Bio-hydrogen: immobilization of enzymes on electrodes modified by clayey nano-particles

In this work, has been studied the immobilization of enzymes inside micro-films constituted of clayey nano-particles and layer by layer nano-assembling of clayey nano-particles and enzyme. Natural clays have very great specific surface areas, very strong ions exchange capacities and a swelling lamellar structure particularly well adapted to the non denaturing adsorption of proteins and charged enzymes. In this study, the enzymes have been extracted of sulfate-reducing bacteria. The immobilization of this system in clayey films has been studied by micro-gravimetry/electrochemistry coupling and the catalytic activity towards the production and the consumption of hydrogen quantified. At first, the clay is deposited in layer of thickness of the micron on the gold or graphite electrode. When the hydrogenase is immobilized in the clayey film, the electro-enzymatic oxidation of hydrogen occurs inside the clayey structure. An electrode able to measure either the hydrogen consumption or its production on a wide pH range as thus been prepared, by co-immobilization of hydrogenase and of MV2+ in montmorillonite films. The catalytic efficiencies obtained by immobilization in the clayey matrix of the two physiological partners, cytochrome c3 and hydrogenase, are strongly improved. Then, this process has been still improved, and three cytochrome c3/clay bilayers have been superposed without loss of the enzymatic activity. (O.M.)