pH Auto-sustain-based Fermentation Fortifies Lactic Acid Bacterial Production of GABA

Gamma-aminobutyric acid (GABA) plays an active role in a number of physiological processes. There is a lot of interest in the production of GABA by lactic acid bacteria. This work developed a pH auto-sustain (PAS)-based GABA fermentation process for Levilactobacillus brevis CD0817, with L-glutamic acid as the substrate. The optimal levels of vital factors, sugar, yeast extract, tween-80, manganese ion, and temperature, that affect GABA synthesis, were 5.0 g/L, 35.0 g/L, 1.0 g/L, 16.0 mg/L, and 30.0°C, respectively. Based on the optimizations, the PAS-based fermentation was performed using a 10 L fermenter. The fermentation produced GABA up to 321.9 ± 6.7 g/L after 48 h, with a productivity of 6.71 g/L/h and a substrate molar conversion rate of 99.6%. The PAS-based fermentation is a promising process for lactic acid bacteria to produce GABA.