Effect of carbon source and high C/N ratio in the cellulosic hydrolysate- based media on the crude lipid contents and unsaturated fatty acid compositions of yeasts

Microbial lipid production by the oleaginous yeast Cryptococcus sp. was studied using glucose and cellulosic hydrolysate as carbon source, to realize the feasiblility of biodiesel production from high-lipid cell culture. The crude lipid contents of Debaryomyces nepalensis and Cryptococcus sp. cultured in YM Agar reached as high as 32-35 % on dry weight basis, which were higher than those of Pseudozyma spp and Moesziomyces eriocauli. Accumulation of lipids strongly depended on the C/N ratio and nitrogen concentration. The highest content of lipids was measured at a C/N ratio of 60-90 and a nitrogen concentration of 0.2% with 60-57% lipids of the dry biomass. The crude lipid contents of biomass could be increased with the addition of carbon source and adjusting the C/N ratio of the cellulosic hydrolysate-based media. Batch cultures using cellulosic hydrolysate demonstrated that there was little inhibitory effect with a reducing sugar concentration of up to 60 g/l. Batch cultures were run for 4 days and reached a dry biomass, lipid concentration, and lipid content of 12.6, 6.3 g/l, and 50.2% (w/w), respectively. The lipids from Cryptococcus sp. contained mainly long-chain saturated and unsaturated fatty acids with 16 and 18 carbon atoms. The four major constituent fatty acids were oleic acid, palmitic acid, stearic acid and linoleic acid. The contents of oleic acid methyl ester and linoleic acid methyl ester were 58.9 % and 7.0 %, respectively. Based on the results, microbial lipids from Cryptococcus sp. are a potential alternative oil resource for biodiesel production.