Effective Production of Glycosyl-steviosides by α-1, 6 Transglucosylation of Dextrin Dextranase

抄録

Dextrin dextranase (EC 2.4. 1.2 ; DDase), which is produced by Acetobacter capsulatus ATCC 11894, acted on a mixture of stevioside and starch hydrolysate with isoamylase, so that the enzyme was found to convert stevioside to predominantly mono-glucosyl-stevioside (SG1) and di-glucosyl-stevioside (SG2), and little of the stevioside initially added remained. SG1 was separated into two compounds (SG1a and SG1b) by reversed-phase high-pressure liquid chromatography. The structures of SG1a, SG1b, and SG2 were analyzed and concluded to be 13-O-(6-α-glucosyl-2-β-glucosyl-β-glucosyl)-19-O-β-glucosyl-steviol, 13-O- [(6-α-glucosyl)(2-β-glucosyl)-β-glucosyl]-19-O-P-glucosyl-steviol, and 13-O-[(6-α-glucosyl)(6-α-glucosyl-2-P-glucosyl)-β-glucosyl]-19-O-β-glucosyl-steviol, respectively. During the reaction for production of glycosylsteviosides, DDase catalyzes transglucosylations from glucosyl donor compounds to stevioside to be SG1a and SG1b, and to SG1b to be SG2 rapidly forming α-1, 6 glucosidic linkages. However transglucosylation to SG1a to be SG2 rarely occurred, and the conversions among stevioside and these glycosyl-steviosides were catalyzed by the action of DDase to transfer α-1, 6 linked glucosyl residues, forming α-1, 6 linkages