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Hydrocarbons released during oil spills are persistent in marine sediments due to the absence of suitable electron acceptors below the oxic zone. Here, we investigated an alternative bioremediation strategy to remove toluene, a model monoaromatic hydrocarbon, using a bioanode. Bioelectrochemical reactors were inoculated with sediment collected from a hydrocarbon-contaminated marine site, and anodes were polarized at 0 mV and + 300 mV (versus an Ag/AgCl [3MKCl] reference electrode). The degradation of toluene was directly linked to current generation of up to 301 mAm(-2) and 431 mAm(-2) for the bioanodes polarized at 0 mV and + 300 mV, respectively. Peak currents decreased over time even after periodic spiking with toluene. The monitoring of sulfate concentrations during bioelectrochemical experiments suggested that sulfur metabolism was involved in toluene degradation at bioanodes. 16S rRNA gene-based Illumina sequencing of the bulk anolyte and anode samples revealed enrichment with electrocatalytically active microorganisms, toluene degraders, and sulfate-reducing microorganisms. Quantitative PCR targeting the alpha-subunit of the dissimilatory sulfite reductase (encoded by dsrA) and the alpha-subunit of the benzylsuccinate synthase (encoded by bssA) confirmed these findings. In particular, members of the family Desulfobulbaceae were enriched concomitantly with current production and toluene degradation. Based on these observations, we propose two mechanisms for bioelectrochemical toluene degradation: (i) direct electron transfer to the anode and/or (ii) sulfide-mediated electron transfer.
Author(s): Daghio M, Vaiopoulou E, Patil SA, Suarez-Suarez A, Head IM, Franzetti A, Rabaey K
Publication type: Article
Publication status: Published
Journal: Applied and Environmental Microbiology
Year: 2016
Volume: 82
Issue: 1
Pages: 297-307
Print publication date: 01/01/2016
Online publication date: 23/10/2015
Acceptance date: 17/10/2015
ISSN (print): 0099-2240
ISSN (electronic): 1098-5336
Publisher: American Society for Microbiology
URL: http://dx.doi.org/10.1128/AEM.02250-15
DOI: 10.1128/AEM.02250-15
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