【作者】 王兆伦；

【导师】 饶力群； 罗泽民；

【作者基本信息】 湖南农业大学 ， 生物化学与分子生物学， 2001， 硕士

【摘要】 甲壳素是一种天然高分子有机化合物，研究甲壳素的脱乙酰化反应和甲壳素衍生物的制备具有重要的应用和开发价值。本论文在总结前人工作的基础上，分别就以下四个方面的内容进行了探讨：1．甲壳素脱乙酰化反应条件的研究：2．不同活化条件下制备羧甲基壳聚糖分析；3．两种水溶性壳聚糖的制备方法比较；4．微晶甲壳素的制备。研究结果如下： 1．选择甲壳素脱乙酰化反应的三个主要影响因素，进行碱浓度／时间和碱浓度/温度双因素正交试验。试验结果表明，甲壳素脱乙酰化反应主要是在碱浓度、温度和时间三因素的综合作用下进行的。对于衡量反应进程的主要指标脱乙酰度来说，随着三因素水平的升高，其值也逐渐增大。碱浓度是影响脱乙酰度大小的最主要因素，温度和时间对脱乙酰度也有很大的影响。在脱乙酰化反应过程前半期，脱乙酰度、粘度随碱浓度的增加而加大，当粘度逐渐增大达到最大值后，反应进入后半期，此时脱乙酰度增大程度放缓，而粘度开始逐步下降。温度对脱乙酰化反应的影响也符合这种趋势，而时间的作用主要是一种量的积累。因此我们认为，脱乙酰化反应前期，主要通过碱的作用进行端基反应，使脱乙酰度显著增高，而后半期主要通过碱和温度的作用，引起糖苷键的断裂，造成粘度的下降。 2．通过对不同活化条件下的壳聚糖羧甲基化试验进行比较，结果表明：壳聚糖羧甲基反应之前溶胀程度的提高，可以增加产物的取代度。碱活化是效率较高的方法之一，短时间活化取代产物主要为O-取代，而长时间活化的取代产物是O-，N-取代，低温可造成甲壳素内部结构的膨胀，使取代反应较容易进行，其取代产物主要为O-取代。 3．用酰氯作为酰化剂，对脱乙酰度为90％以上的壳聚糖进行酰化，控制反应进程得到脱乙酰度为50％左右的壳聚糖，具有较好的水溶性，且成本较低。 4．用两种不同的方法制备微晶壳聚糖，对微晶壳聚糖产品进行结晶试验，获得了较好的结晶产品。 5．用红外光谱对得到的壳聚糖、羧甲基壳聚糖、微品壳聚糖、水溶性壳聚糖进行了定性分析，验证了产品的结构。更多还原

【Abstract】 Chitin is one of a natural macromolecule organic compound. It is very important to study the reactions of chitin deacetylacing and preparation of chitin ramification. Based on the research before, four kinds of studies were made in this paper: a, study on the optimum reaction condition of chitin deacetylacing; b, study on the analysis of carboxymethyl-chitosan made by different ways; c, study on the comparison between two kinds of preparation procedure of dissoluble chitin; d, study on the making of crystallite. The results are as follow:It was proved that three facts, alkali concentration, time and temperature, were very important in chitin deacetylace reaction. The degree of chitin deacetylation, the marker of the chitin deacetylacing reaction, increased with the increasing of the three facts. Among the facts, alkali concentration was the most important fact. And the time and temperature were also contributed much to the reaction, hi the reaction, the changing of viscosity was used to estimate the course of reaction and the contribution of the facts. During the early period of the reaction, the chitin deacetylation and the viscosity increased with the increasing of alkali concentration. After the viscosity arrived at the peak, the degree of chitin deacetylation increased slowly and viscosity did not increased but decreased The same effect of temperature on the changing of the degree of chitin deacetylation and viscosity was found in this paper. The effect of time on them was progressive. Further study showed that during the early reaction, the increasing of the chitin deacetylacing degree was due to the end-hydrolyzed reaction with alkali medium. But during the latter period of the reaction, the indican bonds were destroyed by alkali under higher temperature, and as a result, viscosity decreased in the long run.Compared the chitosan carboxymethylation reaction condition, it was found that the degree of chitosan carboxymethylation increased with a suitable advance activating procedure. Alkali was very powerful activating material. The first step of replacing reaction was that O was replaced by carboxymethyl. And further replacing reaction was that O and N were replaced by carboxymethyl. Freezing was also helpful to activate the chitosan and the main replacing reaction was o-replaced reaction.Acylated by acyl chloride, about 50% of the degree of deacetylation soluble chitosan were obtained from chitosan with more than 90% degree of deacetylation if the reaction conditions were controlled properlyCrystallite chitin was made in two different ways in this paper and chitin crystal was also obtained.Chitosan, carboxymethyl-chitosan, soluble chitosan, and crystallite chitin were qualitatively analysized by intrared spectrum to identify their structures.更多还原