In Germany, a team of microbiologists from Goethe University Frankfurt has found an enzyme in bacteria that live in the absence of air and bind hydrogen directly to CO2, in this way producing formic acid. The process is completely reversible – a basic requirement for hydrogen storage. These acetogenic bacteria, which are found, for example, in the deep sea, feed on carbon dioxide, which they metabolize to formic acid with the aid of hydrogen. Normally, however, this formic acid is just an intermediate product of their metabolism and further digested into acetic acid and ethanol. But the team led by Professor Volker Müller, head of the Department of Molecular Microbiology and Bioenergetics, has adapted the bacteria in such a way that it is possible not only to stop this process at the formic acid stage but also to reverse it. The basic principle has already been patented since 2013.