ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Microbiological Chemistry and Geomicrobiology
This article is part of the Research TopicExtracellular Electron Transfer in MicroorganismsView all articles
Relationship of electrochemical performance and biofilm development of Desulfuromonas acetexigens and Geobacter sulfurreducens in microbial electrolysis cells
Provisionally accepted
- 1Water Chemistry and Water Technology,, Karlsruher Institut fur Technologie Engler-Bunte-Institut, Karlsruhe, Germany
- 2DVGW Research Centre, Engler Bunte Institute, Faculty of Chemical and Process Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
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Desulfuromonas acetexigens has gained attention as a biocatalyst in microbial electrolysis cells (MECs) due to its inability to utilize hydrogen as an electron donor, which favors beneficial Coulombic efficiencies (CE). In this study, the electrochemical performance and biofilm morphology of D. acetexigens were compared with the model organism Geobacter sulfurreducens in flow cell MECs. Biofilm morphology was assessed non-invasively via optical coherence tomography (OCT), providing insight into quantitative parameters, including spatially resolved thickness, biovolume and anode surface coverage. While both species achieved similar maximum current densities when cultivated under identical conditions, D. acetexigens biofilms established faster, generating current after ~ 4 days, whereas G. sulfurreducens exhibited a lag phase of ~ 8 days. Limitations of extracellular electron transfer already occurred at lower average biofilm volumes for D. acetexigens (𝐵𝑉 ̅̅̅̅𝐽̅𝑚𝑎𝑥 ≈ 16 ± 6 µm3 µm-2) than for Geobacter (𝐵𝑉 ̅̅̅̅𝐽̅𝑚𝑎𝑥 ≈ 40 ± 7 µm3 µm-2). One monocultural D. acetexigens cultivation revealed a CE of ~ 96 %, consistent with no detectable hydrogen utilization under the tested condition, while some cultivations showed net acetate increases. Phylogenetic analyses of the latter indicated niche dominance of the target EAM despite homoacetogenic and clostridial contaminants. Production of short-chain fatty acids suggested interspecies metabolic interaction and led to the hypothesis of an electrode-mediated ethanol to acetate fermentation by electroactive microorganisms and ethanol-utilizing contaminants such as the homoacetogen Sporomusa sphaeroides.
Keywords: Biofilm characterization, Biofilm morphology, Desulfuromonas acetexigens, Geobacter, Hydrogen production, Single-chamber microbial electrolysis cell
Received: 24 Nov 2025; Accepted: 29 Jan 2026.
Copyright: © 2026 Rümenapf, Horn and Hille-Reichel. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Andrea Hille-Reichel
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