Effect of the photosynthesis inhibitors on hydrogen production by non-heterocyst cyanobacterial strains

Abstract

The energy of cyanobacterial hydrogen (H2) produced via bio-photolysis is being investigated as a potential solution to early-century environmental challenges. The main limiting factors of cyanobacterial H2 photoproduction are the availability of electrons for [NiFe]-hydrogenase (H2ase) and the suppression of bidirectional H2ase activity induced by O2 acquired from water molecules splitting in photosystem II. The current study investigated how photosynthetic inhibitors (PIs) affected H2 production in non-N2-fixing cyanobacteria. Study findings revealed a rather high H2 yield in Synechocystis sp. PSU 1262, as well as a beneficial (14.2-fold) influence of 500 μmol KCN on the H2 production by the aforesaid strain. A 12/6-h light/dark cycle increased H2 production by 80.3% in cells supplemented with 500 μmol KCN. Under the optimised conditions, the photobiological H2 production of Synechocystis sp. PSU 1262 increased from 49.6 to 1552 nmol H2 mg−1Chl a h−1. PIs suppressed chlorophyll a concentration under illumination, lowering the O2 levels, which enhanced bidirectional H2ase activity in Synechocystis sp. PSU 1262 cells. Applying varied light modes, preceded by the incorporation of PIs at optimal concentrations in H2 production by research cyanobacterial strains, improved the H2 yield and contributed significantly to the research originality.