不同溶氧条件下L-苏氨酸生物合成菌株的代谢流量分析

目的]探索L-苏氨酸生物合成机理及影响因素.方法]建立了大肠杆菌L-苏氨酸的代谢流平衡模型,应用MATLAB软件计算出不同溶氧条件下发酵中后期代谢网络的代谢流分布及理想代谢流分布.结果]5%溶氧条件下,25.5%碳架进入HMP途径,74.5%碳架进入糖酵解途径,获得33.9%质量转化率;20%溶氧条件下,58.08%碳架进入HMP途径,41.92%碳架进入糖酵解途径,获得46.5%质量转化率;结论]与理想代谢流(88.23%质量转化率)相比,应从菌种改造和发酵控制方面通过改变6-磷酸葡萄糖异构酶借以增加HMP途径代谢流量,通过增加磷酸烯醇式丙酮酸羧化反应代谢流提高天冬氨酸族合成代谢流,减少TCA循环代谢流量,从而达到减少副产物生成,增加L-苏氨酸生物合成的目的.

Metabolic Flux Analysis of L-Threonine Biosynthesis Strain under Diverse Dissolved Oxygen Conditions

Objective] The mechanism of L-threonine biosynthesis and its impact factors were explored by metabolic flux analysis. Methods] The metabolic flux balance model of L-threonine synthesis by Escherichia coli was established. Based on this model, the practical and optimal metabolic flux distribution in the middle and late period under different dissolved oxygen concentrations were determined with the linear program planted in MATLAB software. Results] Data indicated that 25.5% of carbon sources were consumed by HMP pathway, resulting in a conversion rate of 33.9% to L-threonine with a 5% dissolved oxygen concentration. With dissolved oxygen concentration of 20%, 58.08% carbon resources entered HMP pathway, giving rise to a 46.5% conversion rate. Conclusion] Compared to the optimal metabolic flux with a carbon conversion rate of 88.23%, glucose-6-phosphate isomerase should be activated by genetic manipulation and fermentation control in order to elevate the HMP pathway flux, and flux towards aspartate amino acids family could be enhanced by increasing phosphoenolpyruvate carboxylase reaction rate. These may lead to a decrease in TCA flux and byproducts, and consequently the L-threonine biosynthesis would be promoted.