基于普鲁兰酶催化脱支和过氧化物酶催化接枝聚合的接枝淀粉制备方法与反应机理及成膜性能调控

The existing grafted starch sizing agent has some disadvantages, such as poor property of film-forming because of its structure containing a high proportion of the amylopectins with short rigid branched chains, and low grafting percentage and grafting efficiency of the commonly-used chemical grafting method. In order to solve these problems, an enzymatic method of grafting with high grafting efficiency will be established for the preparation of grafted starch with excellent film-forming property. A branched chain replacement strategy for redesigning starch structure, which using flexible polymeric chains to replace rigid branched chains of the amylopectins, is put forward. This method utilizes two special enzymatic reactions, pullulanase-catalyzed debranching of the rigid branched chains and peroxidase-catalyzed grafting polymerization of flexible chains onto starch..The study will reveal the characteristics and mechanism of pullulanase-catalyzed debranching and peroxidase-catalyzed grafting polymerization.The relationship between the structure of the grafted starch and its performance will be studied. The project will explore the mediation and strengthening mechanisms of the two involving enzymatic reactions as well as the film-forming properties of starch.In addition, the reinforcing and toughening mechanism caused by the modification of starch structure will also be clarified.The project provides a new perspective on the improvement of film-forming properties of the grafted starch widely used as film-forming materials, according to the new concepts of “the replacement of branched chains” and the biocatalytic reactions, and opens up a completely new route for the green synthesis of grafted starch. The results are also instructive for the controllable bio-functionalization of other natural carbohydrate-based polymers.

针对当前接枝淀粉浆料存在的因含有高比例“刚性短支链”的支链淀粉而导致的成膜性差、常用的化学引发接枝法接枝率和接枝效率低等问题，本课题利用普鲁兰酶催化淀粉脱支刚性支链、过氧化物酶催化氧化淀粉接枝柔性聚合物支链这一反应特性，提出以“柔性聚合物支链”替换“刚性支链”的淀粉分子结构再设计策略，构建一种成膜性能优异、具有高接枝效率的接枝淀粉生物制备方法。 .课题将揭示淀粉“普鲁兰酶脱支降解”、“过氧化物酶催化接枝”的特性和机理，明晰接枝淀粉结构与性能之间的构效关系，探索酶法脱支、接枝聚合反应过程与淀粉成膜性能的调控策略与强化机制，阐明淀粉材料结构再造增强增韧作用机理。所提出的基于“支链替换” 和生物催化接枝反应新理念将为广泛用于成膜材料的接枝淀粉成膜性能的改善提供新的思路，为接枝淀粉的绿色合成开辟新的方法。研究结果对其它碳水化合物基天然高分子材料的酶法可控功能化改性也具有重要指导意义。

针对接枝淀粉浆料存在的因含有高比例“刚性短支链”的支链淀粉而导致的成膜性差、常用的化学引发接枝法接枝率和接枝效率低等问题，利用普鲁兰酶催化淀粉脱支刚性支链、过氧化物酶催化氧化淀粉接枝柔性聚合物支链这一反应特性，提出以“柔性聚合物支链”替换“刚性支链”的淀粉分子结构再设计策略，构建一种成膜性能优异、具有高接枝效率的接枝淀粉生物制备方法。.研究了异淀粉酶部分脱支淀粉对其分子结构和性能的影响。经异淀粉酶部分脱支改性后，淀粉分子的直链淀粉含量和DE值均较原淀粉增加，而分支度则有所降低；淀粉的糊化温度（包括糊化开始、糊化峰值和糊化终止温度）均较原淀粉有所升高，而糊化焓则有所降低；部分脱支改性的蜡质玉米和玉米淀粉对涤/棉粗纱的黏附性均较原淀粉低。.研究了原淀粉精细结构对接枝淀粉结构的影响。接枝淀粉的接枝率与原淀粉的直链淀粉含量间存在正相关；接枝率与βAm和βAp均呈正相关关系，说明直链淀粉结构和支链淀粉结构均会影响淀粉的接枝效果，βAm中βAm,i的影响相对强烈，说明淀粉与丙烯酰胺的接枝共聚反应容易发生在聚合度低的直链淀粉上，βAp中βAp,i的影响相对明显，说明接枝反应更易在支链淀粉的外链上发生。.探讨了HRP酶催化体系下丙烯酸与丙烯酸甲酯共聚的可行性及共聚规律。HRP酶可以催化丙烯酸与丙烯酸甲酯发生共聚反应。Fineman-Ross与Kelen-Tudos计算方法分析得出丙烯酸与丙烯酸甲酯的竞聚率分别为0.485、0.215。表明单体AA相较于MA更容易发生自聚 且AA 与MA的共聚方式趋向于交替共聚。.对HRP酶催化酸解淀粉接枝丙烯酸甲酯、接枝2-丙烯酰氧乙基三甲基氯化铵、接枝丙烯酰胺、接枝丙烯酸/丙烯酸甲酯的浆液浆膜性能进行了研究。表明各单体成功接枝到酸解淀粉颗粒上，接枝改性后淀粉的结晶度无明显变化。流变特性分析表明淀粉接枝改性后浆液黏度增大，黏弹性增加，呈现更具弹性的流体特征。相比于未接枝淀粉，接枝淀粉浆液对涤棉粗纱黏附性有明显提高；浆膜断裂伸长率和断裂强力均有增加，力学性能改善。