Nature’s way to exploit hydrogen as alternative fuel

More than two billion years ago, ancient microbes already started to benefit from H₂ that, until today, serves either as valuable energy source or as a safety valve to liberate excessive reducing power. Both the formation and consumption of H₂ are catalysed by hydrogenases, which are fascinating biocatalysts exhibiting H₂-conversion rates of up to 10,000 molecules per second. All hydrogenases known so far utilise abundant transition metals such as nickel and iron for catalysis, contrary to man-made H₂ catalysts that predominantly rely on the rare precious metal platinum. This situation currently boosts the research on biological and bioinspired H₂-catalysts. Since transition metals are intrinsically susceptible to dioxygen, the catalytic centers of most hydrogenases become inactivated or even destroyed upon interaction with O₂. This property restricts the application of these biocatalysts to anaerobic conditions.

However, some microorganisms are able to gain energy from the controlled combustion of H₂ with dioxygen. This process is mediated by so-called “oxygen-tolerant” [NiFe]-hydrogenases. In this context, O₂ tolerance is defined as the sustained H₂ cycling in presence of O₂. In my seminar, I will briefly introduce the fundamental aspects of how certain [NiFe]-hydrogenases cope with the detrimental effects of O₂. The second part is dedicated to the application of O₂-tolerant hydrogenases in enzymatic fuel cells and light-driven H₂ production.