Production of microbial lipid by Cryptococcus curvatus on rice straw hydrolysates

[Display omitted] •Rice straw, one of the most abundant agricultural byproduct biomass, can be converted to volatile fatty acids (VFAs) via anaerobic digestion.•Microbial lipid can be produced from the rice-straw VFAs by an oleaginous yeast Cryptococcus curvatus..•Biomass and lipid content can be controlled by the pH and initial VFAs concentration.•Specific growth rate of VFAs from rice straw hydrolysates is 40% higher than that of synthetic VFAs in yeast cultivation.•Microbial lipid from the rice-straw VFAs has a potential of economic biodiesel production. Microbial biolipids/biodiesels derived from volatile fatty acids (VFAs) can be a valuable alternative to plant oils if optimum fermentation conditions are determined. VFAs were used for cell mass and microbial lipid production by Cryptococcus curvatus. The lipid content in the cells increased up to 48% and 28% in batch cultures with the use of 20g/L glucose and 6g/L of VFAs as the carbon source, respectively. In this study, C. curvatus used VFAs as a carbon source via anaerobic digestion of rice straw hydrolysates. VFAs produced from rice straw resulted in yield of 0.43g VFAs/g substrate and 40% higher specific growth rate(0.305h−1) than synthetic VFAs. The highest fatty acid composition observed was C18:1, was obtained using glucose and VFAs as the carbon source to yield a cetane number of 56–59, which is suitable for biodiesel production. The cost of microbial lipids was estimated to be 0.30–1.15 USD/L given 0–150 USD/ton of VFAs cost for a yield of 0.17g/g of lipids. Thus, VFAs can be a suitable carbon source for economical biodiesel production.