Thermostable beta-glucosidase from Sulfolobus shibatae was immobilized on silica gel modified or not modified with 3-aminopropyl-triethoxysilane using transglutaminase as a cross-linking factor. Obtained preparations had specific activity of 3883 U/g of the support, when measured at 70 degrees C using o-nitrophenyl beta-D-galactopyranoside (Gal beta oNp) as substrate. The highest immobilization yield of the enzyme was achieved at pH 5.0 in reaction media. The most active preparations of immobilized P-glucosidase were obtained at a transglutaminase concentration of 40 mg/ml at 50 degrees C. The immobilization was almost completely terminated after 100 min of the reaction and prolonged time of this process did not cause considerable changes of the activity of the preparations. The immobilization did not influence considerably on optimum pH and temperature of Gal beta oNp hydrolysis catalyzed by the investigated enzyme (98 degrees C, pH 5.5). The broad substrate specifity and properties of the thermostable beta-glucosidase from S. shibatae immobilized on silica-gel indicate its suitability for hydrolysis of lactose during whey processing. (c) 2006 Elsevier Inc. All rights reserved.