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Abstract
From the mixture of 42-O-β-D-galactosyl-maltose (Gal-G2) and β-cyclodextrin (βCD), novel heterobranched βCDs, (Gal-G2)-βCD and (Gal-G2)2-βCDs, were synthesized by the reverse action of debranching enzyme. The optimum conditions for the production of (Gal-G2)2-βCDs were examined. A mixture of (Gal-G2)2- βCDs was produced in about 4% yield when Aerobacter aerogenes pullulanase (64 units per 1 g of Gal-G2) was incubated with 1.6 M Gal-G2 and 0.16 M βCD at 50°C for 4 days. The reaction products, (Gal-G2)2-βCDs, were separated into three peaks by HPLC analysis on a Hypercarb S column. Their structures were analyzed by fast atom bombardment mass spectroscopy and NMR spectroscopies, and confirmed by comparison of their hydrolyzates by β-galactosidase with the authentic (G2)2-βCDs. The structures of (Gal-G2)-βCD and three components of (Gal-G2)2-βCDs were identified as 6-O-(Gal-G2)-βCD, 61,62-, 61,63- and 61,64-di-O-(Gal-G2)2-βCD, respectively.