(ORDO NEWS) — It may seem surprising, but during difficult times when there is no other food available, some soil bacteria can use traces of hydrogen in the air as a source of energy.
In fact, bacteria remove a staggering 70 million tons of hydrogen annually from the atmosphere, a process that literally shapes the composition of the air we breathe.
We isolated an enzyme that allows some bacteria to consume hydrogen and extract energy from it, and found that it can produce electricity directly when exposed to even a small amount of hydrogen.
As we report in a new paper in the journal Nature, the enzyme could have significant potential to power small sustainable pneumatic devices in the future.
Bacterial genes hold the secret to turning air into electricity
Inspired by this discovery, we analyzed the genetic code of a soil bacterium called Mycobacterium smegmatis that consumes hydrogen from the air.
In these genes is written the blueprint for the production of a molecular machine responsible for consuming hydrogen and converting it into energy for bacteria.
This machine is an enzyme called hydrogenase, and we called it Huc for short.
Hydrogen is the simplest molecule, consisting of two positively charged protons connected by a bond formed by two negatively charged electrons.
Huc breaks this bond, the protons move apart and the electrons are released.
In bacteria, these free electrons then enter a complex circuit called the “electron transport chain” and are used to provide the cell with energy.
Flowing electrons are what electricity is made of, which means that Huc directly converts hydrogen into electrical current.
Hydrogen makes up only 0.00005 percent of the atmosphere. The consumption of this gas at such low concentrations is a challenge that no known catalyst can solve.
In addition, oxygen, which is plentiful in the atmosphere, poisons the activity of most catalysts that consume hydrogen.
Isolation of an enzyme that allows bacteria to live in the air
We wanted to know how Huc overcomes these difficulties, so we set out to isolate it from M. smegmatis cells.
The process for doing this was complex. We first modified the genes in M. smegmatis that allow the bacteria to produce this enzyme.
In doing so, we added a specific chemical sequence to Huc, allowing us to isolate it from M. smegmatis.
It wasn’t easy to get a good look at Hack. It took several years and quite a few experimental dead ends before we finally isolated a high quality sample of the original enzyme.
However, the hard work was worth it as the Huc we received is very stable. . It withstands temperatures from 80℃ to -80℃ without loss of activity.
Molecular scheme for extracting hydrogen from air
After isolating Huc, we began to study it seriously to find out what exactly the enzyme is capable of. How can he turn the hydrogen in the air into a sustainable source of electricity?
Remarkably, we found that even when isolated from bacteria, Huc can consume hydrogen at much lower concentrations than even tiny traces in the air.
In fact, Hooke was still consuming hydrogen, too weak to be detected by our gas chromatograph, the highly sensitive instrument we use to measure gas concentration.
We also found that Hooke is not inhibited by oxygen at all, a property not observed in other hydrogen consuming catalysts.
To evaluate its ability to convert hydrogen into electricity, we used a technique called electrochemistry.
This showed that Huc could convert tiny concentrations of hydrogen in the air directly into electricity, which could power an electrical circuit.
This is a remarkable and unprecedented achievement for a hydrogen consuming catalyst. We used several advanced methods to study how Huc does this at the molecular level.
These include advanced microscopy (cryogenic electron microscopy) and spectroscopy to determine its atomic structure and electrical pathways, pushing the boundaries to obtain the highest resolution enzyme structure ever reported with this method.
Enzymes could use air to power tomorrow’s devices
This research is just beginning, and several technical challenges need to be addressed to realize Huc’s potential.
First, we will need to significantly scale up Huc production. In the lab, we produce Huc in milligrams, but we want to scale it down to grams and eventually kilograms.
However, our work demonstrates that Huc functions as a “natural battery”, producing a constant electric current from air or added hydrogen.
As a result, Huc has significant potential to develop small, environmentally friendly, air-powered devices as an alternative to solar power.
The amount of energy produced by hydrogen in the air would be small, but probably enough to power a biometric monitor, a clock, an LED globe, or a simple computer. With more hydrogen, Huc produces more electricity and can potentially power larger devices.
Another application could be the development of Huc-based bioelectric sensors for hydrogen detection, which can be incredibly sensitive.
Huc can prove invaluable for finding leaks in the infrastructure of our booming hydrogen economy or in healthcare facilities.
In short, this study shows how a fundamental discovery about how bacteria in soil feed can lead to a rethinking of the chemistry of life. Ultimately, this can also lead to the development of future technologies.
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