Effects of selected electron transport chain inhibitors on 24-h hydrogen production by Synechocystis sp. PCC 6803

One factor limiting biosolar hydrogen (H2) production from cyanobacteria is electron availability to the hydrogenase enzyme. In order to optimize 24-h H2 production this study used Response Surface Methodology and Q2, an optimization algorithm, to investigate the effects of five inhibitors of the photosynthetic and respiratory electron transport chains of Synechocystis sp. PCC 6803. Over 3 days of diurnal light/dark cycling, with the optimized combination of 9.4 mM KCN (3.1 μmol 1010 cells−1) and 1.5 mM malonate (0.5 μmol 1010 cells−1) the H2 production was 30-fold higher, in EHB-1 media previously optimized for nitrogen (N), sulfur (S), and carbon (C) concentrations (Burrows et al., 2008). In addition, glycogen concentration was measured over 24 h with two light/dark cycling regimes in both standard BG-11 and EHB-1 media. The results suggest that electron flow as well as glycogen accumulation should be optimized in systems engineered for maximal H2 output.