Sweet-toothed bugs generate electricity

Researchers say the electricity generated by mud-dwelling bacteria from a lump of sugar could power a mobile phone for four days

According to a report in October's Nature Biotechnology magazine, researchers at the University of Massachusetts-Amherst have persuaded mud-dwelling bacteria to generate electricity from sugar.

Fuelled by this unfashionable high-carb diet, the recently identified bacterium, Rhodoferax ferrireducens, releases the energy in sugar molecules by removing electrons. In their natural habitat of Virginia bay sediment, the bacteria pass on the electrons to iron compounds, but in the lab the bacteria have been persuaded to donate them to an electrode as an electric current.

This isn't the first time that bioelectricity has been generated by microbes, but previous efforts relied on unwieldy intermediate chemicals called mediators.

Although the new process is efficient -- up to 83 percent of available electrons can be turned into usable electricity -- it is slow and produces a little current over a long period. Early applications may include a charging mechanism to top up more conventional cells, with particular applications in surgical implants running from blood glucose and sensors extracting electricity from sucrose, fructose or other sugars in the immediate environment.

A single lump of household sugar can produce enough electricity through this method to power a cellphone battery for four days, the researchers say.

The university has a track record in researching ways to use naturally occurring bacteria -- called geobacters -- in a variety of technologies, including the extraction of heavy metals from the environment and biodegrading organic contaminates.

The electrical generation process does produce carbon dioxide, a greenhouse gas, but in smaller amounts per watt than existing ways of generating power by fossil fuel, say the researchers.