Green Valorization of Chromolaena odorata Biomass into Sustainable Cellulose Acetate Butyrate–Zn(OH) 2 Microcapsules for Controlled Antibacterial Release

Green Valorization of Chromolaena odorata Biomass into Sustainable Cellulose Acetate Butyrate–Zn(OH) 2 Microcapsules for Controlled Antibacterial Release | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Green Valorization of Chromolaena odorata Biomass into Sustainable Cellulose Acetate Butyrate–Zn(OH) 2 Microcapsules for Controlled Antibacterial Release Jiraporn Ketwaraporn, Pongthep Jansanthea, Monthakan Boontheung, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8052206/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study presents a green valorization route for Chromolaena odorata biomass through the development of sustainable cellulose acetate butyrate–zinc hydroxide (CAB–Zn(OH) 2 ) hybrid microcapsules for controlled antibacterial release. The process integrates renewable plant feedstock and a biodegradable cellulose-derived polymer using an eco-friendly solvent evaporation method, followed by in situ precipitation of Zn(OH) 2 under mild aqueous conditions. Structural, morphological, and thermal analyses confirmed the successful formation of Zn(OH) 2 -coated CAB microcapsules with improved crystallinity, surface roughness, and thermal stability. Antibacterial activity was evaluated against Escherichia coli and Staphylococcus aureus , revealing that the CAB–Zn–40 formulation exhibited the strongest performance, with minimum inhibitory concentrations of 12.8 mg/mL and 6.4 mg/mL, respectively. The enhanced antibacterial efficacy arises from synergistic interactions between phytochemical constituents of C. odorata extract and the sustained release of Zn 2+ ions, inducing oxidative stress and membrane disruption. This biorefinery-oriented approach demonstrates the conversion of invasive plant biomass into high-value, multifunctional antibacterial materials. The findings highlight a sustainable and scalable pathway for producing bio-based functional composites applicable to wound care, infection-resistant coatings, and active packaging, advancing the principles of circular bioeconomy and environmentally responsible material design. Biomass valorization Biorefinery Cellulose acetate butyrate Zinc hydroxide microcapsules Chromolaena odorata extract Sustainable antibacterial materials Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction The sustainable conversion of renewable biomass into value-added materials has become a central objective in modern biorefinery systems, addressing both resource efficiency and environmental protection. Invasive or underutilized plant species offer abundant, low-cost feedstocks for the production of functional bioproducts within a circular bioeconomy framework [ 1 ]. Among the most pressing societal challenges is the growing threat of antimicrobial resistance, which has intensified the search for antibacterial materials that are both effective and environmentally responsible. Conventional synthetic antimicrobials and polymer-based agents often persist in ecosystems, leading to long-term pollution and biological accumulation. As a result, recent research has increasingly emphasized the valorization of biomass into biodegradable polymer systems that incorporate natural antimicrobial agents, achieving safe, long-lasting, and eco-friendly functionality [ 2 , 3 ]. Plant-derived antimicrobial compounds have emerged as promising alternatives due to their broad-spectrum activity, biocompatibility, and compliance with green chemistry principles. Extracts rich in polyphenols, alkaloids, tannins, and flavonoids exhibit potent antibacterial and antioxidant properties, offering a sustainable pathway for biomass valorization into high-value functional agents. Among these, Chromolaena odorata (Siam weed), a rapidly spreading invasive biomass in tropical regions, represents a renewable feedstock suitable for biorefinery applications [ 4 ]. Its leaf extract demonstrates significant antibacterial, anti-inflammatory, and wound-healing potential [ 5 ]. However, the direct use of such crude extracts limits practical deployment because of their chemical instability, rapid degradation, and lack of controlled release—constraints that reduce long-term efficacy in biomedical and environmental systems [ 6 , 7 ]. Microencapsulation offers a reliable means of converting plant-derived extracts into stable, controllable delivery systems, protecting sensitive phytochemicals and enabling sustained release [ 8 ]. Cellulose acetate butyrate (CAB), derived from lignocellulosic biomass, represents an ideal polymer platform for such conversion, owing to its tunable permeability, compatibility with natural compounds, and environmental degradability [ 9 ]. The integration of CAB into this system aligns with biorefinery strategies for replacing petroleum-based polymers with bio-based, degradable alternatives that reduce waste and environmental burden. To enhance antibacterial performance, surface functionalization with inorganic agents such as zinc compounds can provide synergistic activity. Zinc-based materials are particularly relevant to sustainable material design because of their natural abundance, biocompatibility, and role in biological systems. While zinc oxide (ZnO) nanoparticles have been extensively used, their rapid ion release and potential cytotoxicity raise ecological concerns [ 10 ]. In contrast, zinc hydroxide (Zn(OH) 2 ) provides a controlled Zn 2+ ion release mechanism that ensures prolonged antibacterial action with reduced toxicity [ 11 ]. Nonetheless, integrating Zn(OH) 2 coatings with bio-based polymers and plant-derived antimicrobials within a biomass valorization framework remains underexplored. In this context, the present study contributes to the biorefinery field by demonstrating a green valorization route for C. odorata biomass, wherein leaf extract is encapsulated within CAB microcapsules and subsequently coated with Zn(OH) 2 via in situ precipitation. This approach merges renewable biomass resources, biodegradable polymer matrices, and eco-benign inorganic coatings to generate multifunctional antibacterial materials. The influence of Zn(OH) 2 concentration on the structural, thermal, and antibacterial properties of the resulting hybrids is systematically examined through comprehensive physicochemical characterization. Overall, this work provides a sustainable conversion strategy for transforming invasive biomass into high-value antibacterial materials, advancing the design of environmentally responsible composites for wound care, active packaging, and biorefinery-driven applications. 2. Materials and Biomass Conversion Methods 2.1 Materials All chemicals used were of analytical grade and employed without further purification. Barium chloride dihydrate (BaCl 2 ·2H 2 O, ≥ 99.0%) was obtained from Elago Enterprises (Australia). Chloroform (CHCl 3 , 99.8%) and ethanol (95%) were purchased from RCI LABSCAN (Thailand), while absolute ethanol (99.9%) was obtained from Duksan (Korea). Cellulose acetate butyrate (CAB, Mn ≈ 30,000) and dimethyl sulfoxide (DMSO, 99.9%) were sourced from VWR (UK). Poly(vinyl alcohol) (PVA, analytical reagent grade) was procured from Chem-Supply (Australia), and zinc nitrate hexahydrate (Zn(NO 3 ) 2 ·6H 2 O, 98%) from Loba Chemie Pvt. Ltd. (India). Additional chemicals, including sulfuric acid (H 2 SO 4 , 98%), sodium chloride (NaCl, 99%), and sodium hydroxide (NaOH, 99%), were obtained from RCI LABSCAN. Nutrient broth and agar were supplied by Himedia (India). All aqueous solutions were prepared using deionized (DI) water with a conductivity of < 1 µS/cm. Fresh Chromolaena odorata (Siam weed) leaves were collected from the vicinity of Uttaradit Rajabhat University, Uttaradit Province, Thailand. Leaves were thoroughly washed with DI water to remove debris and microorganisms, air-dried under sunlight for 24–36 hours until fully dehydrated, and then finely chopped to maximize surface area for solvent extraction [ 12 ]. 2.2 Preparation of C. odorata Leaf Extract Extraction of bioactive compounds from Chromolaena odorata biomass was performed as the initial valorization step in the biorefinery-inspired process. Air-dried leaves were used as lignocellulosic feedstock and extracted with 95% ethanol at a 1:10 (w/v) ratio under ambient conditions (25 ± 2°C) for 24 h with intermittent shaking. The mixture was homogenized, filtered through muslin cloth, and vacuum-filtered using Whatman No. 1 paper. The filtrate was concentrated under reduced pressure at 45°C and freeze-dried at − 55°C (0.04 mbar) to obtain a stable green powder, rich in polyphenols, alkaloids, and flavonoids with known antibacterial and antioxidant activity [ 12 ]. The dried extract was stored in a desiccator and used as the core bioactive component for microencapsulation. This green ethanol-based extraction provides an eco-efficient route for converting low-value invasive biomass into a high-value bioactive intermediate, consistent with the principles of circular bioeconomy and sustainable biorefinery processing. 2.3 Preparation of CAB-Based Microcapsules CAB-based microcapsules were fabricated as the core conversion step for integrating biomass-derived extract with a renewable polymer matrix. The process followed green chemistry and biorefinery principles, emphasizing biodegradable materials and low-energy solvent processing. Cellulose acetate butyrate (CAB) was dissolved in 10 mL of ethyl acetate under magnetic stirring to form a homogeneous solution. The C. odorata leaf extract (Section 2.2 ) was added and stirred for 30 min to ensure uniform dispersion. The organic phase was then emulsified into 50 mL of 1% (w/v) poly(vinyl alcohol) (PVA) solution under moderate stirring (600 rpm) to produce a stable oil-in-water emulsion. Microcapsules formed via solvent evaporation as CAB precipitated around the encapsulated extract. The suspension was centrifuged at 4,000 rpm for 10 min, washed three times with deionized water, and air-dried at room temperature for 24 h to obtain CAB– C. odorata core microcapsules. This step converts biomass-derived phytochemicals into a stable, biodegradable delivery system and represents a scalable, eco-friendly approach to producing bio-based functional materials for subsequent Zn(OH) 2 surface modification. 2.4 Surface Coating with Zinc Hydroxide Surface coating of CAB-based microcapsules with Zn(OH) 2 was performed as the final functionalization step in the biomass-to-bioproduct conversion process. The procedure introduced inorganic antibacterial functionality through a mild, aqueous precipitation route consistent with green biorefinery principles. Dried CAB– C. odorata microcapsules (0.5 g) were dispersed in 50 mL of deionized water under stirring at room temperature. Aqueous Zn(NO 3 ) 2 solutions (20–80 mmol/L) were added to control Zn(OH) 2 loading. Sodium hydroxide (0.1 M) was added dropwise until pH ≈ 9.5 to initiate in situ precipitation of Zn(OH) 2 on the microcapsule surfaces. The reaction proceeded for 60 min, followed by centrifugation (4,000 rpm, 10 min), triple washing with deionized water, and drying at 40°C for 24 h. The hybrid samples were labeled CAB–Zn–20, CAB–Zn–40, CAB–Zn–60, and CAB–Zn–80. This eco-safe coating process avoids high temperatures and organic solvents, minimizing energy input and waste generation. The controlled Zn(OH) 2 deposition enhances surface activity and antibacterial performance, representing a sustainable hybridization stage within the biomass valorization framework. 2.5 Characterization of Microcapsules Physicochemical characterization was performed to verify the structural integrity and functional properties of the biomass-derived hybrid microcapsules. Analytical techniques were selected to evaluate each stage of the biorefinery-inspired process, from biomass encapsulation to Zn(OH) 2 surface coating. Fourier-transform infrared spectroscopy (FTIR, Bruker Tensor 27) identified functional groups and chemical interactions among C. odorata phytochemicals, CAB, and Zn(OH) 2 within 4000–400 cm⁻ 1 . X-ray diffraction (XRD, PANalytical X’Pert PRO, Cu Kα, λ = 1.5406 Å) confirmed crystalline phase formation and Zn(OH) 2 incorporation, scanned at 2θ = 10°–80°. Thermogravimetric analysis (TGA, Mettler-Toledo TGA/DSC 1) assessed thermal stability under nitrogen (30–800°C, 10°C min⁻¹), with enhanced stability indicating successful hybridization. Scanning electron microscopy (SEM, Hitachi SU5000) with EDS mapping revealed surface morphology and uniform Zn distribution. Particle size and ζ-potential (Malvern Zetasizer Nano ZS) were measured to evaluate suspension stability. Collectively, these analyses confirm the efficiency of the biomass-to-bioproduct conversion, demonstrating improved material stability and structure–property correlation essential for sustainable antibacterial composites in biorefinery applications. 