Study On Process Of Biological Hydrogen Production From Indirect Photo-hydrolysis By Unicellular Green Algae

H2 production by reversible hydrogenase in green algae is a perfect approach of H2 production by photo-hydrolysis through solar energy. Although there's a long distance to actual use, but recently developed countries have made a large budget for this project, which is one of the important tasks in the International Hydrogen Energy Agreement. In our country, it has not been taken enough attention. As a principle study of H2 production by green algae, the characters and macro regulation will be investigated in this paper. As expected, the results can offer some useful information for farther development.At the beginning, we first found a sort of marine green alga P. subcordiformis in Huanghai Sea near Dalian, it can be able to evolve H2 photosynthetically. Comparing with Chlamydomonas reinhardtii in our lab, the H2 productivity is same.By the elementary macro regulation of H2 production with 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB),N,N'-dicyclohexylcarbodiimide (DCCD), 3-(3,4-dichlorophenyl)-l,l-dimethylurea (DCMU), sodium dithionate, sulfur-deprivation and cell immobilization, the results show that DCCD, immobilization and sulfur-deprivation has a positive effects on the H2 production. Sulfur-deprivation extends the period of H2 evolution and increasesthe H2 production about 10-fold. Farther study of H2 production by P. subcordiformis in sulfur-deprivation medium, we have got the results as below. The optimal parameter is pH 8 and dark incubation 32 h. Much oxygen was evolved in the course of H2 production. Sodium dithionate and DCMU make the system anaerobic, but Ha production didn't increase, even decreased. By addition of sodium acetate, glucose, heteroauxing in the course of illumination and Fe, Ni in the course of algal growth, the H2 production increases by P. subcordiformis.Unlike the regulation of sulfur-deprivation, CCCP was used to regulate the H2 production by P. subcordiformis, the duration of H2 production is from 4 h to 8 h and increases the H2 productivity about 300-fold. The optimal parameters are cells at late logarithm growing period, dark incubation 32 h, cells density 400 X 104cell/ml, pH 8. By regulation H2 production associating with DCCD, CCCP and DCCD have the synergistic effect and the H2 productivity increases about 500-fold. Comparing with the C. reinhardtii in University of California, Berckely, the rate of H2 evolution by P. subcordiformis is a little higher, but the duration of H2 evolution is only 8 h.Comparing to the effects of sulfur-deprivation and CCCP on Ha production of 6 marine green algae and 7 fresh green algae, it was found that CCCP promoted the H2 production of some C. reinhardtii, among of them the H2 production of C reinhardtii se increased 83-fold.Combined CCCP and DCCD to regulation C. reinhardtii se to produce H2, it was found that DCCD and CCCP have some synergistic effect, but DCCD to regulate C. reinhardtii se and P. subcordiformis respectively, the effect of H2 production is C. reinhardtii se more higher than P. subcordiformis.The mechanisms of H2 production between P. subcordiformis and C. reinhardtiise are different. It was hypothesis that all of the electrons originated from photo-hydrolysis by PS II in P. subcordiformis ,but only 80% in C. reinhardtii se and the other originated from fermentation of sugar and protein. All the electrons for H2 production passed through PQ, cyt b6/f. PC, PS I and Fd to hydrogenase, which catalyze the combination of electrons and protons. The limiting factor of the rate of H2 production is the trans-thylakoidal proton gradient.By measuring the physiological state and biochemical contents of P. subcordiformis and Chlamydomonas reinhardtii se before and after regulation of sulfur-deprivation and CCCP, it was found that the change of two algae have different results. The reasons needs farther study and the recycle of the P. subcordiformis indicates that the changes can be recovered.