Efficient Conversion of Crude Glycerol into Triacylglycerol by the Yeast Pseudozyma sp. TYC-2187 for Biodiesel Production

Crude glycerol is a byproduct of biodiesel production. In this study, we isolated a yeast strain that grows vigorously using crude glycerol as a carbon source, and tested the effects of culture conditions on triacylglycerol (TG) production. TYC-2187, isolated from wild grapes and identified as Pseudozyma sp., converted high-concentration crude glycerol into TG more efficiently than other strains of the genus Pseudozyma. Sequence analysis of the 26S rRNA gene D1/D2 domain indicated that TYC-2187 diverged from other strains of the genus Pseudozyma. Optimum culture temperature and optimum initial pH of culture medium, that maximized TG yield of TYC-2187, were 25°C and pH 6.0, respectively. Optimum nitrogen source was yeast extract and optimum concentration was 10 g/L. Optimum concentration of glycerol, when the yeast was cultured for 48 h under optimum conditions, was 80 g/L. TG yield peaked at 15.7 g/L at 48 h and then remained at this level until 66 h. In addition, much of the glycerol in the medium had been consumed by 48 h. Fatty acid composition of TG produced by TYC-2187, including linolenic acid methyl ester content, iodine value, and cetane number, complied with biodiesel standards. These results suggest that the TYC-2187 yeast strain is superbly able to produce TG that is suitable for biodiesel production using crude glycerol.