2.6 Evaluation of antibacterial properties The antibacterial activity of biomass-derived CAB–Zn(OH) 2 hybrid microcapsules was evaluated to verify their performance as sustainable bio-based materials. Tests were conducted against Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923), representing Gram-negative and Gram-positive bacteria relevant to biomedical and environmental applications. A broth microdilution method following CLSI guidelines was used with slight modification for particulate samples. Bacterial suspensions (≈ 1 × 10 6 CFU/mL) were exposed to serial dilutions of CAB–Zn–x microcapsules (x = 20–80 mmol/L Zn precursor) at final concentrations of 0.8–25.6 mg/mL in 96-well plates. After incubation at 37°C for 24 h, the minimum inhibitory concentration (MIC) was identified as the lowest concentration preventing visible growth. Minimum bactericidal concentration (MBC) values were confirmed by plating aliquots from growth-inhibited wells on nutrient agar. All measurements were performed in triplicate, and antibacterial efficiency was expressed as mean MIC and MBC ± SD. The results validated synergistic antibacterial effects between biomass-derived phytochemicals and Zn(OH) 2 coating, linking hybrid composition to functional bioactivity. This evaluation confirms the conversion of renewable biomass into eco-efficient antibacterial composites aligned with biorefinery and circular economy principles. 3. Results and Discussion 3.1 Extraction of Chromolaena odorata Leaves and Microcapsule Appearance The extraction and preparation of Chromolaena odorata (Siam weed) leaf extract are illustrated in Fig. 1 . Freshly harvested leaves (Fig. 1 a) were thoroughly washed, air-dried under ambient conditions (Fig. 1 b), and finely chopped to enhance solvent penetration during extraction. Ethanol was selected as the extraction solvent due to its intermediate polarity and effectiveness in solubilizing a wide range of phytochemicals, including flavonoids, alkaloids, tannins, and chlorophyll—compounds known for their antimicrobial and antioxidant activities [ 13 ]. After rotary evaporation to remove ethanol, the concentrated extract was freeze-dried to yield a stable dark green powder (Fig. 1 c), which was used as the core bioactive agent for microencapsulation. This step demonstrates the valorization of C. odorata leaf biomass into extractives containing bioactive phytochemicals, representing a value-added route for invasive plant utilization. The visual appearance of the resulting microcapsules, prepared using CAB and surface-functionalized with varying concentrations of Zn(OH) 2 , is shown in Fig. 2 . The uncoated microcapsules (CAB-Zn-0; Fig. 2 a) exhibited a deep green color, indicating the presence of exposed extract on the particle surface. With increasing Zn(OH) 2 precursor concentrations from 10 to 40 mM (Figs. 2 b– 2 e), the microcapsules displayed progressively lighter and more uniform coloration, suggesting enhanced surface coverage by the deposited Zn(OH) 2 layer [ 11 ]. This change in visual appearance corresponds to structural modifications confirmed by FTIR and SEM analyses (discussed in subsequent sections), which verify successful Zn(OH) 2 precipitation and surface coating. The Zn(OH) 2 layer serves a dual function: (i) protecting encapsulated phytochemicals from premature degradation [ 14 ] and (ii) enabling controlled release of Zn 2+ ions, which enhance antibacterial efficacy through mechanisms such as membrane disruption and reactive oxygen species (ROS) generation [ 15 ]. These findings establish a direct correlation between Zn(OH) 2 concentration and microcapsule structural attributes, supporting the formulation’s potential as a controlled-release antimicrobial platform for biomedical coatings, wound care, and food-contact materials. 3.2 Characterization of microcapsules 3.2.1 XRD Analysis X-ray diffraction (XRD) was used to assess the crystalline phases of Zn(OH) 2 -coated C. odorata microcapsules (Fig. 3 ). Distinct peaks observed in CAB-Zn-10 to CAB-Zn-40 matched orthorhombic Zn(OH) 2 (JCPDS No. 01-076-1778), with characteristic reflections at 2θ = 20.09°, 20.81°, 24.98°, 27.11°, 27.65°, and 32.73° [ 16 ]. Increasing precursor concentration led to sharper, more intense peaks, indicating progressive crystallization. CAB-Zn-10 showed broad, low-intensity peaks superimposed on an amorphous background, while CAB-Zn-40 exhibited well-defined diffraction patterns, confirming surface deposition of highly crystalline Zn(OH) 2 . Enhanced crystallinity correlates with improved Zn 2+ ion release control and stability—key for antimicrobial efficacy via membrane disruption, ROS generation, and enzyme inhibition [ 17 ]. These findings reinforce that higher Zn(OH) 2 loading improves both structural integrity and sustained antibacterial performance [ 18 ], making CAB-Zn-40 a promising candidate for biomedical and packaging applications. 3.2.2 FTIR Analysis FTIR spectroscopy was used to investigate molecular interactions between C. odorata extract, the CAB matrix, and Zn(OH) 2 coating (Fig. 4 ). The crude extract exhibited a broad O–H stretch at 3317 cm⁻ 1 and prominent peaks at 1618, 1512, and 1348 cm⁻ 1 , consistent with phenolic O–H, aromatic C = C, and C–N/C–O vibrations from bioactive phytochemicals [ 19 , 20 ]. Uncoated microcapsules (CAB-Zn-0) retained key spectral features from both the extract and CAB, including O–H stretching (~ 3400 cm⁻ 1 ) and ester C = O stretching (~ 1700–1600 cm⁻ 1 ), suggesting successful encapsulation and non-covalent interactions [ 21 ]. In Zn(OH) 2 -coated microcapsules (CAB-Zn-40), attenuation of O–H and C = O bands, along with the appearance of Zn–O vibrations at 715 and 545 cm⁻ 1 , indicate coordination between Zn 2+ ions and electron-donating groups in the extract [ 22 ]. These shifts suggest chemical interaction rather than mere surface adsorption. Such coordination is expected to enhance Zn 2+ retention and modulate release kinetics while stabilizing encapsulated actives. This supports a dual-action antimicrobial mechanism: rapid bacteriostasis from phytochemicals and sustained oxidative and enzymatic stress from Zn 2+ ions—highlighting the system’s potential for wound healing, antimicrobial coatings, and active packaging. 3.2.3 EDS Analysis Energy-dispersive X-ray spectroscopy (EDS) was utilized to evaluate the surface elemental composition of Zn(OH) 2 -coated C. odorata microcapsules. Representative spectra are shown in Fig. 5 . Prominent peaks corresponding to carbon (C) and oxygen (O) were detected across all samples, originating from the CAB polymer matrix and plant-derived phytochemicals. The presence of zinc (Zn) in the coated formulations confirmed the successful deposition of Zn(OH) 2 onto the microcapsule surfaces. Minor peaks for gold (Au) and sodium (Na) were also observed. Gold was introduced during the sputter-coating process used for SEM preparation, while sodium likely originated from trace residuals of precursor salts or buffer systems. Importantly, Zn was the only metal with recognized antimicrobial functionality, validating its selective incorporation [ 23 ]. Quantitative EDS analysis revealed a clear, concentration-dependent increase in surface Zn content. Both CAB-Zn-10 and CAB-Zn-20 exhibited low zinc content (~ 0.1 wt%), while CAB-Zn-30 and CAB-Zn-40 demonstrated substantially higher Zn loading (~ 0.5 wt%). This trend is consistent with XRD findings and visually corroborated by SEM observations, indicating that increased precursor concentrations lead to greater Zn(OH) 2 accumulation on the microcapsule surface. The enhanced zinc content in CAB-Zn-30 and CAB-Zn-40 is expected to promote more effective and sustained Zn 2+ ion release, which contributes to antimicrobial activity through multiple mechanisms. These include disruption of microbial membranes, generation of reactive oxygen species (ROS), and inhibition of bacterial enzyme systems. The ability to tune Zn(OH) 2 deposition through precursor concentration offers a valuable design parameter for tailoring antimicrobial efficacy and longevity [ 24 ]. Overall, EDS analysis confirms the uniform and controllable surface functionalization of the microcapsules, supporting the reliability of the fabrication method. These results reinforce the functional role of Zn(OH) 2 in enhancing microcapsule performance, highlighting the potential of CAB-Zn-40 as a scalable and adaptable antimicrobial platform for biomedical, pharmaceutical, and environmental applications. 3.2.4 SEM Analysis Scanning electron microscopy (SEM) was employed to examine the surface morphology of C. odorata -loaded CAB microcapsules coated with increasing concentrations of Zn(OH) 2 (Fig. 6 ). The uncoated control (CAB-Zn-0) exhibited smooth, spherical surfaces, reflecting the uniformity of the CAB matrix and the absence of surface-bound inorganic phases. At 10 mM Zn(OH) 2 (CAB-Zn-10), mild surface roughening and discrete nanoparticle aggregates were observed, indicating initial Zn(OH) 2 nucleation. Increasing the concentration to 20 mM (CAB-Zn-20) led to more continuous and heterogeneous surface coverage, enhancing surface area and potentially facilitating improved Zn 2+ ion diffusion for antibacterial activity [ 25 , 26 ]. At 30 mM (CAB-Zn-30), a denser and more compact coating formed, with aggregated nanoparticle domains promoting prolonged Zn 2+ release and microbial contact. The 40 mM sample (CAB-Zn-40) demonstrated the most extensive and uniform nanoparticle coverage, characterized by a highly textured, near-saturated Zn(OH) 2 layer—providing an optimal interface for sustained ion release, ROS generation, and inhibition of bacterial adhesion or biofilm formation [ 27 ]. These findings highlight a clear, concentration-dependent morphological evolution. The nanostructured coatings in CAB-Zn-30 and CAB-Zn-40 offer enhanced surface functionality and sustained antimicrobial potential, underscoring their suitability for biomedical and environmental applications. 3.2.5 Particle size distribution Analysis Figure 7 and Table 1 illustrate the particle size distribution of C. odorata -loaded CAB microcapsules coated with increasing concentrations of Zn(OH) 2 . A consistent increase in mean diameter was observed with higher precursor concentrations, confirming progressive Zn(OH) 2 deposition. Uncoated microcapsules (CAB-Zn-0) averaged 1013.3 ± 66.5 nm, increasing modestly with 10 mM Zn(OH) 2 (1049.5 ± 74.5 nm) and reaching 1275.3 ± 109.9 nm at 40 mM (CAB-Zn-40). This size enlargement reflects the formation of thicker Zn(OH) 2 shells, which enhance Zn 2+ reservoir capacity and enable sustained, diffusion-controlled ion release. The denser coatings also reduce premature Zn 2+ leaching, promoting prolonged antimicrobial activity [ 28 ]. Additionally, increased particle size and surface roughness may hinder bacterial adhesion, offering synergistic physical–chemical antibacterial effects. CAB-Zn-40, with the largest and most uniform particles, is thus well-suited for durable applications such as wound dressings, antimicrobial coatings, and controlled-release systems. Table 1 Particle size and thermal degradation characteristics of CAB–Zn(OH)₂ microcapsules prepared with different Zn precursor concentrations. Increasing Zn(OH)₂ loading led to larger particle sizes and improved thermal stability, indicating the formation of thicker inorganic coatings and enhanced structural integrity of the hybrid microcapsules. Sample Mean Particle Size (nm) Initial Onset Temperature (°C) Final Onset Temperature (°C) Weight Loss (%) CAB–Zn–0 1013.3 ± 66.5 336.7 385.3 85.90 CAB–Zn–10 1049.5 ± 74.5 252.6 368.8 48.94 CAB–Zn–20 1159.8 ± 58.8 292.8 371.2 37.57 CAB–Zn–30 1202.5 ± 82.8 274.4 371.3 28.33 CAB–Zn–40 1275.3 ± 109.9 287.0 367.8 28.05 3.2.6 TGA Analysis Thermogravimetric analysis (Fig. 8 , Table 1 ) revealed the thermal degradation behavior of C. odorata -loaded CAB microcapsules across varying Zn(OH) 2 coating levels. All samples showed primary mass loss between 250–400°C, attributed to degradation of the CAB matrix and embedded phytochemicals. Uncoated microcapsules (CAB-Zn-0) exhibited the highest weight loss (85.90%) and an onset degradation temperature of 336.7°C, indicating low thermal resistance. Zn(OH) 2 -coated samples showed progressively enhanced thermal stability. Despite a slightly lower onset temperature in CAB-Zn-10 (252.6°C), its reduced weight loss (48.94%) suggests partial stabilization. Further increases in Zn(OH) 2 content led to lower total weight losses: 37.57% (CAB-Zn-20), 28.33% (CAB-Zn-30), and 28.05% (CAB-Zn-40), with CAB-Zn-40 also exhibiting a higher onset temperature (287.0°C). These improvements are attributed to the Zn(OH) 2 coating, which acts as a thermal and oxidative barrier, limiting volatilization of thermolabile components and enhancing structural integrity [ 29 ]. Enhanced thermal resistance supports product longevity and functionality under elevated temperatures—critical for applications such as antimicrobial wound dressings, medical textiles, and heat-resistant packaging—where retention of bioactivity and controlled Zn 2+ release are essential. The enhanced crystallinity and stability indicate that the biopolymer–inorganic hybridization route can upgrade raw biomass into advanced functional materials suitable for bio-based industries. 3.3 Antibacterial Activity The antibacterial efficacy of C. odorata -loaded CAB microcapsules with increasing Zn(OH) 2 coating concentrations was assessed against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) via MIC and MBC assays. Results demonstrated a clear concentration-dependent enhancement in antibacterial performance, particularly against the more resilient E. coli , highlighting the synergistic roles of phytochemicals, sustained Zn 2+ release, and ROS generation. 3.3.1 Minimum Inhibitory Concentration (MIC) MIC values (Fig. 9 ) decreased significantly with higher Zn(OH) 2 content. CAB-Zn-40 exhibited the strongest inhibition, with MICs of 12.8 mg/mL for E. coli and 6.4 mg/mL for S. aureus . While lower Zn(OH) 2 coatings (CAB-Zn-10, CAB-Zn-20) retained activity against S. aureus , they were less effective against E. coli , reflecting differences in cell wall permeability. Enhanced Zn 2+ release and ROS-mediated damage likely account for the increased efficacy in higher-coated systems. 