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Energies 2012, 5(8), 2835-2848;

Continuous Fermentation of Clostridium tyrobutyricum with Partial Cell Recycle as a Long-Term Strategy for Butyric Acid Production

Ralph E. Martin Department of Chemical Engineering, University of Arkansas, 3202 Bell Engineering Center, Fayetteville, AR 72701, USA
Author to whom correspondence should be addressed.
Received: 6 June 2012 / Revised: 16 July 2012 / Accepted: 26 July 2012 / Published: 2 August 2012
(This article belongs to the Special Issue Biomass and Biofuels 2012)
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In making alternative fuels from biomass feedstocks, the production of butyric acid is a key intermediate in the two-step production of butanol. The fermentation of glucose via Clostridium tyrobutyricum to butyric acid produces undesirable byproducts, including lactic acid and acetic acid, which significantly affect the butyric acid yield and productivity. This paper focuses on the production of butyric acid using Clostridium tyrobutyricum in a partial cell recycle mode to improve fermenter yield and productivity. Experiments with fermentation in batch, continuous culture and continuous culture with partial cell recycle by ultrafiltration were conducted. The results show that a continuous fermentation can be sustained for more than 120 days, which is the first reported long-term production of butyric acid in a continuous operation. Further, the results also show that partial cell recycle via membrane ultrafiltration has a great influence on the selectivity and productivity of butyric acid, with an increase in selectivity from ≈9% to 95% butyric acid with productivities as high as 1.13 g/Lh. Continuous fermentation with low dilution rate and high cell recycle ratio has been found to be desirable for optimum productivity and selectivity toward butyric acid and a comprehensive model explaining this phenomenon is given. View Full-Text
Keywords: butyric acid; continuous fermentation; ultrafiltration; Clostridium tyrobutyricum butyric acid; continuous fermentation; ultrafiltration; Clostridium tyrobutyricum

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Du, J.; McGraw, A.; Lorenz, N.; Beitle, R.R.; Clausen, E.C.; Hestekin, J.A. Continuous Fermentation of Clostridium tyrobutyricum with Partial Cell Recycle as a Long-Term Strategy for Butyric Acid Production. Energies 2012, 5, 2835-2848.

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