Alpha-Cyclodextrin Production using Cyclodextrin Glycosyltransferase fromKlebsiella pneumoniae AS-22

Abstract

Alpha-cyclodextrin (α-CD) production, using cyclodextrin glycosyltransferase (CGTase) from Klebsiella pneumoniae AS-22, was investigated in the presence of various complexing agents using raw wheat starch and dextrin as substrates. The addition of many alcohols resulted in increased conversion of both raw wheat starch and dextrin to α-CD. With 125 g/L raw wheat starch, 42.5% (w/w) conversion to CDs was obtained in the presence of 2% (v/v) butan-1-ol. The ratio of α:β-CD formed was 97:3, with negligible formation of γ-CD and malto-oligosaccharides. The production of α-CD was optimized using two-level factorial designs in three variables: dextrin, hexan-1-ol and enzyme concentrations. Under optimum conditions, 12.1% (w/w) conversion of 500 g/L dextrin to total-CDs was achieved. The ratio of α:β:γ-CD formed was 91:3:6, with negligible production of malto-oligosaccharides. This CGTase was strongly inhibited by α:-CD; 50% inhibition of reaction rate was observed at an initial concentration of 4 g/L α:-CD. The effectiveness of an ultrafiltration membrane bioreactor for continuous removal of product was also tested.