A team of microbiologists at Goethe University has succeeded in storing and releasing hydrogen in a controlled manner with the help of bacteria.
This is an important step in the search for CO2-neutral energy sources in the interest of climate protection. The corresponding paper has now been published in the renowned scientific journal “Joule”.
The fight against climate change makes the search for CO2-neutral energy sources increasingly urgent. Green hydrogen, which is produced from water with the help of renewable energies such as wind power or solar energy, is one of the hopefuls.
However, transporting and storing the highly explosive gas is difficult, and researchers worldwide are searching for chemical and biological solutions. A team of microbiologists at Goethe University have found an enzyme in bacteria that live in the absence of air that binds hydrogen directly to CO2, producing formic acid. This process is completely reversible, a basic requirement for hydrogen storage. These acetogenic bacteria, which occur for example in the deep sea, feed on carbon dioxide, which they metabolize to formic acid with the help of hydrogen.
Normally, however, this formic acid is only an intermediate product of their metabolism, which is further digested into vinegar and ethanol. But the team led by Prof. Volker Müller, head of the Department of Molecular Microbiology and Bioenergetics, has adapted the bacteria so that this process can not only be stopped at the formic acid stage, but also reversed. The basic principle has already been patented since 2013.
“The measured rates of CO2 reduction to formic acid and back are the highest ever measured, and they are many times greater than with other biological or chemical catalysts; the bacteria also do not require rare metals or extreme conditions such as high temperatures and high pressures for the reaction, as chemical catalysts do, but do the job at 30 °C and normal pressure,” Müller reports. Now the group is reporting a new success, the development of a biobattery for hydrogen storage using the aforementioned bacteria.
A system in which the bacteria first store hydrogen in one and the same bioreactor and then release it again, as stably as possible over a long period of time, makes sense for municipal or domestic hydrogen storage. Fabian Schwarz, who wrote his doctoral thesis on this topic in Prof. Müller’s laboratory, has succeeded in developing such a bioreactor.
He fed the bacteria with hydrogen for eight hours and then put them on a hydrogen diet during a 16-hour overnight phase. The bacteria then released the hydrogen completely. Genetic engineering techniques were used to eliminate the unwanted formation of acetic acid. “The system ran extremely stably for at least two weeks” explains Fabian Schwarz, who is pleased that this work has been accepted for publication in “Joule”, a prestigious journal for chemical and physical engineering. “It is rather unusual for biologists to publish in this high-profile journal,” Schwarz is pleased to say.
Volker Müller had already dealt with the properties of these special bacteria in his doctoral thesis – and spent years doing basic research on them. “I was interested in how these first organisms organized their life processes and how they managed to grow in the absence of air with simple gases such as hydrogen and carbon dioxide,” he explains. Climate change added a new, applied dimension to his research. Surprisingly for many engineers, biology offers thoroughly practicable solutions.