3.3.2 Minimum Bactericidal Concentration (MBC) MBC data (Table 2 , Figs. 9 – 10 ) closely followed MIC trends. CAB-Zn-40 demonstrated complete bactericidal activity at 12.8 µg/mL against E. coli and 6.4 µg/mL against S. aureus , surpassing the performance of lower Zn(OH) 2 -coated formulations, which required concentrations of 25.6 µg/mL or higher. This enhanced potency is attributed to a combination of mechanisms: disruption of bacterial membranes through Zn 2+ interactions with cell wall components, oxidative damage induced by reactive oxygen species (ROS) targeting lipids, proteins, and nucleic acids, and interference with intracellular processes, including enzymatic inhibition and transcriptional disruption [ 30 ]. In contrast to uncoated microcapsules that rely solely on phytochemical activity, Zn(OH) 2 -coated systems provide a sustained, multi-mechanistic antibacterial response. CAB-Zn-40, in particular, demonstrates superior efficacy along with improved thermal stability, controlled Zn 2+ release, and minimized cytotoxicity risk, making it a compelling candidate for applications requiring long-term antimicrobial performance, such as wound dressings, infection-resistant coatings, and bioactive packaging [ 31 ]. Table 2 Minimum bactericidal concentration (MBC) values of CAB microcapsules against E. coli and S. aureus . The CAB-Zn-40 formulation exhibits the lowest MBCs, reflecting synergistic bactericidal effects from phytochemicals and Zn 2+ ion release. Microcapsule Type MBC ( E. coli ) (µg/mL) MBC ( S. aureus ) (µg/mL) CAB-Zn-0 25.6 25.6 CAB-Zn-10 51.2 51.2 CAB-Zn-20 51.2 25.6 CAB-Zn-30 25.6 12.8 CAB-Zn-40 12.8 6.4 The strong performance of CAB–Zn–40 underscores the potential of biomass-derived formulations as sustainable substitutes for synthetic antimicrobial plastics. 3.4 Mechanistic Insight into Antibacterial Activity The superior antibacterial efficacy of Zn(OH) 2 -coated Chromolaena odorata microcapsules—particularly the CAB-Zn-40 formulation—is attributed to a synergistic set of mechanisms operating at both the surface and intracellular levels (Fig. 11 ). These include sustained Zn 2+ ion release, generation of reactive oxygen species (ROS), bacterial membrane disruption, and metabolic interference. Collectively, these effects contribute to potent and prolonged bactericidal activity. 3.4.1 Zn 2+ -Mediated ROS Generation and Oxidative Stress A key antibacterial mechanism involves the sustained release of Zn 2+ ions from the Zn(OH) 2 -coated microcapsule surface. SEM and EDS analyses confirmed that Zn surface content increases with precursor concentration, facilitating controlled and prolonged ion diffusion into the surrounding medium. Once released, Zn 2+ ions catalyze intracellular redox reactions, generating reactive oxygen species (ROS) including superoxide anions (O 2 ⁻), hydrogen peroxide (H 2 O 2 ), and hydroxyl radicals (•OH) [ 32 , 33 ]. These ROS species exert oxidative stress by targeting bacterial lipids, proteins, and nucleic acids, ultimately leading to cell dysfunction and death. The high crystallinity of Zn(OH) 2 —particularly evident in CAB-Zn-40 as revealed by XRD—further supports its role in enabling sustained Zn 2+ release and consistent ROS generation. These results suggest that Zn(OH) 2 coatings function analogously to ZnO systems, delivering continuous antibacterial action through dual chemical pathways, and thus play a central role in the long-term efficacy of the coated microcapsules. 3.4.2 Bacterial Membrane Disruption SEM analysis revealed a marked increase in surface roughness with higher Zn(OH) 2 loading, particularly in CAB-Zn-30 and CAB-Zn-40. These nanostructured coatings enhance contact with bacterial membranes, intensifying localized Zn 2+ ion release and promoting ROS-induced lipid peroxidation. This behavior is consistent with previous findings on Cu²⁺ systems reported by Pookmanee et al. (2025) [ 34 ]. The resulting membrane damage leads to the leakage of intracellular contents, cytoplasmic collapse, and eventual cell lysis [ 35 ]. The synergistic interplay between chemical factors (Zn 2+ ions and ROS) and physical effects (surface roughness and nanoparticle intrusion) accelerates membrane destabilization. This dual-action mechanism underpins the significantly reduced MIC and MBC values observed in higher Zn(OH) 2 -coated formulations, confirming their potent and irreversible antibacterial activity. 3.4.3 Cellular Dysfunction and Stress Response Beyond membrane-level interactions, Zn 2+ ions interfere with vital intracellular processes. By binding to enzymatic cofactors, Zn 2+ inhibits key metabolic enzymes, disrupts ribosomal function, and impairs DNA replication. Accumulated ROS further aggravates cellular stress, potentially inducing defense responses such as oxidative stress gene expression and DNA repair mechanisms [ 36 ]. Although these molecular responses were not directly evaluated in this study, future transcriptomic or proteomic analyses could provide insight into bacterial adaptation and resistance pathways triggered by Zn(OH) 2 exposure. 3.4.4 Synergistic Antimicrobial Mechanism The antibacterial effect of CAB-Zn-40 is not solely due to Zn(OH) 2 but also enhanced by bioactive phytochemicals from C. odorata . Compounds such as flavonoids, tannins, and alkaloids are known to destabilize membranes and inhibit metabolic enzymes [ 37 , 38 ]. The Zn(OH) 2 coating amplifies this effect by enabling sustained Zn 2+ release and ROS production, resulting in a dual-action antimicrobial system. Additional support is provided by TGA and DLS data, which indicate improved structural stability and encapsulation efficiency at higher Zn(OH) 2 concentrations. These attributes ensure functional retention under environmental or physiological stress and contribute to long-term antimicrobial performance. Together, these mechanistic insights highlight CAB-Zn-40 as a multifunctional antimicrobial platform. By integrating phytochemical bioactivity with sustained-release nanocoating, this system offers a promising strategy for applications requiring prolonged antibacterial efficacy, including wound care, bioactive medical coatings, and antimicrobial packaging materials. 3.5 Comparative Antibacterial Activity Against Staphylococcus aureus and Escherichia coli To contextualize the antibacterial efficacy of the Zn(OH) 2 -coated Chromolaena odorata microcapsules developed in this study, a comparative analysis was conducted using literature-reported plant-based antimicrobial systems (Table 3 ). These systems include uncoated plant extracts, polymer-encapsulated phytochemicals, and metal-functionalized microcapsules. Early studies utilizing C. odorata ethanolic extracts [ 39 ] or isolated flavonoids [ 40 ] demonstrated strong in vitro antibacterial activity, with MIC values ranging from 0.016 to 6.25 mg/mL. However, these formulations suffer from critical limitations—namely, rapid chemical degradation, poor thermal stability, and lack of sustained antimicrobial release—reducing their practical utility in long-term applications. To address these issues, microencapsulation has emerged as a viable strategy. For example, Liu et al. (2023) [ 41 ] reported the encapsulation of cinnamon essential oil in gum arabic/maltodextrin microcapsules, which improved chemical stability and demonstrated moderate antibacterial activity. However, such systems—lacking an inorganic phase—are often limited in durability and spectrum of action under physiologically relevant conditions. In more recent approaches, the integration of antimicrobial metals has shown considerable promise. Li et al. (2023) [ 42 ] developed silver nanoparticle (AgNP)-coated chitosan–gelatin microcapsules containing Ginkgo biloba essential oil, while Sharma et al. (2024) [ 43 ] formulated ZnO-coated chitosan–cellulose microcapsules loaded with Plumeria obtusa extract. These systems leveraged metal ion release to enhance bactericidal activity; however, they often lacked quantitative MIC data or comprehensive benchmarking against plant–metal hybrid systems. In contrast, the CAB-Zn-40 formulation presented in this study uniquely combines plant-derived bioactive compounds, a biodegradable CAB matrix, and a Zn(OH) 2 nanocoating that enables sustained Zn 2+ release and reactive oxygen species (ROS) generation, along with demonstrated thermal stability confirmed by TGA analysis. This formulation achieved MIC values of 12.8 mg/mL against E. coli and 6.4 mg/mL against S. aureus , outperforming several uncoated extract-based systems and rivaling metal-functionalized designs. Additionally, its high crystallinity, structural integrity, and dual-mode antibacterial action position it as a promising candidate for applications requiring both efficacy and durability—such as wound care, biomedical coatings, and active packaging. Table 3 Comparative summary of antimicrobial plant-based microcapsule systems reported in the literature. The CAB-Zn-40 formulation demonstrates favorable performance and stability relative to uncoated and metal-integrated formulations. Plant Extract Encapsulation Material Metal Component Controlled Release Stability Antibacterial Effectiveness (MIC) * Reference C. odorata (ethanol extract) None None No Low (rapid degradation) 6.25 mg/mL ( E. coli ), 3.125 mg/mL ( S. aureus ) [ 39 ] Isolated C. odorata flavonoids None None No Low 0.016–0.031 mg/mL ( both strains ) [ 40 ] Cinnamon essential oil Gum arabic / Maltodextrin None Yes (EO release) High 14 µL/mL ( E. coli ), 7 µL/mL ( S. aureus ) [ 41 ] Ginkgo biloba EO Chitosan–gelatin AgNPs Yes (Ag⁺, EO release) High (spray-dried) Not reported (inhibition zones confirmed) [ 42 ] Plumeria obtusa leaf extract Chitosan–cellulose ZnO nanoparticles Yes (Zn 2+ release) Structurally stable Not reported (qualitative activity) [ 43 ] C. odorata extract Cellulose acetate butyrate (CAB) Zn(OH) 2 coating Yes (Zn 2+ release) High (TGA confirmed) 12.8 mg/mL ( E. coli ), 6.4 mg/mL ( S. aureus ) This study (CAB-Zn-40) * MIC values are reported as published; due to variation in test protocols, results are indicative and not directly comparable. 4. Conclusions This study demonstrates a green valorization pathway for transforming Chromolaena odorata biomass into high-value antibacterial materials within the framework of sustainable biorefinery. A biodegradable cellulose acetate butyrate (CAB) matrix, derived from renewable cellulose resources, was successfully integrated with plant-extracted phytochemicals and coated with zinc hydroxide (Zn(OH) 2 ) via an eco-friendly in situ precipitation process. This mild, solvent-minimized route represents an environmentally responsible conversion process that utilizes invasive plant biomass as a renewable feedstock rather than a waste resource. The resulting CAB–Zn(OH) 2 hybrid microcapsules exhibited enhanced crystallinity, thermal stability, and surface functionality, confirming successful hybridization between the bio-based polymer and inorganic coating. Among the formulations, CAB–Zn–40 displayed the strongest antibacterial performance against Escherichia coli and Staphylococcus aureus , attributed to the synergistic effects of sustained Zn²⁺ release and plant-derived bioactive compounds. This combination produced a durable, controlled-release antibacterial response suitable for biomedical and packaging applications. Beyond material performance, the work highlights a scalable example of biomass-to-bioproduct conversion that aligns with circular bioeconomy principles. The valorization of C. odorata , an invasive tropical species, into a biodegradable antibacterial platform demonstrates how underutilized biomass can be transformed into eco-efficient, high-value functional materials. Future research will focus on evaluating biodegradation kinetics, environmental life-cycle performance, and techno-economic feasibility to further integrate this approach into sustainable biorefinery systems. Declarations Ethical Approval Not applicable. Consent for publication Not applicable. Competing interest The authors declare no conflicts of interest, whether personal relationships or financial considerations, that could have influenced the publication of this study. Funding No funding was received to assist with the preparation of this manuscript. Author Contribution J.K. supervised the study and contributed to conceptualization, methodology, and writing (original draft, review, and editing). M.B. and S.Y. contributed to methodology, investigation, validation. P.K. contributed to methodology, investigation, validation. P.U. performed investigation and validation. P.J. led conceptualization, methodology, writing (original draft, review, and editing). All authors reviewed and approved the final manuscript. Acknowledgement We sincerely appreciate the generous support provided by the Thailand Scientific Research and Innovation (TSRI) for this study. 