This paper presents the immobilization of the Thermoanaerobacter cyclomaltodextrin glucanotransferase (CGTase) enzyme into cross-linked 6% agarose beads activated by high density of linear aldehyde groups (glyoxyl-agarose) that allow the establishment of multi-attachment enzyme-support bonds. The immobilization conditions were 25 degrees C, pH 10 and 5 h of contact time. The immobilization yield was almost 100% and the activity recovery was ca. 32%. The biocatalyst at 85 degrees C was capable of producing cyclodextrins (CDs) from dextrin or soluble starch (both at 1% (w/v)) at a greater rate than the soluble enzyme. In addition, the biocatalyst maintained 90% of its initial activity after 5 h at 85 degrees C. The maximum conversion of dextrin to beta-CD and gamma-CD (total mass of produced CDs/substrate initial mass x 100) was 29% both for the soluble and immobilized enzymes. Using starch as substrate the maximum starch conversion to beta-CD and gamma-CD was 29% and 38%, for the immobilized and soluble enzyme, respectively. The beta-CD selectivity yield [mass of beta-CD produced/(mass of beta-CD produced + mass of gamma-CD produced) x 100] increased from 67.9% for the free enzyme to 85.4% for the immobilized CGTase. (c) 2006 Elsevier Inc. All rights reserved.