Study on Improved Utilization of Sweet Natural Glycosides by Enzymic Transglycosylation

为了提高甜味的强度和品质，研究了甜天然糖苷、甜菊糖苷(S)和苦穗子糖苷(R)的酶转糖基化。利用可溶性淀粉和环糊化葡萄糖基转移酶（CGTase）对S和R中α -1,4-葡萄糖基化产物进行了完全分离和鉴定。S和R的19-羧酸处的β -葡萄糖基酯被β -半乳糖基取代，作为CGTase糖基化的阻滞剂。这两种半乳糖酯都是在CGTase作用下在13-糖基上选择性糖基化的。对上述所有糖基化产物的甜度进行评价，揭示了该系列糖苷的结构-甜度关系。在13位上有3个或4个葡萄糖基的产品在甜度和甜度上都有显著的改善。结果表明，在13位糖基较多的产品，其甜度越低。19位的转糖基化也导致甜度下降。研究了不同条件下S酶转糖基化的区域选择性控制。结果表明，具有强包合性的tubeimoside-I的存在抑制了19位S的糖基化，导致较差甜味剂的产量减少。通过多种α -和β -半乳糖苷酶的半乳糖基化，已经广泛研究了阻断R的19- co - β -葡萄糖基的4-羟基对CGTase糖基化的抑制作用。结果表明，环芽孢杆菌产生的β -半乳糖基化R与乳糖和β -半乳糖苷酶有效地产生19- coo - β -半乳糖-(1 -4)- β -葡萄糖苷。用CGTase对该化合物进行转糖基化，然后用-半乳糖苷酶进行去半乳糖基化，可以得到更好的13位单糖基化、二糖基化或三糖基化的甜味剂。观察了甜菊糖苷、S和雷鲍迪苷a对α -生育酚在水中的增溶作用。少

In order to improve intensity and quality of sweetness, enzymic transglucosylation of sweet natural glycosides, stevioside(S) and rubusoside(R) has been investigated.The complete separation and identification of alpha-1,4-glucosylated products from S and R with soluble starch and cycloddxtringlucosyltransferase (CGTase) were achieved.The beta-glucosyl ester group at 19-carboxylic acid of S and R was chemically replaced by a beta-galactosyl group as a blocker against the glucosylation with CGTase. Both the galactosyl esters were regioselectively glucosylated on the 13-glycosyl moiety with CGTase.The evaluation of sweetness of all of the above glucosylated products revealed the following structure-sweetness relationship of glycosides of this series. Remarkable improvement in both the intensity and quality of sweetness was observed for the products which have three or four glucosyl groups at the 13-position. It was noted that the products having more glucosyl groups at the 13-position sho … More wed less sweetness. Transglucosylation at the 19-position also resulted in the decrease of sweetness.The regioselective control of the enzymic transglycosylation of S has been studied under the various conditions. It was found that in the presence of tubeimoside-I which has the potent inclusion property, the glucosylation of S at the 19-position was suppressed, leading to the decrease of the production of the worse sweeteners.Blocking of the 4-hydroxyl group of the 19-COO-beta-glucosyl group of R against glucosylation with CGTase has been investigated extensively by galactosylation with a variety of alpha- and beta-galactosidases. It was disclosed that beta-galactosylation of R with lactose and beta-galactosidase produced by Bacillus circulans effectively afforded the 19--COO-beta-galactosyl-(l--4)-beta-glucoside. Transgiucosylation of this compound with CGTase followed by de-galactosylation with beta-galactosidase yielded the better sweeteners which were mono-, di- or tri-glucosylated exclusively at 13-position.Solubilization of alpha-tochopherol in water was observed for sweet Stevia glycosides, S and rebaudioside-A. Less