The enzyme Huc has been discovered in a bacterium called Mycobacterium smegmatis, which uses it to produce energy underground using atmospheric hydrogen.
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Scientists have been in pursuit of a source of clean energy for a long time. And the novel study of the discovery of an enzyme that can produce electricity from the air can be the key to new possibilities.
This has been proven by a study published in the journal Nature on March 8 by a team at Monash University in Melbourne, Australia.
Mycobacterium smegmatis is a soil-dwelling bacterium that, in extreme conditions, uses hydrogen in the atmosphere to produce energy.
Prof. Chris Greening, of the Monash University Biomedicine Discovery Institute, said that they already knew about the bacteria that could use a trace of hydrogen in the air for producing energy to survive and grow in conditions like volcanic craters, Antarctic soils, and deep oceans.
This led to the quest for an enzyme or protein present in that bacteria that could produce energy by absorbing hydrogen.
Dr. Rhys Grinter from Monash University revealed that they planned and further managed to isolate the enzyme and demonstrated that the enzyme itself could turn hydrogen present in the air to produce small amounts of electricity. He added that it took them nearly five years to find the enzyme, which they have named Huc.
This is a non-pathogenic, fast-growing bacteria that is used in labs to study the structure of the cell wall of its disease-causing relative, Mycobacterium tuberculosis.
The bacteria are generally found in soil all over the world and are known for their ability to generate energy from hydrogen present in the air. In this way, the bacteria can survive in nutrient-poor and extreme environments like volcanic craters, Antarctic soils, and deep oceans.
Scientists first isolated the Huc enzyme using chromatography, a technique used for the separation of components of a mixture.
Then, the atomic structure of the enzyme was determined using cryogenic electron microscopy, a technique that earned its developers a Nobel Prize in 2017.
After the investigations, it was verified that Huc could turn hydrogen into electrical energy. Dr. Greening stated that they did not know how the bacteria converted hydrogen into electricity until then.
However, at first, scientists were confused by how Huc was able to achieve it considering that there is far more oxygen available in the atmosphere to bind to.
By using cryogenic electron microscopy, it was revealed that special gas channels are used that allow the entry of hydrogen to bind to them and repel oxygen.
Scientists could also understand the procedure behind this using cryogenic electron microscopy.
It was revealed that the enzyme binds to hydrogen present in the air and enables its oxidation, a reaction in which electrons are lost, before passing them on to K2 or vitamin Menaquinone.
Menaquinone then transfers the electrons to the membrane of the bacterium or the other electrode, which produces an electric current. This behaves as a “natural battery”.
Generation of Electricity
At the centre of Huc is an active site, that contains charged ions of iron and nickel.
When the hydrogen molecules (that have one electron and two protons) enter the active site they are trapped between iron and nickel ions and lose their electrons. These electrons are then sent by the enzyme into a flowing stream, generating a current.
Dr. Grinter has stated that the enzyme Huc is extraordinarily efficient.
The enzyme can also consume hydrogen below atmospheric levels, which is unlike any other known chemical catalysts and enzymes. This means it can consume hydrogen, which is as little as 0.00005 percent of what is found in the air we breathe.
It has been revealed that the enzyme can also be stored in its purified form for a long time.
According to Ashleigh Kropp, the enzyme can retain its power to generate electricity even if it has been frozen or heated up to 80⁰ C (176⁰ F) reflecting the fact that the bacteria can survive in an extreme environment.
For now, the researchers have only shown that a small amount of the enzyme can produce an equally small amount of electricity.
According to the researchers, since the bacteria that can produce Huc is easy to grow in large quantities, it can be enough to power small devices.
Grinter said that if the production is scaled up, it could be used for small devices like a wristwatch or even produce bigger hydrogen fuel cells for cars.
The sky is the limit if the possibilities are to be considered.