High-Level Production of l -Methionine by Dynamic Deregulation of Metabolism with Engineered Nonauxotroph Escherichia coli

l -Methionine is the only sulfur-containing amino acid among the essential amino acids, and it is mainly produced by the chemical method in industry so far. The fermentation production of l -methionine by genetically engineered strains is an attractive alternative. Due to the complex metabolic mechanism and multilevel regulation of the synthesis pathway in the organism, the fermentation production of l -methionine by genetically engineered strains was still not satisfied. In this study, the biosynthesis pathway of l -methionine was regulated based on the previous studies. As the competitive pathway and an essential amino acid for cell growth, the biosynthesis pathway of l -lysine was first repaired by complementation of the lysA gene in situ on the genome and then replaced the in situ promoter with the dynamically regulated promoter P fliA to construct a nonauxotroph strain. In addition, the central metabolic pathway and l -cysteine catabolism pathway were further modified to promote the cell growth and enhance the l -methionine production. Finally, the l -methionine fermentation yield in a 5 L bioreactor reached 17.74 g/L without adding exogenous amino acids. These strategies can effectively balance the contradiction between cell growth and l -methionine production and alleviate the complexity of fermentation operation and the cost with auxotroph strains, which provide a reference for the industrial production of l -methionine by microbial fermentation.