Study On The Regulatory Mechanism Of NDH-1 Mediated Electron During Cyanobacterial H₂ Photoproduction

Photobiological hydrogen production by microalgae uses its unique hydrogenase to generate hydrogen and oxygen from solar energy and water,and hydrogen combustion only produces water as a waster product and can be recycled.As a consequence,this is an important strategy to continuously produce clean energy souces.Although the photobiological hydrogen production by microalgae has many advantages over other hydrogen production methods,the production of hydrogen by microalgae has been faced with various challenges during industrial production.The most important reason is that the regulatory pathway of hydrogen metabolism and the mechanism of photobiological hydrogen production are still unclear,which limits the yield of H2 photoproduction.Therefore,it is very important for the H2 photoproduciton field via regulating hydrogen metabolism routes and clarifying the mechanism for photobiological hydrogen production.A ratio of photosynthesis to respiration plays an important role on the yield of photobiological hydrogen production by microalgae.It is well known that cyanobacterial NDH-1 is involved in celluar respiration and cyclic electron transport around photosystem I.These physiological functions imply that NDH-1 may regulate the hydrogen metabolism pathway via mediating these electron transport chains,thereby regulating the yield of hydrogen production in cyanobacteria.Synechocystis sp.strain PCC 6803(hereafter Synechocysits 6803)is a uncellular prokaryote with a clear genetic background and convenient molecular biological manipulations.The bisulfite addition method owns the excellent characteristics of convenient operation and rapid hydrogen production.Therefore,by using Synechocystis 6803 as experimental materials and bisulfite addition as experimental method,we investigated the effect of NDH-1 mediated electron transport on photobiological hydrogen production.Our results indicated that in the background of5 m M Na HSO3,the accumulated H2 level in ?ndh D2 is about 150% and in ?ndh F1 is about 70% compared with the wild-type(WT).In addition,deletion of ndh D2 increases the respiratory activity,whilst deletion of ndhF1 decreases the respiratory activity.Our results further indicated that compared to the WT,PQ pool in ?ndh D2 was at a oxidized state and in ?ndh F1 was at a reduced state.In summary,in the background of bisulfite addition,?ndh D2 mutant owns a high yield of H2 photoproduction via consuming more photosynthetic electrons by its high respiratory activity,suppressing the over-reduction of photosystem I at electon donor side,and maintaining a high electron transportant rate in photosystem I,thereby increasing photobiological hydrogen production.?ndh F1 mutant has an opposite trend.