Enhanced photo-H₂ production of R. faecalis RLD-53 by separation of CO₂ from reaction system

The effect of different gases, CO₂ concentration, and separation of CO₂ from reaction system on photo-fermentation H₂ production was investigated by batch culture in this study. Experimental results showed that different gases (Ar, N₂, CO₂, and air) as gas phase have obviously affected on photo-H₂ production and a high concentration of CO₂ can inhibit the growth and H₂ evolution of Rhodopseudomonas faecalis RLD-53. When CO₂ concentration at 5%, cell increased most rapidly the specific growth rate of 0.489 g/l/h and the specific growth rate fell to be 0.265 g/l/h when CO₂ concentration at 40%. However, the growth of RLD-53 at CO₂ concentration of 60-100% was almost completely inhibited. At CO₂ concentrations of 5% and 10%, the maximum H₂ yield was 2.54 and 2.59 mol-H₂/mol acetate, respectively, and it was similar with the control (2.61 mol-H₂/mol acetate). H₂ not produced when CO₂ concentration at 60-100%. In conclusion, separation of CO₂ from reaction system can stimulate H₂ production in the entire photo-H₂ production process and H₂ yield increased about 12.8-18.85% than the control.