Efficient microbial oil production on crude glycerol by Lipomyces starkeyi AS 2.1560 and its kinetics

The capability of using crude glycerol as the sole carbon source for microbial oil production by Lipomyces starkeyi AS 2.1560 was investigated. The optimal crude glycerol concentration, nitrogen source, C/N ratio, inoculum concentration, culture temperature, and pH for lipid production were 70 g/L, yeast extract + peptone, 60, 10.0%, 30 degrees C, and 6.0, respectively. Under the optimal condition, the maximum biomass, lipid content, lipid yield, and lipid coefficient were 21.1 g/L, 35.7%, 7.5 g/L, and 17.3%, respectively. Methanol present in the crude glycerol had minor inhibition on the lipid production. Addition of 0.05 g/L PEG-200, 0.1 g/L potassium oleate or sodium stearate into the medium enhanced the lipid production by 6.4%, 7.7% and 10.4%, respectively. Lipid fermentation was further performed in a 5 L fermentor and the biomass, lipid content, and lipid yield after 10 days' fermentation were 29.2 g/L, 42.9%, and 12.5 g/L, respectively. The corresponding kinetic models for the cell growth, lipid synthesis, and glycerol consumption were built. The maximum specific growth rate and the correlation coefficient of lipid synthesis to cell growth were 0.40 and 0.56, respectively. This study shows that L starkeyi AS 2.1560 is a promising strain for lipid production on crude glycerol.