Gene modification of Escherichia coli and incorporation of process control to decrease acetate accumulation and increase L-tryptophan production
Gene modification of Escherichia coli and incorporation of process control to decrease acetate accumulation and increase L-tryptophan production
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DOI：
10.1007/s13213-017-1289-8
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发表时间：
2017-08-01
影响因子：
3
通讯作者：
Liu, Hongyan
中科院分区：
文献类型：
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作者：
Lu, Na;Zhang, Bin;Liu, Hongyan
乙酸盐是大肠杆菌培养物中的主要抑制代谢物，通过减少乙酸盐的积累，生物质和所需产物的产量都增加。本研究通过对EY-色氨酸产生菌（BCTRP）的遗传修饰和发酵工艺的优化，降低了EY-色氨酸生产过程中乙酸的积累。由于乙酸盐和其他副产物的低积累以及高生物量生产，缺失了整合膜通透酶IICBGlc（ptsG）的突变体（BCTRPG）产生比缺失磷酸乙酰转移酶（pta）或pta-ptsG的突变体更高浓度的EY-色氨酸。适当的溶解氧（DO）水平，葡萄糖进料模式，和pH控制策略应用于色氨酸生产使用BCTRPG突变体。优化后的BCTRPG菌株乙酸积累量比原菌株减少了71.08%，为0.72 g/L，色氨酸产量比原菌株提高了35.81%，为17.14 g/L。同时，对代谢通量分布的分析表明，乙酸合成通量从初始条件下的19.2%下降到优化条件下的8.4%，色氨酸生成通量为18.5%，是初始条件下的1.89倍。本研究为高水平工业化生产-色氨酸提供了理论基础和技术支持。
Acetate is a primary inhibitory metabolite in cultures of Escherichia coli, and the production of both biomass and desired products are increased by reducing the accumulation of acetate. In this study, the accumulation of acetate during EY-tryptophan production was decreased by genetic modification of EY-tryptophan-producing strain (BCTRP) and optimization of the fermentation process. The mutant (BCTRPG), which has a deletion of the integral membrane permease IICBGlc (ptsG), produces a higher concentration of EY-tryptophan than mutants with deletions of either phosphate acetyltransferase (pta) or pta-ptsG, due to the low accumulation of acetate and other byproducts, as well as high biomass production. The appropriate dissolved oxygen (DO) level, glucose feeding mode, and pH control strategy were applied to -tryptophan production using the BCTRPG mutant. The BCTRPG strain with optimized conditions resulted in a reduction in acetate accumulation (71.08% reduction to 0.72 g/L) and an increase in -tryptophan production (35.81% increase to 17.14 g/L) compared with the BCTRP strain in the original culture condition. Meanwhile, an analysis of the metabolic flux distribution indicated that the acetate synthesis flux decreased from 19.2% (original conditions) to 8.4% (optimized conditions), and the flux of tryptophan formation with the optimized conditions was 18.5%, which was 1.89 times higher than under the original conditions. This study provided the theoretical foundation and technical support for high-level industrialization production of -tryptophan.