Increased productivity of <Emphasis Type="Italic">Clostridium acetobutylicum</Emphasis> fermentation of acetone,butanol, and ethanol by pervaporation through supported ionic liquid membrane

Pervaporation proved to be one of the best methods to remove solvents out of a solvent producing Clostridium acetobutylicum culture. By using an ionic liquid (IL)-polydimethylsiloxane (PDMS) ultrafiltration membrane (pore size 60 nm), we could guarantee high stability and selectivity during all measurements carried out at 37°C. Overall solvent productivity of fermentation connected with continuous product removal by pervaporation was 2.34 g l⁻¹ h⁻¹. The supported ionic liquid membrane (SILM) was impregnated with 15 wt% of a novel ionic liquid (tetrapropylammonium tetracyano-borate) and 85 wt% of polydimethylsiloxane. Pervaporation, accomplished with the optimized SILM, led to stable and efficient removal of the solvents butan-1-ol and acetone out of a C. acetobutylicum culture. By pervaporation through SILM, we removed more butan-1-ol than C. acetobutylicum was able to produce. Therefore, we added an extra dose of butan-1-ol to run fermentation on limiting values where the bacteria would still be able to survive its lethal concentration (15.82 g/l). After pervaporation was switched off, the bacteria died from high concentration of butan-1-ol, which they produced.