title: Enhanced electrical power generation using flame-oxidized stainless steel anode in microbial fuel cells and the anodic community structure.
abstract: BACKGROUND
  Carbon-based materials are commonly used as anodes in microbial fuel cells (MFCs), whereas metal and metal-oxide-based materials are not used frequently because of low electrical output. Stainless steel is a low-cost material with high conductivity and physical strength. In this study, we investigated the power generation using flame-oxidized (FO) stainless steel anodes (SSAs) in single-chambered air-cathode MFCs. The FO-SSA performance was compared to the performance of untreated SSA and carbon cloth anode (CCA), a common carbonaceous electrode. The difference in the anodic community structures was analyzed using high-throughput sequencing of the V4 region in 16S rRNA gene.
  
  
  RESULTS
  Flame oxidation of SSA produced raised node-like sites, predominantly consisting of hematite (Fe2O3), on the surface, as determined by X-ray diffraction spectroscopy. The flame oxidation enhanced the maximum power density (1063 mW/m(2)) in MFCs, which was 184 and 24 % higher than those for untreated SSA and CCA, respectively. The FO-SSA exhibited 8.75 and 2.71 times higher current production than SSA and CCA, respectively, under potentiostatic testing conditions. Bacteria from the genus Geobacter were detected at a remarkably higher frequency in the biofilm formed on the FO-SSA (8.8-9.2 %) than in the biofilms formed on the SSA and CCA (0.7-1.4 %). Bacterial species closely related to Geobacter metallireducens (>99 % identity in the gene sequence) were predominant (93-96 %) among the genus Geobacter in the FO-SSA biofilm, whereas bacteria with a 100 % identity to G. anodireducens were abundant (>55 %) in the SSA and CCA biofilms.
  
  
  CONCLUSIONS
  This is the first demonstration of power generation using an FO-SSA in MFCs. Flame oxidation of the SSA enhances electricity production in MFCs, which is higher than that with the common carbonaceous electrode, CCA. The FO-SSA is not only inexpensive but also can be prepared using a simple method. To our knowledge, this study reveals, for the first time, that the predominant Geobacter species in the biofilm depends on the anode material. The high performance of the FO-SSA could result from the particularly high population of bacteria closely related to G. metallireducens in the biofilm.
authors.affiliation: Animal Waste Management and Environment Division, NARO Institute of Livestock and Grassland Science2, Ikenodai, Tsukuba, 305-0901 Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamashita
authors.affiliation: Animal Waste Management and Environment Division, NARO Institute of Livestock and Grassland Science2, Ikenodai, Tsukuba, 305-0901 Japan.
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Ishida
authors.affiliation: Faculty of Agriculture, Utsunomiya University, 350 Minemachi, Utsunomiya, 321-8505 Japan.
authors.forename: Shiho
authors.initials: S
authors.lastname: Asakawa
authors.affiliation: Agrogenomics Research Center, National Institute of Agrobiological Sciences (NIAS), 1-2 Owashi, Tsukuba, 305-8634 Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kanamori
authors.affiliation: Agrogenomics Research Center, National Institute of Agrobiological Sciences (NIAS), 1-2 Owashi, Tsukuba, 305-8634 Japan.
authors.forename: Harumi
authors.initials: H
authors.lastname: Sasaki
authors.affiliation: Animal Waste Management and Environment Division, NARO Institute of Livestock and Grassland Science2, Ikenodai, Tsukuba, 305-0901 Japan.
authors.forename: Akifumi
authors.initials: A
authors.lastname: Ogino
authors.affiliation: Agrogenomics Research Center, National Institute of Agrobiological Sciences (NIAS), 1-2 Owashi, Tsukuba, 305-8634 Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Katayose
authors.affiliation: Biological Resources and Post-harvest Division, Japan International Research Center for Agricultural Sciences, 1-1 Owashi, Tsukuba, 305-8686 Japan.
authors.forename: Tamao
authors.initials: T
authors.lastname: Hatta
authors.affiliation: Animal Waste Management and Environment Division, NARO Institute of Livestock and Grassland Science2, Ikenodai, Tsukuba, 305-0901 Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yokoyama
keywords: Community structure; Energy recovery; Flame oxidation; Geobacter; Microbial fuel cell; Stainless steel; Wastewater treatment