Microbial fuel cell (MFC) research is a rapidly evolving field that lacks established terminology and methods for the analysis of system performance. This makes it difficult for researchers to compare devices on an equivalent basis. The construction and analysis of MFCs requires knowledge of different scientific and engineering fields, ranging from microbiology and electrochemistry to materials and environmental engineering. Describing MFC systems therefore involves an understanding of these different scientific and engineering principles. In this paper, we provide a review of the different materials and methods used to construct MFCs, techniques used to analyze system performance, and recommendations on what information to include in MFC studies and the most useful ways to present results.

Microbial Fuel Cells: Methodology and Technology†

Previous studies have suggested that members of the Geobacteraceae can use electrodes as electron acceptors for anaerobic respiration. In order to better understand this electron transfer process for energy production, Geobacter sulfurreducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate or hydrogen was the electron donor. The electron-accepting electrodes were maintained at oxidizing potentials by connecting them to similar electrodes in oxygenated medium (fuel cells) or to potentiostats that poised electrodes at +0.2 V versus an Ag/AgCl reference electrode (poised potential). When a small inoculum of G. sulfurreducens was introduced into electrode-containing chambers, electrical current production was dependent upon oxidation of acetate to carbon dioxide and increased exponentially, indicating for the first time that electrode reduction supported the growth of this organism. When the medium was replaced with an anaerobic buffer lacking nutrients required for growth, acetate-dependent electrical current production was unaffected and cells attached to these electrodes continued to generate electrical current for weeks. This represents the first report of microbial electricity production solely by cells attached to an electrode. Electrode-attached cells completely oxidized acetate to levels below detection (<10 micro M), and hydrogen was metabolized to a threshold of 3 Pa. The rates of electron transfer to electrodes (0.21 to 1.2 micro mol of electrons/mg of protein/min) were similar to those observed for respiration with Fe(III) citrate as the electron acceptor (E(o)' =+0.37 V). The production of current in microbial fuel cell (65 mA/m(2) of electrode surface) or poised-potential (163 to 1,143 mA/m(2)) mode was greater than what has been reported for other microbial systems, even those that employed higher cell densities and electron-shuttling compounds. Since acetate was completely oxidized, the efficiency of conversion of organic electron donor to electricity was significantly higher than in previously described microbial fuel cells. These results suggest that the effectiveness of microbial fuel cells can be increased with organisms such as G. sulfurreducens that can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode.

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Electricity production by geobacter sulfurreducens attached to electrodes

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(05)00092-2.pdf

Microbial fuel cells: novel biotechnology for energy generation

Microbial fuel cells (MFCs) are typically designed as a two-chamber system with the bacteria in the anode chamber separated from the cathode chamber by a polymeric proton exchange membrane (PEM). Most MFCs use aqueous cathodes where water is bubbled with air to provide dissolved oxygen to electrode. To increase energy output and reduce the cost of MFCs, we examined power generation in an air-cathode MFC containing carbon electrodes in the presence and absence of a polymeric proton exchange membrane (PEM). Bacteria present in domestic wastewater were used as the biocatalyst, and glucose and wastewater were tested as substrates. Power density was found to be much greater than typically reported for aqueous-cathode MFCs, reaching a maximum of 262 ± 10 mW/m2 (6.6 ± 0.3 mW/L; liquid volume) using glucose. Removing the PEM increased the maximum power density to 494 ± 21 mW/m2 (12.5 ± 0.5 mW/L). Coulombic efficiency was 40−55% with the PEM and 9−12% with the PEM removed, indicating substantial oxygen diffusion i...

Electricity generation using an air-cathode single chamber microbial fuel cell in the presence and absence of a proton exchange membrane.

A state of the art review on microbial fuel cells: A promising technology for wastewater treatment and bioenergy.

