摘要
Abstract
L-Homoserine serves as a precursor of L-methionine and L-threonine,and is also involved in the synthesis of several im-portant compounds such as 1,4-butanediol,spermidine,tetrahydrofolate,and glufosinate,highlighting its significant utility.Microbial fer-mentation offers a promising approach for L-homoserine production due to its low cost and environmental friendliness.In this study,system-atic metabolic engineering was applied to modify the biosynthetic pathway in Escherichia coli for efficient L-homoserine production.Using E.coli W3110 as the initial strain,genes thrB,metA,and lysA were knocked out to block the synthesis of byproducts L-threonine and L-methionine,as well as the competitive L-lysine pathway.Additionally,genes poxB,ldhA,and adhE were deleted to reduce the formation of organic acids and other byproducts.The phosphotransferase system(PTS)was disrupted and replaced by integration of the galP-glk module to restore glucose uptake and enhance the accumulation of the precursor phosphoenolpyruvate.Key genes including asd,ppc,as-pC,and aspA were overexpressed with optimized copy numbers to intensify metabolic flux,and a feedback-resistant thrA gene was inserted into the genome to further augment precursor supply.Finally,L-homoserine export and cofactor availability were reinforced.The engineered strain achieved an L-homoserine titer of 105.44 g/L in a 5 L bioreactor under fed-batch fermentation conditions.This study established a solid foundation for the industrial production of L-homoserine.关键词
大肠杆菌/L-高丝氨酸/代谢改造/拷贝数优化Key words
Escherichia coli/L-homoserine/metabolic engineering/gene copy number optimization
