Butanol production by immobilised Clostridium acetobutylicum in repeated batch, fed-batch, and continuous modes of fermentation

Abstract

Clostridium acetobutylicum immobilised in polyvinylalcohol, lens-shaped hydrogel capsules (LentiKats®) was studied for production of butanol and other products of acetone–butanol–ethanol fermentation. After optimising the immobilisation protocol for anaerobic bacteria, continuous, repeated batch, and fed-batch fermentations in repeated batch mode were performed. Using glucose as a substrate, butanol productivity of 0.41g/L/h and solvent productivity of 0.63g/L/h were observed at a dilution rate of 0.05h−1 during continuous fermentation with a concentrated substrate (60g/L). Through the process of repeated batch fermentation, the duration of fermentation was reduced from 27.8h (free-cell fermentation) to 3.3h (immobilised cells) with a solvent productivity of 0.77g/L/h (butanol 0.57g/L/h). The highest butanol and solvent productivities of 1.21 and 1.91g/L/h were observed during fed-batch fermentation operated in repeated batch mode with yields of butanol (0.15g/g) and solvents (0.24g/g), respectively, produced per gram of glucose.