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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-8052206","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":587387038,"identity":"2253b92f-5fc4-45a4-9576-820e8556b01a","order_by":0,"name":"Jiraporn Ketwaraporn","email":"","orcid":"","institution":"Uttaradit Rajabhat University","correspondingAuthor":false,"prefix":"","firstName":"Jiraporn","middleName":"","lastName":"Ketwaraporn","suffix":""},{"id":587387039,"identity":"f9b80513-a590-4c85-b518-6b6008170afa","order_by":1,"name":"Pongthep Jansanthea","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA90lEQVRIiWNgGAWjYLACxgYQeYCB4QOqCB5wEKqFcQaqCEEtDAzMPMRoMWfvPfz64w6bPAbGw88e27bdS2xgP/yA+eMO3Fose86lWRw8k1bMwHDM3Di3rTixgSfNgOHgGdxaDG7kmBkcbDuc2MBwwEw6ty0ByMgBOqyNoJb/QJXHv0lbgrTwvyGoxfjBwbYDQC1nzKQZQVokCNhi2XPGjOFsW3IxG8OZMsmecwnGbRLPDA6cxaPFnL3H+ENlm10ev8TxbRI/yhJk+/mTHz6oxOcwBgY2CSCdwCZxACLCxgBOCHi1MIOSSQIDfwM+daNgFIyCUTCSAQCwalntXIXX0QAAAABJRU5ErkJggg==","orcid":"","institution":"Uttaradit Rajabhat University","correspondingAuthor":true,"prefix":"","firstName":"Pongthep","middleName":"","lastName":"Jansanthea","suffix":""},{"id":587387040,"identity":"f5d2fa1f-808e-40ac-b1e7-fe5f20076883","order_by":2,"name":"Monthakan Boontheung","email":"","orcid":"","institution":"Uttaradit Rajabhat University","correspondingAuthor":false,"prefix":"","firstName":"Monthakan","middleName":"","lastName":"Boontheung","suffix":""},{"id":587387041,"identity":"6c0cb2d7-9acc-471d-b252-075b074ccfc7","order_by":3,"name":"Suriyun Yimpin","email":"","orcid":"","institution":"Uttaradit Rajabhat University","correspondingAuthor":false,"prefix":"","firstName":"Suriyun","middleName":"","lastName":"Yimpin","suffix":""},{"id":587387042,"identity":"4f6c2a0b-2846-4954-8893-111a2d3214d5","order_by":4,"name":"Parinya Kraivuttinun","email":"","orcid":"","institution":"Uttaradit Rajabhat University","correspondingAuthor":false,"prefix":"","firstName":"Parinya","middleName":"","lastName":"Kraivuttinun","suffix":""},{"id":587387044,"identity":"f25aa3b3-f52e-49c7-b94d-d2bf79dbbb25","order_by":5,"name":"Putthadee Ubolsook","email":"","orcid":"","institution":"Uttaradit Rajabhat University","correspondingAuthor":false,"prefix":"","firstName":"Putthadee","middleName":"","lastName":"Ubolsook","suffix":""}],"badges":[],"createdAt":"2025-11-07 02:23:21","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8052206/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8052206/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":102296848,"identity":"35df878f-5691-4914-b5d8-715044373662","added_by":"auto","created_at":"2026-02-10 10:22:18","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":3129761,"visible":true,"origin":"","legend":"\u003cp\u003eStepwise preparation of \u003cem\u003eChromolaena odorata\u003c/em\u003e extract: (a) freshly harvested leaves, (b) air-dried and chopped material for extraction, and (c) freeze-dried ethanol extract used as the core antimicrobial agent. The process preserves phytochemical integrity and improves storage stability.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/cf851abef77b6d12b0bf8214.png"},{"id":102194745,"identity":"38d42d56-4d1e-4e8d-b709-23f7d0d6248c","added_by":"auto","created_at":"2026-02-09 09:53:03","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":287924,"visible":true,"origin":"","legend":"\u003cp\u003eVisual appearance of CAB microcapsules coated with increasing concentrations of Zn(OH)\u003csub\u003e2\u003c/sub\u003e: (a) CAB-Zn-0, (b) CAB-Zn-10, (c) CAB-Zn-20, (d) CAB-Zn-30, and (e) CAB-Zn-40. The progressive shift in color reflects increasing surface deposition of Zn(OH)\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"image2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/3670f0799ba7f8375af4913d.jpeg"},{"id":102297486,"identity":"d29e4daa-d40b-43d7-9d9a-750c21826876","added_by":"auto","created_at":"2026-02-10 10:27:41","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":197329,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of CAB microcapsules coated with increasing concentrations of Zn(OH)\u003csub\u003e2\u003c/sub\u003e. The progressive emergence and intensification of diffraction peaks confirm successful surface deposition and enhanced crystallinity of orthorhombic Zn(OH)\u003csub\u003e2\u003c/sub\u003e nanostructures.\u003c/p\u003e","description":"","filename":"image3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/285e71b4cdc0d6cdc85da085.jpeg"},{"id":102296923,"identity":"7da3c47f-49fe-4eac-b30b-d74390475fb9","added_by":"auto","created_at":"2026-02-10 10:22:49","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":100721,"visible":true,"origin":"","legend":"\u003cp\u003eFTIR spectra of (a) crude \u003cem\u003eC. odorata\u003c/em\u003e extract, (b) uncoated microcapsules (CAB-Zn-0), and (c) Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated microcapsules (CAB-Zn-40). Spectral changes highlight Zn–O bond formation and reduced hydroxyl/carbonyl signals, indicating coordination between Zn\u003csup\u003e2+\u003c/sup\u003e ions and phytochemical functional groups.\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/7296947b100a530983873152.png"},{"id":102194755,"identity":"824b8182-7f12-425f-b882-ee9f5f940e53","added_by":"auto","created_at":"2026-02-09 09:53:03","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":353283,"visible":true,"origin":"","legend":"\u003cp\u003eEDS spectra of Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated \u003cem\u003eC. odorata\u003c/em\u003e microcapsules. Detected elements include carbon (C), oxygen (O), and zinc (Zn), with gold (Au) from sputter coating. The increasing Zn signal with higher precursor concentrations confirms controlled and reproducible surface deposition of Zn(OH)\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","description":"","filename":"image5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/391af85dab7a06dbf76e4d69.jpeg"},{"id":102296847,"identity":"e9cc954b-0cf5-45e6-899d-9916a54df8a2","added_by":"auto","created_at":"2026-02-10 10:22:18","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":257829,"visible":true,"origin":"","legend":"\u003cp\u003eSEM micrographs showing the surface morphology of CAB microcapsules coated with increasing Zn(OH)\u003csub\u003e2\u003c/sub\u003e concentrations: (a) CAB-Zn-0 (uncoated), (b) CAB-Zn-10, (c) CAB-Zn-20, (d) CAB-Zn-30, and (e) CAB-Zn-40. Increasing surface roughness and nanoparticle coverage with higher Zn(OH)\u003csub\u003e2\u003c/sub\u003e precursor concentrations indicate successful layer formation and suggest improved antimicrobial surface functionality.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/9535f0f36bc3d508278e5d40.png"},{"id":102194748,"identity":"23e89936-9e6f-425a-9c8f-d429308501a6","added_by":"auto","created_at":"2026-02-09 09:53:03","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":52883,"visible":true,"origin":"","legend":"\u003cp\u003eParticle size distribution profiles of CAB microcapsules coated with increasing Zn(OH)\u003csub\u003e2\u003c/sub\u003e concentrations. Higher Zn precursor levels result in larger and more uniform microcapsules, supporting enhanced controlled-release behavior.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/75bc35767ab8e0359026ab2f.png"},{"id":102194749,"identity":"3a8fc95f-427b-432e-a811-212f74ccda74","added_by":"auto","created_at":"2026-02-09 09:53:03","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":36940,"visible":true,"origin":"","legend":"\u003cp\u003eTGA thermograms of CAB microcapsules with and without Zn(OH)\u003csub\u003e2\u003c/sub\u003e coatings. Coated formulations demonstrate reduced weight loss and improved thermal stability, confirming the protective role of Zn(OH)\u003csub\u003e2\u003c/sub\u003e in preserving structural integrity and phytochemical content during thermal stress.\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/2bda4c52f205cbdb7e5b8c3b.png"},{"id":102297113,"identity":"03d588ac-2292-45d0-9a1d-85d25b2c8a75","added_by":"auto","created_at":"2026-02-10 10:25:53","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":319234,"visible":true,"origin":"","legend":"\u003cp\u003eMinimum inhibitory concentration (MIC) values for CAB microcapsules with varying Zn(OH)\u003csub\u003e2\u003c/sub\u003e concentrations against \u003cem\u003eE. coli\u003c/em\u003e and \u003cem\u003eS. aureus\u003c/em\u003e. Enhanced antibacterial activity is observed with increasing Zn(OH)\u003csub\u003e2\u003c/sub\u003e loading, with CAB-Zn-40 exhibiting the lowest MICs.\u003c/p\u003e","description":"","filename":"image9.png","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/6c65c46d8639b6e0ee6a0711.png"},{"id":102194754,"identity":"625d3e7c-cad1-47d1-9e2b-ae906044cf41","added_by":"auto","created_at":"2026-02-09 09:53:03","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":330820,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative spread plate images illustrating the bactericidal activity of Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated microcapsules against \u003cem\u003eS. aureus\u003c/em\u003e. CAB-Zn-40 achieves complete colony inhibition at low concentrations, confirming potent antimicrobial action.\u003c/p\u003e","description":"","filename":"image10.png","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/e17f6c10d03249f085e1245f.png"},{"id":102194752,"identity":"7f9b8bab-efac-443a-b7f8-81ab125e51ec","added_by":"auto","created_at":"2026-02-09 09:53:03","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":516299,"visible":true,"origin":"","legend":"\u003cp\u003eProposed antibacterial mechanism of Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated CAB microcapsules. Sustained Zn\u003csup\u003e2+\u003c/sup\u003e ion release and ROS generation disrupt bacterial membranes, induce oxidative stress, and interfere with intracellular processes. Phytochemicals from \u003cem\u003eC. odorata\u003c/em\u003e act synergistically, enhancing antimicrobial efficacy.\u003c/p\u003e","description":"","filename":"image11.png","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/3a0c66029d5fe8e5cb9b765a.png"},{"id":108492946,"identity":"51c1cad2-98ef-40c9-91aa-10a8f0c2e925","added_by":"auto","created_at":"2026-05-05 09:59:04","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5806086,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8052206/v1/0d40e9ce-cbc6-4104-9a2e-6071568d9198.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Green Valorization of Chromolaena odorata Biomass into Sustainable Cellulose Acetate Butyrate–Zn(OH) 2 Microcapsules for Controlled Antibacterial Release","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe sustainable conversion of renewable biomass into value-added materials has become a central objective in modern biorefinery systems, addressing both resource efficiency and environmental protection. Invasive or underutilized plant species offer abundant, low-cost feedstocks for the production of functional bioproducts within a circular bioeconomy framework [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Among the most pressing societal challenges is the growing threat of antimicrobial resistance, which has intensified the search for antibacterial materials that are both effective and environmentally responsible. Conventional synthetic antimicrobials and polymer-based agents often persist in ecosystems, leading to long-term pollution and biological accumulation. As a result, recent research has increasingly emphasized the valorization of biomass into biodegradable polymer systems that incorporate natural antimicrobial agents, achieving safe, long-lasting, and eco-friendly functionality [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e Plant-derived antimicrobial compounds have emerged as promising alternatives due to their broad-spectrum activity, biocompatibility, and compliance with green chemistry principles. Extracts rich in polyphenols, alkaloids, tannins, and flavonoids exhibit potent antibacterial and antioxidant properties, offering a sustainable pathway for biomass valorization into high-value functional agents. Among these, \u003cem\u003eChromolaena odorata\u003c/em\u003e (Siam weed), a rapidly spreading invasive biomass in tropical regions, represents a renewable feedstock suitable for biorefinery applications [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Its leaf extract demonstrates significant antibacterial, anti-inflammatory, and wound-healing potential [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. However, the direct use of such crude extracts limits practical deployment because of their chemical instability, rapid degradation, and lack of controlled release\u0026mdash;constraints that reduce long-term efficacy in biomedical and environmental systems [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMicroencapsulation offers a reliable means of converting plant-derived extracts into stable, controllable delivery systems, protecting sensitive phytochemicals and enabling sustained release [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Cellulose acetate butyrate (CAB), derived from lignocellulosic biomass, represents an ideal polymer platform for such conversion, owing to its tunable permeability, compatibility with natural compounds, and environmental degradability [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The integration of CAB into this system aligns with biorefinery strategies for replacing petroleum-based polymers with bio-based, degradable alternatives that reduce waste and environmental burden.\u003c/p\u003e \u003cp\u003eTo enhance antibacterial performance, surface functionalization with inorganic agents such as zinc compounds can provide synergistic activity. Zinc-based materials are particularly relevant to sustainable material design because of their natural abundance, biocompatibility, and role in biological systems. While zinc oxide (ZnO) nanoparticles have been extensively used, their rapid ion release and potential cytotoxicity raise ecological concerns [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In contrast, zinc hydroxide (Zn(OH)\u003csub\u003e2\u003c/sub\u003e) provides a controlled Zn\u003csup\u003e2+\u003c/sup\u003e ion release mechanism that ensures prolonged antibacterial action with reduced toxicity [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Nonetheless, integrating Zn(OH)\u003csub\u003e2\u003c/sub\u003e coatings with bio-based polymers and plant-derived antimicrobials within a biomass valorization framework remains underexplored.