Partial deficiency of G6PDH results in lower osmotolerance to glycerol and glycerol biosynthesis of candida glycerinogenes

Candida glycerinogenes, an osmotolerant yeast, is currently used commercially in China for the production of glycerol. In this study, the osmotolerance of C. glycerinogenes 14-2, a partial glucose 6-phosphate dehydrogenase (G6PDH) deficiency mutant, to high glucose, NaCl or glycerol concentration was tested, and then the fermentation performance of the mutant was investigated. The mutant showed almost the same osmotolerance to glucose and NaCl as the wild type strain, but poor osmotolerance to glycerol. With low glucose (135 g/L), the mutant produced 34.0 g/L glycerol like its parent strain, while 27.7 % less than the control strain with high glucose (252 g/L). Under the both conditions, the specific glucose consumption rate and the specific glycerol formation rate of the mutant were much lower than those of the wild type strain, especially with high glucose. The partial deficiency of G6PDH resulted in declined tolerance to glycerol and poor performance of glycerol fermentation of C. glycerinogenes. The present study indicates that HMP plays important roles in osmoadaptation and glycerol biosynthesis of C. glycerinogenes. The research sheds new light on mechanism of osmoadaptation of yeast.