Synchronization of lipid-based biofuel production with waste treatment using oleaginous bacteria: A biorefinery concept

The use of oleaginous bacteria to produce lipid-based biofuels from organic waste is an emerging approach. The present study was designed to isolate oleaginous bacteria capable of growing on food-processing waste to produce bio-fuels on a sustainable basis. About 26 oleaginous bacteria were isolated from natural crude oils using Luria-Bertani (LB) medium under nitrogen-deficient conditions. The GC-MS analysis confirmed the ability of 10 isolates to produce free fatty acids, where oleic acid appeared to be the most recurring compound among the identified fatty acids. The results of aerobic wet digestion (batch mode) showed the potential of the strain KM15 for simultaneous lipid accumulation and waste treatment. Among different types of waste, removal of volatile solids (VS) up to 38.5% and oxidizable organic matter removal (COD-based) up to 48.9% was achieved by strain KM15, while simultaneously showing an accumulation of lipids up to 41.5% in 96 h. The degradation efficiency of organic matter was 30.9% and 31% for apple and orange waste after 96 h with a lipid accumulation of 21% and 25% respectively. Overall, Bacillus cerus strain KM15 was the most effective strain in the degradation of mango waste and, correspondingly, the production of biolipids from waste. This study illustrates the concept of biorefinery for sustainable waste management and simultaneous production of lipid-based biofuels. The use of waste as the sole source of nutrition could be a key factor in reducing the total production cost of lipid-based bacteriological biorefineries.