Deletion of odhA or pyc improves production of γ-aminobutyric acid and its precursor L-glutamate in recombinant Corynebacterium glutamicum.

Abstract

To enhance γ-aminobutyric acid (GABA) production in recombinant Corynebacterium glutamicum, metabolic engineering strategies were used to improve the supply of the GABA precursor, L-glutamate. C. glutamicum ATCC13032 co-expressing two glutamate decarboxylase genes (gadB1 and gadB2) was constructed in a previous study Shi et al. (J Ind Microbiol Biotechnol 40:1285-1296, 2013) to synthesize GABA from endogenous L-glutamate. To improve its L-glutamate supply, new strains were constructed here. First, the odhA and pyc genes were deleted separately. Then, a gadB1-gadB2 co-expression plasmid was transferred into ΔodhA, Δpyc, and ATCC13032, resulting in recombinant strains SNW201, SNW202, and SNW200, respectively. After fermenting for 72 h, GABA production increased to 29.5 ± 1.1 and 24.9 ± 0.7 g/l in SNW201 and SNW202, respectively, which was significantly higher than that in SNW200 (19.4 ± 2.6 g/l). The GABA conversion ratios of SNW201 and SNW202 reached 0.98 and 0.96 mol/mol, respectively. The recombinant strains SNW201 and SNW202 can be used as candidates for GABA production.