碳源对圆酵母(Torula sp.)B84512发酵合成赤藓糖醇及副产物甘油的影响

研究了圆酵母(Torula sp.)B84512以不同碳源发酵产赤藓糖醇过程中副产物甘油的生成与消耗情况。发现该菌株在以任何碳源为底物发酵过程中均会产生甘油,且在发酵中后期甘油逐渐被消耗。以甘油为唯一碳源时该菌株合成赤藓糖醇的速率及产率均低于葡萄糖。葡萄糖为圆酵母B84512发酵产赤藓糖醇的最佳碳源。采用分批补料的方式提高赤藓糖醇的产率并期望能抑制甘油的生成,实验结果表明补料至总糖浓度为50%时赤藓糖醇产量最高为253 g/L,产率为1.03 g/(L.h)。但甘油产量与葡萄糖的浓度呈正相关,分批补料并不能有效抑制甘油的生成,反而导致发酵周期大大延长,对于工业化生产极其不利。通过对甘油的生成及消耗过程中关键酶胞浆3-磷酸甘油脱氢酶(ctGPD)、3-磷酸甘油酯酶(GPP)、线粒体3-磷酸甘油脱氢酶(mtGPD)酶活测定,确定胞浆3-磷酸甘油脱氢酶为甘油合成途径的关键酶,为以后对圆酵母B84512中甘油代谢途径的基因工程改造选育奠定了基础。

Effect of carbon sources on the formation of erythritol and by-product glycerol during fermentation of Torula sp

The effect of different carbon sources used in the fermentation of Torula sp.on the formation and consumption of the by-product glycerol during the production of erythritol through was analyzed in this study.Results showed that glycerol could be synthesized through any carbon source,and it was consumed gradually in the middle and late phase of fermentation.The productivity of erythritol was higher with glucose than that with glycerol.Glusoe was determined as the best carbon sources.In order to improve the productivity of erythritol and tried to inhibit the formation of glycerol,a fed-batch process was designed.The result showed that when the initial glucose concentration was adjusted to 500 g/L in the production stage,253 g/L of overall erythritol was achieved and the productivity was 1.03 g/(L·h).But the content of glycerol was positively correlated with the content of carbon source and led the fermentation time greatly extended.Certainly,it is harmful to the fermentation.Based on the detection of the key enzymes in the glycerol formation and dissimilation process such as cytoplasm glycerol 3-phosphate dehydrogenase(ctGPD) and glycerol 3-phosphatase(GPP) and Mitochondrial glycerol 3-phosphate dehydrogenase(mtGPD),foundation for gene-knockout in the process of glycerol metabolism in Torula sp.B84512 was laid.