Utilizing Potential Oleaginous Microbes for Lipid Based Biofuel Production From Food Processing Waste

Abstract

The adoption of alternative energy resources is essential in the current scenario of energy demand to reduce dependence on fossil fuels. The production of biofuels from oleaginous microorganisms is of increasing interest because of its potential benefits on plant-based biofuels. The sustainability of microbial biofuel and its complete independence from food crops make it an attractive option for biofuel production. However, one of the key barriers identified in the commercialization of biofuel from oleaginous microbes is to find a low-cost substrate to reduce the capital cost. In this study, the biofuel potential of bacterial lipids is successfully presented using food waste as a substrate. Oleaginous bacteria (n= 24) were isolated from crude oil and screened for their ability to store lipids using different types of food processing waste (apple, orange and mango waste) as a substrate. Five potent strains were used to test their tendency to reduce the pollution load in terms of removal of organic matter from different types of waste, in which strain KM9 and strain KM15 (Bacillus cereus) had the competent potential for degradation. The strain KM15 represented a greater potential for degradation of mango waste (volatile solids and COD removal up to 38.5% and 48.9%, respectively) while simultaneously exhibiting lipid accumulation up to 41.5% in 96 hours. Strain KM9 showed the highest potential for the treatment of orange waste with 47% removal of VS and 60% removal of COD. Further experiments confirmed the potential of KM9 to degrade citrus waste. The comparative study of strain KM9 with R. erythropolis (known oleaginous strain) showed that biomass production could be increased by supplementation of waste with nitrogen and carbon sources. xix These two strains also represented the potential for storing considerable lipids using waste as a substrate and modified limonene medium. GC-MS analysis revealed that both strains (KM9 and KM15) were able to store more saturated fatty acids (SFA) (38.4% and 39%, respectively) in their cells using a modified limonene medium compared to waste as substrate, however, the use of orange waste triggered the accumulation of monounsaturated fatty acids (MUFA). The high proportion of palmitic acid and stearic acid indicated its close resemblance to plant-based biofuels. The results of this study not only provide insights into the accumulation of bacterial lipids for sustainable biofuel production in order to meet the growing energy demand, but also offer an added benefit of minimizing waste.