Electrochemical characterization of Geobacter sulfurreducens cells immobilized on graphite paper electrodes

Authors

  • Shweta Srikanth,

    1. Department of Microbiology, BioTechnology Institute, University of Minnesota, 140 Gortner, 1479 Gortner Ave, St. Paul, Minnesota 55108; telephone: 612-624-8619; fax: 612-625-1700
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  • Enrico Marsili,

    1. Department of Microbiology, BioTechnology Institute, University of Minnesota, 140 Gortner, 1479 Gortner Ave, St. Paul, Minnesota 55108; telephone: 612-624-8619; fax: 612-625-1700
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  • Michael C. Flickinger,

    1. Department of Biochemistry, Molecular Biology, and Biophysics, BioTechnology Institute, University of Minnesota, St. Paul, Minnesota
    Current affiliation:
    1. Departments of Microbiology, Chemical and Biomolecular Engineering, and Biomanufacturing Training and Education Center (BTEC), North Carolina State University, Campus Box 7928, Raleigh, North Carolina 27695-7928.
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  • Daniel R. Bond

    Corresponding author
    1. Department of Microbiology, BioTechnology Institute, University of Minnesota, 140 Gortner, 1479 Gortner Ave, St. Paul, Minnesota 55108; telephone: 612-624-8619; fax: 612-625-1700
    • Department of Microbiology, BioTechnology Institute, University of Minnesota, 140 Gortner, 1479 Gortner Ave, St. Paul, Minnesota 55108; telephone: 612-624-8619; fax: 612-625-1700
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Abstract

Bacteria able to transfer electrons to conductive surfaces are of interest as catalysts in microbial fuel cells, as well as in bioprocessing, bioremediation, and corrosion. New procedures for immobilization of Geobacter sulfurreducens on graphite electrodes are described that allow routine, repeatable electrochemical analysis of cell–electrode interactions. Immediately after immobilizing G. sulfurreducens on electrodes, electrical current was obtained without addition of exogenous electron shuttles or electroactive polymers. Voltammetry and impedance analysis of pectin-immobilized bacteria transferring electrons to electrode surfaces could also be performed. Cyclic voltammetry of immobilized cells revealed voltage-dependent catalytic current similar to what is commonly observed with adsorbed enzymes, with catalytic waves centered at −0.15 V (vs. SHE). Electrodes maintained at +0.25 V (vs. SHE) initially produced 0.52 A/m2 in the presence of acetate as the electron donor. Electrical Impedance Spectroscopy of coatings was also consistent with a catalytic mechanism, controlled by charge transfer rate. When electrodes were maintained at an oxidizing potential for 24 h, electron transfer to electrodes increased to 1.75 A/m2. These observations of electron transfer by pectin-entrapped G. sulfurreducens appear to reflect native mechanisms used for respiration. The ability of washed G. sulfurreducens cells to immediately produce electrical current was consistent with the external surface of this bacterium possessing a pathway linking oxidative metabolism to extracellular electron transfer. This electrochemical activity of pectin-immobilized bacteria illustrates a strategy for preparation of catalytic electrodes and study of Geobacter under defined conditions. Biotechnol. Bioeng. 2008;99: 1065–1073. © 2007 Wiley Periodicals, Inc.

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