Influence of culture conditions on the bioreduction of organic acids to alcohols by thermoanaerobacter pseudoethanolicus

Sean Michael Scully, Aaron E. Brown, Yannick Mueller-Hilger, Andrew B. Ross, Jóhann Örlygsson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Thermoanaerobacter species have recently been observed to reduce carboxylic acids to their corresponding alcohols. The present investigation shows that Thermoanaerobacter pseudoethanolicus converts C2–C6 short-chain fatty acids (SCFAs) to their corresponding alcohols in the presence of glucose. The conversion yields varied from 21% of 3-methyl-1-butyrate to 57.9% of 1-pentanoate being converted to their corresponding alcohols. Slightly acidic culture conditions (pH 6.5) was optimal for the reduction. By increasing the initial glucose concentration, an increase in the conversion of SCFAs reduced to their corresponding alcohols was observed. Inhibitory experiments on C2–C8 alcohols showed that C4 and higher alcohols are inhibitory to T. pseudoethanolicus suggesting that other culture modes may be necessary to improve the amount of fatty acids reduced to the analogous alcohol. The reduction of SCFAs to their corresponding alcohols was further demonstrated using13C-labelled fatty acids and the conversion was followed kinetically. Finally, increased activity of alcohol dehydrogenase (ADH) and aldehyde oxidation activity was observed in cultures of T. pseudoethanolicus grown on glucose as compared to glucose supplemented with either 3-methyl-1-butyrate or pentanoate, using both NADH and NADPH as cofactors, although the presence of the latter showed higher ADH and aldehyde oxidoreductase (ALDH) activity.

Original languageEnglish
Article number162
Pages (from-to)1-24
Number of pages24
JournalMicroorganisms
Volume9
Issue number1
DOIs
Publication statusPublished - Jan 2021

Bibliographical note

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Other keywords

  • Biocatalysis
  • Bioreduction
  • Carboxylic acids
  • Extremophile
  • Fusel alcohols
  • Thermophile
  • Volatile fatty acids

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