HYDROGEN-PEROXIDE PHOTOPRODUCTION BY IMMOBILIZED CELLS OF THE BLUE-GREEN-ALGA ANABAENA-VARIABILIS - A WAY TO SOLAR-ENERGY CONVERSION

A photosystem for hydrogen peroxide photoproduction formed by immobilized cells of the blue-green alga. Anabaena variabilis and the redox mediator methyl viologen is described. Hydrogen peroxide is produced in a redox catalyst cycle in which methyl viologen is reduced by electrons from water obtained by the photosynthetic apparatus of the algae using solar energy, and reoxidized by the introduction of oxygen into the solution. Hydrogen peroxide is produced during methyl viologen re-oxidation in two steps by means of the formation of superoxide. Experimental conditions for maximum photoproduction (catalyst charge, chlorophyll, and agar final concentration for cell immobilization) have been investigated using a continuous photosystem with immobilized A. variabilis as photocatalyst. Under the determined optimum conditions, the photosystem produces hydrogen peroxide at a rate of 100-mu-moles/mg Ch1 . h, maintaining the production for several hours, and with an energy conversion efficiency of about 2%. Taking into account the use of hydrogen Peroxide as fuel, this photosystem can be a useful tool in the storage of solar energy.