“We found that it had the unique ability to oxidize sugars with the reduction of iron oxides,” Lovley stated in a press release. This was of interest to us because last year we reported in Science that another group of iron reducers, known as Geobacter, could transfer electrons to electrodes. We reasoned that Rhodoferax might be able to do the same thing, which proved to be the case.
The bioreaction was found to work not only with glucose but also with the fruit sugar fructose, with sucrose (found in sugar cane and sugar beet) and even xylose, a sugary byproduct of wood and straw. In addition, the bacterium is rugged and stable, able to grow at temperatures ranging from four to 30 C, with 25 C the optimum. All of the fuel is used up. If engineering obstacles can be overcome and manufacturing techniques devised, a power cell based on this process could one day be as compact as household batteries.
The downside, as noted in coverage in USA Today, is that it’s a slow process. That cup of sugar could take weeks to digest. Still, a slow but steady trickle of electricity can be used to charge up a battery, which can then discharge large amounts of power when needed.
Added Lovley,“There are still issues with getting a high enough voltage and converting the sugar to electricity fast enough. Although the process is highly efficient, it is slow. And as the process is right now, were not talking about a lot of power. Its barely enough to run a calculator, but we did it using unpolished graphite as a receptor. There are almost certainly better electroactive materials. The other thing that limits this is that the microorganisms have to attach to the surface of the receptor, so were working with polymer scientists, such as Tom Russell at UMass Amherst, to find a receptor with a maximally uneven surface, so more microbes can attach to it.”
The organism was isolated in Lovleys microbiology lab at the University of
Massachusetts Amherst from aquifer sediments in Virginia during a U.S. Department of Energy study. The research was supported by the Office of Naval Research and the Defense Advanced Research Projects Agency, as well as the Department of Energy. Professor Lovleys and postdoctoral researcher Swades Chaudhuri’s findings will appear in the October issue of Nature Biotechnology.