A Redox Hydrogel Protects the O2-Sensitive [FeFe]-Hydrogenase from Chlamydomonas reinhardtii from Oxidative Damage

The integration of sensitive catalysts in redox matrices opens up the possibility for their protection from deactivating molecules such as O-2. [FeFe]-hydrogenases are enzymes catalyzing H-2 oxidation/production which are irreversibly deactivated by O-2. Therefore, their use under aerobic conditions has never been achieved. Integration of such hydrogenases in viologen-modified hydrogel films allows the enzyme to maintain catalytic current for H-2 oxidation in the presence of O-2, demonstrating a protection mechanism independent of reactivation processes. Within the hydrogel, electrons from the hydrogenase-catalyzed H-2 oxidation are shuttled to the hydrogel-solution interface for O-2 reduction. Hence, the harmful O-2 molecules do not reach the hydrogenase. We illustrate the potential applications of this protection concept with a biofuel cell under H-2/O-2 mixed feed.