Fermentative production of γ(gamma)-aminobutyric acid by Lactobacillus brevis L2 using wheat bran and millet bran supplemented with glutamate

A Lactobacillus strain L2 that produced a higher amount of gamma(gamma)-aminobutyric acid (GABA) was isolated from traditional pickles. Phylogenetic analysis based on the 16S rDNA sequence and morphological and biochemical studies indicated that it may belong to Lactobacillus brevis. Under un-optimized conditions in MRS broth with 2% monosodium glutamate (L-MSG), it produced GABA at a concentration of 9.822 g/L after 48 h. On the principle of maximum economic benefit, the next work describes the optimization of fermentation variables for the production of GABA by Lactobacillus brevis L2 using wheat bran (WB) and millet bran (MB) supplemented with L-MSG. Based on a single-factor-at- a-time optimization strategy, we determined the optimal cultivation conditions of the GABA production using WB and MB as described below: initial pH 4.00, reaction temperature 30 degrees C and the reaction time 72 h. Subsequently, the D-optimal mixture design was applied to optimize the ratio of the three kinds of components above-mentioned for GABA production. The results showed that when the mixing ratio of WB, MB and L-MSG reached 22.454: 20.000: 57.546 (g/L), the maximum GABA yield of Lactobacillus brevis L2 reached 27.2069 g/L. Analysis of variance for the regression model suggested that the GABA yield showed close agreement with the model prediction.