Comparison of covalent and physical immobilization of lipase in gigaporous polymeric microspheres.

Lipase (EC 3.1.1.3) is a versatile enzyme which has been widely used in ester-reaction industries. We have previously discovered that gigaporous polystyrene (PST) microspheres can be used as a novel immobilization carrier for lipase. In this work, a series of gigaporous microspheres with different densities of epoxy group including poly(glycidyl methacrylate) (PGMA) and poly(styrene-co-glycidyl methacrylate) [P(ST-GMA)] were evaluated as lipase immobilization carriers, which were also compared with gigaporous PST microspheres and the commercial immobilized lipase Novozym 435. Lipase immobilized in gigaporous PGMA microspheres showed the highest activity yield, reusability, and stability as well as the best affinity for the substrate. The characterizations of adsorption curves, the change of epoxy group amounts, and hydrophobic-hydrophilic properties of the microspheres were carried out to investigate the interaction between lipase molecules and carriers. It was found that covalent binding played a key role in improving the properties of lipase immobilized in gigaporous PGMA microspheres.