\u003c/p\u003e \u003cp\u003eIn this context, the present study contributes to the biorefinery field by demonstrating a green valorization route for \u003cem\u003eC. odorata\u003c/em\u003e biomass, wherein leaf extract is encapsulated within CAB microcapsules and subsequently coated with Zn(OH)\u003csub\u003e2\u003c/sub\u003e via in situ precipitation. This approach merges renewable biomass resources, biodegradable polymer matrices, and eco-benign inorganic coatings to generate multifunctional antibacterial materials. The influence of Zn(OH)\u003csub\u003e2\u003c/sub\u003e concentration on the structural, thermal, and antibacterial properties of the resulting hybrids is systematically examined through comprehensive physicochemical characterization. Overall, this work provides a sustainable conversion strategy for transforming invasive biomass into high-value antibacterial materials, advancing the design of environmentally responsible composites for wound care, active packaging, and biorefinery-driven applications.\u003c/p\u003e"},{"header":"2. Materials and Biomass Conversion Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Materials\u003c/h2\u003e \u003cp\u003eAll chemicals used were of analytical grade and employed without further purification. Barium chloride dihydrate (BaCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO, \u0026ge;\u0026thinsp;99.0%) was obtained from Elago Enterprises (Australia). Chloroform (CHCl\u003csub\u003e3\u003c/sub\u003e, 99.8%) and ethanol (95%) were purchased from RCI LABSCAN (Thailand), while absolute ethanol (99.9%) was obtained from Duksan (Korea). Cellulose acetate butyrate (CAB, Mn\u0026thinsp;\u0026asymp;\u0026thinsp;30,000) and dimethyl sulfoxide (DMSO, 99.9%) were sourced from VWR (UK). Poly(vinyl alcohol) (PVA, analytical reagent grade) was procured from Chem-Supply (Australia), and zinc nitrate hexahydrate (Zn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO, 98%) from Loba Chemie Pvt. Ltd. (India). Additional chemicals, including sulfuric acid (H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e, 98%), sodium chloride (NaCl, 99%), and sodium hydroxide (NaOH, 99%), were obtained from RCI LABSCAN. Nutrient broth and agar were supplied by Himedia (India). All aqueous solutions were prepared using deionized (DI) water with a conductivity of \u0026lt;\u0026thinsp;1 \u0026micro;S/cm.\u003c/p\u003e \u003cp\u003eFresh \u003cem\u003eChromolaena odorata\u003c/em\u003e (Siam weed) leaves were collected from the vicinity of Uttaradit Rajabhat University, Uttaradit Province, Thailand. Leaves were thoroughly washed with DI water to remove debris and microorganisms, air-dried under sunlight for 24\u0026ndash;36 hours until fully dehydrated, and then finely chopped to maximize surface area for solvent extraction [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Preparation of C. odorata Leaf Extract\u003c/h2\u003e \u003cp\u003eExtraction of bioactive compounds from \u003cem\u003eChromolaena odorata\u003c/em\u003e biomass was performed as the initial valorization step in the biorefinery-inspired process. Air-dried leaves were used as lignocellulosic feedstock and extracted with 95% ethanol at a 1:10 (w/v) ratio under ambient conditions (25\u0026thinsp;\u0026plusmn;\u0026thinsp;2\u0026deg;C) for 24 h with intermittent shaking. The mixture was homogenized, filtered through muslin cloth, and vacuum-filtered using Whatman No. 1 paper.\u003c/p\u003e \u003cp\u003eThe filtrate was concentrated under reduced pressure at 45\u0026deg;C and freeze-dried at \u0026minus;\u0026thinsp;55\u0026deg;C (0.04 mbar) to obtain a stable green powder, rich in polyphenols, alkaloids, and flavonoids with known antibacterial and antioxidant activity [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The dried extract was stored in a desiccator and used as the core bioactive component for microencapsulation.\u003c/p\u003e \u003cp\u003eThis green ethanol-based extraction provides an eco-efficient route for converting low-value invasive biomass into a high-value bioactive intermediate, consistent with the principles of circular bioeconomy and sustainable biorefinery processing.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Preparation of CAB-Based Microcapsules\u003c/h2\u003e \u003cp\u003eCAB-based microcapsules were fabricated as the core conversion step for integrating biomass-derived extract with a renewable polymer matrix. The process followed green chemistry and biorefinery principles, emphasizing biodegradable materials and low-energy solvent processing.\u003c/p\u003e \u003cp\u003eCellulose acetate butyrate (CAB) was dissolved in 10 mL of ethyl acetate under magnetic stirring to form a homogeneous solution. The \u003cem\u003eC. odorata\u003c/em\u003e leaf extract (Section \u003cspan refid=\"Sec4\" class=\"InternalRef\"\u003e2.2\u003c/span\u003e) was added and stirred for 30 min to ensure uniform dispersion. The organic phase was then emulsified into 50 mL of 1% (w/v) poly(vinyl alcohol) (PVA) solution under moderate stirring (600 rpm) to produce a stable oil-in-water emulsion.\u003c/p\u003e \u003cp\u003eMicrocapsules formed via solvent evaporation as CAB precipitated around the encapsulated extract. The suspension was centrifuged at 4,000 rpm for 10 min, washed three times with deionized water, and air-dried at room temperature for 24 h to obtain CAB\u0026ndash;\u003cem\u003eC. odorata\u003c/em\u003e core microcapsules.\u003c/p\u003e \u003cp\u003eThis step converts biomass-derived phytochemicals into a stable, biodegradable delivery system and represents a scalable, eco-friendly approach to producing bio-based functional materials for subsequent Zn(OH)\u003csub\u003e2\u003c/sub\u003e surface modification.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Surface Coating with Zinc Hydroxide\u003c/h2\u003e \u003cp\u003eSurface coating of CAB-based microcapsules with Zn(OH)\u003csub\u003e2\u003c/sub\u003e was performed as the final functionalization step in the biomass-to-bioproduct conversion process. The procedure introduced inorganic antibacterial functionality through a mild, aqueous precipitation route consistent with green biorefinery principles.\u003c/p\u003e \u003cp\u003eDried CAB\u0026ndash;\u003cem\u003eC. odorata\u003c/em\u003e microcapsules (0.5 g) were dispersed in 50 mL of deionized water under stirring at room temperature. Aqueous Zn(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e solutions (20\u0026ndash;80 mmol/L) were added to control Zn(OH)\u003csub\u003e2\u003c/sub\u003e loading. Sodium hydroxide (0.1 M) was added dropwise until pH\u0026thinsp;\u0026asymp;\u0026thinsp;9.5 to initiate in situ precipitation of Zn(OH)\u003csub\u003e2\u003c/sub\u003e on the microcapsule surfaces. The reaction proceeded for 60 min, followed by centrifugation (4,000 rpm, 10 min), triple washing with deionized water, and drying at 40\u0026deg;C for 24 h.\u003c/p\u003e \u003cp\u003eThe hybrid samples were labeled CAB\u0026ndash;Zn\u0026ndash;20, CAB\u0026ndash;Zn\u0026ndash;40, CAB\u0026ndash;Zn\u0026ndash;60, and CAB\u0026ndash;Zn\u0026ndash;80. This eco-safe coating process avoids high temperatures and organic solvents, minimizing energy input and waste generation. The controlled Zn(OH)\u003csub\u003e2\u003c/sub\u003e deposition enhances surface activity and antibacterial performance, representing a sustainable hybridization stage within the biomass valorization framework.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Characterization of Microcapsules\u003c/h2\u003e \u003cp\u003ePhysicochemical characterization was performed to verify the structural integrity and functional properties of the biomass-derived hybrid microcapsules. Analytical techniques were selected to evaluate each stage of the biorefinery-inspired process, from biomass encapsulation to Zn(OH)\u003csub\u003e2\u003c/sub\u003e surface coating. Fourier-transform infrared spectroscopy (FTIR, Bruker Tensor 27) identified functional groups and chemical interactions among \u003cem\u003eC. odorata\u003c/em\u003e phytochemicals, CAB, and Zn(OH)\u003csub\u003e2\u003c/sub\u003e within 4000\u0026ndash;400 cm⁻\u003csup\u003e1\u003c/sup\u003e. X-ray diffraction (XRD, PANalytical X\u0026rsquo;Pert PRO, Cu Kα, λ\u0026thinsp;=\u0026thinsp;1.5406 \u0026Aring;) confirmed crystalline phase formation and Zn(OH)\u003csub\u003e2\u003c/sub\u003e incorporation, scanned at 2θ\u0026thinsp;=\u0026thinsp;10\u0026deg;\u0026ndash;80\u0026deg;. Thermogravimetric analysis (TGA, Mettler-Toledo TGA/DSC 1) assessed thermal stability under nitrogen (30\u0026ndash;800\u0026deg;C, 10\u0026deg;C min⁻\u0026sup1;), with enhanced stability indicating successful hybridization. Scanning electron microscopy (SEM, Hitachi SU5000) with EDS mapping revealed surface morphology and uniform Zn distribution. Particle size and ζ-potential (Malvern Zetasizer Nano ZS) were measured to evaluate suspension stability. Collectively, these analyses confirm the efficiency of the biomass-to-bioproduct conversion, demonstrating improved material stability and structure\u0026ndash;property correlation essential for sustainable antibacterial composites in biorefinery applications.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6 Evaluation of antibacterial properties\u003c/h2\u003e \u003cp\u003eThe antibacterial activity of biomass-derived CAB\u0026ndash;Zn(OH)\u003csub\u003e2\u003c/sub\u003e hybrid microcapsules was evaluated to verify their performance as sustainable bio-based materials. Tests were conducted against \u003cem\u003eEscherichia coli\u003c/em\u003e (ATCC 25922) and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e (ATCC 25923), representing Gram-negative and Gram-positive bacteria relevant to biomedical and environmental applications.\u003c/p\u003e \u003cp\u003eA broth microdilution method following CLSI guidelines was used with slight modification for particulate samples. Bacterial suspensions (\u0026asymp;\u0026thinsp;1 \u0026times; 10\u003csup\u003e6\u003c/sup\u003e CFU/mL) were exposed to serial dilutions of CAB\u0026ndash;Zn\u0026ndash;x microcapsules (x\u0026thinsp;=\u0026thinsp;20\u0026ndash;80 mmol/L Zn precursor) at final concentrations of 0.8\u0026ndash;25.6 mg/mL in 96-well plates. After incubation at 37\u0026deg;C for 24 h, the minimum inhibitory concentration (MIC) was identified as the lowest concentration preventing visible growth. Minimum bactericidal concentration (MBC) values were confirmed by plating aliquots from growth-inhibited wells on nutrient agar.\u003c/p\u003e \u003cp\u003eAll measurements were performed in triplicate, and antibacterial efficiency was expressed as mean MIC and MBC\u0026thinsp;\u0026plusmn;\u0026thinsp;SD. The results validated synergistic antibacterial effects between biomass-derived phytochemicals and Zn(OH)\u003csub\u003e2\u003c/sub\u003e coating, linking hybrid composition to functional bioactivity. This evaluation confirms the conversion of renewable biomass into eco-efficient antibacterial composites aligned with biorefinery and circular economy principles.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Extraction of Chromolaena odorata Leaves and Microcapsule Appearance\u003c/h2\u003e \u003cp\u003eThe extraction and preparation of \u003cem\u003eChromolaena odorata\u003c/em\u003e (Siam weed) leaf extract are illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Freshly harvested leaves (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea) were thoroughly washed, air-dried under ambient conditions (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), and finely chopped to enhance solvent penetration during extraction. Ethanol was selected as the extraction solvent due to its intermediate polarity and effectiveness in solubilizing a wide range of phytochemicals, including flavonoids, alkaloids, tannins, and chlorophyll\u0026mdash;compounds known for their antimicrobial and antioxidant activities [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. After rotary evaporation to remove ethanol, the concentrated extract was freeze-dried to yield a stable dark green powder (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec), which was used as the core bioactive agent for microencapsulation. This step demonstrates the valorization of \u003cem\u003eC. odorata\u003c/em\u003e leaf biomass into extractives containing bioactive phytochemicals, representing a value-added route for invasive plant utilization.\u003c/p\u003e \u003cp\u003eThe visual appearance of the resulting microcapsules, prepared using CAB and surface-functionalized with varying concentrations of Zn(OH)\u003csub\u003e2\u003c/sub\u003e, is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The uncoated microcapsules (CAB-Zn-0; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea) exhibited a deep green color, indicating the presence of exposed extract on the particle surface. With increasing Zn(OH)\u003csub\u003e2\u003c/sub\u003e precursor concentrations from 10 to 40 mM (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb\u0026ndash;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee), the microcapsules displayed progressively lighter and more uniform coloration, suggesting enhanced surface coverage by the deposited Zn(OH)\u003csub\u003e2\u003c/sub\u003e layer [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThis change in visual appearance corresponds to structural modifications confirmed by FTIR and SEM analyses (discussed in subsequent sections), which verify successful Zn(OH)\u003csub\u003e2\u003c/sub\u003e precipitation and surface coating. The Zn(OH)\u003csub\u003e2\u003c/sub\u003e layer serves a dual function: (i) protecting encapsulated phytochemicals from premature degradation [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] and (ii) enabling controlled release of Zn\u003csup\u003e2+\u003c/sup\u003e ions, which enhance antibacterial efficacy through mechanisms such as membrane disruption and reactive oxygen species (ROS) generation [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThese findings establish a direct correlation between Zn(OH)\u003csub\u003e2\u003c/sub\u003e concentration and microcapsule structural attributes, supporting the formulation\u0026rsquo;s potential as a controlled-release antimicrobial platform for biomedical coatings, wound care, and food-contact materials.