National and Local United Engineering Lab of Metabolic Control Fermentation Technology, Tianjin University of Science and Technology, Tianjin, 300457, China.
Biotechnol Lett. 2013 Jun;35(6):943-50. doi: 10.1007/s10529-013-1241-3. Epub 2013 May 21.
During L-glutamate production, phosphoenolpyruvate carboxylase and pyruvate carboxylase (PCx) play important roles in supplying oxaloacetate to the tricarboxylic acid cycle. To explore the significance of PCx for L-glutamate overproduction, the pyc gene encoding PCx was amplified in Corynebacterium glutamicum GDK-9 triggered by biotin limitation and CN1021 triggered by a temperature shock, respectively. In the fed-batch cultures, GDK-9pXMJ19pyc exhibited 7.4 % lower L-alanine excretion and no improved L-glutamate production. In contrast, CN1021pXMJ19pyc finally exhibited 13 % lower L-alanine excretion and identical L-glutamate production, however, 8.5 % higher L-glutamate production was detected during a short period of the fermentation. It was indicated that pyc overexpression in L-glutamate producer strains, especially CN1021, increased the supply of oxaloacetate for L-glutamate synthesis and decreased byproduct excretion at the pyruvate node.
在 L-谷氨酸生产过程中，磷酸烯醇丙酮酸羧化酶和丙酮酸羧化酶（PCx）在为三羧酸循环提供草酰乙酸方面发挥着重要作用。为了探讨 PCx 对 L-谷氨酸过量生产的意义，分别通过生物素限制触发的谷氨酸棒杆菌 GDK-9 和温度冲击触发的 CN1021 扩增了编码 PCx 的 pyc 基因。在分批补料培养中，GDK-9pXMJ19pyc 的 L-丙氨酸排泄量降低了 7.4%，但 L-谷氨酸的产量没有提高。相比之下，CN1021pXMJ19pyc 最终的 L-丙氨酸排泄量降低了 13%，L-谷氨酸的产量相同，但在发酵的短时间内检测到 8.5%更高的 L-谷氨酸产量。这表明，在 L-谷氨酸生产菌株中，特别是在 CN1021 中过表达 pyc 增加了草酰乙酸的供应，用于 L-谷氨酸的合成，并减少了丙酮酸节点的副产物排泄。
