Electrochemically active microorganisms from an acid mine drainage-affected site promote cathode oxidation in microbial fuel cells

Type
Article

Authors
Rojas, Claudia
Vargas, Ignacio T.
Bruns, Mary Ann
Regan, John M.

Online Publication Date
2017-08-03

Print Publication Date
2017-12

Date
2017-08-03

Abstract
The limited database of acidophilic or acidotolerant electrochemically active microorganisms prevents advancements on microbial fuel cells (MFCs) operated under low pH. In this study, three MFCs were used to enrich cathodic biofilms using acid mine drainage (AMD) sediments as inoculum. Linear sweep voltammetry showed cathodic current plateaus of 5.5 (± 0.7) mA at about − 170 mV vs Ag/AgCl and 8.5 (± 0.9) mA between − 500 mV to − 450 mV vs Ag/AgCl for biofilms developed on small graphite fiber brushes. After gamma irradiation, biocathodes exhibited a decrease in current density approaching that of abiotic controls. Electrochemical impedance spectroscopy showed six-fold lower charge transfer resistance with viable biofilm. Pyrosequencing data showed that Proteobacteria and Firmicutes dominated the biofilms. Acidithiobacillus representatives were enriched in some biocathodes, supporting the potential importance of these known iron and sulfur oxidizers as cathodic biocatalysts. Other acidophilic chemolithoautotrophs identified included Sulfobacillus and Leptospirillum species. The presence of chemoautotrophs was consistent with functional capabilities predicted by PICRUSt related to carbon fixation pathways in prokaryotic microorganisms. Acidophilic or acidotolerant heterotrophs were also abundant; however, their contribution to cathodic performance is unknown. This study directs subsequent research efforts to particular groups of AMD-associated bacteria that are electrochemically active on cathodes.

Citation
Rojas C, Vargas IT, Bruns MA, Regan JM (2017) Electrochemically active microorganisms from an acid mine drainage-affected site promote cathode oxidation in microbial fuel cells. Bioelectrochemistry 118: 139–146. Available: http://dx.doi.org/10.1016/j.bioelechem.2017.07.013.

Acknowledgements
This research was supported by: Award KUS-I1-003-13 from the King Abdullah University of Science and Technology (KAUST); FONDECYT project 11110112/2011 under the Centro de Desarrollo Urbano Sustentable (CEDEUS)CONICYT/FONDAP/15110020; and the Postdoctoral funding program of the School of Engineering at the Pontificia Universidad Católica de Chile (period 2014–2015).

Publisher
Elsevier BV

Journal
Bioelectrochemistry

DOI
10.1016/j.bioelechem.2017.07.013

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