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Characterization of microcapsules\u003c/h2\u003e \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e \u003ch2\u003e3.2.1 XRD Analysis\u003c/h2\u003e \u003cp\u003eX-ray diffraction (XRD) was used to assess the crystalline phases of Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated \u003cem\u003eC. odorata\u003c/em\u003e microcapsules (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Distinct peaks observed in CAB-Zn-10 to CAB-Zn-40 matched orthorhombic Zn(OH)\u003csub\u003e2\u003c/sub\u003e (JCPDS No. 01-076-1778), with characteristic reflections at 2θ\u0026thinsp;=\u0026thinsp;20.09\u0026deg;, 20.81\u0026deg;, 24.98\u0026deg;, 27.11\u0026deg;, 27.65\u0026deg;, and 32.73\u0026deg; [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Increasing precursor concentration led to sharper, more intense peaks, indicating progressive crystallization.\u003c/p\u003e \u003cp\u003eCAB-Zn-10 showed broad, low-intensity peaks superimposed on an amorphous background, while CAB-Zn-40 exhibited well-defined diffraction patterns, confirming surface deposition of highly crystalline Zn(OH)\u003csub\u003e2\u003c/sub\u003e. Enhanced crystallinity correlates with improved Zn\u003csup\u003e2+\u003c/sup\u003e ion release control and stability\u0026mdash;key for antimicrobial efficacy via membrane disruption, ROS generation, and enzyme inhibition [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. These findings reinforce that higher Zn(OH)\u003csub\u003e2\u003c/sub\u003e loading improves both structural integrity and sustained antibacterial performance [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], making CAB-Zn-40 a promising candidate for biomedical and packaging applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e \u003ch2\u003e3.2.2 FTIR Analysis\u003c/h2\u003e \u003cp\u003eFTIR spectroscopy was used to investigate molecular interactions between \u003cem\u003eC. odorata\u003c/em\u003e extract, the CAB matrix, and Zn(OH)\u003csub\u003e2\u003c/sub\u003e coating (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). The crude extract exhibited a broad O\u0026ndash;H stretch at 3317 cm⁻\u003csup\u003e1\u003c/sup\u003e and prominent peaks at 1618, 1512, and 1348 cm⁻\u003csup\u003e1\u003c/sup\u003e, consistent with phenolic O\u0026ndash;H, aromatic C\u0026thinsp;=\u0026thinsp;C, and C\u0026ndash;N/C\u0026ndash;O vibrations from bioactive phytochemicals [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eUncoated microcapsules (CAB-Zn-0) retained key spectral features from both the extract and CAB, including O\u0026ndash;H stretching (~\u0026thinsp;3400 cm⁻\u003csup\u003e1\u003c/sup\u003e) and ester C\u0026thinsp;=\u0026thinsp;O stretching (~\u0026thinsp;1700\u0026ndash;1600 cm⁻\u003csup\u003e1\u003c/sup\u003e), suggesting successful encapsulation and non-covalent interactions [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated microcapsules (CAB-Zn-40), attenuation of O\u0026ndash;H and C\u0026thinsp;=\u0026thinsp;O bands, along with the appearance of Zn\u0026ndash;O vibrations at 715 and 545 cm⁻\u003csup\u003e1\u003c/sup\u003e, indicate coordination between Zn\u003csup\u003e2+\u003c/sup\u003e ions and electron-donating groups in the extract [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. These shifts suggest chemical interaction rather than mere surface adsorption.\u003c/p\u003e \u003cp\u003eSuch coordination is expected to enhance Zn\u003csup\u003e2+\u003c/sup\u003e retention and modulate release kinetics while stabilizing encapsulated actives. This supports a dual-action antimicrobial mechanism: rapid bacteriostasis from phytochemicals and sustained oxidative and enzymatic stress from Zn\u003csup\u003e2+\u003c/sup\u003e ions\u0026mdash;highlighting the system\u0026rsquo;s potential for wound healing, antimicrobial coatings, and active packaging.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e \u003ch2\u003e3.2.3 EDS Analysis\u003c/h2\u003e \u003cp\u003eEnergy-dispersive X-ray spectroscopy (EDS) was utilized to evaluate the surface elemental composition of Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated \u003cem\u003eC. odorata\u003c/em\u003e microcapsules. Representative spectra are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. Prominent peaks corresponding to carbon (C) and oxygen (O) were detected across all samples, originating from the CAB polymer matrix and plant-derived phytochemicals. The presence of zinc (Zn) in the coated formulations confirmed the successful deposition of Zn(OH)\u003csub\u003e2\u003c/sub\u003e onto the microcapsule surfaces.\u003c/p\u003e \u003cp\u003eMinor peaks for gold (Au) and sodium (Na) were also observed. Gold was introduced during the sputter-coating process used for SEM preparation, while sodium likely originated from trace residuals of precursor salts or buffer systems. Importantly, Zn was the only metal with recognized antimicrobial functionality, validating its selective incorporation [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eQuantitative EDS analysis revealed a clear, concentration-dependent increase in surface Zn content. Both CAB-Zn-10 and CAB-Zn-20 exhibited low zinc content (~\u0026thinsp;0.1 wt%), while CAB-Zn-30 and CAB-Zn-40 demonstrated substantially higher Zn loading (~\u0026thinsp;0.5 wt%). This trend is consistent with XRD findings and visually corroborated by SEM observations, indicating that increased precursor concentrations lead to greater Zn(OH)\u003csub\u003e2\u003c/sub\u003e accumulation on the microcapsule surface.\u003c/p\u003e \u003cp\u003eThe enhanced zinc content in CAB-Zn-30 and CAB-Zn-40 is expected to promote more effective and sustained Zn\u003csup\u003e2+\u003c/sup\u003e ion release, which contributes to antimicrobial activity through multiple mechanisms. These include disruption of microbial membranes, generation of reactive oxygen species (ROS), and inhibition of bacterial enzyme systems. The ability to tune Zn(OH)\u003csub\u003e2\u003c/sub\u003e deposition through precursor concentration offers a valuable design parameter for tailoring antimicrobial efficacy and longevity [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOverall, EDS analysis confirms the uniform and controllable surface functionalization of the microcapsules, supporting the reliability of the fabrication method. These results reinforce the functional role of Zn(OH)\u003csub\u003e2\u003c/sub\u003e in enhancing microcapsule performance, highlighting the potential of CAB-Zn-40 as a scalable and adaptable antimicrobial platform for biomedical, pharmaceutical, and environmental applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.2.4 SEM Analysis\u003c/h2\u003e \u003cp\u003eScanning electron microscopy (SEM) was employed to examine the surface morphology of \u003cem\u003eC. odorata\u003c/em\u003e-loaded CAB microcapsules coated with increasing concentrations of Zn(OH)\u003csub\u003e2\u003c/sub\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). The uncoated control (CAB-Zn-0) exhibited smooth, spherical surfaces, reflecting the uniformity of the CAB matrix and the absence of surface-bound inorganic phases.\u003c/p\u003e \u003cp\u003eAt 10 mM Zn(OH)\u003csub\u003e2\u003c/sub\u003e (CAB-Zn-10), mild surface roughening and discrete nanoparticle aggregates were observed, indicating initial Zn(OH)\u003csub\u003e2\u003c/sub\u003e nucleation. Increasing the concentration to 20 mM (CAB-Zn-20) led to more continuous and heterogeneous surface coverage, enhancing surface area and potentially facilitating improved Zn\u003csup\u003e2+\u003c/sup\u003e ion diffusion for antibacterial activity [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAt 30 mM (CAB-Zn-30), a denser and more compact coating formed, with aggregated nanoparticle domains promoting prolonged Zn\u003csup\u003e2+\u003c/sup\u003e release and microbial contact. The 40 mM sample (CAB-Zn-40) demonstrated the most extensive and uniform nanoparticle coverage, characterized by a highly textured, near-saturated Zn(OH)\u003csub\u003e2\u003c/sub\u003e layer\u0026mdash;providing an optimal interface for sustained ion release, ROS generation, and inhibition of bacterial adhesion or biofilm formation [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThese findings highlight a clear, concentration-dependent morphological evolution. The nanostructured coatings in CAB-Zn-30 and CAB-Zn-40 offer enhanced surface functionality and sustained antimicrobial potential, underscoring their suitability for biomedical and environmental applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e3.2.5 Particle size distribution Analysis\u003c/h2\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e illustrate the particle size distribution of \u003cem\u003eC. odorata\u003c/em\u003e-loaded CAB microcapsules coated with increasing concentrations of Zn(OH)\u003csub\u003e2\u003c/sub\u003e. A consistent increase in mean diameter was observed with higher precursor concentrations, confirming progressive Zn(OH)\u003csub\u003e2\u003c/sub\u003e deposition. Uncoated microcapsules (CAB-Zn-0) averaged 1013.3\u0026thinsp;\u0026plusmn;\u0026thinsp;66.5 nm, increasing modestly with 10 mM Zn(OH)\u003csub\u003e2\u003c/sub\u003e (1049.5\u0026thinsp;\u0026plusmn;\u0026thinsp;74.5 nm) and reaching 1275.3\u0026thinsp;\u0026plusmn;\u0026thinsp;109.9 nm at 40 mM (CAB-Zn-40).\u003c/p\u003e \u003cp\u003eThis size enlargement reflects the formation of thicker Zn(OH)\u003csub\u003e2\u003c/sub\u003e shells, which enhance Zn\u003csup\u003e2+\u003c/sup\u003e reservoir capacity and enable sustained, diffusion-controlled ion release. The denser coatings also reduce premature Zn\u003csup\u003e2+\u003c/sup\u003e leaching, promoting prolonged antimicrobial activity [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Additionally, increased particle size and surface roughness may hinder bacterial adhesion, offering synergistic physical\u0026ndash;chemical antibacterial effects. CAB-Zn-40, with the largest and most uniform particles, is thus well-suited for durable applications such as wound dressings, antimicrobial coatings, and controlled-release systems.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eParticle size and thermal degradation characteristics of CAB\u0026ndash;Zn(OH)₂ microcapsules prepared with different Zn precursor concentrations. Increasing Zn(OH)₂ loading led to larger particle sizes and improved thermal stability, indicating the formation of thicker inorganic coatings and enhanced structural integrity of the hybrid microcapsules.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSample\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean Particle Size (nm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eInitial Onset Temperature (\u0026deg;C)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFinal Onset Temperature (\u0026deg;C)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eWeight Loss (%)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB\u0026ndash;Zn\u0026ndash;0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1013.3\u0026thinsp;\u0026plusmn;\u0026thinsp;66.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e336.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e385.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e85.90\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB\u0026ndash;Zn\u0026ndash;10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1049.5\u0026thinsp;\u0026plusmn;\u0026thinsp;74.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e252.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e368.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e48.94\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB\u0026ndash;Zn\u0026ndash;20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1159.8\u0026thinsp;\u0026plusmn;\u0026thinsp;58.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e292.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e371.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e37.57\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB\u0026ndash;Zn\u0026ndash;30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1202.5\u0026thinsp;\u0026plusmn;\u0026thinsp;82.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e274.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e371.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e28.33\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB\u0026ndash;Zn\u0026ndash;40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e1275.3\u0026thinsp;\u0026plusmn;\u0026thinsp;109.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e287.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e367.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e28.