant and soil health without causing adverse environmental effects. Microalgal biomass is particularly well-suited for biofertilizer production due to its rich content of amino acids and plant hormones, which contribute to improved plant growth, nutrient uptake, and stress resilience (Dagnaisser et al. 2023). For optimal biofertilizer efficacy, microalgal biomass should be especially rich in carbohydrates and proteins.\u003c/p\u003e\u003cp\u003eRecent research indicates that microalgae cultivated in brewery effluents can serve the dual purpose of effluent treatment and biofertilizer production. Among the studies reviewed, the \u003cem\u003eChlorella\u003c/em\u003e genus emerged as the most promising candidate. In both pure cultures and co-cultivation systems, \u003cem\u003eChlorella\u003c/em\u003e spp. exhibited high protein content and favorable carbohydrate levels, particularly when grown in non-sterilized brewery effluents (NSBE). The methodologies employed in these studies (see Table 8) produced biomass not only capable of enhancing plant growth but also suitable for soil rehabilitation (Dagnaisser et al. 2023).\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 8.\u003c/strong\u003e Microalgal biomass with potential use as biofertilizer in selected articles in SRL\u003c/p\u003e\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"604\"\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003eSpecies of microalgae\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003eCarbohydrates (%m/m)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003eProteins (%m/m)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eReference\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cem\u003eChlorella\u003c/em\u003e sp.\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003e7.8\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e63.0 (under heterotrophic conditions)\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eWang (2022)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cem\u003eScenedesmus obliquus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003e30.2\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e31.4\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eFerreira et al. (2018)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cem\u003eChlorella\u003c/em\u003e sp. L166, \u003cem\u003eChlorella sorokiniana\u003c/em\u003e UTEX1602 and \u003cem\u003eScenedesmus\u0026nbsp;\u003c/em\u003esp. 336\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 170px;\"\u003e\n \u003cp\u003e13.9\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 180px;\"\u003e\n \u003cp\u003e64.9\u003c/p\u003e\n \u003c/td\u003e\u003ctd style=\"width: 104px;\"\u003e\n \u003cp\u003eDias et al. (2022)\u003c/p\u003e\n \u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003cp\u003eThese findings suggest that microalgae-based biofertilizers represent a viable and environmentally friendly alternative to synthetic fertilizers worldwide, with the potential to simultaneously enhance agricultural productivity and promote environmental sustainability.\u003c/p\u003e"},{"header":"6. Limitations and future directions","content":"\u003cp\u003eThe industrial application of brewery wastewater treatment using microalgae still faces several limitations. One major challenge is the high turbidity of brewery effluents, which can significantly hinder microalgal photosynthesis, thereby necessitating pre-treatment of the wastewater (Simate et al. 2011). Furthermore, the considerable variability in the physicochemical properties of brewery effluents—depending on factors such as brewery size, processes, and beer type—complicates the development of a standardized, scalable process with high replicability (Umamaheswari and Shanthakumar 2016).\u003c/p\u003e\n\u003cp\u003eA promising strategy involves designing a well-defined and targeted approach that includes the selection of specific microalgae strains, a particular effluent type, an appropriate pre-treatment method, and clearly defined biomass characteristics. By narrowing the number of variables, such an approach enhances reproducibility and facilitates process optimization (Dias et al. 2022).\u003c/p\u003e\n\u003cp\u003eGiven the versatility of microalgae-based treatment systems, it is possible to simultaneously refine specific operational procedures and expand broader scientific understanding. This dual effort can support the wider adoption of microalgal technologies for bioproduct generation, positioning brewery effluents as a sustainable cultivation medium and contributing to the advancement of a circular bioeconomy (Ferreira et al. 2018).