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 metI made the engineered E. coli ΔmetJ ΔmetI/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 ΔmetJ/pTrcA*H. Furthermore, deletion of lysA, which blocks the lysine biosynthesis pathway, led to a further 8.5‐fold increase in L‐methionine titer of E. coli ΔmetJ ΔmetI ΔlysA/pTrcA*H. Finally, addition of Na2S2O3 to the media led to an increase of fermentation titer of 11.45%. After optimization, constructed E. coli ΔmetJ ΔmetI ΔlysA/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. Methionine is an essential sulfur containing amino acid which is wildly used in feed stock industry and for medical purpose. The authors engineered Escherichia coli W3110 to produce L‐methionine from glucose. The main strategies include disruption of metJ, overexpression of homoserine O‐transsuccinylase (metA) together with methionine exporter (yjeH), partial disruption of methionine transporter MetD and deletion of lysA to block the competitive pathway. The fed‐batch fermentation of the final strain resulted in 9.75 g/L of L‐methionine after optimization.