P146: GABA (γ-aminobutyric acid) production through metaboically engineered Escherichia coli

Gamma-aminobutyric acid (GABA) is produced via the decarboxylation of L-glutamate, which is catalyzed by glutamate decarboxylase (GAD). In Escherichia coli, two glutamate decarboxylases (GadA and GadB) and a putative glutamate/GABA antiporter (gadC) constitutes the gad acid resistance system controlling the acidification of the cytosolic environment. In this study, gadA, gadB gene encoding glutamate decarboxylase and gadC gene encoding putative glutamate/GABA antiporter were overexpressed in E. coli to enhance the GABA production. To see the effect of each enzymes, the gene were overexpressed with following combination; gadA (pHA), gadB (pHB), gadA & gadC (pHAC), gadB & gadC (pHBC). The γ-aminobutyrate aminotransferase which is encoded by gabT converts GABA into succinate semialdehyde and may reduces GABA concentration in the medium. Hence, the effect of gabT gene knockout was also surveyed. 5.5 g/L of GABA was produced by gadB & gadC gene overexpressed gabT mutant strain from 10 g/L of monosodium glutamate. The yield was 89.7% of theoretical maximum yield. [This work was supported by the R&D Program of MKE/KEIT (10033199)]