TITLE:
Suppression of Methane Gas Emissions and Analysis of the Electrode Microbial Community in a Sediment-Based Bio-Electrochemical System
AUTHORS:
Yoshiyuki Ueno, Yoji Kitajima
KEYWORDS:
Microbial Fuel Cell, Bio-Electrochemical System, Methanogenesis, Electricigens, Green House Gas
JOURNAL NAME:
Advances in Microbiology,
Vol.4 No.5,
April
24,
2014
ABSTRACT: The effects of
bioelectrochemical systems (BESs) for the suppression of methane gas emissions
from sediment were examined using a laboratory-scale reactor system. Methane
gas emissions from acetate were suppressed by approximately 36% from control
based on the installation of a BES in which carbon-graphite electrodes were
buried in sediment and arbitrarily set at certain oxidative potentials (+300 mV
vs Ag/AgCl) using a potentiostat. Meanwhile, methane gas emissions increased
in the BES reactor where the electrode potential was set at -200 mV. Results obtained from pyrotag sequencing analysis of the microbial community on the
surface of the buried electrodes targeting 16S rRNA genes demonstrated that the
genusGeobacterhad drastically
propagated in a sample from the reactor where the electrodes were buried.
Quantitative analysis of 16S rRNA genes of archaea also revealed that the
archaeal population had decreased to approximately 1/6 of its original level
on the electrode of the BES set at +300 mV. This implied that the
oxidation-reduction potential (ORP) in the sediment was raised to the
inhibition level for methanogenesis in the vicinity of the buried electrode.
Analysis of electron flux in the experiment revealed that electrons
intrinsically used for methanogenesis were recovered via current generation
in the sediment where a potential of +300 mV was set for the electrode,
although most electrons donated from acetate were captured by oxygen
respiration and other electron-accepting reactions. These results imply that
BES technology is suitable for use as a tool for controlling re-dox-dependent
reactions in natural environments, and that it also brought about changes in
the microbial population structure and methanogenic activity in sediment.