Time course of extracellular GABA production by C. glutamicum GAD, and GAD∆ pknG from 100 g L−1glucose. C. glutamicum strains GAD, and GAD∆pknG were cultured separately in 20 mL of GP2 medium containing 100 g L−1 glucose and 25 μg mL−1 kanamycin in 200-mL baffled flasks. Fermentation was performed at 30°C for 168 hours at 120 rpm. A: Extracellular GABA concentrations (closed symbols) and glucose concentrations (open symbols) of C. glutamicum strains GAD (squares) and GAD∆pknG (circles ) were monitored. B: Extracellular glutamate concentrations (open symbols) and the OD600 (closed symbols) of the C. glutamicum strains GAD (squares), and GAD∆pknG (circles) were monitored throughout the fermentation. Data are expressed as the mean and standard error from three independent experiments.