\u003c/p\u003e\n\n\n\n"},{"header":"7. Conclusions","content":"\u003cp\u003eThis literature review has demonstrated the significant potential of microalgae as a sustainable and efficient solution for brewery effluent treatment. The analysis of recent studies reveals that microalgae, particularly species from the genera \u003cem\u003eChlorella\u003c/em\u003e and \u003cem\u003eScenedesmus\u003c/em\u003e, can achieve high levels of organic pollutant removal (comparable to conventional methods) while simultaneously generating biomass suitable to produce biofuels and biofertilizers. Co-cultivation strategies, especially those involving bacteria, consistently enhanced both treatment efficiency and biomass yield, highlighting the benefits of synergistic interactions in wastewater bioremediation.\u003c/p\u003e\u003cp\u003eFurthermore, the review underscores the relevance of microalgae in the context of a circular bioeconomy by valorizing brewery waste streams and contributing to the generation of high-value bioproducts. However, challenges remain, including the standardization of cultivation processes and the variability of effluent compositions, which complicate the scalability and replicability of these systems in industrial settings.\u003c/p\u003e\u003cp\u003eMicroalgae-based treatment systems offer a promising alternative to traditional brewery wastewater management, with the added advantage of resource recovery. With continued innovation and supportive regulatory frameworks, these systems could play a pivotal role in promoting sustainable practices and environmental stewardship across the brewing industry.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003ePedro H. B. de Souza Silva is thankful for his doctoral fellowship provided by CAPES (Coordination for the Improvement of Higher Education Personnel).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003eThis work was supported by the S\u0026atilde;o Paulo Research Foundation (FAPESP) [grant number #2022/15007-0].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interests:\u003c/strong\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003ePedro Henrique Barboza de Souza Silva\u003c/strong\u003e\u003cstrong\u003e:\u003c/strong\u003eWriting - original Draft preparation, Data analysis;\u0026nbsp;\u003cstrong\u003eGianluca Degli Esposti:\u0026nbsp;\u003c/strong\u003eReview \u0026amp; Editing;\u0026nbsp;\u003cstrong\u003eDanielle Maass:\u0026nbsp;\u003c/strong\u003eIdea for the article, Critical Review \u0026amp; Editing, Supervision;\u0026nbsp;\u003cstrong\u003eNoreyni Christophe Grego Ndiaye:\u003c/strong\u003e Funding acquisition,\u0026nbsp;Critical Review; Guilherme Arantes Pedro:\u0026nbsp;Critical Review \u0026amp; Editing, Data analysis.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability:\u0026nbsp;\u003c/strong\u003eThe data supporting the findings of this study are openly available in the UNIFESP Repository at https://repositorio.unifesp.br/.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval:\u0026nbsp;\u003c/strong\u003eThis is not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Participate:\u0026nbsp;\u003c/strong\u003eThis is not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to Publish:\u0026nbsp;\u003c/strong\u003eThis is not applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAssaf A (2017) Microalgae Found Growing in Effluents and Producing Biofuels. Tratamento de \u0026Aacute;gua. https://tratamentodeagua.com.br/pesquisa-encontra-microalgas-que-crescem-em-efluentes-e-geram-biocombustiveis/. Accessed 8 February 2024\u003c/li\u003e\n\u003cli\u003eAshraf A, Ramamurthy R, Rene ER (2021) Wastewater treatment and resource recovery technologies in the brewery industry: Current trends and emerging practices. Sustain Energy Technol Assess 47:101432. https://doi.org/10.1016/j.seta.2021.101432\u003c/li\u003e\n\u003cli\u003eBone RA, Landrum JT, Fernandez L (2020) Dietary guidance for lutein: consideration for intake recommendations is scientifically supported. Am J Clin Nutr 110(6):1236\u0026ndash;1245. https://doi.org/10.1007/s00394-017-1580-2 \u003c/li\u003e\n\u003cli\u003eConway J (2024) Global beer industry. Statista. https://www.statista.com/topics/7974/global-beer-industry/. Accessed 24 March 2025\u003c/li\u003e\n\u003cli\u003eCust\u0026oacute;dio P, Soares O, Dourado Z (2023) Beer Day: Production Grows 7.7% and Brazil Maintains Third Place Among the World\u0026rsquo;s Largest Producers. https://brasil61.com/n/dia-da-cerveja-producao-cresce-7-7-e-brasil-mantem-terceira-posicao-entre-os-maiores-produtores-do-mundo-bras239138. Accessed 18 December 2024\u003c/li\u003e\n\u003cli\u003eDagnaisser LS, dos Santos MGB, Rita AVS, Cardoso JC, de Carvalho DF, de Mendon\u0026ccedil;a HV (2022) Microalgae as Bio-fertilizer: a New Strategy for Advancing Modern Agriculture, Wastewater Bioremediation, and Atmospheric Carbon Mitigation. Water Air Soil Pollut 