TY - JOUR
T1 - Population dynamics and current-generation mechanisms in cassette-electrode microbial fuel cells
AU - Watanabe, Kazuya
AU - Miyahara, Morio
AU - Shimoyama, Takefumi
AU - Hashimoto, Kazuhito
N1 - Funding Information:
Acknowledgments We thank Ayako Matsuzawa and Reiko Hirano for technical assistance. This work was supported by the Exploratory Research for Advanced Technology (ERATO) program of the Japan Science and Technology Agency (JST).
PY - 2011/12
Y1 - 2011/12
N2 - Cassette-electrode microbial fuel cells (CE-MFCs) have been demonstrated useful to treat biomass wastes and recover electric energy from them. In order to reveal electricity-generation mechanisms in CE-MFCs, the present study operated a bench-scale reactor (1 l in capacity; approximately 1,000 cm 2 in anode and cathode areas) for treating a high-strength model organic wastewater (comprised of starch, peptone, and fish extract). Approximately 1 month was needed for the bench reactor to attain a stable performance, after which volumetric maximum power densities persisted between 120 and 150 mW/l throughout the experiment (for over 2 months). Temporal increases in the external resistance were found to induce subsequent increases in power outputs. After electric output became stable, electrolyte and anode were sampled from the reactor for evaluating their current-generation abilities; it was estimated that most of current (over 80%) was generated by microbes in the electrolyte. Cyclic voltammetry of an electrolyte supernatant detected several electron shuttles with different standard redox potentials at high concentrations (equivalent to or more than 100 μM 5-hydroxy-1,4- naphthoquinone). Denaturing gradient gel electrophoresis and quantitative real-time PCR of 16S ribosomal RNA gene fragments showed that bacteria related to the genus Dysgonomonas occurred abundantly in association with the increases in power outputs. These results suggest that mediated electron transfer was the main mechanism for electricity generation in CE-MFC, where high-concentration electron shuttles and Dysgonomonas bacteria played important roles.
AB - Cassette-electrode microbial fuel cells (CE-MFCs) have been demonstrated useful to treat biomass wastes and recover electric energy from them. In order to reveal electricity-generation mechanisms in CE-MFCs, the present study operated a bench-scale reactor (1 l in capacity; approximately 1,000 cm 2 in anode and cathode areas) for treating a high-strength model organic wastewater (comprised of starch, peptone, and fish extract). Approximately 1 month was needed for the bench reactor to attain a stable performance, after which volumetric maximum power densities persisted between 120 and 150 mW/l throughout the experiment (for over 2 months). Temporal increases in the external resistance were found to induce subsequent increases in power outputs. After electric output became stable, electrolyte and anode were sampled from the reactor for evaluating their current-generation abilities; it was estimated that most of current (over 80%) was generated by microbes in the electrolyte. Cyclic voltammetry of an electrolyte supernatant detected several electron shuttles with different standard redox potentials at high concentrations (equivalent to or more than 100 μM 5-hydroxy-1,4- naphthoquinone). Denaturing gradient gel electrophoresis and quantitative real-time PCR of 16S ribosomal RNA gene fragments showed that bacteria related to the genus Dysgonomonas occurred abundantly in association with the increases in power outputs. These results suggest that mediated electron transfer was the main mechanism for electricity generation in CE-MFC, where high-concentration electron shuttles and Dysgonomonas bacteria played important roles.
KW - Electricity
KW - Electron shuttle
KW - Extracellular electron transfer
KW - Phylogeny
KW - Waste treatment
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U2 - 10.1007/s00253-011-3598-3
DO - 10.1007/s00253-011-3598-3
M3 - Article
C2 - 21983705
AN - SCOPUS:82455171830
VL - 92
SP - 1307
EP - 1314
JO - Applied Microbiology and Biotechnology
JF - Applied Microbiology and Biotechnology
SN - 0175-7598
IS - 6
ER -