Abstract Download (8.38MB)

Name (Title):
Kazuhito Hashimoto (Professor)
Affiliation:
Department Applied Chemistry, The University of Tokyo
ERATO/JST, HASHIMOTO Light Energy Conversion Project
Address:
7-3-1, Hongo, Bunkyo-ku Tokyo 113-8656, Japan
Email: hahsimoto@light.t.tu-tokyo.ac.jp
Home Page: http://www.light.t.u-tokyo.ac.jp/english/
Presentation Title:
Bacterial Electron Transfer and Electricity Generation in the Genus Shewanella : A Strategy to
Improve Current Generation
Abstract:
It was first shown more than 90 years ago that
microorganisms can generate electricity in a course of
metabolism. This has attracted much recent attentions for its
application in biological fuel cells. However, serious
problems of low current density of this system compared to
the existing platinum- or enzyme-based chemical fuel cells
have prevented them from being applied in energy
production systems for practical use. We found that this
problem can be solved essentially by introducing the
bacteria/semiconductor network on electrode surfaces.
Herein we report the c-Cyt-mediated ET from Shewanella
loihica PV-4 to semiconducting α-Fe2O3 film electrodes, and
the subsequent findings of drastic improvements of microbial
current generation achieved by the self-constructed Shewanella/α-Fe2O3 electrical network.
Extracellar ET from Shewanella loihica PV-4 to ITO electrode was studied using a singlechamber
three-electrode system with lactate being used as a carbon source and an electron donor. A
flat ITO glass was used as a working electrode. The current was generated immediately after adding
the suspension of condensed cells into the reactor. The current increased gradually with time and
reached a constant value It is likely that the current generation was a consequence of direct electrical
connections of the cells to the ITO electrode, followed by the injection of electrons from c-Cyt to the
electrode.
It is to be noted that the current, however, showed practically no dependence on the cell density.
In-situ optical microscope observation of the ITO electrode revealed that the surface was completely
covered with the cells and there were abundant planktonic cells in the reactor solution. This implies
that the current generation from S. loihica are dominated by the cells attached directly to the
electrode surface. In turn, inefficient long-distance ET processes of S. loihica is a main reason for
low current density of this system.
Upon adding the α-Fe2O3 colloids, however, the current
showed a steep rise until reaching the maximum value at
approximately 50 times larger. SEM observation revealed
the formation of thick layers composed of cells and
colloids, in which the outer surfaces of the cells are
covered with the α-Fe2O3 colloids. These results suggest
that the drastic enhancement (> 300-fold) of the redox
currents is due to the interconnection of S. loihica through
α-Fe2O3 network acting as ET conduits, which enables a
number of cells located at a long distance from the electrode to participate in the current generation.
References:
(1) R. Nakamura, F. Kai, A. Okamoto, G.J. Newton, K. Hashimoto, Angew. Chem. Int. Ed. 2009,
48, 508 –511
(2) R. Nakamura, K. Ishi, K. Hashimoto, Angew. Chem. Int. Ed. 2009 (in press)
34
Oral Presentation 34