Bioconversion of Gamma-Aminobutyric Acid from Monosodium Glutamate by Lactobacillus brevis Bmb5

Gamma-aminobutyric acid (GABA) plays important roles in host physiology. However, the effects of GABA are greatly restricted due to its low bioavailability in the human body. Here, a high acid-tolerance GABA-producing strain, Lactobacillus brevis Bmb5, was isolated from kimchi. Bmb5 converted glutamate to GABA (7.23 +/- 0.68 mu g/mu l) at a rate of 72.3%. The expression of gadB gene, encoding the enzyme involved in the decarboxylation of glutamate to GABA, was decreased upon incubation. Our findings indicate GABA production in Bmb5 is not directly correlated with gadB gene expression, providing new insight into the mechanisms underlying GABA production in Lactobacillus.