Application of Wafer-Enhanced Electrodeionization in a Continuous Fermentation Process to Produce Butyric Acid with Clostridium tyrobutyricum

Abstract

Butryic acid is an organic acid which can be produced from Clostridium tyrobutyricum. This organic acid has many applications in food and perfumes as well serving as the first step in a two-step butanol production process. However, the fermentation is product inhibited as well as producing by-products of acetic acid and lactic acid. Electrodialysis and electrodeionization were explored as ways to separate butyric acid from a fermentation broth, in situ. For butyric acid system, the current resistance for ED was almost half that of EDI indicating that ED might be a better option for a pure component separation. However, in a simulated broth containing butyric, lactic, and acetic acid, the opposite trend was found to be true. These results were used to design a fermentation experiment where ED and EDI were used to separate butyric acid from an actual fermentation. It is shown that the percentage of butyric acid (compared to other organic acids) is 84%, 85%, and 92% for no separation, ED, and EDI, respectively. Further, the productivity rate is enhanced by almost 220% when comparing EDI to no separation indicating that it may make sense to use EDI for the separation of butyric acid from a Clostridium tyrobutryicum fermentation.

Keywords:

• electrodialysis
• butyric acid
• Clostridium tyrobutyricum
• electrodeionization

ACKNOWLEDGEMENTS

The authors would like to thank the following staff and students from the University of Arkansas: Tom Potts and George Fordyce. We would also like to thank the Ralph E. Martin Department of Chemical Engineering, the Walton Foundation, the University of Arkansas Honors College, the State of Arkansas Undergraduate Research Foundation (SURF), and the Mack Blackwell Rural Transportation Center for financial support of this project.

Notes

*ED values for α _B/A = 1.06, α_B/L = 1.28, current efficiency = 0.52 and current resistance = 78, respectively, at pH 7.0. Values reported as % increase relative to ED.

*Wafer 1: Amberlite IRA-67 and Amberlite IRC-120 thickness 3 mm.

*Wafer 2: Amberlite IRA-743 and Amberlite IRC-120 thickness 3 mm.