The Formation of Amylose-Granules from Cyclomaltodextrin Glucanotransferase by a-Cyclodextrin

Abstract

Cyclomaltodextrin glucanotransferase (CGTase) from Bacillus stearothermophilus formed amylose-granules from α-cyclodextrin (α-CD). The formation of amylose-granules was mainly affected by the substrate concentration and the temperature of reaction condition. The maximum yield was 96% when the enzyme acted on 35% of α-CD at 30t. The amylose-granules were spherical with the diameter of 3-20 pm, and were soluble in alkaline solution but insoluble in hot water. The dissolved amylose formed iodine complex having Amax of 560-580 nm and was almost hydrolyzed to maltose by the action of β-amylase. The amylose had number-average molecular weight of 5500-7000, i. e., 34-43 glucose units. The granules gave B-type similar to potato starch on X-ray diffraction and were observed polarized-cross on microscopy. CGTases from other bacteria also produced the similar amylose-granules to those by Bacillus stearothermophilus enzyme.