Trans-Esterifiable Bio Lipids Synthesis in Bacterial Isolates Using Limonene Containing Waste

Abstract Bio-oil is recognized as a sustainable eco-friendly source of energy and a potential candidate to substitute the use of petro-diesel. In the present study, cultivation of a novel oleaginous culture KM9 was evaluated for bio-oil production potential and compared with a known oleaginous specie R. erythropolis. These strains were assessed for biomass production and growth was optimized for their respective nutrient requirements and physiochemical conditions. The cultivation of strains was also evaluated for their potential to use orange waste as substrate, lipid accumulation and simultaneous waste minimization. The results showed that KM9 reduced more than 50% of organic matters from the waste (47% VS removal and 60% COD removal) and achieved a maximum lipid accumulation of up to 38% of cell dry weight (CDW). In contrast, R. erythropolis stored a maximum of 27% lipids in the cell biomass. Florescence microscopy confirmed the accumulation of lipids by both strains. GC-MS of the trans esterified lipids revealed that both strains tended to store more saturated fatty acids (SFA) (38.39% by KM9 and 39% by R. erythropolis) when using limonene modified media. However, the use of orange waste triggered the accumulation of mono unsaturated fatty acids (MUFA). The high proportion of palmitic acid and stearic acid indicated its close resemblance to the plant based bio-oils. This study gave insight about bacterial lipid accumulation in the novel isolate KM9 for bio-oil production, which also provided additional benefit of waste minimization. Therefore, the oleaginous KM9 can be used to produce microbial lipids as a potential alternative oil from orange wastes, providing a novel process for sustainable production of biodiesel to meet escalating energy demands and waste minimization and utilization into value added products.