高效合成L-高丝氨酸大肠杆菌基因工程菌株的构建

Construction of Escherichia coli Chassis for Efficient Production of L-Homoserine

针对现有L-高丝氨酸生产菌株因营养缺陷需在发酵过程中添加L-苏氨酸等物质的问题,以大肠杆菌为底盘细胞,构建1株非营养缺陷型L-高丝氨酸高产菌株。首先通过下调thrB和thrC的转录弱化L-高丝氨酸的降解途径;并过表达thrA、ppc和pntAB以强化L-高丝氨酸合成代谢流、提高前体物以及辅酶供应;在此基础上过表达rhtA增强L-高丝氨酸输出。获得的菌株H-10经5 L发酵罐发酵48 h,L-高丝氨酸产量达到52.1 g/L,转化率为43%(以占葡萄糖质量计),均高于现有报道。

Nutrients such as L-threonine need to be added during the fermentation of L-homoserine by auxotrophic strains.In this study,a non-auxotrophic Escherichia coli chassis for the high-yield production of L-homoserine was constructed.The expression of thrB and thrC were down-regulated to attenuate the degradation of L-homoserine;then the overexpression of thrA,ppc and pntAB was performed to reinforce the synthetic flux and improve precursor supply and NADPH generation;finally,rhtA was overexpressed to elevate L-homoserine efflux.After 48 h fermentation in a 5 L fermenter,the constructed strain H-10 produced 52.1 g/L of L-homoserine with a percentage transformation of glucose of 43%,which is higher than the values reported in the literature.