Enhanced electrical power generation using flame-oxidized stainless steel anode in microbial fuel cells and the anodic community structure. Issue 1 (December 2016) - Yamashita, Takahiro
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 (Fe2 O3 ), on the surface, as determined by X-ray diffraction spectroscopy. The flame oxidation enhanced the maximum power density (1063 mW/m2 ) 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 genusGeobacter 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 toGeobacter metallireducens (>99 % identity in the gene sequence) were predominant (93–96 %) among the genusGeobacter in the FO-SSA biofilm, whereas bacteria with a 100 % identity toG. 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 predominantGeobacter 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 toG. metallireducens in the biofilm.