233:477. https://doi.org/10.1007/s11270-022-05917-x\u003c/li\u003e\n\u003cli\u003eDias C, Reis A, Santos JAL, Gouveia L, da Silva TL (2022) Primary brewery wastewater as feedstock for the yeast \u003cem\u003eRhodosporidium toruloides\u003c/em\u003e and the microalga \u003cem\u003eTetradesmus obliquus\u003c/em\u003e mixed cultures with lipid production. Process Biochem 113:71\u0026ndash;86. https://doi.org/10.1016/j.procbio.2021.12.019 \u003c/li\u003e\n\u003cli\u003eFerreira A, Ribeiro B, Marques PASS, Ferreira AF, Dias AP, Pinheiro HM, Reis A, Gouveia L (2017) \u003cem\u003eScenedesmus obliquus\u003c/em\u003e mediated brewery wastewater remediation and CO\u003csub\u003e2\u003c/sub\u003e biofixation for green energy purposes. J Clean Prod 165:1316\u0026ndash;1327. https://doi.org/10.1016/j.jclepro.2017.07.232\u003c/li\u003e\n\u003cli\u003eFerreira A, Marques P, Ribeiro B, Assemany P, deMendon\u0026ccedil;a HV, Barata A, Oliveira AC, Reis A, Pinheiro HM, Gouveia L (2018) Combining biotechnology with circular bioeconomy: From poultry, swine, cattle, brewery, dairy and urban wastewaters to biohydrogen. Environ Res 164:32\u0026ndash;38. https://doi.org/10.1016/j.envres.2018.02.007\u003c/li\u003e\n\u003cli\u003eFillaudeau L, Blanpain-Avet P, Daufin G (2006) Wastewater and waste management in brewing industries. J Clean Prod 14(5):463\u0026ndash;471. https://doi.org/10.1016/j.jclepro.2005.01.002\u003c/li\u003e\n\u003cli\u003eGrand View Research (2024) Global lutein market size \u0026amp; outlook, 2023\u0026ndash;2030. https://www.grandviewresearch.com/horizon/outlook/lutein-market-size/global. Accessed 11 February 2025\u003c/li\u003e\n\u003cli\u003eHan X, Hu X, Yin Q, Li S, Song C(2021) Intensification of brewery wastewater purification integrated with CO\u003csub\u003e2\u003c/sub\u003e fixation via microalgae co-cultivation. J Environ Chem Eng 9(4):105710. https://doi.org/10.1016/j.jece.2021.105710\u003c/li\u003e\n\u003cli\u003eHe Y, Lian j, Wang l, Su H, Tan H, Xu Q, Wang H, Li Y, Li M, Han D, Hu Q (2022) Enhanced brewery wastewater purification and microalgal production through algal-bacterial synergy. J Clean Prod 376:134361. https://doi.org/10.1016/j.jclepro.2022.134361\u003c/li\u003e\n\u003cli\u003eLima MC, de Albuquerque TS (2021) A brief trajectory of the recent environmental issue in China. Revista Eletr\u0026ocirc;nica de Jornalismo Cient\u0026iacute;fico. https://www.comciencia.br/uma-breve-trajetoria-da-questao-ambiental-recente-na-china/. Accessed 11 February 2025\u003c/li\u003e\n\u003cli\u003eMarques MP, Ara\u0026uacute;jo NS, Gomes PF, Ruggeri J\u0026uacute;nior HC (2017) Evaluation of effluent treatment efficiency from a stamping industry using chemical coagulation. Rev Eletr\u0026ocirc;nica Eng Civ 20(10):1-16\u003c/li\u003e\n\u003cli\u003eOliveira C (2018) Prevention and adaptation to climate change through biotechnological resources in the construction of resilient cities: a systematic literature review. Dissertation, Federal University of Sao Paulo\u003c/li\u003e\n\u003cli\u003eOu X (2025) Beer production in China. Statista. https://www.statista.com/statistics/279239/beer-production-in-china/. Accessed 15 May 2025\u003c/li\u003e\n\u003cli\u003eRossoti SC, Mockaitis G (2011) Brazil in the production of biofuel through microalgae: autotrophic cultivation and challenges. XXIX Congress. https://www.prp.unicamp.br/inscricao-congresso/resumos/2021P19165A36593O5277.pdf. Accessed 15 May 2025\u003c/li\u003e\n\u003cli\u003eSapientia (2022) Pollution by synthetic fertilizers. https://www.cursosapientia.com.br/conteudo/noticias/poluicao-por-fertilizantes-sinteticos. Accessed 05 May 2025\u003c/li\u003e\n\u003cli\u003eSegura Munoz S, Takayanagui AMM, Santos CB (2002) Systematic literature review and meta-analysis: basic notions on design, interpretation, and application in the health area. Proceedings of the 8. Brazilian Nursing Communication Symposium. http://www.proceedings.scielo.br/scielo.php?script=sci_arttext\u0026amp;pid=MSC0000000052002000200010\u0026amp;lng=en\u0026amp;nrm=iso. Accessed 05 May 2025\u003c/li\u003e\n\u003cli\u003eSimate GS, Cluett J, Iyuke SE, Musapatika ET, Ndlovu S, Walubita LF, Alvarez AE (2011) The treatment of brewery wastewater for reuse: State of the art. Desalinisation 273(2\u0026ndash;3):235-247. https://doi.org/10.1016/j.desal.2011.02.035\u003c/li\u003e\n\u003cli\u003eSong C, Hu X, Liu Z, Li S, Kitamura Y (2020) Combination of brewery wastewater purification and CO\u003csub\u003e2\u003c/sub\u003e fixation with potential value-added ingredients production via different microalgae strains cultivation. J Clean Prod 268:122332. https://doi.org/10.1016/j.jclepro.2020.122332\u003c/li\u003e\n\u003cli\u003eSu H, Wang K, Lian J, Wang L, He Y, Li M, Han D, Hu Q (2023) Advanced treatment and resource recovery of brewery