A novel biological process to convert renewable biomass to acetone and butanol (AB)

Butanol is an industrially important fuel and chemical that can be produced from renewable agricultural crops and residues by fermentation. However, this fermentation suffers from butanol toxicity, resulting in accumulation of < 20 g/L butanol in batch reactors. To solve butanol toxicity (to the culture) and recovery problems and make butanol fermentation a commercially viable process, gas stripping, a novel technique to separate butanol was applied to this fermentation. For this application, fermentation gases (CO₂ and H₂ produced in this fermentation) were used to remove butanol from the reactor simultaneously as AB (acetone is a byproduct of this fermentation) was produced. In this process, AB production was more due in part to efficient utilization of acids (reaction intermediates of acetone and butanol). As butanol was produced in the system, butanol was recovered simultaneously. To overcome the problem of accumulation of nonvolatile inhibitory components, a continuous system was initiated where a continuous small bleed was withdrawn from the reactor. Simultaneous recovery of butanol (integrated process) relieved butanol toxicity, improved reactor productivity and yield, and resulted in concentrated product stream for further separation and purification. The yield was improved due to efficient utilization of acetic and butyric acids that are reaction intermediates to acetone and butanol. This is an abstract of a paper presented at the AIChE Annual Meeting (Austin, TX 11/7-12/2004).