Researchers at the
University of Massachusetts
Amherst have used forced evolution to get
more power from bacterial fuel cells.
According to the University, a film of
natural geobacter
sulfurreducens strain DL-1 can produce
1.4A/m2 and 0.5 W/m2 in a fuel cell.
By culturing DL-1 in a graphite electrode at -400mV (against
Ag/AgCl) for five months, selective pressure produced a strain that
the University claims can produce densities of 7.6A/m2
and 3.9W/m2.
"In very short order we increased the power output by
eight-fold, as a conservative estimate," said researcher Derek
Lovley. "With this, we've broken through the plateau in power
production that's been holding us back in recent years."
Geobacter has hair-like 'pili' 3 to 5nm in diameter and several
microns long that can move electrons.
"Pili are the secret to this particular microbe's ability to
produce electric current from organic waste and sediment," said the
University. "Geobacter's pili seem critical for forming the
bio-film which aids transfer of the electron products to iron in
soil and sediment."
The evolves strain, dubbed KN400, has more pili than DL-1, and
its films have a lower resistance: 15mΩ/m2 compared with
130 for DL-1.
Lovely was part of a team that discovered geobacter, which
respires iron and other metals instead of oxygen, in sediment under
the Potomac River in 1987.
Originally investigated as a way of cleaning up contamination,
it's electro-activity was discovered in 2002.
The electrically conductive pili were discovered in 2005.
Taking a reading from fuel cells