Figure 3. Time course of BD production during SSF in a 5–l stirred bioreactor.

▪: cell density, OD₆₂₀; •: glucose concentration; ▴: AC concentration; ▾: BD concentration. The cultivation was carried out at an initial pH of 7.0. When pH decreased to 6.0, it was maintained at 6.0 in the fermentation processes by automatic addition of 4 M H₃PO₄ or 6 M KOH using a program-controlled peristaltic pump. The agitation speed was 500 rpm and aeration rate was 1.0 vvm.