Process optimization of acetone-butanol-ethanol fermentation integrated with pervaporation for enhanced butanol production

Abstract

As an important industrial chemical and promising biofuel, biobutanol has attracted extensive attention while still facing the challenges of low production efficiency and yield. The major obstacle comes from product inhibition by high concentration of butanol, therefore in this study pervaporation was used and integrated with acetone-butanol-ethanol fermentation by Clostridium beijerinckii ZL01 to achieve in situ butanol removal from fermentation broth and relieve the inhibition by butanol accumulation. By optimization of integration time, flow rate and initial glucose concentration, the optimal conditions were determined as integration time of 12 h, flow rate of 30 L/h and initial glucose concentration of 90 g/L. The integration of pervaporation dramatically shortened the overall fermentation time from 70 h to 40 h, and increased the total solvents production from 14.30 g/L to 30.83 g/L and the sugar-to-solvent conversion ratio of C. beijerinckii ZL01 from 0.16 g/g to 0.34 g/g for batch fermentation. The adoption of fed-batch fermentation further improved the total solvents concentration to 61.32 g/L and sugar-to-solvent conversion ratio to 0.44 g/g. An unusual accumulation of ethanol was observed in the late stage of fed-batch fermentation, which requires further investigation.