Unlimited clean energy is often regarded by scientists as the “holy grail,” and now a new study suggests the answer could lie with an enzyme.
Scientists at Monash University in Australia have discovered ‘Huc’ – an enzyme that can convert hydrogen in the air into electricity.
They extracted the enzyme from a common soil-dwelling bacteria called Mycobacterium smegmatis.
Huc allows the bacteria to convert hydrogen in the atmosphere into usable energy so that it can continue to thrive deep underground.
Researchers say that if enough of the enzyme can be harvested, it could allow us to replace solar-powered devices with “air-powered” versions.
Scientists at Australia’s Monash University have discovered ‘Huc’ – a biological catalyst that can convert hydrogen into electrical current
They were able to extract it from a common soil-dwelling bacteria called Mycobacterium smegmatis . Pictured: Scanning electron microscopy image of Mycobacterium smegmatis
Enzymes are substances produced by living organisms that accelerate or enable certain chemical reactions, including those that generate energy.
HOW DOES HUC MAKE ELECTRICITY FROM HYDROGEN?
Huc generates electricity from hydrogen in the bacteria Mycobacterium smegmatis.
After hydrogen bonds to Huc, the electrons are transferred to an iron-sulfur cluster in the enzyme.
These clusters pass the electrons on to a molecule of vitamin menquinone, which has also bound itself to the enzyme at another location.
This transfer turns the menquinone into menaquinol, which travels to the bacteria’s membrane.
There it comes into contact with another enzyme which removes its electrons and turns it back into menquinone.
These electrons then form an electric current on the membrane.
Previous research has shown that some types of bacteria can convert hydrogen in the air into energy to help them survive in nutrient-poor environments.
These include Antarctic soils, volcanic craters and the deep ocean, according to study author Dr. Chris Greening.
For the newspaper, published today in Natureshow the Melbourne-based researchers how to extract one of the enzymes responsible for this conversion reaction.
They then used a new technique called cryogenic electron microscopy — which won the developers a Nobel Prize in 2017 — to determine Huc’s atomic structure.
This technique involves cooling the sample to cryogenic temperatures – below -238°F (-150°C) – and bombarding it with electrons.
These pass through and are captured by a camera to produce an extremely high resolution image.
Specifically, Huc turns hydrogen into electrical energy, and cryogenic electron microscopy also helped scientists understand this process.
“We didn’t know how they did this until now,” Dr Greening said.
The enzyme binds to hydrogen and allows the oxidation – a reaction in which it loses electrons before passing them on to the vitamin menaquinone, or K2.
Menaquinone is then able to transfer electrons to the bacteria’s membrane or another electrode, producing an electrical current as a ‘natural battery’.
Researchers used a new technique called cryogenic electron microscopy — which won the developers a Nobel Prize in 2017 — to determine Huc’s atomic structure (pictured)
Cryogenic electron microscopy images revealed that Huc uses special gas channels (marked) that allow hydrogen to enter and bind to it, but repel oxygen
Mycobacterium smegmatis (pictured) is found all over the world in soil, water and sewage and is easy to grow in the lab. This means there is a cheap, ethical and sustainable way to get their hands on Huc, giving researchers great potential to scale up the process
The scientists were initially confused about how Huc could achieve this, when there is much more oxygen available in the atmosphere to which it could bind.
However, the cryogenic electron microscopy images revealed that it uses special gas channels that allow hydrogen to enter and bind to it, but repels oxygen.
“Huc is extremely efficient,” said Dr. Rhys Griinter.
“Unlike all other known enzymes and chemical catalysts, it consumes hydrogen even below atmospheric levels — just 0.00005 percent of the air we breathe.”
The researchers also found that Huc is still capable of generating electricity even after being frozen or heated to temperatures of 176°F (80°C).
‘This reflects that this enzyme helps bacteria survive in the most extreme environments,’ says PhD student Ashleigh Kropp.
Mycobacterium smegmatis is found in soil, water and sewage around the world, and is easy to grow and manipulate in the lab.
This means there is a cheap, ethical and sustainable way to get their hands on Huc, giving researchers great potential to scale up electricity generation.
“Once we produce Huc in sufficient quantities, the sky is literally the limit to use it to produce clean energy,” said Dr Griinter.
Plastic waste can be a thing of the past thanks to the PET-eating enzyme
Plastic waste dumped in the landfill could be cleaned up faster than expected after engineers developed an enzyme that can break it down in just a few hours.
Millions of tons of plastic are left behind each year, accumulating in landfills and polluting the land and waterways – usually taking ages to break down.
A team from the University of Texas at Austin has developed a new enzyme variant that could boost recycling at scale, reducing the impact of plastic pollution.
The work focused on PET (polyethylene terephthalate), a polymer found in most consumer plastics, including bottles, packaging and some textiles.
The enzyme, called FAST-PETase, was able to complete a “circular process” where the plastic is broken down into smaller parts and chemically reassembled in just 24 hours.
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