'Biofuel cells' could power gadgets with energy drinks

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Scanning electron micrograph of mitochondria (SPL)
Image caption,
The 'biofuel cells' work by borrowing technology from living cells

Battery-like "biofuel cells" could in the future run on an energy drink or even vegetable oil, says a researcher.

A prototype cell has been described at a meeting of the American Chemical Society in the US.

The idea makes use of mitochondria, the power stations that in most living cells turn food into energy.

While applications may be far in the future, the work is a milestone in the integration of parts of a living cell into an electronic device.

Shelley Minteer of St Louis University in Missouri, US, said the devices could in the future replace disposable batteries in some applications.

Dr Minteer has been part of a wider research effort that is borrowing some of nature's tricks for energy production.

Typically this involves the breaking down and rebuilding of molecules in a form that can be used by cells. That process unleashes electrons along the way - electrons that can be corralled and become electricity.

Until now, the efforts of Dr Minteer and her collaborators have focused on the use of enzymes, molecules that are expert at breaking down particular "fuel" molecules such as methanol or glucose.

But the new effort makes use of one of the living cell's tiny constituent parts known as mitochondria.

These are a whole ensemble of enzymes working together to convert a range of "fuel" molecules into a form that cells can directly use.

"In order to be able to completely consume a fuel... you need a whole series of enzymes, anywhere from three, for something simple, to 22 for something like glucose, and you need to get these enzymes to work together," Dr Minteer told BBC News."The mitochondria channel the fuel from enzyme one directly to enzyme two and so on; they do this metabolism far more efficiently than we do by putting a soup of enzymes down on the electrode."

The demonstration device has only been used with simple fuels made of a single type of molecule, as the enzyme approaches have required until now. But future efforts will aim to make the cells work with more familiar sources of energy.

"Mitochondria can break down a wide variety of fuels," Dr Minteer explained.

"That means it can handle fuel mixtures that you might see in, say, an energy drink or a protein shake."

'New domain'

The work remains firmly at the experimental stage, and the researchers are working to change the materials used in the biofuel cells to make them produce more power.

However, the biofuel cell application may not be the most relevant focus, said Plamen Atanassov, director of the Center for Emerging Energy Technologies at the University of New Mexico.

Professor Atanassov told BBC News that the work was a "seminal achievement for biotechnology to be able to introduce [cell parts] into technical devices, especially in the context of energy harvesting," but conceded that "whether it will have an immediate practical application remains to be seen".

He said that "with all the acceleration that technology advances give us, things don't happen overnight", observing that it was a full 50 years between the first demonstration of a standard fuel cell and the Gemini space missions that first used them.

"The main contribution for this work is in the fundamental bridging of biotechnology and nanotechnology," he explained.

"It ultimately may lead to the introduction of a whole new domain of fuels that we would never otherwise be able to tap."

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