大肠杆菌磷酸烯醇式丙酮酸-糖磷酸转移酶系统改造对产L-色氨酸的影响

Effect of PTS modifications on L-tryptophan production in Escherichia coli

摘要:

L-色氨酸是芳香族氨基酸的一种，被广泛应用于医药、食品和饲料等领域。大肠杆菌磷酸烯醇式丙酮酸-糖磷酸转移酶系统 (PTS系统) 在葡萄糖转运和磷酸化过程中起重要作用，是糖代谢基因表达调控的核心。利用Red同源重组系统，构建包含两类典型PTS系统突变 (ptsHIcrr- glf-glk+和ptsG-) 的L-色氨酸生产菌，并对相关菌株进行补料分批发酵研究。结果表明，不同类型PTS系统突变对菌体生长、L-色氨酸产量、糖酸转化率及副产物生成均有较大影响。与出发菌相比，ptsHIcrr- glf-glk+突变株最高OD600达到125，提高47.0%，产酸38.5 g/L，提高25.9%，糖酸转化率16.7%，提高26.5%，乙酸生成略有增加；ptsG-突变株最高OD600达到100，提高17.6%，产酸33.4 g/L，提高9.4%，糖酸转化率15.5%，提高17.4%，乙酸生成略有减少。对葡萄糖转运系统的进一步研究将为大肠杆菌合成L-色氨酸效率的提升提供帮助。

Abstract:

L-tryptophan, one of the aromatic amino acids, is widely used in the fields of medicine, food and feed additives. The phosphoenolpyruvate-carbohydrate phosphotransferase system (PTS) plays an important role in glucose transport and phosphorylation in Escherichia coli. PTS-mediated regulation dominates the carbohydrates’ uptake and metabolism in E. coli. We constructed L-tryptophan-producing bacteria containing two typical PTS mutations (ptsHIcrr- glf-glk+ and ptsG-) by Red homologous recombination system, and studied 50 L jar fermenter using fed-batch fermentation. Both PTS system mutants had a great impact on the biomass (increasing 47.0% and 17.6%, respectively), L-tryptophan production (increasing 25.9% and 9.4%, respectively), glucose conversion rate (increasing 26.5% and 17.4%, respectively) and byproduct acetic acid generation (slightly increased and decreased，respectively).