Capability of immobilized Clostridium beijerinckii for batch and repeated-batch butanol fermentation from sweet sorghum stem juice in various bioreactors

Abstract

Mixing in bioreactors is important for butanol fermentations. The type of impeller (6-blade disc, 2-pitch blade and 3-pitch blade turbines) in a stirred-tank bioreactor (STR) did not affect butanol production by immobilized Clostridium beijerinckii TISTR 1461 on bamboo chopstick pieces. Using a spin-filter in the STR could reduce the fermentation time from 48 h to 36 h. Butanol production from sweet sorghum stem juice (butanol concentration, PB, ∼11 g/L and butanol productivity, QB, 0.30 g/L·h) by the immobilized cells in an internal loop gas-lift bioreactor using a carrier inside the draft tube were similar to those using an STR with a 6-blade disc turbine integrated with a spin-filter. Repeated-batch butanol fermentation in the internal loop gas-lift bioreactor could be operated for four cycles. However, high levels of butanol production could be maintained for only two cycles. Simultaneous immobilization and fermentation was a suitable process for repeated-batch fermentation by immobilized cells. An internal loop gas-lift bioreactor is a potential low-cost bioreactor for batch and repeated-batch butanol fermentation by the immobilized cells.