[NewCandle] Evolving microbes for fuel cells/xmutation?

[Keith Nagel]

Striking another blow for Darwin, researchers at U of M. have evolved
a natural bacteria to be more efficient at producing anodic
current. One wonders what the limiting factor might be: at
those current densities, with active carbon substrates, one
could produce some serious power. 

http://www.sciencedaily.com/releases/2009/07/090729210821.htm

On a related subject, was there ever any followup research
concerning baterial transmutations as described by Kevran
et al. I found nothing on Jed's site.

K. 

>From the abstract:
Geobacter sulfurreducens produces current densities in
microbial fuel cells that are among the highest known for pure
cultures. The possibility of adapting this organism to produce
even higher current densities was evaluated. A system in which
a graphite anode was poised at 400 mV (versus Ag/AgCl) was
inoculated with the wild-type strain of G. sulfurreducens,
strain DL-1. An isolate, designated strain KN400, was
recovered from the biofilm after 5 months of growth on the
electrode. KN400 was much more effective in current production
than strain DL-1. This was apparent with anodes poised at 400
mV, as well as in systems run in true fuel cell mode. KN400
had current (7.6 A/m2) and power (3.9 W/m2) densities that
respectively were substantially higher than those of DL1 (1.4
A/m2 and 0.5 W/m2).

On a per cell basis KN400 was more effective in current
production than DL1, requiring thinner biofilms to make
equivalent current. The enhanced capacity for current
production in KN400 was associated with a greater abundance of
electrically conductive microbial nanowires than DL1 and lower
internal resistance (0.015 versus 0.130 /m2) and mass transfer
limitation in KN400 fuel cells. KN400 produced flagella,
whereas DL1 does not. Surprisingly, KN400 had much less outer-
surface c-type cytochromes than DL1. KN400 also had a greater
propensity to form biofilms on glass or graphite than DL1,
even when growing with the soluble electron acceptor,
fumarate.

These results demonstrate that it is possible to enhance the
ability of microorganisms to electrochemically interact with
electrodes with the appropriate selective pressure and that
improved current production is associated with clear
differences in the properties of the outer surface of the cell
that may provide insights into the mechanisms for microbe-
electrode interactions.