Ongoing global climate change, driven by greenhouse gas emissions and fossil resource exploitation, increases demand for renewable energy sources. Especially green H2 is an emerging emission-free alternative. Biological solar H2 is produced as a byproduct of photosynthesis by green algae and cyanobacteria via hydrogenases. H2 production is electron-dependent and limited by the electron availability. However, recent studies have shown that coupling of the hydrogenase to the Photosystem I (PSI) ensures a spatial proximity to the FeS cluster of PSI subunit PsaC so that the electron flow can be channelled towards H2 production1,2.
The goal of this study is to establish efficient solar H2 production in the filamentous and biofilm forming cyanobacterium Phormidium lacuna.
To achieve this, different types of hydrogenases from various organisms are coupled to a full-length or truncated version of PSI subunit PsaD from P. lacuna and genomically integrated via natural transformation3 into P. lacuna. H2 production of the mutants are then measured via gas chromatography or H2 microsensor relative to the wild type P. lacuna. Via biochemical analyses the coupling of the hydrogenases to PsaD are verified.
Preliminary results from the H2 measurements of a coupled NiFe-hydrogenase to a full-length version of PsaD, show no increase in H2 production, although western blot analyses using an anti-PsaD antibody verify the presence of PsaD chimeras. Sequencing results of the mutants also show a correctly integrated hydrogenase gene.
Based on the results a truncated PsaD is coupled to various hydrogenases which might ensure a closer proximity to the FeS cluster and possibly a higher H2 production yield respectively. Two possible truncated PsaD versions as well as two hydrogenases from Chlamydomonas reinhardtii and Cupriavidus necator are currently investigated.
Appel, J. et al. Nat Energy 5, 458–467; DOI: 10.1038/s41560-020-0609-6 (2020).Kanygin, A. et al. Energy Environ. Sci. 13, 2903–2914; DOI: 10.1039/C9EE03859K (2020).Nies, F. et al. PLOS ONE 15, e0234440; DOI: 10.1371/journal.pone.0234440 (2020).