Acetone-free biobutanol production: Past and recent advances in the Isopropanol-Butanol-Ethanol (IBE) fermentation

[Display omitted] •We document the technology development timeline for IBE fermentation.•We examined advances in microorganisms, feedstock, and fermentation equipment.•We estimated their impact on the number of fermentation tanks at an IBE plant.•IBE productivity above 1 g/L·h has marginal effects on capital investment.•We assessed ongoing pilot-plant activities to produce IBE from woody feedstock. Production of butanol for fuel via the conventional Acetone-Butanol-Ethanol fermentation has been considered economically risky because of a potential oversupply of acetone. Alternatively, acetone is converted into isopropanol by specific solventogenic Clostridium species in the Isopropanol-Butanol-Ethanol (IBE) fermentation. This route, although less efficient, has been gaining attention because IBE mixtures are a potential fuel. The present work is dedicated to reviewing past and recent advances in microorganisms, feedstock, and fermentation equipment for IBE production. In our analysis we demonstrate the importance of novel engineered IBE-producing Clostridium strains and cell retention systems to decrease the staggering number of fermentation tanks required by IBE plants equipped with conventional technology. We also summarize the recent progress on recovery techniques integrated with fermentation, especially gas stripping. In addition, we assessed ongoing pilot-plant efforts that have been enabling IBE production from woody feedstock.