Efficient production of L-homoserine in Corynebacterium glutamicum ATCC 13032 by redistribution of metabolic flux

L-Homoserine is a platform chemical used for the production of l-methionine and other valuable compounds. In this study, we constructed an initial l-homoserine-producing strain by metabolic engineering of Corynebacterium glutamicum ATCC 13032, including deletion of thrB, mcbR, and metD and overexpression of lysC, asd, and hom, resulting in a strain capable of producing 1.2 g/L l-homoserine and 4.8 g/L l-lysine. The metabolic flux of l-homoserine was further enhanced by overexpressing feedback-insensitive pyruvate carboxylase (encoded by pyc) from C. glutamicum ATCC 13032 and l-aspartate aminotransferase (encoded by aspC) from E. coli in order to increase oxaloacetate and l-aspartate supplies. Additionally, overexpression of brnFE, which encodes the two-component export system, improved l-homoserine production by 2-fold, suggesting involvement of the brnFE operon in l-homoserine export. Moreover, attenuated expression of dapA and icd downregulated l-lysine biosynthesis and the TCA cycle, resulting in a 25.9 % increase in l-homoserine production (up to 3.4 g/L). Furthermore, overexpression of lysCT311I, asd from C. glutamicum ATCC 13032, and the thrAS345F from E. coli K12-MG1655 resulted in l-homoserine production of 8.8 g/L and demonstrated C. glutamicum as having great potential for industrial production of l-homoserine and l-methionine.