谷氨酸棒杆菌SYPS-062合成L-丝氨酸的代谢通量分析

Metabolic flux analysis of L-serine synthesis by Corynebacterium glutamicum SYPS-062

摘要:

以一株由自然界筛选获得的能够利用糖质原料直接产L-丝氨酸的谷氨酸棒杆菌Corynebacterium glutamicum SYPS-062为研究对象，考察了一碳单元循环中的辅因子—叶酸和维生素B12对菌株生长、蔗糖消耗及L-丝氨酸生成的影响，同时对处于对数生长期的菌株进行了代谢流量分析。结果发现，添加扰动因子叶酸和维生素B12对磷酸戊糖途径 (HMP) 碳流影响较大，碳源主要用于细胞生长及合成能量，而流向目的产物L-丝氨酸的碳流减少。同时在添加维生素B12时，增大了G3P节点的L-丝氨酸合成途径的分流比，但造成三羧酸循环 (TCA) 的流量不足，需要大量回补，从而限制了产物合成速率的进一步提高。

Abstract:

Corynebacterium glutamicum SYPS-062 was an L-serine producing strain stored at our lab and could produce L-serine directly from sugar. We studied the effects of cofactors in one carbon unit metabolism-folate and VB12 on the cell growth, sucrose consumption and L-serine production by SYPS-062. In the same time, the metabolic flux distribution was determined in different conditions. The supplementation of folate or VB12 enhanced the cell growth, energy synthesis, and finally increased the flux of pentose phosphate pathway (HMP), whereas the carbon flux to L-serine was decreased. The addition of VB12 not only increased the ratio of L-serine synthesis pathway on G3P joint, but also caused the insufficiency of tricarboxylic acid cycle (TCA ) flux, which needed more anaplerotic reaction flux to replenish TCA cycle, that was an important limiting factor for the further increasing of the L-serine productivity.