Engineered E. coli to generate electricity from wastewater

The organism fared better at converting organic waste to electricity than even some famous and exotic electricity producing microbes
Ameya Paleja
Artist's illustration of E.coli
Artist's illustration of E.coli

Artur Plawgo/iStock 

Scientists at the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland have successfully engineered E.coli to generate electricity from wastewater, a press release said. The engineered bacterium performed even better than organisms known to produce electricity when exposed to wastewater.

Escherichia coli, commonly known as E.coli, is a rod-shaped bacterium commonly found in the lower gut of organisms. However, it has become a favorite of microbial researchers worldwide for the ease with which its genetic structure can be manipulated. It has, therefore, become an indispensable part of research and industrial projects.

The organism may now be on its way to solving wastewater management problems after EPFL researchers equipped it with the genetic machinery to make electricity. Wastewater management is a process that typically requires the expenditure of energy to process organic wastes. However, with the bioengineering organism, the researchers are able to achieve two goals in one: process organic waste and generate electricity as well.

How E.coli can produce electricity

Multiple microbial organisms are occurring in the natural world that can generate electricity on their own. E. coli, however, isn't one of them. The researchers turned to Shewanella oneidensis MR-1, an organism popular for its electricity-generating abilities, and transferred components that it utilizes into their E. coli in the lab.

The Shewanella species can produce electricity using extracellular electron transfer or EET. This is an anaerobic process, - that occurs in the absence of oxygen, where the bacterium transfers electrons from inside the cell to the compounds in the environment.

Apart from the genetic machinery needed to do this, the organism also requires certain catalysts or specific chemicals in the environment for the EET to begin. Interestingly, the EPFL team, led by Ardemis Boghossian, a professor at the Institute of Chemical Sciences and Engineering at EPFL, managed to get the E. coli to function without these molecules being present.

Engineered E. coli to generate electricity from wastewater
Flasks containing the electricity-producing E. coli.

E.coli beats exotic microbes

The researchers found that, unlike exotic electricity-producing microbes, its engineered E.coli was able to carry out EET with a wide range of organic substrates. The tricky part of the engineering process was to ensure that the genetically imported pathway spanned the inner and outer membranes of the cell to ensure that the electrons were given into the environment.

Once that was achieved, the team saw that its approach superseded previous attempts to generate EET in E.coli and produced three times more electricity than before. When the team tested organisms in wastewater from a local brewery, it found that while exotic electricity-producing microbes struggled, its engineered E.coli flourished in the waste.

The application of such an organism is not limited to producing electricity from wastewater alone. It can be further deployed in microbial fuel cells, electrosynthesis, and biosensing applications.

"Our work is quite timely, as engineered bioelectric microbes are pushing the boundaries in more and more real-world applications", said Mohammed Mouhib, the lead author of the paper published today in the journal Joule.

"With all the current research efforts in the field, we are excited about the future of bioelectric bacteria and can’t wait for us and others to push this technology into new scales,” he added.

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