Continuous Butanol Fermentation by Clostridium Beijerinckii in a Fibrous Bed Bioreactor with Online Gas Stripping for Simultaneous Product Recovery

Butanol has similar fuel properties to gasoline and is a better biofuel than ethanol. It can be produced from renewable resources through acetone-butanol-ethanol (ABE) fermentation by solventogenic clostridia. ABE fermentation was only second to ethanol fermentation among all industrial fermentations in the 1950s. However, this practice gradually declined due to its low yield, titer, and productivity. These limitations can be overcome by operating ABE fermentation in a fibrous bed bioreactor (FBB) with a hyper-butanol producing mutant of Clostridium beijerinckii, which was adapted in the FBB to tolerate and produce more butanol. In this work, a single-pass continuous FBB fermentation coupled with online gas stripping for butanol recovery was developed. Compared to conventional free-cell batch fermentation, the continuous FBB fermentation with gas stripping gave a high butanol productivity of ~15 g/L/h with a high butanol titer of >150 g/L in the gas stripping condensate that can be easily purified by distillation with a low energy input. This novel process can significantly reduce biobutanol production cost to less than $2 per gallon.