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 PfliA 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.

Automated summary

L-Methionine, the only sulfur-containing amino acid among the essential amino acids, is mainly produced by chemical methods in industry. This study focuses on the fermentation production of L-methionine by genetically engineered strains. By regulating the biosynthesis pathway and modifying central metabolic pathways and L-cysteine catabolism pathway, the researchers achieved a fermentation yield of 17.74 g/L in a 5 L bioreactor without adding exogenous amino acids. These strategies effectively balance cell growth and L-methionine production and provide insights for the industrial production of L-methionine by microbial fermentation.