Metabolic engineering of Escherichia coli for microbial production of L‐methionine

ABSTRACT L‐methionine has attracted a great deal of attention for its nutritional, pharmaceutical, and clinical applications. In this study, Escherichia coli W3110 was engineered via deletion of a negative transcriptional regulator MetJ and over‐expression of homoserine O‐succinyltransferase MetA together with efflux transporter YjeH, resulting in L‐methionine overproduction which is up to 413.16 mg/L. The partial inactivation of the L‐methionine import system MetD via disruption of met I made the engineered E. coli Δ met J Δ met I/pTrcA*H more tolerant to high L‐ethionine concentration and accumulated L‐methionine to a level 43.65% higher than that of E. coli W3110 Δ met J/pTrcA*H. Furthermore, deletion of lys A, which blocks the lysine biosynthesis pathway, led to a further 8.5‐fold increase in L‐methionine titer of E. coli Δ met J Δ met I Δ lys A/pTrcA*H. Finally, addition of Na 2 S 2 O 3 to the media led to an increase of fermentation titer of 11.45%. After optimization, constructed E. coli Δ met J Δ met I Δ lys A/pTrcA*H was able to produce 9.75 g/L L‐methionine with productivity of 0.20 g/L/h in a 5 L bioreactor. This novel metabolically tailored strain of E. coli provides an efficient platform for microbial production of L‐methionine. Biotechnol. Bioeng. 2017;114: 843–851. © 2016 Wiley Periodicals, Inc.