Effect of operational conditions on the rate of citric acid production by rotating disk contactor using Aspergillus niger

Abstract The effect of operational conditions such as the specific biofilm area, oxygen concentration, and rotation speed on citric acid production by a rotating disk contactor (RDC) was examined. The overall productivity for a repeated batch culture was also compared with that for a non-repeated batch culture. The citric acid production rate per unit biofilm area ( P ) was almost constant regardless of the value of the specific film area. The rotation speed of the disks had no effect on P in the range of 5–20 rpm. The apparent saturation constant of dissolved oxygen concentration was 2.05 mg/ l . Overall citric acid productivity for a 3-times-repeated batch culture was 1.7 times higher than that for the non-repeated batch culture.