title: Conductive iron oxides accelerate thermophilic methanogenesis from acetate and propionate.
abstract: Anaerobic digester is one of the attractive technologies for treatment of organic wastes and wastewater, while continuous development and improvements on their stable operation with efficient organic removal are required. Particles of conductive iron oxides (e.g., magnetite) are known to facilitate microbial interspecies electron transfer (termed as electric syntrophy). Electric syntrophy has been reported to enhance methanogenic degradation of organic acids by mesophilic communities in soil and anaerobic digester. Here we investigated the effects of supplementation of conductive iron oxides (magnetite) on thermophilic methanogenic microbial communities derived from a thermophilic anaerobic digester. Supplementation of magnetite accelerated methanogenesis from acetate and propionate under thermophilic conditions, while supplementation of ferrihydrite also accelerated methanogenesis from propionate. Microbial community analysis revealed that supplementation of magnetite drastically changed bacterial populations in the methanogenic acetate-degrading cultures, in which Tepidoanaerobacter sp. and Coprothermobacter sp. dominated. These results suggest that supplementation of magnetite induce electric syntrophy between organic acid-oxidizing bacteria and methanogenic archaea and accelerate methanogenesis even under thermophilic conditions. Findings from this study would provide a possibility for the achievement of stably operating thermophilic anaerobic digestion systems with high efficiency for removal of organics and generation of CH4.
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Chihaya
authors.initials: C
authors.lastname: Yamada
authors.affiliation: Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, 2-17-2-1 Tsukisamu-Higashi, Toyohira, Sapporo, Hokkaido 062-8517, Japan; Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita-9 Nishi-9, Kita-ku, Sapporo, Hokkaido 060-8589, Japan; Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan.
authors.forename: Souichiro
authors.initials: S
authors.lastname: Kato
authors.affiliation: Kajima Technical Research Institute, 2-19-1 Tobitakyu, Chofu-shi, Tokyo 182-0036, Japan.
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Ueno
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. Electronic address: amishii@mail.ecc.u-tokyo.ac.jp.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ishii
authors.affiliation: Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Igarashi
mesh_terms: D019342:Acetic Acid / Q000378:metabolism*; D000693:Anaerobiosis; D001105:Archaea / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism*; D004579:Electron Transport; D005285:Fermentation; D005290:Ferric Compounds / Q000378:metabolism; D052203:Ferrosoferric Oxide / Q000378:metabolism*; D008697:Methane / Q000378:metabolism*; D011422:Propionates / Q000378:metabolism*; D013696:Temperature
chemical_list: D005290:Ferric Compounds; D011422:Propionates; C092844:ferric oxyhydroxide; C029658:propionic acid; D008697:Methane; D019342:Acetic Acid; D052203:Ferrosoferric Oxide
keywords: CH(4); Conductive iron oxides; Degradation of organic acid; Magnetite; Methane production; Methanogenic degradation; Syntrophic relationship; Thermophilic anaerobic digestion; Thermophilic methane fermentation