Enhanced isopropanol–butanol–ethanol (IBE) production in immobilized column reactor using modified Clostridium acetobutylicum DSM792

• Metabolic engineering to convert acetone into isopropanol.
• Continuous immobilized fermentation to validate industrial feasibility of strain.
• Optimization of bioprocess to enhance the solvent yield and productivity.
• Utilization of lignocellulosic spent liquor as a substrate for the fermentation.

The co-production of acetone during traditional butanol fermentation (acetone–butanol–ethanol) lowers the yield of alcohol biofuels. The present study was aimed to develop an improved Clostridium acetobutylicum strain with enhanced alcohol fuel production capability. The previously developed IBE (isopropanol-butanol-ethanol) producing C. acetobutylicum DSM792-ADH strain was further optimized to enhance the solvent productivity and yield. Immobilized cell column reactor was used to investigate the effect of dilution rate on IBE fermentation. Pure glucose, artificial sugar mixture and SEW spent liquor from spruce chips were used as substrates to study the behavior of the modified microorganism. The highest total solvent concentrations of approximately 10.60 g l−1, 10 g l−1 and 6 g l−1 were obtained when glucose, sugar mixture and SEW spent liquor were used as substrates respectively. The modified microorganism could effectively utilize the lignocellulosic biomass hydrolyzate (SEW spent liquor) to yield a solvent productivity of 1.67 g l−1 h−1.