Metabolic Pathway Optimization of Methionine Biosynthesis Using Recombinant Escherichia Coli

L-methionine as a sulfur-containing amino acid has important physiological functions and application values. In order to improve methionine biosynthesis, feedback repression of methionine synthesis was partially alleviated by knocking out the encoding repressor protein gene metJ and the encoding homoserine kinase gene thrB. The results show that methionine accumulation can reach to 0.18 g·L^-1 using the resulting strain. Based on the known functional genes related to methionine accumulation, synthesis and metabolism of methionine was optimized concerning methionine metabolism network and transportation by knockout and overexpression techniques. Effects of key steps in methionine pathway, methionine transportation, threonine synthesis pathway and methionine recycling pathway were also investigated, and the metabolic network of E. coli was optimized. Transportation of methionine to extracellular was enhanced. Methionine concentration can reach to 0.40 g·L^-1 after 24 h cultivation of the optimized strain. This work is helpful in the improvement of methionine biosynthesis.