Abstract:

The objectives of this work were to explore the factors influencing gamma-aminobutyric acid (GABA)
accumulation by Lactobacillus plantarum NDC75017 and the relevant metabolic mechanism. Response surface
methodology (RSM) was adopted to optimize the fermentation conditions for GABA production. Then, GABA production
and the expression of glutamic acid decarboxylase (GAD) encoding gene gadB at different time points were measured by high
performance liquid chromatography (HPLC) and real-time reverse transcription PCR (real-time RT-PCR), respectively. The
optimal concentrations of L-mono sodium glutamate (L-MSG) and 5’-pridoxal phosphate (PLP), and initial fermentation pH
were 68.03 mmol/L, 20.92 μmol/L, and 4.65, respectively. Meanwhile, the yield of GABA was also significantly affected by the
interactions between L-MSG and PLP, and between PLP and pH (P < 0.05). In the fermentation process (0–48 h), the expression
of gadB increased at first and then decreased after 24 h, which was different from the variation trend of GABA production. These
results indicated that the concentrations of L-MSG and PLP, initial fermentation pH, and their interactions could significantly affect
GABA accumulation by L. plantarum NDC75017. Meanwhile, in addition to GAD and gadB, other related enzymes and genes
related to the GABA shunt might be also involved in the synthesis of GABA by L. plantarum NDC75017.

Key words: gamma-aminobutyric acid, Lactobacillus plantarum, glutamic acid decarboxylase, fermentation