Get access

Biocatalytic reduction of short-chain carboxylic acids into their corresponding alcohols with syngas fermentation

Authors

  • Jose M. Perez,

    1. Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York 14853; telephone: 607-255-2480; fax: 607-255-4080
    Search for more papers by this author
  • Hanno Richter,

    1. Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York 14853; telephone: 607-255-2480; fax: 607-255-4080
    Search for more papers by this author
  • Sarah E. Loftus,

    1. Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York 14853; telephone: 607-255-2480; fax: 607-255-4080
    Search for more papers by this author
  • Largus T. Angenent

    Corresponding author
    1. Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York 14853; telephone: 607-255-2480; fax: 607-255-4080
    • Department of Biological and Environmental Engineering, Cornell University, Ithaca, New York 14853; telephone: 607-255-2480; fax: 607-255-4080.
    Search for more papers by this author

  • Jose M. Perez and Hanno Richter contributed equally to this work.

  • The authors have no conflict of interest to declare.

Abstract

Short-chain carboxylic acids generated by various mixed- or pure-culture fermentation processes have been considered valuable precursors for production of bioalcohols. While conversion of carboxylic acids into alcohols is routinely performed with catalytic hydrogenation or with strong chemical reducing agents, here, a biological conversion route was explored. The potential of carboxydotrophic bacteria, such as Clostridium ljungdahlii and Clostridium ragsdalei, as biocatalysts for conversion of short-chain carboxylic acids into alcohols, using syngas as a source of electrons and energy is demonstrated. Acetic acid, propionic acid, n-butyric acid, isobutyric acid, n-valeric acid, and n-caproic acid were converted into their corresponding alcohols. Furthermore, biomass yields and fermentation stoichiometry from the experimental data were modeled to determine how much metabolic energy C. ljungdahlii generated during syngas fermentation. An ATP yield of 0.4–0.5 mol of ATP per mol CO consumed was calculated in the presence of hydrogen. The ratio of protons pumped across the cell membrane versus electrons transferred from ferredoxin to NAD+ via the Rnf complex is suggested to be 1.0. Based on these results, we provide suggestions how n-butyric acid to n-butanol conversion via syngas fermentation can be further improved. Biotechnol. Bioeng. 2013; 110: 1066–1077. © 2012 Wiley Periodicals, Inc.

Ancillary