Stevioside and rebaudioside A are the chief diterpene glycosides present in the leaves of Stevia rebaudiana. Rebaudioside A imparts a desirable sweet taste， while stevioside produces a residual bitter aftertaste. Enzymatic synthesis of rebaudioside A from stevioside can increase the ratio of rebaudioside A to stevioside in steviol glycoside products， providing a conceivable strategy to improve the organoleptic properties of steviol glycoside products. Here， we demonstrate the efficient conversion of stevioside to rebaudioside A by coupling the activities of recombinant UDP-glucosyltransferase UGT76G1 from S. rebaudiana and sucrose synthase AtSUS1 from Arabidopsis thaliana. The conversion occurred via rege... More
Stevioside and rebaudioside A are the chief diterpene glycosides present in the leaves of Stevia rebaudiana. Rebaudioside A imparts a desirable sweet taste， while stevioside produces a residual bitter aftertaste. Enzymatic synthesis of rebaudioside A from stevioside can increase the ratio of rebaudioside A to stevioside in steviol glycoside products， providing a conceivable strategy to improve the organoleptic properties of steviol glycoside products. Here， we demonstrate the efficient conversion of stevioside to rebaudioside A by coupling the activities of recombinant UDP-glucosyltransferase UGT76G1 from S. rebaudiana and sucrose synthase AtSUS1 from Arabidopsis thaliana. The conversion occurred via regeneration of UDP-glucose by AtSUS1. UDP was applicable as the initial material instead of UDP-glucose for UDP-glucose recycling. The amount of UDP could be greatly reduced in the reaction mixture. Rebaudioside A yield in 30 h with 2.4 mM stevioside， 7.2 mM sucrose， and 0.006 mM UDP was 78%.
