Immobilization of soybean peroxidase on aminopropyl glass beads: Structural and kinetic studies

The enzyme Soybean Peroxidase (SBP) is able to catalyse the oxidation of a large number of substrates and is characterized by high resistance to both chemical and thermal denaturation. In this contribution SBP was covalently immobilized on aminopropyl glass beads (APG) in order to obtain a solid biocatalyst, useful either in degradation of pollutants or in specific oxidative reactions. Several samples of immobilized SBP were first synthesized and then characterized by means of some experimental techniques (FT-IR, ESR, and UV-visible spectroscopies, gas-volumetric adsorption of nitrogen at 77K, SEM). Moreover, different kinetic measurements were carried out to determine activity and stability properties of these biocatalysts. Our data indicate that (i) the SBP catalytic site was partially modified during the immobilization process, but the enzyme retained about 35% of its specific activity after immobilization, and (ii) the biocatalyst exhibits a significant improvement of SBP stability over time, preserving up to 50% of its initial activity after 70 days of storage and 85% when used in ten consecutive reaction cycles.