Methanothrix enhances biogas upgrading in microbial electrolysis cell via direct electron transfer

[Display omitted] •Bioelectrochemical methane upgrading was achieved via DET.•Biogas with >90% methane content was generated when −500 mV potential was applied.•8.2% of the CO2 was converted to methane under the applied potential condition.•Species from the genera Methanothrix and Azonexus domina...

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Bibliographic Details
Published in:Bioresource technology 2019-11, Vol.291, p.121877-121877, Article 121877
Main Authors: Liu, Chuanqi, Sun, Dezhi, Zhao, Zhiqiang, Dang, Yan, Holmes, Dawn E.
Format: Article
Language:English
Subjects:
acetates
anaerobic digestion
Azonexus
biogas
Biogas upgrading
carbon dioxide
cathodes
CO2 reduction
decarboxylation
Direct electron transfer
Electromethanogenesis
electron transfer
methane
methanogens
Microbial electrolysis cell
microbial electrolysis cells
sludge
transcriptomics
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Summary:[Display omitted] •Bioelectrochemical methane upgrading was achieved via DET.•Biogas with >90% methane content was generated when −500 mV potential was applied.•8.2% of the CO2 was converted to methane under the applied potential condition.•Species from the genera Methanothrix and Azonexus dominated the cathode community.•Genes for DIET-based growth were highly transcribed by Methanothrix on cathode. Bioelectrochemical conversion of CO2 to CH4 is a promising way to increase the calorific value of biogas produced during anaerobic digestion. There are two groups of methanogens enriched in these systems, hydrogenotrophs and acetoclastic methanogens that can also directly accept electrons from an electrode or another microorganism. In this study, a microbial electrolysis cell (MEC) poised at −500 mV (vs. SHE) was operated for biogas upgrading. Methane content in the biogas increased from 71% to >90%, and 8.2% of the CO2 was converted to methane. Methanothrix, an acetoclastic methanogen that can participate in direct electron transfer (DET), and Azonexus, an acetate-oxidizing electrogen, were enriched on the cathode. Transcriptomics revealed that Methanothrix on the cathode were using the CO2 reduction pathway, while Methanothrix in the bulk sludge were using the acetate decarboxylation pathway for production of methane. These results show that stimulation of DET in MEC enhances biogas-upgrading processes.
ISSN:0960-8524
1873-2976
DOI:10.1016/j.biortech.2019.121877