Multiple paths of electron flow to current in microbial electrolysis cells fed with low and high concentrations of propionate
- 819 Downloads
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.
KeywordsElectron 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.
- Belay N, Sparling R, Daniels L (1986) Relationship of formate to growth and methanogenesis by Methanococcus thermolithotrophicus. Appl Environ Microb 52(5):1080–1085Google Scholar
- Fernandez AS, Hashsham SA, Dollhopf SL, Raskin L, Glagoleva O, Dazzo FB, Hickey RF, Criddle CS, Tiedje JM (2000) Flexible community structure correlates with stable community function in methanogenic bioreactor communities perturbed by glucose. Appl Environ Microbiol 66(9):4058–4067CrossRefPubMedPubMedCentralGoogle Scholar
- Hashsham SA, Fernandez AS, Dollhopf SL, Dazzo FB, Hickey RF, Tiedje JM, Criddle CS (2000) Parallel processing of substrate correlates with greater functional stability in methanogenic bioreactor communities perturbed by glucose. Appl Environ Microbiol 66(9):4050–4057CrossRefPubMedPubMedCentralGoogle Scholar
- Kamlage B, Gruhl B, Blaut M (1997) Isolation and characterization of two new homoacetogenic hydrogen-utilizing bacteria from the human intestinal tract that are closely related to Clostridium coccoides. App Environ Microbiol 63(5):1732–1738Google Scholar
- Klindworth A, Pruesse E, Schweer T, Peplies J, Quast C, Horn M, Glöckner FO (2012) Evaluation of general 16S ribosomal RNA gene PCR primers for classical and next-generation sequencing-based diversity studies. Nucleic acids Res:gks808Google Scholar
- Lovley DR, Giovannoni SJ, White DC, Champine JE, Phillips E, Gorby YA, Goodwin S (1993) Geobacter metallireducens gen. nov. sp. nov., a microorganism capable of coupling the complete oxidation of organic compounds to the reduction of iron and other metals. Arch Microbiol 159(4):336–344CrossRefPubMedGoogle Scholar
- Rittmann BE, McCarty PL (2001) Environmental biotechnology. McGraw-Hill New YorkGoogle Scholar
- Siegert M, Li X-F, Yates MD, Logan BE (2015) The presence of hydrogenotrophic methanogens in the inoculum improves methane gas production in microbial electrolysis cells. Front Microbiol 778(5):1–12Google Scholar
- Werner JJ, Garcia ML, Perkins SD, Yarasheski KE, Smith SR, Muegge BD, Stadermann FJ, DeRito CM, Floss C, Madsen EL (2014) Microbial community dynamics and stability during an ammonia-induced shift to syntrophic acetate oxidation. Appl Environ Microbiol 80(11):3375–3383CrossRefPubMedPubMedCentralGoogle Scholar