Résumé
Coupling sugar is a kind of new sweetener which can substitute sucrose. It has a good application prospect in food, medicine and other fields because of its good coloration, water retention and anti caries. The purpose of this study was to find cheap and easily available donor and acceptor, and to optimize the preparation process of coupling sugar by using β-cyclodextrin glycosyltransferase from Bacilluscirculans 251. Using sucrose as acceptor, the factors of preparing coupling sugar was optimized, including enzyme dosage, starch types, temperature, pH, ratio of starch/sucrose, and cooperation of isoamylase and β-CGTase. When 105 g/L potato starch and 95 g/L sucrose was used as substrates, the yield of coupling sugar reached 88.4%, which was catalyzed by 13.5 U/g immobilized β-CGTase and 45.0 U/g isoamylase under the conditions of pH 5.5 and 40 °C for 21 h. In this study, isoamylase and β-CGTase were used to prepare coupling sugar innovatively. This method had obvious advantages in yield and cost, which laid both theoretical and experimental foundation for the industrial enzymatic preparation of coupling sugars.