Enzyme generates electricity out of thin air
A team of scientists have discovered an enzyme that converts trace amounts of hydrogen in the air into energy to power wearables or act as a sensor.
While the research is at an early stage, the discovery of the enzyme, called Huc, has considerable potential to develop small air-powered devices, for example as an alternative to solar-powered devices. It could also be used as a sensor for hydrogen as it produces electrical current when hydrogen is present. When Huc is placed in an electrical circuit, this current can be measured to determine the hydrogen concentration as a very sensitive sensor.
The research team, led by Dr Rhys Grinter, Ashleigh Kropp, and Professor Chris Greening from the Monash University Biomedicine Discovery Institute in Melbourne, Australia, produced and analyzed the hydrogen-consuming [NiFe]-hydrogenase Huc enzyme from a common soil bacterium called Mycobacterium smegmatis.
“We’ve known for some time that bacteria can use the trace hydrogen in the air as a source of energy,” said Prof Greening. “But we didn’t know how they did this, until now.”
Molecular modelling and simulations were performed by Oxford Biochemistry and Queens College undergraduate Jack Badley and postdoctoral research fellow Dr Ruyu Jiya, under the supervision of Professor Syma Khalid (Professor of Computational Microbiology in the Department of Biochemistry, Oxford). Greening is also an alumnus of the Department of Biochemistry at Oxford.
Many bacteria use hydrogen from the atmosphere as an energy source in nutrient-poor environments. The researchers extracted the enzyme responsible for using atmospheric hydrogen from a bacterium called Mycobacterium smegmatis. They showed that this Huc enzyme turns hydrogen gas into an electrical current. The enzyme is extraordinarily efficient and is able to consume hydrogen below atmospheric levels – as little as 0.00005% in air.
Huc is red–brown in colour, consistent with the presence of multiple metal clusters, and is highly stable at room temperature with a melting temperature of 78.3 °C. It can also be frozen and synthesized in large quantities.
The peer-reviewed paper in Nature is at www.nature.com/articles/s41586-023-05781-7
As might be expected, verification of this capability is key, so the researchers used several cutting-edge methods to reveal the molecular blueprint of atmospheric hydrogen oxidation. They used advanced microscopy (cryo-EM) to determine its atomic structure and electrical pathways.
Electrochemistry was used to demonstrate the purified enzyme creates electricity at minute hydrogen concentrations. Molecular modelling and simulations were used to identify the specific regions of the protein which allow hydrogen gas to enter the active site of the protein where it is transformed, but prevent oxygen getting through.
The bacteria that produce enzymes like Huc are common and can be grown in large quantities, meaning we have access to a sustainable source of the enzyme. Dr. Grinter says that a key objective for future work is to scale up Huc production.
“Once we produce Huc in sufficient quantities, the sky is quite literally the limit for using it to produce clean energy,” said Grinter.