Engineering of Corynebacterium glutamicum to Enhance L-ornithine Production by Gene Knockout and Comparative Proteomic Analysis

Engineered Corynebacterium glutamicum was constructed for L-ornithine production by disrupting genes of argF and proB to prevent the flux away from L-ornithine. Effect of the inactivation of 2-oxoglutarate dehydrogenase complex (ODHC) on L-ornithine production was also investigated. It was found that the inactivation of ODHC by knockout of the kgd gene enhanced L-ornithine production. The engineered C. glutamicum ATCC13032 (Delta argF Delta proB Delta kgd) produced L-ornithine up to 4.78 g.L-1 from 0.24 g.L-1 of the wild-type strain. In order to understand the mechanism of L-ornithine production in C. glutamicum ATCC13032 (Delta argF Delta proB Delta kgd) and find out new strategies for further enhancing L-ornithine production, the comparative proteome between the wild-type and the engineered strain was analyzed. L-Ornithine overproduction in the engineered strain was related to the up-regulation of the expression levels of enzymes involved in L-ornithine biosynthesis pathway and down-regulation of the expression levels of proteins involved in pentose phosphate pathway. The overexpression of genes in the upstream pathway of glutamate to increase the availability of endogenous glutamate may further increase ornithine production in the engineered C. glutamicum and the ornithine synthesis enzymes (ArgCJBD) may not be the limiting enzymes in the engineered C. glutamicum.