Fig. 7

Time course of cell growth, GABA production and residual MSG during the two-stage fed-batch fermentation. L. brevis 9530: pNZ8148-gadBC was cultured in a 5-L fermentor under the following conditions: medium volume 2 L, inoculum size 10% (v/v), agitation speed 100 rpm, and fermentation time 102 h. After cultivation at pH 5.2 and 35 °C for 24 h, the culture temperature and pH were changed and maintained at 40 °C and 4.4, respectively, during the second phase (24–102 h). At 24 h, 36 h, 48 h and 72 h, 200-mL aliquots of MSG (140 g per aliquot) were supplemented into the bioreactor. The pH was maintained at the set value with the addition of 3 mol/L H₂SO₄ and 3 mol/L NaOH