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e \u003ch2\u003e3.2.6 TGA Analysis\u003c/h2\u003e \u003cp\u003eThermogravimetric analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) revealed the thermal degradation behavior of \u003cem\u003eC. odorata\u003c/em\u003e-loaded CAB microcapsules across varying Zn(OH)\u003csub\u003e2\u003c/sub\u003e coating levels. All samples showed primary mass loss between 250\u0026ndash;400\u0026deg;C, attributed to degradation of the CAB matrix and embedded phytochemicals. Uncoated microcapsules (CAB-Zn-0) exhibited the highest weight loss (85.90%) and an onset degradation temperature of 336.7\u0026deg;C, indicating low thermal resistance.\u003c/p\u003e \u003cp\u003eZn(OH)\u003csub\u003e2\u003c/sub\u003e-coated samples showed progressively enhanced thermal stability. Despite a slightly lower onset temperature in CAB-Zn-10 (252.6\u0026deg;C), its reduced weight loss (48.94%) suggests partial stabilization. Further increases in Zn(OH)\u003csub\u003e2\u003c/sub\u003e content led to lower total weight losses: 37.57% (CAB-Zn-20), 28.33% (CAB-Zn-30), and 28.05% (CAB-Zn-40), with CAB-Zn-40 also exhibiting a higher onset temperature (287.0\u0026deg;C).\u003c/p\u003e \u003cp\u003eThese improvements are attributed to the Zn(OH)\u003csub\u003e2\u003c/sub\u003e coating, which acts as a thermal and oxidative barrier, limiting volatilization of thermolabile components and enhancing structural integrity [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Enhanced thermal resistance supports product longevity and functionality under elevated temperatures\u0026mdash;critical for applications such as antimicrobial wound dressings, medical textiles, and heat-resistant packaging\u0026mdash;where retention of bioactivity and controlled Zn\u003csup\u003e2+\u003c/sup\u003e release are essential.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe enhanced crystallinity and stability indicate that the biopolymer\u0026ndash;inorganic hybridization route can upgrade raw biomass into advanced functional materials suitable for bio-based industries.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Antibacterial Activity\u003c/h2\u003e \u003cp\u003eThe antibacterial efficacy of \u003cem\u003eC. odorata\u003c/em\u003e-loaded CAB microcapsules with increasing Zn(OH)\u003csub\u003e2\u003c/sub\u003e coating concentrations was assessed against \u003cem\u003eEscherichia coli\u003c/em\u003e (Gram-negative) and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e (Gram-positive) via MIC and MBC assays. Results demonstrated a clear concentration-dependent enhancement in antibacterial performance, particularly against the more resilient \u003cem\u003eE. coli\u003c/em\u003e, highlighting the synergistic roles of phytochemicals, sustained Zn\u003csup\u003e2+\u003c/sup\u003e release, and ROS generation.\u003c/p\u003e \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e \u003ch2\u003e3.3.1 Minimum Inhibitory Concentration (MIC)\u003c/h2\u003e \u003cp\u003eMIC values (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e) decreased significantly with higher Zn(OH)\u003csub\u003e2\u003c/sub\u003e content. CAB-Zn-40 exhibited the strongest inhibition, with MICs of 12.8 mg/mL for \u003cem\u003eE. coli\u003c/em\u003e and 6.4 mg/mL for \u003cem\u003eS. aureus\u003c/em\u003e. While lower Zn(OH)\u003csub\u003e2\u003c/sub\u003e coatings (CAB-Zn-10, CAB-Zn-20) retained activity against \u003cem\u003eS. aureus\u003c/em\u003e, they were less effective against \u003cem\u003eE. coli\u003c/em\u003e, reflecting differences in cell wall permeability. Enhanced Zn\u003csup\u003e2+\u003c/sup\u003e release and ROS-mediated damage likely account for the increased efficacy in higher-coated systems.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e \u003ch2\u003e3.3.2 Minimum Bactericidal Concentration (MBC)\u003c/h2\u003e \u003cp\u003eMBC data (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Figs.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e) closely followed MIC trends. CAB-Zn-40 demonstrated complete bactericidal activity at 12.8 \u0026micro;g/mL against \u003cem\u003eE. coli\u003c/em\u003e and 6.4 \u0026micro;g/mL against \u003cem\u003eS. aureus\u003c/em\u003e, surpassing the performance of lower Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated formulations, which required concentrations of 25.6 \u0026micro;g/mL or higher. This enhanced potency is attributed to a combination of mechanisms: disruption of bacterial membranes through Zn\u003csup\u003e2+\u003c/sup\u003e interactions with cell wall components, oxidative damage induced by reactive oxygen species (ROS) targeting lipids, proteins, and nucleic acids, and interference with intracellular processes, including enzymatic inhibition and transcriptional disruption [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn contrast to uncoated microcapsules that rely solely on phytochemical activity, Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated systems provide a sustained, multi-mechanistic antibacterial response. CAB-Zn-40, in particular, demonstrates superior efficacy along with improved thermal stability, controlled Zn\u003csup\u003e2+\u003c/sup\u003e release, and minimized cytotoxicity risk, making it a compelling candidate for applications requiring long-term antimicrobial performance, such as wound dressings, infection-resistant coatings, and bioactive packaging [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMinimum bactericidal concentration (MBC) values of CAB microcapsules against \u003cem\u003eE. coli\u003c/em\u003e and \u003cem\u003eS. aureus\u003c/em\u003e. The CAB-Zn-40 formulation exhibits the lowest MBCs, reflecting synergistic bactericidal effects from phytochemicals and Zn\u003csup\u003e2+\u003c/sup\u003e ion release.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"3\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMicrocapsule Type\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMBC (\u003cem\u003eE. coli\u003c/em\u003e) (\u0026micro;g/mL)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMBC (\u003cem\u003eS. aureus\u003c/em\u003e) (\u0026micro;g/mL)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB-Zn-0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e25.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB-Zn-10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e51.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e51.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB-Zn-20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e51.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB-Zn-30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e25.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e12.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCAB-Zn-40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e6.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe strong performance of CAB\u0026ndash;Zn\u0026ndash;40 underscores the potential of biomass-derived formulations as sustainable substitutes for synthetic antimicrobial plastics.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Mechanistic Insight into Antibacterial Activity\u003c/h2\u003e \u003cp\u003eThe superior antibacterial efficacy of Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated \u003cem\u003eChromolaena odorata\u003c/em\u003e microcapsules\u0026mdash;particularly the CAB-Zn-40 formulation\u0026mdash;is attributed to a synergistic set of mechanisms operating at both the surface and intracellular levels (Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e11\u003c/span\u003e). These include sustained Zn\u003csup\u003e2+\u003c/sup\u003e ion release, generation of reactive oxygen species (ROS), bacterial membrane disruption, and metabolic interference. Collectively, these effects contribute to potent and prolonged bactericidal activity.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cdiv id=\"Sec22\" class=\"Section3\"\u003e \u003ch2\u003e3.4.1 Zn\u003csup\u003e2+\u003c/sup\u003e-Mediated ROS Generation and Oxidative Stress\u003c/h2\u003e \u003cp\u003eA key antibacterial mechanism involves the sustained release of Zn\u003csup\u003e2+\u003c/sup\u003e ions from the Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated microcapsule surface. SEM and EDS analyses confirmed that Zn surface content increases with precursor concentration, facilitating controlled and prolonged ion diffusion into the surrounding medium. Once released, Zn\u003csup\u003e2+\u003c/sup\u003e ions catalyze intracellular redox reactions, generating reactive oxygen species (ROS) including superoxide anions (O\u003csub\u003e2\u003c/sub\u003e⁻), hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e), and hydroxyl radicals (\u0026bull;OH) [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e, \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThese ROS species exert oxidative stress by targeting bacterial lipids, proteins, and nucleic acids, ultimately leading to cell dysfunction and death. The high crystallinity of Zn(OH)\u003csub\u003e2\u003c/sub\u003e\u0026mdash;particularly evident in CAB-Zn-40 as revealed by XRD\u0026mdash;further supports its role in enabling sustained Zn\u003csup\u003e2+\u003c/sup\u003e release and consistent ROS generation. These results suggest that Zn(OH)\u003csub\u003e2\u003c/sub\u003e coatings function analogously to ZnO systems, delivering continuous antibacterial action through dual chemical pathways, and thus play a central role in the long-term efficacy of the coated microcapsules.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e \u003ch2\u003e3.4.2 Bacterial Membrane Disruption\u003c/h2\u003e \u003cp\u003eSEM analysis revealed a marked increase in surface roughness with higher Zn(OH)\u003csub\u003e2\u003c/sub\u003e loading, particularly in CAB-Zn-30 and CAB-Zn-40. These nanostructured coatings enhance contact with bacterial membranes, intensifying localized Zn\u003csup\u003e2+\u003c/sup\u003e ion release and promoting ROS-induced lipid peroxidation. This behavior is consistent with previous findings on Cu\u0026sup2;⁺ systems reported by Pookmanee et al. (2025) [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe resulting membrane damage leads to the leakage of intracellular contents, cytoplasmic collapse, and eventual cell lysis [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. The synergistic interplay between chemical factors (Zn\u003csup\u003e2+\u003c/sup\u003e ions and ROS) and physical effects (surface roughness and nanoparticle intrusion) accelerates membrane destabilization. This dual-action mechanism underpins the significantly reduced MIC and MBC values observed in higher Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated formulations, confirming their potent and irreversible antibacterial activity.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec24\" class=\"Section3\"\u003e \u003ch2\u003e3.4.3 Cellular Dysfunction and Stress Response\u003c/h2\u003e \u003cp\u003eBeyond membrane-level interactions, Zn\u003csup\u003e2+\u003c/sup\u003e ions interfere with vital intracellular processes. By binding to enzymatic cofactors, Zn\u003csup\u003e2+\u003c/sup\u003e inhibits key metabolic enzymes, disrupts ribosomal function, and impairs DNA replication. Accumulated ROS further aggravates cellular stress, potentially inducing defense responses such as oxidative stress gene expression and DNA repair mechanisms [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlthough these molecular responses were not directly evaluated in this study, future transcriptomic or proteomic analyses could provide insight into bacterial adaptation and resistance pathways triggered by Zn(OH)\u003csub\u003e2\u003c/sub\u003e exposure.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec25\" class=\"Section3\"\u003e \u003ch2\u003e3.4.4 Synergistic Antimicrobial Mechanism\u003c/h2\u003e \u003cp\u003eThe antibacterial effect of CAB-Zn-40 is not solely due to Zn(OH)\u003csub\u003e2\u003c/sub\u003e but also enhanced by bioactive phytochemicals from \u003cem\u003eC. odorata\u003c/em\u003e. Compounds such as flavonoids, tannins, and alkaloids are known to destabilize membranes and inhibit metabolic enzymes [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. The Zn(OH)\u003csub\u003e2\u003c/sub\u003e coating amplifies this effect by enabling sustained Zn\u003csup\u003e2+\u003c/sup\u003e release and ROS production, resulting in a dual-action antimicrobial system.\u003c/p\u003e \u003cp\u003eAdditional support is provided by TGA and DLS data, which indicate improved structural stability and encapsulation efficiency at higher Zn(OH)\u003csub\u003e2\u003c/sub\u003e concentrations. These attributes ensure functional retention under environmental or physiological stress and contribute to long-term antimicrobial performance.\u003c/p\u003e \u003cp\u003eTogether, these mechanistic insights highlight CAB-Zn-40 as a multifunctional antimicrobial platform. By integrating phytochemical bioactivity with sustained-release nanocoating, this system offers a promising strategy for applications requiring prolonged antibacterial efficacy, including wound care, bioactive medical coatings, and antimicrobial packaging materials.\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec26\" class=\"Section2\"\u003e \u003ch2\u003e3.5 Comparative Antibacterial Activity Against Staphylococcus aureus and Escherichia coli\u003c/h2\u003e \u003cp\u003eTo contextualize the antibacterial efficacy of the Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated \u003cem\u003eChromolaena odorata\u003c/em\u003e microcapsules developed in this study, a comparative analysis was conducted using literature-reported plant-based antimicrobial systems (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). These systems include uncoated plant extracts, polymer-encapsulated phytochemicals, and metal-functionalized microcapsules.