Acetone-butanol-ethanol production using pH control strategy and immobilized cells in an integrated fermentation-pervaporation process

The effects of pH and cell immobilization on acetone-butanol-ethanol (ABE) production coupled with a pervaporation membrane have been investigated using Clostridium acetobutylicum XY16. The solvent productivity of 0.29 g/L/h was obtained using a two-stage controlled-pH in the coupled process, which was 11% higher than a previous process without pH control, nevertheless, membrane was still fouled. Furthermore, butanol in the fermenter remained below the critical concentration using a larger membrane, solvent productivity achieved 0.38 g/L/h. However, these methods could not prevent membrane fouling, the average permeation flux and butanol separation factor decreased by 41.6% and 31.3%. Then, sugarcane bagasse was used as a cell immobilization carrier and applied to the coupled process; many cells aggregated and adsorbed on sugarcane bagasse surface, the dry cell weight (DCW) in broth was maintained at 1.1 g/L. Membrane fouling was relieved, the pervaporation maintained a steady state for more than 90 h, the average permeation flux was 0.676 kg/m2/h, which only decreased by 13.9% compared to that in the initial stage, and the butanol separation factor remained stable. A maximum solvent productivity of 0.62 g/L/h was also obtained. Thus, the pH control and cell immobilization are efficient methods for high-intensity ABE production with in situ recovery.