Multi-step metabolic engineering Corynebacterium glutamicum ATCC13032 to produce L-methionine

L-Methionine is widely used in food, agricultural and pharmaceutical industries. In this study, the L-methionine production in Corynebacterium glutamicum ATCC13032 was promoted by eliminating the feedback inhibition of key rate-limiting enzymes, blocking L-threonine biosynthesis, and strengthening the downstream pathway of L-homoserine. ATCC13032 does not accumulate L-threonine, we found that overexpressing the genes lysC and hom^G378S could accumulate 0.6 g/L L-threonine. Deleting the genes thrB, McbR, and metD in ATCC13032 could accumulate 0.49 g/L L-methionine. Next, enhancing oxaloacetate supply, overexpressing brnFE, and deleting Ncgl2640 that involved in the repression of sulphuric metabolism could accumulate 0.92 g/L L-methionine. Further overexpressing the genes related to L-homoserine downstream pathway, the resulting strain ZBW011/pEC-metYX could produce 1.82 g/L L-methionine. Finally, the gene pyk2 was deleted and the final strain ZBW014/pEC-metYX produced 7.06 g/L L-methionine in a 2.4-L fermenter. The strategies presented in this study would be useful to engineer C. glutamicum for industrial L-methionine production.