Effect of tungstate on acetate and ethanol production by the electrosynthetic bacterium Sporomusa ovata

Fariza Ammam, Pier-Luc Tremblay, Dawid Mariusz Lizak, Tian Zhang

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Microbial electrosynthesis (MES) and gas fermentation are bioenergy technologies in which a microbial catalyst reduces CO2 into organic carbon molecules with electrons from the cathode of a bioelectrochemical system or from gases such as H2. The acetogen Sporomusa ovata has the capacity of reducing CO2 into commodity chemicals by both gas fermentation and MES. Acetate is often the only product generated by S. ovata during autotrophic growth. In this study, trace elements in S. ovata growth medium were optimized to improve MES and gas fermentation productivity. Augmenting tungstate concentration resulted in a 2.9-fold increase in ethanol production by S. ovata during H2:CO2-dependent growth. It also promoted electrosynthesis of ethanol in a S. ovata-driven MES reactor and increased acetate production 4.4-fold compared to unmodified medium. Furthermore, fatty acids propionate and butyrate were successfully converted to their corresponding alcohols 1-propanol and 1-butanol by S. ovata during gas fermentation. Increasing tungstate concentration enhanced conversion efficiency for both propionate and butyrate. Gene expression analysis suggested that tungsten-containing aldehyde ferredoxin oxidoreductases (AORs) and a tungsten-containing formate dehydrogenase (FDH) were involved in the improved biosynthesis of acetate, ethanol, 1-propanol, and 1-butanol. AORs and FDH contribute to the fatty acids re-assimilation pathway and the Wood-Ljungdahl pathway, respectively. This study presented here shows that optimization of microbial catalyst growth medium can improve productivity and lead to the biosynthesis of different products by gas fermentation and MES. It also provides insights on the metabolism of biofuels production in acetogens and demonstrates that S. ovata has an important untapped metabolic potential for the production of other chemicals than acetate via CO2-converting bioprocesses including MES.
Original languageEnglish
Article number163
JournalBiotechnology for Biofuels
Number of pages10
Publication statusPublished - 2016

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This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.


  • Aldehyde ferredoxin oxidoreductase
  • Gas fermentation
  • Medium optimization
  • Microbial electrosynthesis
  • Sporomusa ovata


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