Mass production of γ-Aminobutyric acid by semi-continuous fermentation using ceramic support by Lactobacillus brevis RK03

Abstract We evaluated γ-aminobutyric acid (GABA) production by Lactobacillus brevis RK03 immobilized fermentation using three types of porous ceramic materials, All Clean (AC), Ocean Free (OF), and Power Material (PM). Almost same surface areas of the three porous ceramic materials were used to perform batch cultures with a modified GM broth and 500 mM monosodium glutamate (MSG). PM produced the highest GABA production after 96 h with an MSG conversion rate of 96.5% at pH 4.5 and 10% bacterial inoculum growing in a 500 mL flask. We then developed a semi-continuous GABA fermentation system by culturing 10% cells in the 500 mL flask comprising AC, OF, and PM carriers with similar surface areas and 500 mM MSG, for 288 h and five cycles at 30 °C. PM produced the highest GABA yield with a 86% conversion rate after five cycles. Semi-continuous fermentation was performed in a 10 L fermenter; MSG conversion rates still reached 97.3% or more following 25 consecutive fermentations, resulting in a maximum GABA yield, which was high for five cycles. Therefore, PM was the best carrier for continuous fermentation of GABA after 25 cycles and 1,200 h. PM can be applied to industrial mass production of GABA.