高分子量右旋糖酐的酶法合成、改性及其絮凝作用的研究

发布时间：2018-05-01 02:34

  本文选题：右旋糖酐蔗糖酶 + 高分子右旋糖酐　； 参考：《合肥工业大学》2017年硕士论文

【摘要】：右旋糖酐是一类在医学和工业领域有重要作用的中性多糖,可合成高效、环保的新型生物多糖絮凝剂,具有广阔的应用前景。该生物多糖絮凝剂的絮凝性能与右旋糖酐分子量及其改性作用有关。本研究在前期研究的基础上进行了高分子量右旋糖酐的生产工艺研究,并对高分子右旋糖酐进行接枝共聚和酯化改性,获得了有良好絮凝性能的生物多糖絮凝剂,具体研究结果如下:(1)论文首先从改变底物浓度、酶用量和投料方式出发,对右旋糖酐蔗糖酶以蔗糖为底物催化合成高分子右旋糖酐的工艺进行了研究。实验结果表明,当蔗糖底物浓度为1000mM,右旋糖酐蔗糖酶投加量为0.8U/mL时,在25℃条件下发酵24小时可获得分子量为1132万的右旋糖酐;采用浓度由高到低的均衡间歇补料方式可以使合成的右旋糖酐分子量更高。研究发现酶催化反应副产物果糖的积累会抑制右旋糖酐链的增长,反应后期体系粘度的增高会阻碍右旋糖酐链的延长。(2)其次对高分子右旋糖酐与丙烯酰胺(AM)的接枝共聚反应进行研究,获取具有良好絮凝性能的右旋糖酐衍生物,并分析了接枝产物的絮凝机制。实验结果表明,当引发剂浓度为2mmol/L,m(AM):m(右旋糖酐)为2.0:1,反应时间为3.5小时,反应温度为35℃时,接枝反应单体转化率达到95.4%。模拟水样絮凝实验结果表明,pH为6.0时,投入0.5mg/L接枝产物处理赤铁矿悬浊液时去浊度为94%,投入4.15mg/L接枝产物处理高岭土悬浊液时去浊度为91.2%。絮凝剂在絮凝过程中起主要作用的是电中和和架桥吸附,同时伴随网捕、基团反应等多种作用发生,协同絮凝。(3)最后对高分子右旋糖酐与氨基酸的酯化反应进行了初探,对酯化产物进行了结构、性质分析并检测其絮凝性能。实验结果表明,酯化过程破坏了右旋糖酐分子的无定形区并对糖酐的结晶区也产生影响,酯化过程反应速率慢,取代程度不高。高岭土实验结果表明,该产物在酸性条件下絮凝效果较好,酯化产物投加量为15mg/L时,去浊度可达91.7%。高分子右旋糖酐的酯化产物在水溶液中呈无规则线型分布,具有可伸展性和柔顺性,含有多个吸附位点,对水体系中的胶体颗粒有较好的凝集成团能力,促进杂质的沉降。综上,本研究为高分子量右旋糖酐催化合成与工业化生产提供了理论依据,为高分子量右旋糖酐衍生物的合成与多糖絮凝剂的制备及其应用打下基础。
[Abstract]:Dextran is a kind of neutral polysaccharide which plays an important role in medicine and industry. It can be used as a new biological polysaccharide flocculant with high efficiency and environmental protection. The flocculation property of the biopolysaccharide flocculant is related to the molecular weight of dextran and its modification. On the basis of previous studies, the production process of high molecular weight dextran was studied, and the graft copolymerization and esterification modification of high molecular weight dextran were carried out, and the biopolysaccharide flocculant with good flocculation performance was obtained. The main results are as follows: (1) in order to change the substrate concentration, the amount of enzyme and the way of feeding, the process of synthesis of polymer dextran catalyzed by sucrose by sucrose was studied in this paper. The results showed that when the concentration of sucrose substrate was 1000mm and the dosage of dextran sucrase was 0.8U/mL, the dextran with molecular weight of 11.32 million could be obtained by fermentation at 25 鈩，

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