Biochemical Properties of Novel Steviol Glucosides Synthesized by Using Dextransucrase

Abstract

Abstract Steviol glycosides is nature, non-caloric sweet-tasting organic molecules, present in extracts of the scrub plant Stevia reabaudiana. Steviol glycosides are composed of various glycosides such as stevioiside, rebaudioside A-E, rubusoside, dulcoside A and have a sweetness of about 30 to 150 times that of sugar, and has thermal stability, pH stability, and non fermentation characteristics and is therefore used as an alternative sweetener. However, the bitter aftertaste of steviol glycosides restricts its use in consumer foods and beverages. In this study, enzymatic transglucosylation using dextransucrase from Leuconostoc mesenteroides B-512FMCM was used in the biotransformation of steviol glycosides to partially reduce bitter aftertaste of steviol glycosides. Using RSM, the conversion of stevioside and rebaudioside A was estimated to be 86.8% and 73.6% at the optimal conditions of steviol glycosides 37.3 mg / ml, sucrose 381.3 mM and 2.7 U/mL. Each puried steviol glucosides was purified using HP-20 resin, HPLC-PAD equipped with NH2, C18 column. The structures of steviol glucosides ware determined as 13-O-β-sophorosyl-19-O-β-isomaltosyl-steviol,13-O-[β-(1→6)glucosyl]-β-glucosylsophorosyl-19-O-β-isomaltosyl-steviol, 13-O-β-sophorosyl-19-O-β-isomaltotriosyl-steviol, 13-O-[α-neohesperidosyl-(1→3)-β-glucosyl-(1→6)-α-glucosyl]-19-O-β-glucosyl-steviol, 13-O-[β-sophorosyl-(1→3)-β-glucosyl]-19-O-β-isomaltosyl-steviol by MALDI-TOF and NMR. Steviol glucosides have higher stability under pH 2, at 60 ℃ condition and have the property of reducing the insoluble glucan production of mutansucrase. In addition, Steviol glucosides have a very high level of water-solubility enhancement when dissolved in water with water-insoluble compounds such as pterostilbene, curcuminoid and idebenone. This improvement in water solubility makes it possible to expect an improvement in bioavailability.