Lipid from yeast fermentation: Effects of cultural conditions on lipid production and its characteristics of rhodotorula glutinis

Abstract To produce lipids from microbial origins, Rhodotorula glutinis (syn. Rhodotorula gracilis) NRRL Y‐1091 was cultured in batch and continuous systems under nitrogen‐ and carbon‐limited conditions. The lipid production patterns are shown to be different from each other depending on growing conditions. In continuous cultures under nitrogen‐limited conditions, the maximum lipid accumulation was observed at the lowest dilution rate examined, giving the efficiency of substrate conversion of 16.4 g lipid per 100 g glucose consumed. As the dilution rate increased, cell biomass, lipid content, lipid productivity and lipid yield decreased. In carbon‐limited continuous cultures, cell biomass decreased with increasing dilution rate, but lipid content remained almost constant. Neutral lipid portions in nitrogen‐limited cultured yeast cells decreased as the dilution rate increased, and glyco‐ and phospholipid portions showed the reverse trend. Major components in the neutral lipid portions in yeast cells are triglyceride, free fatty acid, steryl ester and sterol. Phosphatidylserine was the predominant phospholipid in yeast cells. The dilution rate also affected the fatty acid composition of all lipid portions; polyunsaturated fatty acids increased and saturated and monounsaturated fatty acids decreased with increasing dilution rates. The degrees of unsaturation of each lipid class and total lipids were also increased by increasing the dilution rate.