Hydrogenases from the hyperthermophilic bacterium Aquifex aeolicus: electrocatalysis of the hydrogen production/consumption reactions at carbon electrodes

Hydrogenase-Coated Carbon Nanotubes for Efficient H2 Oxidation

“…When the hydrogenase was deposited directly on an unmodified MWCNTs electrode, catalytic currents were detected, although considerably lower than those obtained by covalent immobilization. Direct adsorption of hydrogensases on carbon electrodes and their electrocatalytic properties have been described before by several authors. ,− However, Figure shows that in this case the operational stability of the immobilized hydrogenase was very low; after 6 days there was seldom any catalytic current of H 2 oxidation. On the contrary, the electrodes with hydrogenase immobilized by covalent bonds were very stable.…”

“…Direct adsorption of hydrogensases on carbon electrodes and their electrocatalytic properties have been described before by several authors. 5,[8][9][10][11] However, Figure 5 shows that in this case the operational stability of the immobilized hydrogenase was very low; after 6 days there was seldom any catalytic current of H 2 oxidation. On the contrary, the electrodes with hydrogenase immobilized by covalent bonds were very stable.…”

“…The attachment of this type of redox enzymes to electrodes is of great interest as it has potential applications for development of biological water electrolysis or fuel cells , and electrochemical biosensors that would improve H 2 technology as an energetic alternative to fossil fuels combustion. Several authors have reported direct electron transfer of hydrogenase molecules adsorbed on macroscopic carbon electrodes. ,− Recently, we have reported a method for covalent immobilization of a hydrogenase with adequate orientation for direct electron transfer toward a highly oriented pyrolytic graphite edge (PGE) electrode that allowed a very stable current due to electroenzymatic oxidation of H 2 …”

“…Several authors have reported direct electron transfer of hydrogenase molecules adsorbed on macroscopic carbon electrodes. 5,[8][9][10][11] Recently, we have reported a method for covalent immobilization of a hydrogenase with adequate orientation for direct electron transfer toward a highly oriented pyrolytic graphite edge (PGE) electrode that allowed a very stable current due to electroenzymatic oxidation of H 2 . 12 In this work we report the fabrication of a gold electrode based on microelectronic technologies to which multiwalled carbon nanotubes (MWCNTs) have been grown, 13 electrochemically functionalized, and then covalently modified with hydrogenase molecules in order to obtain a miniaturized biotechnological device that gives high current densities of H 2 oxidation with enhanced stability.…”

Enhanced Oxygen-Tolerance of the Full Heterotrimeric Membrane-Bound [NiFe]-Hydrogenase of Ralstonia eutropha

“…9b , 13 In addition to crystallography and spectroscopy, protein film electrochemistry (PFE) has been invaluable in elucidating the inactivation–reactivation mechanism. 4e , 7g , 14 PFE provides a direct way for monitoring catalytic turnover by adsorbing the protein on the surface of an electrode (typically a graphite electrode) and controlling the enzymatic activity via the electrode potential. PFE studies have shown that [NiFe]-hydrogenases are inactivated at high potentials in anaerobic conditions and that inactivation is faster at low H 2 concentrations (in the low μM range).…”