Scientists Engineer E. Coli Bacteria to Generate Electricity
A team of researchers from the Swiss Federal Institute of Technology Lausanne (EPFL) has engineered one of the most common bacteria, Escherichia coli (E. coli), to generate electricity from brewery wastewater, surpassing the latest bioengineering strains in the process. This breakthrough was reported by Science Alert.
Since 1911, when British mycologist Michael Cressé Potter observed that yeast in beer production could produce electricity, scientists have sought to harness the potential of microbial fuel cells. However, the efficiency of these tiny "bioreactors" has been too low for practical use. Moreover, microbes have proven to be selective in the substrates they metabolize to generate electricity.
"While there are exotic microbes that naturally produce electricity, they can only do so in the presence of specific chemicals," explains senior author and chemical engineer Artemis Bogosyan from EPFL.
To enhance E. coli's ability to generate electricity, researchers modified its genome to include instructions for protein complexes found in Shewanella oneidensis, one of the most well-known bacterial electricity generators. S. oneidensis produces an electron flow when it reduces metals, an electrical signal used, for example, in detecting toxic metals like arsenic in prototypes of systems.
By incorporating all the components of the electricity generation pathway from S. oneidensis into E. coli, lead author Mohammed Muhib, Bogosyan, and their colleagues doubled its electroactivity compared to previously created strains (which included only part of S. oneidensis).
However, these experiments were conducted in a single chamber under laboratory conditions. The true test of any potential technology lies in its ability to function in industrial settings.
Previous research explored using algae to treat brewery wastewater. Breweries need to treat water used for grain washing and tank cleaning before disposal, as it contains a complex mixture of sugar, starch, alcohol, and yeast that can lead to undesirable microbial growth if not treated.
Therefore, the team tested their E. coli system on a sample of wastewater collected from a local brewery in Lausanne, Switzerland, which the modified bacteria readily consumed over 50 hours.
"Our bioengineered electric bacteria thrived exponentially, feeding on these waste products," says Bogosyan, while S. oneidensis, used as a comparator, couldn't metabolize mixed effluents.
This makes the engineered E. coli much more suitable for treating industrial wastewater, even though its electricity generation potential is still slower than that of S. oneidensis, according to the researchers.
E. coli's appetite for various chemical substrates also means that the engineered bacteria could be adapted for different waste streams and feedstocks.
In any case, researchers will need to determine whether their modified E. coli can process industrial volumes. If successful, this could lead to significant energy savings.