title: Silica immobilization of Geobacter sulfurreducens for constructing ready-to-use artificial bioelectrodes.
abstract: Microbial electrochemical technologies (METs) rely on the control of interactions between microorganisms and electronic devices, enabling to transform chemical energy into electricity. We report a new approach to construct ready-to-use artificial bioelectrodes by immobilizing Geobacter sulfurreducens cells in composite materials associating silica gel and carbon felt fibres. Viability test confirmed that the majority of bacteria (ca. 70 ± 5%) survived the encapsulation process in silica and that cell density did not increase in 96 h. The double entrapment within the silica-carbon composite prevented bacterial release from the electrode but allowed a suitable mass transport (ca. 5 min after electron donor pulse), making the electrochemical characterization of the system possible. The artificial bioelectrodes were evaluated in three-electrode reactors and the maximum current displayed was ca. 220 and 150 μA cm-3using acetate and lactate as electron donors respectively. Cyclic voltammetry of acetate-fed bioelectrodes revealed a sigmoidal catalytic oxidation wave, typical of more advanced-stage biofilms. The presence of G. sulfurreducens within composites was ascertained by SEM analysis, suggesting that only part of the bacterial population was in direct contact with the carbon fibres. Preliminary analyses of the transcriptomic response of immobilized G. sulfurreducens enlightened that encapsulation mainly induces an osmotic stress to the cells. Therefore, ready-to-use artificial bioelectrodes represent a versatile time- and cost-saving strategy for microbial electrochemical systems.
authors.affiliation: Department of Chemical Engineering, University of Alcalá, Alcalá de Henares, Madrid, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Estevez-Canales
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), 4 place Jussieu, F-75005, Paris, France.
authors.forename: David
authors.initials: D
authors.lastname: Pinto
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), 4 place Jussieu, F-75005, Paris, France.
authors.forename: Thibaud
authors.initials: T
authors.lastname: Coradin
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Collège de France, Laboratoire de Chimie de la Matière Condensée de Paris (LCMCP), 4 place Jussieu, F-75005, Paris, France.
authors.forename: Christel
authors.initials: C
authors.lastname: Laberty-Robert
authors.affiliation: Department of Chemical Engineering, University of Alcalá, Alcalá de Henares, Madrid, Spain.|IMDEA Water Institute, Alcalá de Henares, Spain.
authors.forename: Abraham
authors.initials: A
authors.lastname: Esteve-Núñez
mesh_terms: D001674:Bioelectric Energy Sources; D002244:Carbon; D018914:Cells, Immobilized / Q000378:metabolism*; D004560:Electricity; D004566:Electrodes / Q000382:microbiology*; D020869:Gene Expression Profiling; D045302:Geobacter / Q000235:genetics / Q000378:metabolism*; D008660:Metabolism; D050296:Microbial Viability; D009997:Osmotic Pressure; D058428:Silica Gel
chemical_list: D058428:Silica Gel; D002244:Carbon