A two-stage pH control method was employed in batch fermentation of curdlan by Alcaligenes faecalis WX-C12 where cell-growth stage was constantly controlled at pH 7.0 and stationary stage was controlled at a constant pH as well. The influence of pH control on the curdlan production was investigated. The optimal pH control of batch process for curdlan production was obtained when cell-growth stage was controlled at pH 7.0 and stationary stage was constantly controlled at pH 5.6. Production and productivity of curdlan, Q p and Y P/ S reached 28.19 g/L, 291 mg/(L·h), 132.27 mg/(L·h·g) and 0.659, an improvement of 20.4 %, 38.1 %,38.1 % and 29.5 % compared to a pH uncontrolled operation respectively.
