Microbial conversion of Limonene-containing waste into transesterifiable bio-lipids: Evaluating oleaginous bacterial isolates

Bio-oil is increasingly recognized as a sustainable and eco-friendly energy source, offering a viable alternative to petro-diesel. This study evaluates the bio-oil production potential of a novel oleaginous strain, KM9 (Serratia surfactantfaciens YD25) compared with the known oleaginous species R. erythropolis. Growth conditions and nutrient requirements were optimized for both strains to maximize biomass production and lipid accumulation. Utilizing orange waste as a substrate not only contributes to waste minimization but also provides a renewable carbon source for microbial lipid synthesis. KM9 demonstrated exceptional performance, achieving 50% reduction in organic matter from the orange waste while simultaneously accumulating lipids upto 38% of its dry cell weight. Gas chromatography-mass spectrometry (GC–MS) analysis of the transesterified lipids revealed that both KM9 and R. erythropoliss produced comparable levels of saturated fatty acids (38.39% and 39%, respectively), when cultivated in limonene-modified media. Notably, the use of orange waste stimulated the production of monounsaturated fatty acids (MUFAs), particularly palmitic and stearic acids, resulting in a lipid profile closely resembling that of plant-based bio-oils. These findings highlight the promising potential of the oleaginous strain KM9 for producing microbial lipids from orange waste, contributing to sustainable biodiesel production and effectively valorizing a significant agricultural waste stream.