Photocatalytic hydrogen production and polypeptides capable of same

Abstract

An isolated polypeptide comprising a hydrogen generating enzyme attached to a heterologous ferredoxin is disclosed, as well as polynucleotides encoding same, nucleic acid constructs capable of expressing same and cells expressing same. A method for generating hydrogen using the isolated polypeptide is also disclosed.

What is claimed is: 
     
         1 . An isolated polypeptide comprising an algal Fe-only hydrogenase attached to an algal ferredoxin, wherein the polypeptide is capable of generating at least four time more hydrogen from electrons donated thereto from methyl viologen than native hydrogenase. 
     
     
         2 . The isolated polypeptide of  claim 1 , further comprising a linker, capable of linking said algal Fe-only hydrogenase to said plant ferredoxin. 
     
     
         3 . The isolated polypeptide of  claim 2 , wherein said linker is a peptide bond. 
     
     
         4 . The isolated polypeptide of  claim 2 , wherein said linker comprises a repeat sequence of glycine and serine. 
     
     
         5 . An isolated polynucleotide encoding the polypeptide of  claim 1 . 
     
     
         6 . A cell comprising the isolated polynucleotide of  claim 5 . 
     
     
         7 . The cell of  claim 6 , being selected from the group consisting of a cyanobacterial cell, an algal cell and a higher plant cell. 
     
     
         8 . A method of generating hydrogen, the method comprising combining the polypeptide of  claim 1  with an electron donor so as to generate an electron transfer chain, wherein said electron transfer chain is configured such that said electron donor is capable of donating electrons to the polypeptide of  claim 1 , thereby generating hydrogen. 
     
     
         9 . The method of  claim 8 , wherein the generating hydrogen is effected under anaerobic conditions. 
     
     
         10 . The method of  claim 8 , wherein said electron donor is selected from the group consisting of a biomolecule, a chemical, water, an electrode and a combination of the above. 
     
     
         11 . The method of  claim 10 , wherein said biomolecule comprises Photosystem I (PSI) or rhodopsin. 
     
     
         12 . The method of  claim 8 , further comprising harvesting the hydrogen following the generating. 
     
     
         13 . The method of  claim 8 , wherein said combining is effected in a cell-free system. 
     
     
         14 . The method of  claim 8 , wherein said combining is effected in a cellular system. 
     
     
         15 . The method of  claim 14 , wherein said cellular system is selected from the group consisting of a cyanobacteria, an algae and a higher plant. 
     
     
         16 . The method of  claim 14 , further comprising down-regulating an expression of endogenous ferredoxin in said cellular system. 
     
     
         17 . A system comprising the polypeptide of  claim 1  and an electron donor. 
     
     
         18 . The system of  claim 17 , wherein said electron donor comprises an agent selected from the group consisting of a biomolecule, a chemical, water, an electrode and any combination of the above. 
     
     
         19 . The system of  claim 17 , wherein said electron donor comprises PS-1 or rhodopsin. 
     
     
         20 . The system of  claim 18 , wherein said biomolecule is comprised in particles. 
     
     
         21 . The system of  claim 19 , being expressed in cells. 
     
     
         22 . A bioreactor for producing hydrogen, comprising:
 a vessel holding a hydrogen producing system, said system comprising a suspension of the polypeptide of  claim 1  and PSI;   a light providing apparatus comprising an optic fiber, said light providing apparatus being configured to provide light of a selected spectrum to said system; and   a gas liquid separation membrane for separating gas leaving the suspension from said suspension.   
     
     
         23 . The bioreactor of  claim 22 , wherein said system comprises a suspension of cells.