微生物多糖可德胶的区域选择性取代及其衍生物的功能性和流变学研究

多糖是一类十分重要的天然大分子，具有独特的构象结构、功能以及物化性质。对多糖进行化学改性以提高其功能性和发掘其工业应用前景一直广受关注。本项目拟采用区域选择性取代方法，发展一类有别于beta-1, 4型纤维素和alpha-1, 4型淀粉的，基于具有生物活性的beta-1, 3型葡聚糖可德胶的典型功能性酯类和醚类新产物，并研究其分子构象、流变学性质及构效关系。通过揭示不同位点取代对螺旋结构解离和自组装的影响，阐明分子构象变化的机理；通过精确调控取代分布和取代度揭示不同取代方式对分子构象和性能的影响，阐明凝胶机理和溶液行为。服务于国民经济发展和相关工业化应用的需求，发掘可量大面广应用的可德胶衍生物的新功能，特别是从流变学角度发掘原可德胶不具有的、有重大应用价值的增稠性、乳化性、界面活性和粘弹性，建立可德胶衍生物结构与性能之间的关系，为新型微生物葡聚糖衍生物的开发和应用提供理论依据和技术支持。

Polysaccharides are important natural biopolymers with special conformation and structures, functions and physicochemical properties. Chemical modification of polysaccharides to improve their functionality and find their industrial applied prospect have attracted great interests in scientific and industrial fields. The aim of the project is to develop a series of novel and functional ester and ether derivatives from the microbial polysaccharide of bioactive curdlan, a beta-1, 3-glucan, different from beta-1, 4-glucan of cellulose and alpha-1, 4-glucan of starch, by using regioselective substitution, and thereby study their molecular conformation, rheological properties and structure-property relationship. The driving force and mechanism of conformation change will be clarified by investigating the influence of regioselective substitution at different positions in anhydroglucose unit on the triple-helix dissociation and single-helix self-assembly behaviour of curdlan. We will also investigate the effect of degree of substitution and distribution of substitution on the molecular conformation and properties, and further elaborate the gelation mechanism and solution behaviour of curdlan. To meet the needs of the national economic development and the requirements of industrial applications, new functionalities of the regioselectively substituted curdlan derivatives, especially rheological properties such as thickening, emulsification, and interfacial activity/viscoelasticity that native curdlan does not possess and have tremendous practical values largely and widely in many industrial fields will be explored. The structure-property relationship of regioselectively substituted curdlan derivatives will provide theoretical basis and technical support for the development and new applications of microbial polysaccharide derivatives.