Repeated-batch fermentation by immobilization of Clostridium beijerinckii NCIMB 8052 in a fibrous bed bioreactor for ABE (acetone-butanol-ethanol) production

Abstract

In this study, a fibrous bed bioreactor (FBB) system was used to produce ABE (acetone-butanol-ethanol) by immobilized cells of Clostridium beijerinckii NCIMB 8052. To obtain the maximum ABE productivity and yield and maintain the stability of a repeated-batch fermentation process in the FBB system, the optimal dilution rate (0.17 min−1) and initial glucose concentration (18 g/l) in the bioreactor were determined. When the repeated-batch fermentation was maintained at 11 cycles under the optimal conditions, an average of 4.9 g/l butanol (maximum 5.3 g/l) was achieved with an average solvent productivity of 1.0 g/l/h and a yield of 0.41 g/g (maxima of 1.1 g/l/h and 0.43 g/g, respectively). However, the solvent productivity and yield in batch fermentation of free cells were just 0.29 g/l/h and 0.36 g/g, respectively. In addition, scanning electron micrographs demonstrated that C. beijerinckii cells can be adsorbed onto a cotton towel and they exhibited a significantly different morphology compared to immobilized Clostridium acetobutylicum.