Applied Microbiology and Biotechnology

, Volume 100, Issue 13, pp 5999–6011 | Cite as

Multiple paths of electron flow to current in microbial electrolysis cells fed with low and high concentrations of propionate

  • Ananda Rao Hari
  • Krishna P. Katuri
  • Eduardo Gorron
  • Bruce E. Logan
  • Pascal E. SaikalyEmail author
Environmental biotechnology


Microbial electrolysis cells (MECs) provide a viable approach for bioenergy generation from fermentable substrates such as propionate. However, the paths of electron flow during propionate oxidation in the anode of MECs are unknown. Here, the paths of electron flow involved in propionate oxidation in the anode of two-chambered MECs were examined at low (4.5 mM) and high (36 mM) propionate concentrations. Electron mass balances and microbial community analysis revealed that multiple paths of electron flow (via acetate/H2 or acetate/formate) to current could occur simultaneously during propionate oxidation regardless of the concentration tested. Current (57–96 %) was the largest electron sink and methane (0–2.3 %) production was relatively unimportant at both concentrations based on electron balances. At a low propionate concentration, reactors supplemented with 2-bromoethanesulfonate had slightly higher coulombic efficiencies than reactors lacking this methanogenesis inhibitor. However, an opposite trend was observed at high propionate concentration, where reactors supplemented with 2-bromoethanesulfonate had a lower coulombic efficiency and there was a greater percentage of electron loss (23.5 %) to undefined sinks compared to reactors without 2-bromoethanesulfonate (11.2 %). Propionate removal efficiencies were 98 % (low propionate concentration) and 78 % (high propionate concentration). Analysis of 16S rRNA gene pyrosequencing revealed the dominance of sequences most similar to Geobacter sulfurreducens PCA and G. sulfurreducens subsp. ethanolicus. Collectively, these results provide new insights on the paths of electron flow during propionate oxidation in the anode of MECs fed with low and high propionate concentrations.


Electron flow Propionate Microbial electrolysis cell Methanogenesis 



This work was sponsored by a Ph.D. fellowship, a Global Research Partnership-Collaborative Fellows Award (GRP-CF-2011-15-S), and Center Competitive Funding (FCC/1/1971-05-01) to P.E.S. from King Abdullah University of Science and Technology (KAUST). Special thanks are extended to Bioscience Core Laboratory at KAUST for 454 pyrosequencing.

Compliance with ethical standards

This article does not contain studies with human participants or animals performed by any of the authors.

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

253_2016_7402_MOESM1_ESM.pdf (803 kb)
ESM 1 (PDF 803 kb)


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Copyright information

© Springer-Verlag Berlin Heidelberg 2016

Authors and Affiliations

  • Ananda Rao Hari
    • 1
  • Krishna P. Katuri
    • 1
  • Eduardo Gorron
    • 1
  • Bruce E. Logan
    • 2
  • Pascal E. Saikaly
    • 1
    Email author
  1. 1.Biological and Environmental Sciences and Engineering Division, Water Desalination and Reuse Research CenterKing Abdullah University of Science and TechnologyThuwalSaudi Arabia
  2. 2.Department of Civil and Environmental EngineeringThe Pennsylvania State UniversityUniversity ParkUSA

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