Abstract: In this study, Lactobacillus brevis BS2, a high yield gamma-aminobutyric acid (γ-GABA)-producing strain capable of enriching Zn, was used to conduct batch and fed-batch fermentation in a 15-L fermenter for exploring the biotransformation of γ-GABA. An initial pH of 5 was used for batch fermentation with and without holding pH at 5. As a result of holding pH, the production ofγ-GABA was considerably increased and sodium glutamate and glucose were almost all consumed at the time points of 32 h and 44 h, respectively. When the initial pH of 5 was held during the fermentation, adding 200 mL of 630 g/L sodium glutamate and 200 mL of 550 g/L glucose (18 min needed at the same flow rate of 11.1 mL/min) was necessary at the time points of 32 h and 44 h, respectively. As a result, the glucose and sodium glutamate in the medium were both over 18 g/L at the end of their additions, which basically reached their initial levels before the fermentation. At 56 h, almost all glutamate was depleted and the production of γ-GABA reached 22.5 g/L. Finally, the second addition of sodium glutamate was done as described above at 56 h. The production of γ-GABA was over 33 g/L at 104 h.

Key words: γ-aminobutyric acid, Lactobacillus, batch fermentation