wastewater by co-cultivation of filamentous microalga \u003cem\u003eTribonema aequale\u003c/em\u003e and autochthonous bacteria. J Environ Manage 348:119285. https://doi.org/10.1016/j.jenvman.2023.119285\u003c/li\u003e\n\u003cli\u003eUmamaheswari J, Shanthakumar S (2016) Efficacy of microalgae for industrial wastewater treatment: a review on operating conditions, treatment efficiency and biomass productivity. Rev Environ Sci Biotechnol 15:265\u0026ndash;284. https://doi.org/10.1007/s11157-016-9397-7 \u003c/li\u003e\n\u003cli\u003eUnited Nations (UN). Sustainable Development Goals: United Nations. https://brasil.un.org/pt-br/sdgs. Accessed 11 February 2025\u003c/li\u003e\n\u003cli\u003eUSDA Foreign Agricultural Service (2022) China Beer Market Overview. GAIN Report Number CH2022-0002. United States Department of Agriculture, Foreign Agricultural Service, Beijing ATO.\u003c/li\u003e\n\u003cli\u003eWang S, Yin C, Yang Z, Hu X, Liu Z, Song W (2022) Assessing the potential of \u003cem\u003eChlorella sp.\u003c/em\u003e for treatment and resource utilization of brewery wastewater coupled with bioproduct production. J Clean Prod 367:132939. https://doi.org/10.1016/j.jclepro.2022.132939\u003c/li\u003e\n\u003cli\u003eYirgu Z, Leta S, Hussen A, Khan MM, Aragaw T (2021) Optimization of microwave-assisted carbohydrate extraction from indigenous \u003cem\u003eScenedesmus sp.\u003c/em\u003e grown in brewery effluent using response surface methodology. Heliyon 7(5):e07115. https://doi.org/10.1016/j.heliyon.2021.e07115\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Microalgae, Brewery wastewater, Bioremediation, Biofuels, Circular bioeconomy, Biofertilizer","lastPublishedDoi":"10.21203/rs.3.rs-6719777/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6719777/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"The brewing industry, a major contributor to global wastewater production, generates effluents rich in organic matter and nutrients, presenting both an environmental challenge and an opportunity for biotechnological innovation. This systematic literature review explores the potential of microalgae in the treatment of brewery effluents and the production of high-value bioproducts. Several peer-reviewed studies published between 2017 and 2024 were analyzed, focusing on microalgal species, cultivation strategies, treatment efficacy, and biomass applications. Chlorella and Scenedesmus emerged as the most effective genera, achieving chemical oxygen demand (COD) removal rates of up to 88.52% and demonstrating strong biomass productivity. Co-cultivation with bacteria enhanced pollutant removal and lipid accumulation, underscoring the synergy between microalgae and native microbiota. The biomass derived from brewery effluent treatment was found to be rich in carbohydrates, lipids, and proteins, supporting its use in biofuel and biofertilizer production. Despite promising results, industrial-scale implementation remains constrained by variability in effluent composition and the need for standardized processes. The findings emphasize the dual environmental and economic benefits of integrating microalgal systems into brewery wastewater management and highlight the untapped potential for bioproduct development in line with circular bioeconomy principles.","manuscriptTitle":"Harnessing brewing industry effluents for microalgal bioproducts: a systematic review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-04 19:36:34","doi":"10.21203/rs.3.rs-6719777/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2025-07-17T21:45:55+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-06-03T09:16:36+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-03T09:14:57+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2025-05-27T13:17:37+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-05-26T04:24:16+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2025-05-22T09:03:24+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"4bbc6f34-029d-4a0e-b4bc-56818917a64d","owner":[],"postedDate":"June 4th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-10-20T15:59:29+00:00","versionOfRecord":{"articleIdentity":"rs-6719777","link":"https://doi.org/10.1007/s11356-025-37057-0","journal":{"identity":"environmental-science-and-pollution-research","isVorOnly":false,"title":"Environmental Science and Pollution Research"},"publishedOn":"2025-10-17 15:56:55","publishedOnDateReadable":"October 17th, 2025"},"versionCreatedAt":"2025-06-04 19:36:34","video":"","vorDoi":"10.1007/s11356-025-37057-0","vorDoiUrl":"https://doi.org/10.1007/s11356-025-37057-0","workflowStages":[]},"version":"v1","identity":"rs-6719777","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6719777","identity":"rs-6719777","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}