Biotechnological Production of Highly Soluble Daidzein Glycosides Using Thermotoga maritima Maltosyltransferase

The use of soybean isoflavones in food products is limited due to their low hydrophilicity. To enhance its solubility, the isoflavone daidzin was transglycosylated as a model compound using Thermotoga maritima maltosyltransferase (MTase). Four novel transglycosylation products of daidzin were identified by TLC and MALDI-TOF MS: daidzein 7-O-triglucoside, daidzein 7-O-pentaglucoside, daidzein 7-O-heptaglucoside, and daidzein 7-O-nonaglucoside. The major product, daidzein 7-O-triglucoside, was purified by C(18) and gel filtration chromatography, and its molecular structure was determined using UV, IR, MALDI-TOF MS, and NMR. The solubility of daidzein 7-O-triglucoside was 7.5 x 10(4) times that of daidzin, suggesting that the transglycosylation greatly enhanced its water solubility.