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Electricity from wastewater – the tantalising promise of synthetic biology

Prof. Alfonta's lab is developing a way of placing chemical wires into E. coli - making a biological fuel cell. Image: Shutterstock/SARANS
Prof. Alfonta's lab is developing a way of placing chemical wires into E. coli - making a biological fuel cell. Image: Shutterstock/SARANS

Microbes that produce electricity by feeding on waste could be available within a decade, thanks to cutting-edge technology which is able to adapt the way that organisms function.

Biologically powered batteries are a direct result of synthetic biology – a branch of biology that uses the building blocks of living organisms and rearranges them to adapt the way they behave.

The idea of a biologically powered battery isn’t new, however up until now it’s been impossible to make one which produces enough current to be of any practical use.

Previous types of biological fuel cells have in general either used enzymes or microorganisms to turn fuel into electricity. However, the problem is that enzymes need to be replenished, and microorganisms transfer electrons too slowly.

Now technology part-developed under the PROTLEGO project, funded by the European Research Council (ERC), has used synthetic biology to produce the best of both worlds, developing organisms which don’t need to be replenished and can transfer electrons quickly, thereby producing useable amounts of electricity.

Chemical wire

Under the PROTLEGO project, which runs until 2015, principal investigator Professor Lital Alfonta at the Ben-Gurion University of the Negev, Israel, and her team have worked on a way to add new unnatural amino acids to proteins, incorporating new chemicals into them and, as a result, changing their functions.

‘Electrons flow through the molecular wire that we introduced into the system.’

Professor Lital Alfonta at the Ben-Gurion University of the Negev, Israel.

Now they are using this method to create a chemical wire in the bacteria Escherichia coli which allows electrons to move easily – making a biological fuel cell.

‘When we bring the fuel in, it is oxidised and electrons flow through the molecular wire that we introduced into the system, to the electrode,’ said Prof. Alfonta.

‘The outcome of using such a wired system was that we received a very high power output.’

At the moment, the biological fuel cells the researchers have developed use glucose as a fuel, so the next step is to adapt them to use renewable energy sources.

‘Glucose is a very expensive fuel – it’s not the fuel of the future,’ Prof. Alfonta said.

Instead she hopes that plant-like organisms called algae may be a good fuel source. ‘It’s very easy to cultivate, it doesn’t need fresh water and it doesn’t need land to be grown. It basically converts the energy of the sun to complex fuels that can be digested by different enzymes,’ she said.

The ultimate goal is to use wastewater as a fuel, but that is up to a decade away as more work needs to be done to make sure the organisms are safe to release into the real world.

‘Since we have so many questions, I think it’s too early to release our bacteria to the bigger systems,’ said Prof. Alfonta. ‘We’re still trying to answer very basic questions.’

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