Breakthrough in Electricity-Producing Microbe

University of Massachusetts researchers have made a breakthrough with "Geobacter," a microbe that produces electric current from mud and wastewater. A conservative estimate puts the energy output increase at eight times that of the original organism, potentially allowing applications far beyond that of extracting electricity from mud. "Now, planning can move forward to design microbial fuel cells that convert waste water and renewable biomass to electricity, treat a single home's waste while producing localized power (especially attractive in developing countries), power mobile electronics, vehicles and implanted medical devices, and drive bioremediation of contaminated environments."

Re:I, for one...

[reverseengineer]

Well, this bacterium was originally discovered feeding off the muck at the bottom of the Potomac River. Make of that what you will....

Details from the published paper

[Grond]

First, a citation to the published paper: Hana Yi, et al., Selection of a variant of Geobacter sulfurreducens with enhanced capacity for current production in microbial fuel cells, Biosensors and Bioelectronics, Volume 24, Issue 12, 15 August 2009, Pages 3498-3503.

The extrapolated current density was 7.4 ± 0.1 A/m2. The individual fuel cells produced 14mA, which was sustained for 24 months.

Re:Details from the published paper

[reverseengineer]

Here's the abstract from the paper (with some line breaks inserted for readability):

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.

Re:This is no joke!

[socrplayr813]

I really hope you're kidding (I can't tell).

While I'm not an expert on the technology, I think I can pretty safely say that everything you said is a load of electrified crap.

Re:I, for one...

[killthepoor187]

The sun is powered by nuclear fusion in it's core.

http://science.howstuffworks.com/sun2.htm [howstuffworks.com]

Photos

[anukit]

Some technical info and photos: http://www.geobacter.org/publications/19487117/ [geobacter.org]

Re:Mostly Fact-free FA

[reverseengineer]

In the abstract for the actual journal article, they report the outputs for their mutant strain as current 7.6 amps per square meter and power 3.9 watts per square meter. Which is to say about 0.76mA per square centimeter, so not a gigantic number, but more impressive than what the parent predicts. One important factor that would make power generation using these microbes more attractive is that you could put them in a fuel cell that has a tremendous surface area to volume ratio.

Geobacter is an obligate anaerobe, so it does not require- indeed, cannot tolerate- access to the atmosphere, and it is not photosynthetic. You can buy carbon black, which makes a fine electrode, with a surface area to volume ratio of greater than 50 square meters per cubic centimeter. In the described experiment, they grew the bacterium on graphite, so carbon black should not pose an obstacle. A cubic meter of carbon black would have a surface area of about 50 square kilometers, but a mass of about 2 tons. An output of 3.9W/m^2 over 50 million square meters is 195 megawatts, which isn't shabby considering your input would be wastewater. Now, of course, that number is a wildly optimistic figure- good luck covering that much surface area with a bacterial biofilm- but it does suggest that you could produce enough power to say, make a wastewater treatment facility self-sufficient.

Re:Not So Fast

[devonbowen]

They would be de-energized. But the nutrients would remain. Nutrients are the building blocks needed by photosynthetic organisms to build carbohydrates (nitrogen, phosphorus, potassium, etc). So de-energized compost piles would still be good places for plants to grow.

Devon