Immobilization of biomaterials into organic-inorganic matrices

We compared activities and mechanical properties of two Lipolase 100 L biocatalysts that differed in the manner of their entrapment into organic-inorganic matrices. Model reactions for evaluation of the activities of the biocatalysts were esterification of stearic acid with aliphatic alcohols in hexane, toluene and acetone and the hydrolysis of canola oil. In the first process, one step sol-gel technique, the enzyme was entrapped into silica prepolymers prepared from tetramethoxysilane, methyltrimethoxysilane, propyltrimethoxysilane and (3-aminopropyl)triethoxysilane. The two-step process was based on immobilization by sorption of enzyme on fine inorganic particles and their subsequent entrapment into a silicone based polymer. In a typical example Lipolase100 L was sorbed on the surface of poly(methylhydroxysiloxane) particles that were entrapped into poly(dimethylsiloxane) and cross-linked. The biocatalysts were shaped by molding. The one- step biocatalysts were fragile and hard. Mechanical properties of the two-step biocatalysts were changed from the hard, high abrasion resistant material, to elastic rubber. The activities of two-step biocatalysts (22.5 mg(protein)/g(biocatalyst)) were proportional to their swelling of the biocatalyst in reaction media and were to a certain extent insensitive to modifications of the elasticity and dimensions of biocatalyst particles. In the esterification of stearic acid, the activity of two-step immobilized lipases was higher than that of the commercial sol-gel lipase Fluka.