Generation of molecular hydrogen (H₂) by microalgae and their biocatalysts

Molecular hydrogen (H 2 ) is a potent fuel and required for many industrial synthetic processes. To date, its large-scale production is highly energy-intensive and mostly based on fossil fuels. Biological H 2 generation is widespread in nature and could alleviate many of the impacts associated with current H 2 technologies. Several species of microalgae and cyanobacteria can produce H 2 employing the process of photosynthesis, that is, they use light as the energy-source, and obtain the required electrons from water. Large-scale H 2 production by algae requires specialized fermenters whose design needs expertise both in biology and process engineering. Cell-free or electrode systems employing the natural biocatalysts could be employed alternatively. Because H 2 converting biocatalysts are specialized proteins mostly sensitive towards air, the implementation of cell-free systems on a large scale requires manufacturing and processing pipelines different from existing enzyme technologies.