\u003c/p\u003e \u003cp\u003eEarly studies utilizing \u003cem\u003eC. odorata\u003c/em\u003e ethanolic extracts [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] or isolated flavonoids [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] demonstrated strong in vitro antibacterial activity, with MIC values ranging from 0.016 to 6.25 mg/mL. However, these formulations suffer from critical limitations\u0026mdash;namely, rapid chemical degradation, poor thermal stability, and lack of sustained antimicrobial release\u0026mdash;reducing their practical utility in long-term applications.\u003c/p\u003e \u003cp\u003eTo address these issues, microencapsulation has emerged as a viable strategy. For example, Liu et al. (2023) [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e] reported the encapsulation of cinnamon essential oil in gum arabic/maltodextrin microcapsules, which improved chemical stability and demonstrated moderate antibacterial activity. However, such systems\u0026mdash;lacking an inorganic phase\u0026mdash;are often limited in durability and spectrum of action under physiologically relevant conditions.\u003c/p\u003e \u003cp\u003eIn more recent approaches, the integration of antimicrobial metals has shown considerable promise. Li et al. (2023) [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e] developed silver nanoparticle (AgNP)-coated chitosan\u0026ndash;gelatin microcapsules containing \u003cem\u003eGinkgo biloba\u003c/em\u003e essential oil, while Sharma et al. (2024) [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e] formulated ZnO-coated chitosan\u0026ndash;cellulose microcapsules loaded with \u003cem\u003ePlumeria obtusa\u003c/em\u003e extract. These systems leveraged metal ion release to enhance bactericidal activity; however, they often lacked quantitative MIC data or comprehensive benchmarking against plant\u0026ndash;metal hybrid systems. In contrast, the CAB-Zn-40 formulation presented in this study uniquely combines plant-derived bioactive compounds, a biodegradable CAB matrix, and a Zn(OH)\u003csub\u003e2\u003c/sub\u003e nanocoating that enables sustained Zn\u003csup\u003e2+\u003c/sup\u003e release and reactive oxygen species (ROS) generation, along with demonstrated thermal stability confirmed by TGA analysis.\u003c/p\u003e \u003cp\u003eThis formulation achieved MIC values of 12.8 mg/mL against \u003cem\u003eE. coli\u003c/em\u003e and 6.4 mg/mL against \u003cem\u003eS. aureus\u003c/em\u003e, outperforming several uncoated extract-based systems and rivaling metal-functionalized designs. Additionally, its high crystallinity, structural integrity, and dual-mode antibacterial action position it as a promising candidate for applications requiring both efficacy and durability\u0026mdash;such as wound care, biomedical coatings, and active packaging.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparative summary of antimicrobial plant-based microcapsule systems reported in the literature. The CAB-Zn-40 formulation demonstrates favorable performance and stability relative to uncoated and metal-integrated formulations.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePlant Extract\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEncapsulation Material\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMetal Component\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eControlled Release\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eStability\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eAntibacterial Effectiveness (MIC)\u003c/em\u003e*\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eC. odorata\u003c/em\u003e (ethanol extract)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLow (rapid degradation)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.25 mg/mL (\u003cem\u003eE. coli\u003c/em\u003e), 3.125 mg/mL (\u003cem\u003eS. aureus\u003c/em\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eIsolated \u003cem\u003eC. odorata\u003c/em\u003e flavonoids\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLow\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.016\u0026ndash;0.031 mg/mL (\u003cem\u003eboth strains\u003c/em\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCinnamon essential oil\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGum arabic / Maltodextrin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNone\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes (EO release)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHigh\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e14 \u0026micro;L/mL (\u003cem\u003eE. coli\u003c/em\u003e), 7 \u0026micro;L/mL (\u003cem\u003eS. aureus\u003c/em\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eGinkgo biloba\u003c/em\u003e EO\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChitosan\u0026ndash;gelatin\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAgNPs\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes (Ag⁺, EO release)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHigh (spray-dried)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNot reported (inhibition zones confirmed)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003ePlumeria obtusa\u003c/em\u003e leaf extract\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eChitosan\u0026ndash;cellulose\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eZnO nanoparticles\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes (Zn\u003csup\u003e2+\u003c/sup\u003e release)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eStructurally stable\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNot reported (qualitative activity)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e[\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eC. odorata\u003c/em\u003e extract\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCellulose acetate butyrate (CAB)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eZn(OH)\u003csub\u003e2\u003c/sub\u003e coating\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eYes (Zn\u003csup\u003e2+\u003c/sup\u003e release)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eHigh (TGA confirmed)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e12.8 mg/mL (\u003cem\u003eE. coli\u003c/em\u003e), 6.4 mg/mL (\u003cem\u003eS. aureus\u003c/em\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eThis study (CAB-Zn-40)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e* MIC values are reported as published; due to variation in test protocols, results are indicative and not directly comparable.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThis study demonstrates a green valorization pathway for transforming \u003cem\u003eChromolaena odorata\u003c/em\u003e biomass into high-value antibacterial materials within the framework of sustainable biorefinery. A biodegradable cellulose acetate butyrate (CAB) matrix, derived from renewable cellulose resources, was successfully integrated with plant-extracted phytochemicals and coated with zinc hydroxide (Zn(OH)\u003csub\u003e2\u003c/sub\u003e) via an eco-friendly in situ precipitation process. This mild, solvent-minimized route represents an environmentally responsible conversion process that utilizes invasive plant biomass as a renewable feedstock rather than a waste resource.\u003c/p\u003e \u003cp\u003eThe resulting CAB\u0026ndash;Zn(OH)\u003csub\u003e2\u003c/sub\u003e hybrid microcapsules exhibited enhanced crystallinity, thermal stability, and surface functionality, confirming successful hybridization between the bio-based polymer and inorganic coating. Among the formulations, CAB\u0026ndash;Zn\u0026ndash;40 displayed the strongest antibacterial performance against \u003cem\u003eEscherichia coli\u003c/em\u003e and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e, attributed to the synergistic effects of sustained Zn\u0026sup2;⁺ release and plant-derived bioactive compounds. This combination produced a durable, controlled-release antibacterial response suitable for biomedical and packaging applications.\u003c/p\u003e \u003cp\u003eBeyond material performance, the work highlights a scalable example of biomass-to-bioproduct conversion that aligns with circular bioeconomy principles. The valorization of \u003cem\u003eC. odorata\u003c/em\u003e, an invasive tropical species, into a biodegradable antibacterial platform demonstrates how underutilized biomass can be transformed into eco-efficient, high-value functional materials. Future research will focus on evaluating biodegradation kinetics, environmental life-cycle performance, and techno-economic feasibility to further integrate this approach into sustainable biorefinery systems.\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eEthical Approval\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e \u003cp\u003e \u003cstrong\u003eCompeting interest\u003c/strong\u003e \u003cp\u003eThe authors declare no conflicts of interest, whether personal relationships or financial considerations, that could have influenced the publication of this study.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding\u003c/h2\u003e \u003cp\u003eNo funding was received to assist with the preparation of this manuscript.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eJ.K. supervised the study and contributed to conceptualization, methodology, and writing (original draft, review, and editing). M.B. and S.Y. contributed to methodology, investigation, validation. P.K. contributed to methodology, investigation, validation. P.U. performed investigation and validation. P.J. led conceptualization, methodology, writing (original draft, review, and editing). All authors reviewed and approved the final manuscript.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe sincerely appreciate the generous support provided by the Thailand Scientific Research and Innovation (TSRI) for this study.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data are available from the corresponding author upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eFerdinand AS, Coppo MJ, Howden BP, Browning GF (2023) Tackling antimicrobial resistance by integrating One Health and the Sustainable Development Goals. 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Biomed Mater 19:025014. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1088/1748-605X/ad1df7\u003c/span\u003e\u003cspan address=\"10.1088/1748-605X/ad1df7\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Biomass valorization, Biorefinery, Cellulose acetate butyrate, Zinc hydroxide microcapsules, Chromolaena odorata extract, Sustainable antibacterial materials","lastPublishedDoi":"10.21203/rs.3.rs-8052206/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8052206/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study presents a green valorization route for \u003cem\u003eChromolaena odorata\u003c/em\u003e biomass through the development of sustainable cellulose acetate butyrate\u0026ndash;zinc hydroxide (CAB\u0026ndash;Zn(OH)\u003csub\u003e2\u003c/sub\u003e) hybrid microcapsules for controlled antibacterial release. The process integrates renewable plant feedstock and a biodegradable cellulose-derived polymer using an eco-friendly solvent evaporation method, followed by in situ precipitation of Zn(OH)\u003csub\u003e2\u003c/sub\u003e under mild aqueous conditions. Structural, morphological, and thermal analyses confirmed the successful formation of Zn(OH)\u003csub\u003e2\u003c/sub\u003e-coated CAB microcapsules with improved crystallinity, surface roughness, and thermal stability. Antibacterial activity was evaluated against \u003cem\u003eEscherichia coli\u003c/em\u003e and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e, revealing that the CAB\u0026ndash;Zn\u0026ndash;40 formulation exhibited the strongest performance, with minimum inhibitory concentrations of 12.8 mg/mL and 6.4 mg/mL, respectively. The enhanced antibacterial efficacy arises from synergistic interactions between phytochemical constituents of \u003cem\u003eC. odorata\u003c/em\u003e extract and the sustained release of Zn\u003csup\u003e2+\u003c/sup\u003e ions, inducing oxidative stress and membrane disruption. This biorefinery-oriented approach demonstrates the conversion of invasive plant biomass into high-value, multifunctional antibacterial materials. The findings highlight a sustainable and scalable pathway for producing bio-based functional composites applicable to wound care, infection-resistant coatings, and active packaging, advancing the principles of circular bioeconomy and environmentally responsible material design.\u003c/p\u003e","manuscriptTitle":"Green Valorization of Chromolaena odorata Biomass into Sustainable Cellulose Acetate Butyrate–Zn(OH) 2 Microcapsules for Controlled Antibacterial Release","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-09 09:52:58","doi":"10.21203/rs.3.rs-8052206/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"30856ba3-3bda-48a9-898a-01e3489137d4","owner":[],"postedDate":"February 9th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Rejected","date":"2026-05-03T16:43:17+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-05-03T16:54:57+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-09 09:52:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8052206","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8052206","identity":"rs-8052206","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}