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Microbial ‘slime’ powered fuel cell

Biotechnology is not all ‘genetically modified foods‘ or ‘silver bullet‘ medical treatments.  At the more mucky end of biotechnology scientists have doubled the power output of a microbial fuel cell that employs an artificial biofilm.

A biofilm — or ‘slime’ — coats the carbon electrodes of the microbial fuel cell and as the bacteria feed, they produce electrons which pass into the electrodes and generate electricity.

Microbial fuel cells, which work in a similar way to a battery, use bacteria to convert organic compounds directly into electricity by a process known as bio-catalytic oxidation.

Bacillus stratosphericus — a microbe commonly found in high concentrations in the stratosphere (10-50 kilometres above the earth’s surface) — is a key component of this new ‘super’ biofilm.

Isolating 75 different species of bacteria from the Wear Estuary, Country Durham, UK, the team tested the power-generation of each one using a microbial fuel cell.

By selecting the best species of bacteria, a kind of microbial “pick and mix,” they were able to create an artificial biofilm, doubling the electrical output of the microbial fuel cell from 105 Watts per cubic metre to 200 Watts per cubic metre.

While still relatively low, this would be enough power to run an electric light and could provide a much needed power source in parts of the world without electricity.

Among the ‘super’ bugs was B. stratosphericus, a microbe normally found in the atmosphere but brought down to Earth as a result of atmospheric cycling processes and isolated by the team from the bed of the River Wear.

As well as B. stratosphericus, other electricity-generating bugs in the mix were Bacillus altitudinis — another bug from the upper atmosphere — and a new member of the phylum Bacteroidetes.

This is the first time individual microbes have been studied and selected in this way. Finding B. stratosphericus was quite a surprise but what it demonstrates is the potential of this technique for the future — there are billions of microbes out there with the potential to generate power.

The use of microbes to generate electricity is not a new concept and has been used in the treatment of waste water and sewage plants.

Until now, the biofilm has been allowed to grow un-checked but this new study shows for the first time that by manipulating the biofilm you can significantly increase the electrical output of the fuel cell.

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