Synthesis of Polysaccharides by Using Enzyme Catalyst

以β-D-纤维二糖氟为底物，在乙腈/醋酸盐缓冲液（pH5.5：1）中进行酶促聚合，首次实现了纤维素的体外非生物合成。在较高底物浓度或较高乙腈浓度的反应条件下，纤维低聚糖的生成占优势。本发明以糖基氟化物为底物，在有机/水混合溶剂中水解酶催化合成麦芽寡糖和非天然寡糖的方法已成功地应用于麦芽寡糖和非天然寡糖的合成。一种纤维素酶催化的烷基纤维二糖的立体选择性乳糖基化，产生在非还原末端具有D-半乳糖单元的新寡糖，以及β-半乳糖苷酶催化的末端D-半乳糖单元的区域选择性裂解，半乳糖单位的产品。

The in vitro synthesis of cellulose via a nonbiosynthetic path has been achieved for the first time by condensation of beta-D-cellobiosyl fluoride as substrate for cellulase in a mixed solvent of acetonitrile/acetate buffer (pH 5,5:1)(enzymatic polymerization). Under reaction condition of a higher substrate concentration or higher acetonitrile concentration, cellooligosaccharides were produced predominantly. The present method of using a glycosyl fluoride as substrate for a hydrolytic enzyme in an organic/water mixed solvent has successfully been applied to synthesis of maltooligosaccharides and unnatural oligosaccharides.A new methodology for regio and stereoselective synthesis of cellooligosaccharide derivatives has been developed by utilizing the following two enzymatic reactions : A cellulase-catalyzed stereoselective lactosylation of an alkyl cellobioside giving rise to a new oligosaccharide having a D-galactose unit at the nonreducing end and a beta-galactosidase-catalyzed regioselective cleavage of the terminal D-galactose unit of the product.