A single step purification process for cyclodextrin glucanotransferase from a Bacillus sp. isolated from soil

Cyclodextrin glucanotransferase (CGTase) is a commercially important enzyme which catalyses the formation of cyclodextrins (CDs) from starch. A CGTase producing bacterium was isolated from soil which gave a fairly high enzyme activity of 7.5 U mL(-1) after 24 h of growth which was further increased to 22 U mL(-1) by proper media design. The enzyme was purified to homogeneity by a novel single affinity precipitation step which resulted in a very high recovery of more than 90%. The molecular weight, as determined by SDS-PAGE, was found to be 68 kDa. The pH optimum was found to be 6.6 while a temperature optimum of 65 degrees C was observed. The enzyme exhibited a fairly high degree of functional stability with little loss of activity, even after 8 h of incubation at 65 degrees C. Ca++ had little effect on the activity of the enzyme while urea at 10 mM concentration increased the activity of the enzyme by more than 200%, suggesting that it is a unique enzyme.