Engineering of Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002 for the photocatalytic production of hydrogen.

In recent years, global warming and the energy crisis driven by fossil fuel usage have underscored the urgent need for the development of renewable energy sources. Hydrogen, as a green and zero-emission energy carrier, presents a promising alternative to fossil fuels and offers a viable solution to current global challenges [1]. Nevertheless, conventional methods, including water electrolysis powered by renewable energy, still suffer from limited thermodynamic efficiency and infrastructure costs [2]. In this scenario, the project “Enzimi artificiali per la produzione fotocatalitica di idrogeno in batteri fotosintetici” (ART-2-HYDROGEN), conducted by the University of Parma, aims to develop a sustainable and autonomous system for hydrogen production using engineered photosynthetic cyanobacteria. The primary objective of the project is the realization of a laboratory-scale prototype capable of efficiently producing molecular hydrogen using only visible light as an energy input. This approach offers a promising route towards scalable, eco-friendly hydrogen production, circumventing the limitations associated with conventional electrochemical methods that often require substantial electrical energy input, frequently derived from non-renewable sources. To achieve this goal, a plasmid containing genes for the expression of an artificial protein anchored to their outer membrane has been produced for the purpose of genetic engineering of Synechocystis sp. PCC 6803 and Synechococcus sp. PCC 7002. This protein is a component of artificial enzymes on cyanobacterial outer membrane. These latter are constructed via the SpyTag/SpyCatcher system and are functionalized with photochemical and redox catalytic centers. Preliminary results indicated that the engineered Synechocystis sp. PCC 6803 expresses the membrane protein linked to the SpyCatcher. The photochemical and redox catalytic centers will bind to the cyanobacterial cell wall through the SpyTag, optimizing interaction with photosynthetic electron donors. By overcoming the limitations of natural enzymatic systems and directly utilizing photosynthetic reducing power, this approach has the potential to establish a new class of sustainable biohybrid devices for clean energy applications