Roles of export genes cgmA and lysE for the production of l-arginine and l-citrulline by Corynebacterium glutamicum

l-arginine is a semi-essential amino acid with application in cosmetic, pharmaceutical, and food industries. Metabolic engineering strategies have been applied for overproduction of l-arginine by Corynebacterium glutamicum. LysE was the only known l-arginine exporter of this bacterium. However, an l-arginine-producing strain carrying a deletion of lysE still accumulated about 10 mM l-arginine in the growth medium. Overexpression of the putative putrescine and cadaverine export permease gene cgmA was shown to compensate for the lack of lysE with regard to l-arginine export. Moreover, plasmid-borne overexpression of cgmA rescued the toxic effect caused by feeding of the dipeptide Arg-Ala to lysE-deficient C. glutamicum and argO-deficient Escherichia coli strains. Deletion of the repressor gene cgmR improved l-arginine titers by 5 %. Production of l-lysine and l-citrulline was not affected by cgmA overexpression. Taken together, CgmA may function as an export system not only for the diamine putrescine and cadaverine but also for l-arginine. The major export system for l-lysine and l-arginine LysE may also play a role in l-citrulline export since production of l-citrulline was reduced when lysE was deleted and improved by 45 % when lysE was overproduced.