AN OBSCURE bacterium that can break down industrial waste while generating an electrical current could form the heart of a novel battery.
It may not be the first bacterium to produce a current as it munches but it is one of the most efficient, says the team working on the bugs at the University of Massachusetts, Amherst. And it isn鈥檛 fussy about what it eats.
The idea of harnessing sugar-eating bacteria to generate power is not new. But most candidates either do not convert the energy in sugars very efficiently or are extremely picky about which sugars they will tuck into.
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Enter Rhodoferax ferrireducens, a bacterium described for the first time this year. Found in iron-rich soil, it breaks down sugars by stripping them of electrons, which it dumps onto iron in its surroundings. A fuel cell can exploit this to generate a current.
R. ferrireducens is particularly good at this process. When connected to an electrical circuit and bathed in a glucose broth the bugs strip 83 per cent of the available electrons from their food (Nature Biotechnology, DOI: 10.1038/nbt867). This compares with a meagre 10 per cent efficiency for most bacteria and suggests that the sugar is almost completely oxidised to CO2 and water.
Unlike some other bacteria, R. ferrireducens is partial to a variety of sugars including xylose, an important waste product generated by paper manufacture. John Greenman, an expert in microbial fuel cells at the University of the West of England, Bristol, says the bugs could be used to clean up paper mill effluent. 鈥淭he advantage is that they can remove every last scrap,鈥� he says.
The system is not capable of producing much power at the moment, partly because the bacteria do not pack tightly enough on the electrode. But Derek Lovley, who did the experiments with Swades Chaudhuri, thinks that porous electrodes would allow more bacteria to get a foothold.