A novel electrochemically active and Fe(III)-reducing bacterium phylogenetically related to Clostridium butyricum isolated from a microbial fuel cell

Anaerobic digestion sludge was cultivated in an electrochemical bioreactor (ECB) to enrich the hydrogenotrophic methanogens A modified graphite felt cathode with neutral red (NR-cathode) was charged with electrochemical reducing power generated from a solar cell The methane and carbon dioxide collected in a Teflon bag from the ECB were more than 80 ml/l of reactant/day and less than 20 ml/l of reactant/day, respectively, whereas the methane and carbon dioxide collected from a conventional bioreactor (CB) was around 40 ml/l of reactant/day, respectively Moreover, the maximal volume ratios of methane to carbon dioxide (M/C ratio) collected in the Teflon bag from the ECB and CB were 7 and 1, respectively The most predominant methanogens isolated from the CB on the 20 th , 80 th , and 150 th days of incubation were hydrogenotrophs The methanogenic diversity analyzed by temperature gradient gel electrophoresis (TGGE) of the 16S rDNA variable region was higher in the ECB than in the CB The DNA extracted from the TGGE bands was more than 95% homologous with hydrogenotrophic methanogens in the ECB, but was an aceticlastic methanogen in the CB In conclusion, the ECB was demonstrated as a useful system for enriching hydrogenotrophic methanogens and increasing the M/C ratio of the gas product

Enrichment of Hydrogenotrophic Methanogens in Coupling with Methane Production Using Electrochemical Bioreactor

The SCBFC was composed of bilayered cathode, the outside of which was modified with Fe 3+ (graphite-Fe(III) cathode) and the inside of which was porcelain membrane, and of an anode which was modified with Mn 4+ (graphite-Mn(IV) anode). The graphite-Fe(II), graphite-Mn(IV), and porcelain membrane were designed to have micropores. The outside of the cathode was exposed to the atmosphere and the inside was contacted with porcelain membrane. In all SCBFCS the graphite-Fe(III) was used as a cathode, and graphite-Mn(IV) and normal graphite were used as anodes, for comparison of the function between normal graphite and graphite-Mn(IV) anode. The potential difference between graphite-Mn(IV) anode and graphite-Fe(III) cathode was about 0.3 volt, which is the source for the electron driving force from anode to cathode. In chemical fuel cells composed of the graphite-Mn(IV) anode and graphite-Fe(III) cathode, a current of maximal 13 mA was produced coupled to oxidation of NADH to NAD - ; the current was not produced in SCBFC with normal graphite anode. When growing and resting cells of E. coli were applied to the SCBFC with graphite-Mn(IV) anode, the electricity production and substrate consumption were 6 to 7 times higher than in the SCBFC with normal graphite anode, and when we applied anaerobic sewage sludge to SCBFC with graphite-Mn(IV) anode, the electricity production and substrate consumption were 3 to 5 times higher than in the SCBFC with normal graphite anode. These results suggest that useful electric energy might possibly be produced from SCBFC without electron mediators, electrode-active bacteria, and extra energy consumption for the aeration of catholyte, but with wastewater as a fuel.

Application of Single-Compartment Bacterial Fuel Cell (SCBFC) Using Modified Electrodes with Metal Ions to Wastewater Treatment Reactor

In a bacterial denitrification test with Pseudomonas sp. and anaerobic consortium, more nitrates and less substrate were consumed but less metabolic nitrite was produced under an anaerobic H 2 condition rather than under N 2 condition. In a bioelectrochemical denitrification test with the same organisms, the electrochemically reduced neutral red was confirmed to be a substitute electron donor and a reducing power like H 2 . The biocatalytic activity of membrane-free bacterial extract, membrane fraction, and intact cell for bioelectrochemical denitrification was measured using cyclic voltammetry. When neutral red was used as an electron mediator, the electron transfer from electrode to electron acceptor (nitrate) via neutral red was not observed in the cyclic voltammogram with the membrane-free bacterial extract, but it was confirmed to gradually increase in proportion to the concentration of nitrate in that of the membrane fraction and the intact cell of Pseudomonas sp.

Bioelectrochemical denitrification by Pseudomonas sp. or anaerobic bacterial consortium

Cloning, Sequencing and Functional Expression in Escherichia coli of dmc Gene Encoding Periplasmic Tetraheme Cytochrome c3from Desulphovibrio desulphuricans M6

Yong Keun Park

Papers

A novel electrochemically active and Fe(III)-reducing bacterium phylogenetically related to Clostridium butyricum isolated from a microbial fuel cell

Enrichment of Hydrogenotrophic Methanogens in Coupling with Methane Production Using Electrochemical Bioreactor

Application of Single-Compartment Bacterial Fuel Cell (SCBFC) Using Modified Electrodes with Metal Ions to Wastewater Treatment Reactor

Bioelectrochemical denitrification by Pseudomonas sp. or anaerobic bacterial consortium

Cloning, Sequencing and Functional Expression in Escherichia coli of dmc Gene Encoding Periplasmic Tetraheme Cytochrome c3from Desulphovibrio desulphuricans M6