Abstract: L-Methionine is the only sulfur-containing essential amino acid. It acts as a precursor in the synthesis of various biologically active substances and participates in various metabolic pathways in the body. It is widely used in food, animal feed, medicine, cosmetics, and other fields. In recent years, since L-methionine is the only essential amino acid that cannot be industrially produced by microbial fermentation, the potential of metabolic engineering to improve L-methionine production has received widespread attention from researchers around the world. In this paper, the biosynthesis pathways and metabolic regulation mechanisms of L-methionine in Corynebacterium glutamicum and Escherichia coli are analyzed and compared. The metabolic engineering strategies to produce L-methionine are reviewed from five aspects: the removal of feedback inhibition of key enzymes, the cut-off or weakening of branch metabolic pathways, the optimization of the central metabolic regulatory network, the enhancement of cofactor supply, and the optimization of transport systems, and recent progress in research on the biosynthesis of L-methionine is summarized. Finally, future prospects are also discussed. It is hoped that this review will provide a basis for the breeding of high-yield L-methionine-producing strains.

Key words: L-methionine; metabolic engineering; biosynthesis; Corynebacterium glutamicum; Escherichia coli