| Platymonas subcordiformis, a marine green alga, is found to producehydrogen from water and sun light. Hydrogen evolution of this alga can beincreased by 300 folds when adding CCCP (Carbonyl cyanide m-chlorophenylhydrazone). To further improve hydrogen production, it is important to optimizethe bio-process. Immobilization is one of the promising techniques to increase thehydrogen evolution, which therefore becomes the subject of this project.In this thesis, the two stage hydrogen evolution process of P. subcordiformiswas studied. A stirred photo-bioreactor was constructed with the D.O. and pHmonitoring probe. The mechanism of enhanced hydrogen evolution isinvestigated.P. subcordiformis was immobilized in various size of beads under theaddition of 15μM CCCP for H2 evolution. Alginate is the best material for P.subcordiformis cells immobilization. Among 5 different metal cations tested asalginate stabilizing agents, calcium alginate beads increased H2 evolution activityby 20% compared with the control. The optimum bead diameter forphoto-hydrogen evolution is 1mm. At a wide range of cell loading the hydrogenyield is stable. The best dark incubation time is 24h. Under these conditions, theoptimum pH range is broadened with a shift of 0.5-1 pH to the acidic condition.The optimum temperature and light intensity for hydrogen evolution are 25℃and4000 LX respectively.After hydrogen evolution in one cycle, the beads that were washed with 2 %DMSO could be re-cultured. The cells which were re-cultured for 7 days,showed a similar photo-hydrogen evolution activity, in a second cycle. Thisresult indicates that the reuse of immobilized cells for repeated hydrogenevolution is feasible; however the stability of beads needs to be improvedfurther.
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