Low Power Microwave Assisted Transglycosylation of Stevioside Using Cyclodextrin Glucanotransferase Toruzyme 3.0L

Abstract: Enzymatic transglycosylation of stevioside usually takes long reaction time and concerns thermo-deactivation of the enzyme. In this article, using a thermophilic enzyme and employing low power microwave irradiation, transglycosylation of stevioside was speeded up over 10-folds with cyclodextrin glycanotransferase Toruzyme 3.0L. The effects of reaction parameters including microwave power, temperature, mass ratio of the reactants, pH and enzyme loading on the conversion of stevioside were studied. The highest stevioside conversion reached 63.73% under microwave in 3min, which accelerated the reaction 20 times compared with that obtained via conventional heating. The product was mainly composed of mono- and di- glucosylated stevioside, both kinetic and thermodynamic stimulation did not enhance the formation of high grafted steviosides. The microwave-assisted reaction reached equilibrium only in 3min when 10U/g stevioside or higher was applied. It was concluded that the hydrolysis instead of enzyme thermo-deactivation caused the quick reaction equilibrium.