Hybrid Ordered Mesoporous Materials as Supports for Permanent Enzyme Immobilization Through Non-covalent Interactions

The mild nature of enzyme-support binding through non-covalent interactions, which allows catalytic activity preservation and easy immobilization procedure, can be exploited and improved by the use of hybrid ordered mesoporous materials as supports. These materials combine the presence of organic groups (used to promote interactions with side groups of surface amino acids of the protein molecule) with a uniform porous network. Their pore connectivity permits a good diffusion of the enzyme when the pore diameter is higher than molecular dimensions of the enzyme. This leads to high immobilization and good diffusion of substrates and products and, therefore, to high catalytic efficiency. The design of the support is based on the knowledge of the protein characteristics. In this work a lipase and laccase immobilization has been considered. Materials functionalized with hydrophobic groups are designed to immobilize lipase, with a hydrophobic domain on the external surface. Laccase has an isoelectric point of 4.2, so the support is functionalized with amine groups to enhance electrostatic interactions at pH close to neutral. Moreover, enzyme dimensions must be known in order to design a material with the appropriate pore diameter. Pore size must be enough to permit a good diffusion of the enzyme molecules, while a close match of both sizes limits protein unfolding and thus preserves catalytic activity, increases enzyme stability, and makes the immobilization irreversible. The systems based on non-covalent interactions have the unique property of avoiding enzyme leaching. In other words, the advantages of both covalent and non-covalent enzyme-support binding can be simultaneously achieved.