Cathodic microbial community adaptation to the removal of chlorinated herbicide in soil microbial fuel cells
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The microbial fuel cell (MFC) that uses a solid electrode as the inexhaustible electron acceptor is an innovative remediation technology that simultaneously generates bioelectricity. Chlorinated pollutants are better metabolized by reductive dechlorination in proximity to the cathode. Here, the removal efficiency of the herbicide metolachlor (ML) increased by 262 and 176% in soil MFCs that were spiked with 10 (C10) and 20 mg/kg (C20) of ML, respectively, relative to the non-electrode controls. The bioelectricity output of the C10 and C20 increased by over two- and eightfold, respectively, compared to that of the non-ML control, with maximum current densities of 49.6 ± 2.5 (C10) and 78.9 ± 0.6 mA/m2 (C20). Based on correlations between ML concentrations and species abundances in the MFCs, it was inferred that Azohydromonas sp., Sphingomonas sp., and Pontibacter sp. play a major role in ML removal around the cathode, with peak removal efficiencies of 56 ± 1% (C10) and 58 ± 1% (C20). Moreover, Clostridium sp., Geobacter sp., Bacillus sp., Romboutsia sp., and Terrisporobacter sp. may be electricigens or closely related microbes due to the significant positive correlation between the bioelectricity generation levels and their abundances around the anode. This study suggests that a directional adaptation of the microbial community has taken place to increase both the removal of chlorinated herbicides around the cathode and the generation of bioelectricity around the anode in bioelectrochemical remediation systems.
KeywordsSoil microbial fuel cell Herbicide metolachlor Electroremediation Azohydromonas sp. Clostridium sp.
This study was financially supported by the Special Fund for Agro-Scientific Research in the Public Interest of China (No. 201503107-7), the Natural Science Foundation of Tianjin (No. 16JCQNJC08800), the National Natural Science Foundation of China (No. 41601536), the National Key R&D Program of China (No. 2017YFD0800704), the Opening Foundation of Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria (2017-05), and the Central Public-interest Scientific Institution Basal Research Fund.
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Conflict of interest
The authors declare that they have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
Informed consent was obtained from all individual participants included in the study.
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