耐温谷氨酸棒杆菌的选育及其高温谷氨酸发酵代谢流量分析

Breeding of a thermotolerant Corybacterium glutamicum and its metabolic flux analysis of L-glutamic acid fermentation

采用基因组改组的方法选育获得的一株耐温谷氨酸棒杆菌F343,并比较了F343与其出发菌株S9114在39℃发酵谷氨酸时的发酵特性和代谢流量。结果表明:耐温菌F343的比生长速率、比谷氨酸积累速率可维持在较高的水平;通过发酵中后期代谢流量分析发现耐温菌F343在磷酸烯醇式丙酮酸(PEP)节点处,磷酸烯醇式丙酮酸羧化酶(PEPc)催化的CO_2回补支路反应代谢流增加;α-酮戊二酸(KG)节点处,谷氨酸氢酶(GDH)催化的产生谷氨酸的支路代谢通量增加。此外,高温发酵谷氨酸时,耐温菌F343高温发酵谷氨酸过程产生的乳酸等副产物较出发菌株S9114少。通过改善种子质量,F343在高温发酵30 h产酸达到10.1%,较出发菌株提高67%。

A strain F343 with both higher yield and good thermo tolerance was obtained by genome shuffling. The fermentation and the metabolic flux performances of 17343 compared with the initial strain Corynebacterium glutamicum S9114 were studied. Thet results showed that the fermentation performances of the F343 significantly improved. When using 5-L jar glucose fermentation, the production of L-glutamie acid was up to 10.1% after 30 h, which was increased 67 % compared with that of the initial strain. During the whole fermentation, the strain F343 had a high level of the specific growth rate and the special glutamate production rate. Analysis the metabolic flux of the product-period, the PEP node and the KG node were found different between the strain F343 and the stain S＇9114, the metabolic flux at the branch path, catalyzed by the phosphoenolpyruvate carboxylase （PEPc） and the glutamate dehydrogenase （GDH）, were higher in fermentation of F343 than S9114. In addition, the by-products of L-glutamate fermentation at the high temperature were lower correspondingly.