氧化还原电位调控对钝齿棒杆菌代谢通量分布的影响

Effect of Redox Potential Regulation on Metabolic Flux Distribution of Corynebacterium crenatum

研究不同氧化还原电位对钝齿棒杆菌厌氧发酵特性的影响,并对菌株的代谢通量分布特征进行了分析。结果表明,氧化还原电位由-56 m V降为-400 m V时,发酵液中琥珀酸质量浓度由14 g/L上升为20.2 g/L,乳酸质量浓度由44.9 g/L下降为35.2 g/L。代谢通量分析结果表明,降低氧化还原电位对6-磷酸葡萄糖与磷酸烯醇式丙酮酸节点处的代谢流分布影响显著。氧化还原电位为-400 m V时,胞内戊糖磷酸途径(pentose phosphate pathway,HMP)代谢通量与-56 m V相比增加了1.74倍,由磷酸烯醇式丙酮酸流向C4途径的代谢通量与-56 m V相比增加了78%,琥珀酸通量由31.73 mmol/(L·g·h)增加到56.53 mmol/(L·g·h),乳酸代谢通量由159.73 mmol/(L·g·h)下降为133.50 mmol/(L·g·h)。研究结果表明6-磷酸葡萄糖与磷酸烯醇式丙酮酸节点是影响钝齿棒杆菌厌氧发酵产琥珀酸的关键节点,为后期通过菌种改造以调节乳酸和琥珀酸的生成比、实现乳酸与琥珀酸联产奠定了基础。

For the co-production of lactic acid and succinic acid, the effect of redox potential regulation on the fermentation process of Corynebacterium crenatum was studied and the metabolic flux distribution was also analyzed. When the redox potential level was changed from-56 to-400 m V, the concentration of succinic acid in the fermented broth increased from 14 to 20.2 g/L;meanwhile, the concentration of lactic acid decreased from 44.9 to 35.2 g/L. The results of metabolic flux analysis indicated the metabolic flux distribution at the glucose 6-phosphate and phosphoenolpyruvate nodes were affected significantly. Compared with the value obtained at-56 m V, the flux of pentose phosphate pathway（HMP） pathway increased by 2.74 fold and the flux from phosphoenolpyruvate to oxaloacetate increased by 78%. As a result, the flux of succinic acid increased from 31.73 to 56.53 mmol/（L·g·h） and the flux of lactic acid decreased from 159.73 to 133.50 mmol/（L·g·h）. The results of this study demonstrated that glucose 6-phosphate and phosphoenolpyruvate were the key nodes that could affect the production of succinic acid by C. crenatum fermentation under anaerobic conditions, which has contributed to the co-production of lactic acid and succinic acid by manipulating wild-type C. crenatum to change the ratio of succinic acid/lactic acid through metabolic engineering.