Monash University Biomedicine Discovery Institute (Melbourne) researcher and former University of Otago PhD graduate Professor Chris Greening is one of three Monash researchers who have found Huc — an enzyme from the common soil bacterium Mycobacterium smegmatis, which consumes hydrogen in the atmosphere to create an electrical current.
Prof Greening discovered Mycobacterium smegmatis consumed hydrogen in 2014 while completing his PhD, which aimed to solve the great disappearing hydrogen gas mystery.
For the past 40 years, scientists have known 80% of all hydrogen released into the air is rapidly removed through soil activity, but exactly what was carrying out the recycling remained unclear.
His work with other Otago scientists provided a more detailed answer, uncovering microbial soil processes that help ensure that hydrogen — an explosive gas — remains at low levels in the atmosphere.
Prof Greening has since gone on to work with fellow Monash researcher Dr Rhys Grinter and PhD student Ashleigh Kropp.
Prof Greening said recent work by the team had shown many bacteria used hydrogen from the atmosphere as an energy source in nutrient-poor environments.
"We've known for some time that bacteria can use the trace hydrogen in the air as a source of energy to help them grow and survive, including in Antarctic soils, volcanic craters, and the deep ocean.
"But we didn't know how they did this, until now."
They used advanced microscopy (cryo-EM) to determine its atomic structure and electrical pathways, pushing boundaries to produce the most resolved enzyme structure reported by this method to date.
They also used a technique called electrochemistry, to show the purified enzyme creates electricity at minute hydrogen concentrations.
"Huc is extraordinarily efficient.
"Unlike all other known enzymes and chemical catalysts, it even consumes hydrogen below atmospheric levels — as little as 0.00005% of the air we breathe."
Laboratory work performed by Ms Kropp showed it was also possible to store purified Huc for long periods.
"It is astonishingly stable.
"It is possible to freeze the enzyme or heat it to 80degC, and it retains its power to generate energy.
"This reflects that this enzyme helps bacteria to survive in the most extreme environments."
Dr Grinter said Huc was a "natural battery" that produced a sustained electrical current from air or added hydrogen.
While the research was still at an early stage, the discovery had considerable potential to develop small air-powered devices, for example as an alternative to solar-powered devices.
He said the bacteria that produced enzymes like Huc were common, and could be grown in large quantities, meaning the world had access to a sustainable source of the enzyme.
A key objective for future work was 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," he said.
