Characterisation of cyclodextrin glucanotransferase from Bacillus circulans ATCC 21783 in terms of cyclodextrin production

Abstract

Cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) from Bacillus circulans ATCC 21783 was purified by ultrafiltration and a consecutive starch adsorption. Total enzyme yield of 75.5% and purification factor of 13.7 were achieved. CGTase was most active at 65 °C, possessed two clearly revealed pH-optima at 6.0 and 8.6 and retained from 75 to 100% of its initial activity in a wide range of pH, between 5.0 and 11.0. The cyclising activity was enhanced by 1 mM CaCl2 or 4 mM CoCl2. The enzyme was thermostable up to 70 °C, and 64% of the original activity remained at 70 °C after 30 min heat treatment. Up to 41% conversion into cyclodextrins was obtained from 40 g 1-1 starch without using any additives. This CGTase produced two types of cyclodextrins, beta and gamma, in a ratio 73:27 after 4 h reaction time at 65 °C. This feature of the enzyme could be of interest for industrial cyclodextrin production.