The photosynthesis reaction allows the harvesting of solar energy to chemical energy by splitting water into protons, electrons, and oxygen. Photosynthesis eventually uses these electrons and protons in the sugar metabolism by fixing carbon dioxide. In contrast, certain organisms host genes to efficiently combine electrons and protons to form molecular hydrogen, but this reaction is inhibited by the oxygen from photosynthesis. The PhotoSynH2 project aims at engineering photosynthetic bacteria (cyanobacteria) encoding new genes able to link both reactions while preventing both the inhibition by oxygen and the dissipation of electrons in metabolic reactions. We will employ a novel synthetic biology approach – we call photosynthetic electron focusing – that involves re-engineering the genes involved in photosynthesis and the associated metabolism to completely direct the water-splitting electrons to produce molecular hydrogen. The bacteria will also be engineered to grow in seawater and wastewater, and to harvest solar energy efficiently when deployed in large-scale photobioreactors. We will demonstrate the industrial feasibility and scalability by building a large-scale photobioreactor plant hosting our engineered bacteria. The theoretical estimates for hydrogen production costs with our engineered bacteria and novel photobioreactors could be as low as 5€/kg, rendering our proposed technology cost competitive compared to current systems integrating photovoltaics and electrolysers.

The PhotoSynH2 consortium is led by Prof. Alfonso Jaramillo (CSIC) and funded by the European Commission under the EIC Pathfinder programme.