Chromosomal editing of Corynebacterium glutamicum ATCC 13032 to produce gamma-aminobutyric acid.

Abstract

Corynebacterium glutamicum has been used as a sustainable microbial producer for various bioproducts using cheap biomass resources. In this study, a high GABA-producing C. glutamicum strain was constructed by chromosomal editing. Lactobacillus brevis-derived gadB2 was introduced into the chromosome of C. glutamicum ATCC 13032 to produce gamma-aminobutyric acid and simultaneously blocked the biosynthesis of lactate and acetate. GABA transport and degradation in C. glutamicum were also blocked to improve GABA production. As precursor of GABA, l-glutamic acid synthesis in C. glutamicum was enhanced by introducing E. coli gdhA encoding glutamic dehydrogenase, and the copy numbers of gdhA and gadB2 were also optimized for higher GABA production. The final C. glutamicum strain CGY705 could produce 33.17 g/L GABA from glucose in a 2.4-L bioreactor after 78 h fed-batch fermentation. Since all deletion and expression of genes were performed using chromosomal editing, fermentation of the GABA-producing strains constructed in this study does not need supplementation of any antibiotics and inducers. The strategy used in this study has potential value in the development of GABA-producing bacteria.