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.