Figure 1: Effect of nitrate and fructose on the initial hydrogen production rate in Synechocystis sp. PCC 6803-GT. The hydrogen production was evaluated by the measurements of the amount of hydrogen per culture volume after 48 h incubation of cells in HEPES buffer solutions (a) without nitrate or fructose, (b) without nitrate and with 50 mmol/L fructose, (c) with 18 mmol/L NaNO3 and without fructose, and (d) with 50 mmol/L fructose and 18 mmol/L NaNO3. All experiments were carried out in duplicate.