The effect of Ni2+, Fe2+ and Mg2+ concentration on photo-hydrogen production by Rhodopseudomonas faecalis RLD-53

In the present study, the effect of Ni2+ (0–10 μmol/l), Fe2+ (0–200 μmol/l) and Mg2+ (0–15 mmol/l) concentration on photo-hydrogen production from acetate was investigated by batch culture. Results showed that under a proper concentration range, Ni2+ was able to enhance the hydrogen production rate and the hydrogen yield; Fe2+ was able to increase the hydrogen yield, and hydrogen production rate was enhanced only when the culturing time was 24–72 h. Ni2+ and Fe2+ at a higher concentration inhibited cell growth. When Ni2+ and Fe2+ concentrations were 4 μmol/l and 80 μmol/l, respectively, maximal hydrogen yield of 2.87 and 2.78 mol H2/mol acetate was obtained when batch culturing at 35 °C with initial pH 7.0. Mg2+ did not significantly affect hydrogen production and hydrogen yield which maintained at about 2.45 mol H2/mol acetate, but it was favorable to cell growth.