Bacteria Discovered To Convert Sugar Directly Into Electricity
By rickyjames, Section News Posted on Mon Sep 08, 2003 at 02:44:58 AM PST
A microbe called Rhodoferax ferrireducens, found in the mud at Oyster Bay, Virginia, has been discovered to transfer electrons directly onto an electrode as it metabolizes sugar into electricity. "You can harvest enough electricity to power a cell phone battery for about four days from a sugar cube," researcher Derek Lovley says. "A cup of sugar contains enough power to light a 60-watt light bulb for about 17 hours." This process is accomplished at an astonishing 80% efficiency and produces only carbon dioxide gas as a byproduct. Previous similar reactions progressed at only 1% efficiency and required toxic metallic mediator chemicals to assist, avoided here because the bacteria grows happily as a slime colony directly on the electrode plates. "I don't want to give the impression that it's 'Back to the Future' where we stuff a banana in the engine and go, but it's a pretty good leap from where microbial fuel cells were before," notes Lovley.
"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.
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