Researchers have engineered the common E. Coli bacteria to produce electricity from a wide range of common sources, including wastewaster. The findings, presented in the journal Joule, could be a boon for wastewater treatment while also producing energy.
Traditional wastewater treatment plants consume a large amount of energy and produce about 3 percent of greenhouse gas emissions. Using bacteria to convert wastewater into electricity technology could help reduce that environmental impact.
“Because our technology relies on E. coli, a common microbe, we have the flexibility to apply this technology anywhere in the world, using a wide range of waste sources,” says Ardemis Boghossian, a professor at the Institute of Chemical Sciences and Engineering of the Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland.
Plus, she says, the finding has “significant implications for bioelectronics. It allows us to create electronic devices that are powered by living microbes, and the applications are nearly limitless.”
Bacteria can break down carbon-containing organic compounds into other chemicals. Scientists have tapped this bacterial ability to turn human waste into fuel, and to engineer special types of bacteria that can digest sugars to make the building blocks of fuels, drugs, and plastics such as nylon.
Some microbes also naturally produce electricity when they consume organic materials. But they can only do so in the presence of certain chemicals, says Boghossian. Researchers have tried to harness bacteria to produce electricity by making battery-like devices called microbial fuel cells.
“Microbial fuel cells use an electrode to extract electricity from bacteria,” she explains. “Optimizing the interface between the electrode and the bacteria is key to maximizing the performance of this technology.” While previous work focused on engineering the electrodes to optimize this interface, Boghossian and her colleagues focused on engineering the bacteria.
The EPFL researchers transferred genetic components from Shewanella oneidensis MR-1, a microbe that has electricity-producing prowess, into E. coli. This gave E. Coli the ability to transfer electrons from inside the cell into the outside environment to produce electricity.
E. Coli encompasses a large group of different kinds of bacteria. Some are harmless and live in the intestines humans and animals, but other strains can cause illness when consumed typically through food. E. Coli are also some of the most widely studied microbes in the world.
Unlike the other electricity-producing microbes, the engineered E. Coli was able to generate electricity by breaking down a range of organic materials and without catalysts. In tests on wastewater that the team collected a local brewery, the exotic microbes couldn’t survive, while the engineered E. Coli were able to flourish.
Implementation is a very real next step for this technology, Boghossian says. That’s because the engineered bacteria are highly complementary with microbial fuel cells, which are already in use at many wastewater plants.
These existing fuel cells rely on bacteria that are inefficient at producing electricity, or bacteria that can produce electricity from only a limited range of sources. Adding the new engineered bacteria could boost electricity production, she says. “In the end, we would need to rely on both engineered bacteria and electrodes to create a technology that is ideal for producing electricity from waste.”
Source: Mohammed Mouhib et al. Extracellular electron transfer pathways to enhance the electroactivity of modified Escherichia coli. Joule, 2023.