Characterization of cyclodextrin glycosyltransferase immobilized on silica microspheres via aminopropyltrimethoxysilane as a “spacer arm”

In this work, the enzymatic properties of immobilized cyclodextrin glycosyltransferase (CGTase) of Thermoanaerobacter sp. were investigated and compared with the soluble form of the enzyme. CGTase was immobilized on mesoporous silica microspheres synthesized using polyethylene glycol 400 as swelling agent, silanized with 3-aminopropyltrimethoxysilane (APTMS), and activated with glutaraldehyde prior to immobilization. This innovative approach for support preparation produced high yields of immobilization (83%) and activity recoveries (73%), which are the highest so far reported for CGTase. The soluble enzyme (CGTase) and its immobilized form (ImCGTase) showed similar values for the optimal pH activity, while optimal reaction temperatures were found to be 100 °C and 80 °C, respectively. The immobilized enzyme showed similar values for Km and thermal stabilities with the soluble form, while its Vmax was lower. The immobilized enzyme was tested in repeated batches in order to simulate recovery and reuse, keeping about 60% of the initial catalytic activity after 15 cycles, showing its good chemical and mechanical resistance.