Optimization of two-staged bio-hydrogen production by immobilized Microcystis aeruginosa

Two-staged bio-hydrogen production was investigated in Microcystis aeruginosa. Stage-I comprised aerobic growth of immobilized algal cells for three days while anaerobic conditions were established in stage-II by sulfur deprivation and photo inhibition under high light intensity. Hydrogen evolution was investigated under fully dark, fully light and partially dark conditions (24 h in dark and light thereafter) using diverse carbon sources and pH values. Full light proved to be most effective with a hydrogen volume of 490 ± 3 ml/L at an average rate of 9.42 ml/h/L. The growth period could be reduced to 2 days in fully dark and fully light conditions. The hydrogen evolution was optimum at pH 9.0 with malt extract as carbon source for M. aeruginosa. However, the optimum pH value was lowered to 8.0 when optical fiber was used as an internal light source during stage-I.

► We optimized two-stage hydrogen production by investigating the effects of light and carbon sources.
► Among various patterns of light, fully light condition proved to be most effective.
► The use of optical fiber slowed down the rate of hydrogen production.
► Malt extract resulted in maximum hydrogen production.