Increased L-ornithine production in Corynebacterium glutamicum by overexpression of a gene encoding a putative...

Overexpression of the NCgl0462 open reading frame, encoding a class II aminotransferase, was studied in conjunction with other enzymes in L-ornithine biosynthesis in an L-ornithine-producing strain. Expression of the wild-type NCgl0462 open reading frame, which displayed aminotransferase activity, was amplified by placing it under the control of the glyceraldehyde 3-phosphate dehydrogenase gene promoter in the pEK0 plasmid and in the genome. L-Ornithine production in Corynebacterium glutamicum SJC8260 harboring plasmid and the genomic NCgl0462 open reading frame was increased by 8.8 and 21.6%, respectively. In addition, the combined overexpression of the NCgl0462 open reading frame within the genome along with the mutated L-ornithine biosynthesis genes (argCJBD) placed in the pEK0 plasmid in C. glutamicum SJC8260 resulted in significant improvement in L-ornithine production (12.48 g/l for combined overexpression compared with 8.42 g/l for the control). These results suggest that overexpression of the aminotransferase-encoding NCgl0462 open reading frame plays an unequivocal role in the L-ornithine biosynthetic pathway, with overlapping substrate specificity in C. glutamicum.