Abstract

An E. coli strain in which all known pathways of threonine catabolism were inactivated (Δtdh, ΔltaE, ΔilvA, ΔtdcB, ΔyiaY) has been constructed. It was shown that the expression of heterologous citramalate synthase from Leptospira interrogans in an E. coli strain carrying the ΔilvA deletion can serve as an alternative pathway for isoleucine synthesis. It was observed that cimA overexpression has a negative effect on threonine production. We developed a system for regulated gene expression based on the inducible promoter PLtetO and TetR, a repressor of the tetracycline operon. The threonine-producing strain B-1201, in which the cimA gene is expressed under the control of the regulated promoter, was constructed. When the B-1201 strain was cultivated in a fermenter, a correlation was established between the threonine productivity and the expression level of the cimA gene, and the optimal inductor content for the maximum threonine accumulation was also determined.

中文翻译：

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在产苏氨酸的大肠杆菌中异亮氨酸合成的替代途径的使用

摘要

的大肠杆菌，其中所有已知的苏氨酸分解代谢途径被灭活株（Δ TDH， Δ ltaE， Δ的ilvA， Δ TDCB，ΔyiaY）已构建。结果表明，从异源柠苹酸合酶的表达问号钩端螺旋体在一个大肠杆菌菌株携带Δ的ilvA缺失可以用作异亮氨酸的合成的替代途径。观察到，cimA过表达对苏氨酸产生具有负面影响。我们基于诱导型启动子PLtetO和TetR开发了调控基因表达的系统，四环素操纵子的阻遏物。构建了苏氨酸产生菌株B-1201，其中在受调控的启动子的控制下表达cimA基因。在发酵罐中培养B-1201菌株时，苏氨酸生产力与cimA基因表达水平之间建立了相关性，并且还确定了最大苏氨酸积累的最佳诱导物含量。