Full Paper Testing of Bacteria Gluconobacter oxydans and Electron Transport Mediators Composition for Application in Biofuel Cell Anatoly Reshetilov , a * Sergey Alferov , b Ludmila Tomashevskaya, a Ol)ga Ponamoreva c a G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms RAS, 142290 Pushchino, Moscow, Russia *e-mail: anatol@ibpm.pushchino.ru b Pushchino State University, 142290 Pushchino, prospect Nauki 7, Russia c Tula State University, 300600 Tula, prospect Lenina 92, Russia Received: July 6, 2006 Accepted: July 27, 2006 Abstract The dependence of EMF, current and voltage at a fixed load, and the fuel cell inner resistance on anolyte composition has been studied using microbial fuel cell (MFC) model. Strain Gluconobacter oxydans subsp. industrius VKM B-1280 was a biocatalyst; glucose was used as a fuel. The following anolyte compositions were considered: (1) water-soluble mediator 2,6-dichlorophenol indophenol (DCPIP) in combination with suspension and immobilized bacteria and (2) hydrophobic mediators ferrocene and 1,1’-dimethylferrocene in combination with immobilized bacteria. It was shown that DCPIP in combination with immobilized bacteria versus the cell suspension increases the generated EMF for 36%, current for 25%, power for 56%, and inner resistance for 14%. Ferrocene seems to be more preferable as compared with 1,1’-dimethylferrocene. Ferrocene gives higher values of the generated EMF (for 8%) and current (for 47%), as well as decreases the inner resistance of MFC for 38%. The proposed system can be used for rapid qualitative and quantitative assessment of the “fuel-cell-mediator-electrode” interaction under charge transfer and is used in the search of effective anolyte compositions. Keywords: Microbial biofuel cell, Electron transfer mediators, Bacteria Gluconobacter oxydans , Glucose DOI: 10.1002/elan.200603624 1. Introduction Biofuel cell (BFC) converts the energy from biochemical oxidation of organic substrates into electric energy. At early stages of development (in the 1960s) it was planned to use BFCinspacearea[1,2].Inthe1970–90s,thequestionasto the use of BFC for partial solution of energy and environ- mental problems was discussed [3]. Recently, the possibility of using BFC as EMF sources for microdevices implanted into human organism to provide the functioning of drug dosage systems has been studied [1, 4, 5]. BFC development seems to be prospective for each of the above applications and this fact stimulates the corresponding research. A number of reviews are dedicated to theoretical analysis and consideration of the parameters of typical BFC developed by now [1, 5, 6]. Biocatalysts for BFC may be enzymes or microbial cells [5, 6], and cells of warm-blooded animals [7]. Each type of biocatalystshasitsownadvantages.So,enzymesarethought to be more preferable for fuel cell as compared with cells, becausetheyareexpectedtoincreasetheconversionrateof substrates, to facilitate the maintenance of the set, and to stabilize the parameters of the biofuel cell [8]. At the same time, microorganisms have been proved useful for mini- BFC generating high-density currents [3]. Microbial cells are more preferable as compared with enzymes, because in this case the biomaterial costs much less. Microorganisms generally oxidize a wide range of substrates and thus are more universal catalysts for various organic substances as fuels. The application of acetobacteria Gluconobacter genus as a biocatalyst is a study of interest. The cells of these microorganisms are characterized by membrane localiza- tion of the key metabolic enzymes, which facilitates the accessofsubstratestoactiveenzymecenters[9].Membrane localizationoftheenzymesissupposedtobeafactorofeasy access for electron transport mediators as well. Micro- organisms of this genus have been effectively used in microbial mediator biosensors which, in respect to the principlesofmeasurement,areclosetoBFC.Thepossibility of EMF generation by BFC containing the bacterial suspension of Gluconobacter oxydans subsp. industrius VKM B-1280, with 2,6-dichlorophenol indophenol as medi- ator, was shown experimentally [10]. The parameters describing BFC functioning are gener- ated power, current density, voltage at open circuit, and currentatshortcircuit.Nolessimportantparameterisinner resistance, which influences the above energy parameters. In this study with a simplified BFC model, the comparative assessmentsofparameterswereperformedforthefollowing anolytereservoircompositions:(1)“water-solublemediator – cell suspension”, (2) “water-soluble mediator – immobi- lized cells”, and (3) “immobilized cells – water-insoluble mediators”. Such succession of compositions has been 2030 Electroanalysis 18, 2006, No.19-20, 2030–2034 # 2006 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim