Improvement of the ammonia assimilation for enhancing L-arginine production of Corynebacterium crenatum.

There are four nitrogen atoms in L-arginine molecule and the nitrogen content is 32.1%. By now, metabolic engineering for L-arginine production strain improvement was focused on carbon flux optimization. In previous work, we obtained an L-arginine-producing Corynebacterium crenatum SDNN403 (ARG) through screening and mutation breeding. In this paper, a strain engineering strategy focusing on nitrogen supply and ammonium assimilation for L-arginine production was performed. Firstly, the effects of nitrogen atom donor (L-glutamate, L-glutamine and L-aspartate) addition on L-arginine production of ARG were studied, and the addition of L-glutamine and L-aspartate was beneficial for L-arginine production. Then, the glutamine synthetase gene glnA and aspartase gene aspA from E. coli were overexpressed in ARG for increasing the L-glutamine and L-aspartate synthesis, and the L-arginine production was effectively increased. In addition, the L-glutamate supply re-emerged as a limiting factor for L-arginine biosynthesis. Finally, the glutamate dehydrogenase gene gdh was co-overexpressed for further enhancement of L-arginine production. The final strain could produce 53.2 g l-1 of L-arginine, which was increased by 41.5% compared to ARG in fed-batch fermentation.