Sweet sorghum syrup as a renewable material for microbial lipid production

• In shaking flasks, Cryptococcus curvatus utilized glucose, fructose and sucrose sequentially.
• In a fermentor with oxygen supply, C. curvatus utilized the three sugars simultaneously.
• A fed-batch cultivation led to a lipid productivity of 4.0 g/L-day.
• Intracellular lipids (78%) can be extracted in 4 min by use of microwave irradiation.

Cryptococcus curvatus, an oleaginous yeast strain was observed to grow on sweet sorghum syrup derived from sorghum juice. In a batch cultivation mode, within the tested range of total sugar concentrations from 11.7 to 34.0 g/L, no substrate inhibition to cell growth was detected. C. curvatus utilized glucose, fructose, and sucrose sequentially. In a fed-batch process, however, this yeast consumed the three sugars more rapidly and simultaneously. Within three days, a biomass density of 23.6 g/L was obtained. The overall lipid productivity was 4.0 g/L-day. Through use of microwave-assisted lipid extraction, 78.1% of available lipid was extracted out of C. curvatus cells in 4 min using methanol as the only solvent. This study demonstrated that fermentation of C. curvatus using sorghum syrup will result in high lipid yield.