Butanol is an excellent substitution of gasoline, which can use in the interior combustion engine without any modification of engine. About 50 years ago, the acetone-butanol-ethanol fermentation process, employing bacterium Clostridium acetobutylicum to convert biomass to butanol, was the most popular way to produce butanol. But this process has some drawbacks in that many bi-products are produced. Besides butanol, the fermentation also produces acetic, butyric and lactic acids when fermentation passes through acidogenesis phase..

In this project, we propose a continuous two stage fermentation/membrane separation system that is based on the work of Ramey (1998) where two organisms, Clostridium acetobutylicum and Clostridium tyrobutyricum, are used in tandem to produce butyric acid (with lactic and acetic) in the first fermentation and butanol (with acetone and ethanol) in the second fermentation. Ramey (1998) proposed liquid-liquid extraction for product removal, but this process has problems with solvent entrainment and selectivity. We are working to demonstrate that selective removal of butyric acid from the first stage by a novel membrane technique that will produce higher yields and productivity than current technology.

During this presentation, we will demonstrate the continuous conversion of sugars to butyric acid using hollow fiber cell recycle and electrodeionization for continuous recovery. We will show how this increases the amount of butyric acid that can be made and will also talk about other applications in the biorefinery as well.

References

Ramey, D.E., “Continuous, Two Stage, Dual Path Anaerobic Fermentation of Butanol and Other Organic Solvents Using Two Different Strains of Bacteria,” U.S. Patent 5,753,474, May 19, 1998.