Immobilized enzymes in ordered mesoporous silica materials and improvement of their stability and catalytic activity in an organic solvent

Enzyme immobilization in mesoporous materials with various pore sizes was studied. The size of the mesopores was controlled by means of the combination of the alkyl chain lengths of surfactants and a swelling agent (triisopropyl benzene). Enzymes were selectively adsorbed to FSM-16 and MCM-41 prepared with a cationic surfactant, whose pore sizes were over the molecular diameters of the enzymes, and were not adsorbed significantly to SBA-15 prepared with a non-ionic surfactant. The higher adsorption as to FSM-16 or MCM-41 rather than on SBA-15 may be due to the ionic characteristics of the mesopore, which would be consistent with the observed larger adsorption capacity as to the cationic pigment rather than the anionic pigment of these materials. Enzymes, horseradish peroxidase and subtilisin, immobilized in FSM-16 showed the best stability and peak catalytic activity in an organic solvent when the average mesopore size just exceeded the molecular diameters of the enzymes.