High lipid accumulation potential of the oleaginous yeast Cryptococcus albidus and fungus Fusarium oxysporum was demonstrated using volatile fatty acids (VFA) produced from anaerobic acidogenesis of organic waste as the sole carbon and energy source. Batch cultivations with five different initial COD:N ratios of 5:1, 25:1, 50:1, 125:1, 250:1 were used to determine the optimum COD:N ratio for lipid production to be 25:1. The lipid accumulation was higher in nitrogen limited cultures and the maximum intracellular lipid content of 28.81% (w/w) was obtained in the batch experiment at a COD:N ratio of 250:1. Cells were also grown in a chemostat operated at the optimum COD:N ratio and the intracellular lipid content in the chemostat was 29.71%. Gas chromatography analysis revealed that the microbial lipid composition was similar to commercial biodiesel feedstock and the major fatty acids were palmitic acid [C16:0] (28%) and oleic acid [C18:1] (50%). Degree of unsaturation of fatty acids was found to increase with increasing initial nitrogen concentration. Based on our results, VFA are an inexpensive and commercially lucrative alternate carbon source for lipid accumulation. Whole genome sequencing and proteome mapping is currently underway to understand the metabolic factors and pathways affecting the overall lipid yield from VFA. Our process combined with the in situextraction of lipids from the waste, resulted in a 40% increase in the final yield of biodiesel. Thus, enhanced microbial lipid production from organic waste streams represents a very novel and extremely flexible platform technology, which can achieve sanitation and resource recovery in conjunction.

Conversion of organic-waste derived volatile fatty acids into biodiesel through enhanced microbial lipid production:  A novel platform technology

248th National Meeting (2014)

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