title: Comparative metabolic state of microflora on the surface of the anode electrode in a microbial fuel cell operated at different pH conditions.
abstract: The metabolic state of microflora (mixed microbial cultures) in microbial fuel cells (MFCs) is currently unclear. Metabolomic analyses were conducted of microflora growing on the anodic electrodes of MFCs operated at pH 7.0, 5.5, or 4.0 and utilizing starch as the major carbon substrate. A much higher current was produced at pH 7.0 than at pH 5.5 and 4.0, correlating with an increased population ratio of Geobacter species to the total bacteria growing on the electrode. Most intracellular metabolites related to the tricarboxylic acid (TCA) cycle were present at a higher level at pH 7.0 than at pH 5.5 and 4.0, and the levels of metabolites correlated well with the obtained current densities. A high intracellular adenosine triphosphate (ATP)/adenosine diphosphate (ADP) ratio at pH 7.0, compared to at pH 5.5 and 4.0, likewise supported current production. Overall, the metabolomic analyses demonstrated that activation of the TCA cycle and increased ATP generation are critical parameters for electricity generation by microflora.
authors.affiliation: Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo, 657-8501, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Sasaki
authors.affiliation: Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo, 657-8501, Japan.
authors.forename: Kengo
authors.initials: K
authors.lastname: Sasaki
authors.affiliation: Institute for Frontier Science Initiative, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan.
authors.forename: Yota
authors.initials: Y
authors.lastname: Tsuge
authors.affiliation: Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodaicho, Nada-ku, Kobe, Hyogo, 657-8501, Japan. akondo@kobe-u.ac.jp.|Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe, Hyogo, 657-8501, Japan. akondo@kobe-u.ac.jp.|RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan. akondo@kobe-u.ac.jp.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
keywords: ATP generation; Intracellular metabolomic analysis; Microbial fuel cell; Microflora; TCA cycle