[Study on the organic acids metabolism in Candida glycerolgenesis under different fermentation conditions]

The organic acids in Candida glycerolgenesis fermentation medium affected both the glycerol yield and quality. When other fermentation condition was constant, the total acidity in medium increased when the volumetric ratio of medium to flask and corn steep liquid concentration were increased. When the volumetric ratio of medium to flask was 0.20 and the corn steep liquid concentration was 8 g/L, there have high yield of pyruvate and lactate produced at growth phase, 4.1 g/L and 1.0 g/L, respectively, which are two times than control sample at usual fermentation condition, hence, the glycerol yield was lower. However, the volumetric ratio of medium to flask was 0.08 and the corn steep liquid concentration was 4 g/L, the yield of pyruvate and lactate were lower and the glycerol yield was higher, but the acetate could be accumulated to 2.6 g/L. The organic acids also could be metabolized in final fermentation process, such as the initial glucose concentration was 100 g/L, after the glucose was completely utilized, both the glycerol and organic acids concentration decreased, and pyruvate or lactate could be converted to acetate in following fermentation process. In addition, the additive also can change the production of organic acids, with the addition of 1% oleic acid or VB1 the acetate concentration could be decreased and increased the production of pyruvate, hence, improved the yield of glycerol. While the fluoro-pyruvate or sulphite were added in medium, the acetate was increased largely and ketoglutarate was decreased accordingly, also increase the glycerol yields about 20%.