Oxygen-tolerant hydrogenases in hydrogen-based technologies

To develop a viable H-2 technology, production of H-2 has to be significantly enlarged by using renewable resources. One option of generating H-2 is the photosynthetic conversion of sunlight and water directly to H-2 and O-2. Photosystems and hydrogenases are currently being exploited for the design of efficient H-2-producing systems that require highly active and O-2-tolerant biocatalysts. This communication focuses on two challenging features: hydrogenases that produce H-2 in the presence of O-2, and direct electron transfer between photosystem I (PS I) and hydrogenase. The latter is accomplished by connecting both modules through a protein fusion or a synthetic molecular wire. These are first steps toward a photosynthetic microbial cell or a semi-synthetic system that may be employed in future H-2-based technologies.