Synthesis of Novel Heterobranched β-Cyclodextrins from 4²-O-β-D-Galactosyl- Maltose and β-Cyclodextrin by the Reverse Action of Pullulanase, and Isolation and Characterization of the Products

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.