不同溶氧对谷氨酸棒杆菌代谢的影响

【目的】以谷氨酸棒杆菌为研究对象,分别控制在0、30%、50%3种溶氧水平下进行发酵,分析不同溶氧水平下代谢的变化。【方法】通过检测发酵代谢物中有机酸、氨基酸的含量,以及测定代谢途径中关键酶活性及其编码基因的表达情况来考察不同溶氧水平下物质代谢发生的变化。通过检测胞内还原力和ATP的含量来分析不同溶氧水平对能量代谢产生的影响。【结果】谷氨酸棒杆菌代谢支路受溶氧的影响而发生改变,氨基酸、有机酸的产量也随之改变。特别是在低溶氧(0)情况下,细胞内氧化磷酸化减弱,导致维持生命活动所必需的ATP供应减少,因此细胞通过增强底物水平磷酸化来产生ATP以满足生命活动的需求。在此情况下,胞内NADH得到较多积累,TCA循环代谢流量减小,而转向糖酵解、乙醛酸循环等,并且这个过程伴随多种杂酸包括乳酸、缬氨酸、亮氨酸等的产生,必将影响目的产物的产量。【结论】研究结果对于进一步采取措施优化溶氧的控制策略,提高目的产物的产量具有指导意义。

Effect of different dissolved oxygen concentrations on metabolism in Corynebacterium glutamicum

Objective] We cultivated Corynebacterium glutamicum under 0, 30 and 50% dissolved oxygen (DO) to study the change of metabolism. Methods] The change of substance metabolism was studied by detecting the content of organic acids and amino acids, the activity of key enzymes and expression of their coding genes under different DO level. Meanwhile, the effect of different DO level on energy metabolism was analyzed by detecting the content of cellular reducing power and ATP. Results] DO level affected metabolism in C. glutamicum and the content of organic acids and amino acids was also changed. Especially under low DO level, cellular oxidative phosphorylation was weakened, resulting in the decrease of ATP provided for life activity. Therefore, the excessive substrate-level phosphorylation was needed to generate ATP for meeting the demand of life activity. In this case, the accumulation of cellular NADH increased; the flow of TCA cycle decreased and switched to the glycolysis pathway and glyoxylate cycle. As a result, a variety of organic acids and amino acids was generated, including lactate, valine and leucine and so on, which can further influence the production of target product under zero dissolved oxygen concentration. Conclusion] The results are of certain guiding significance for taking further measures to optimize the control strategy of dissolved oxygen and improve product yield in fermentation of Corynebacterium glutamicum.