物理方法在壳聚糖降解中的应用

作为一种资源丰富、用途广泛的天然高分子化合物,壳聚糖广泛应用于化工、食品、农业、环保、医药等众多领域,由于分子量对壳聚糖的性质有很大影响,不同分子量的壳聚糖性质差异很大,将壳聚糖降解到需要的分子量是其应用的前提.概述了壳聚糖低聚物在实际中的应用,详细介绍了物理降解方法的研究进展.     

辐射在壳聚糖降解中应用

作为一种资源丰富、用途广泛天然高分子化合物,壳聚糖广泛应用于化工、食品、农业、环保、医药等众多领域,由于分子量对壳聚糖性质具有很大影响,不同分子量壳聚糖性质差异很大,将壳聚糖降解到需要分子量是其应用前提。辐射降解壳聚糖方法,有能量使用率高,环境污染小等特点;但目前存在辐射处理量小,产品成本高,降解率有待提高等不足。该文概述壳聚糖低聚物在实际中应用,详细介绍辐射降解方法研究进展。     

物理方法在壳聚糖降解中的应用

作为一种资源丰富、用途广泛的天然高分子化合物，壳聚糖广泛应用于化工、食品、农业、环保、医药等众多领域，由于分子量对壳聚糖的性质有很大影响，不同分子量的壳聚糖性质差异很大，将壳聚糖降解到需要的分子量是其应用的前提。目前主要使用化学降解法，其存在降解效率低，产品成本高，环境污染大等不足。概述了壳聚糖低聚物在实际中的应用，详细介绍了物理降解方法的研究进展。     

低聚壳聚糖制备及其在功能食品中应用

甲壳素是N-乙酰葡萄糖胺的聚合物,甲壳素脱乙酰后为壳聚糖,壳聚糖糖苷键断裂降解为低分子量壳聚糖。功能食品是指适宜特定人群食用、不以治疗疾病为目的、可调节人体生理机能的一类食品。低聚壳聚糖具有许多特殊的理化性质和生理功能,已广泛应用于食品、医药、化妆品、农业生产、环保等领域。本文综述了低聚壳聚糖的制备及其在功能食品中的应用情况。     

高速剪切作用对壳聚糖的降解效果研究

采用高速剪切技术对壳聚糖的机械降解过程进行了研究。考察了剪切时间、转速、温度、壳聚糖原溶液浓度、分子量和溶液pH等因素对壳聚糖降解效果的影响。以壳聚糖的动力黏度下降率来反映壳聚糖的降解程度,分别采用傅立叶变换红外光谱及凝胶渗透色谱对壳聚糖降解前后的结构和分子量分布进行了分析。研究结果表明,纯机械作用能够促进壳聚糖的降解,当壳聚糖原溶液浓度为3 g/L,分子量为100×104,pH为4.6,温度为40 ℃,降解时间为40 min,转速为20000 r/min时,降解效果最明显,动力黏度下降率为20.27%。研究还发现黏度对壳聚糖的机械降解过程有一定影响,当壳聚糖原溶液黏度为4.0 mPa·s时,壳聚糖的黏度下降率最大。本文为深入探究壳聚糖降解机理提供了理论依据。     

臭氧降解制备低聚壳聚糖的研究

为制备分子量较低的可溶于水的低聚壳聚糖,研究了在乙酸均相体系中臭氧对壳聚糖的氧化降解过程,采用凝胶渗透色谱法(GPC)跟踪测定了壳聚糖氧化降解过程中分子量及其分布的变化,探索制备不同分子量低聚壳聚糖的适宜条件。结果表明,壳聚糖降解的最佳条件为氧气流量1.2L/min、处理时间20min、壳聚糖浓度2g/L,此条件下水溶性低聚壳聚糖得率为66.7%,其平均相对分子量为9500u。     

壳聚糖的降解及其对真丝绸抗皱性能的影响

本文采用H2O2氧化降解法对壳聚糖进行降解,对降解前后壳聚糖的分子量、脱乙酰度及聚集态结构进行测定和分析,并探讨壳聚糖对真丝绸抗皱性能的影响.结果表明,降解后壳聚糖的分子量明显降低,脱乙酰度提高,分子间作用力减弱,结晶度降低,热稳定性下降.壳聚糖可以明显改善真丝织物的抗皱性能,且降解后分子量较小的壳聚糖对织物的抗皱性能更佳.     

微波强化壳聚糖固相酸降解研究

本文研究了微波强化下的壳聚糖固相酸降解反应,分析了降解过程中微波辐射功率和盐酸用量等参数对降解产物分子量变化的影响,并利用红外光谱和核磁共振氢谱对降解产物的结构进行了表征.研究表明,微波辐射功率和盐酸用量的增加均有利于壳聚糖分子量的降低.采用微波辐射壳聚糖固相酸化物料15 min,即可获得重均分子量低于50000的低分...     

超声波-微波协同H_2O_2降解壳聚糖的研究

采用正交实验方法优化超声波-微波联合H2O2氧化降解制备水溶性低分子量壳聚糖,并对水溶性低分子量壳聚糖进行红外光谱表征及热稳定性测定。正交实验结果显示,H2O2浓度8%,H2O2氧化10 min,超声-微波联合降解3 min,制备得到平均分子量为3.52 ku的低分子量壳聚糖。红外光谱分析表明壳聚糖在降解过程中分子骨架结构保持不变,引起了β(1→4)糖苷键部分断裂,降解过程伴随脱乙酰反应发生;差热分析表明降解后的低分子量水溶性壳聚糖的热稳定性低于原料壳聚糖。     

氧化降解壳聚糖在大豆纤维染色中的应用

利用双氧水氧化降解壳聚糖(CTS),采用粘度稀释法测定降解前后壳聚糖的分子量。将降解后不同分子量的壳聚糖溶解于1%醋酸溶液中处理大豆纤维织物,进行正交实验,研究对大豆纤维染色的增深效果。结果表明,降解后的分子量为11.7万壳聚糖在温度80℃,浓度4g/L,时间20min处理大豆纤维织物达到的增深效果最好;降解后的分子量为2.42万壳聚糖在温度80℃,浓度1g/L,时间20min处理大豆纤维织物达到的增深效果最好。将CTS应用于大豆纤维织物的表面改性,在不降低染色牢度的情况下可以改善活性染料的染色效果。     

壳聚糖及其降解产物黏均分子质量的测定

测定降解前、后壳聚糖的分子质量,用0.1 mol.L-1乙酸-0.2 mol.L-1氯化钠溶液做溶剂,采用黏度法进行测定。测得未降解壳聚糖[η]为407.6,分子质量约为5.7×105,降解180 min壳聚糖[η]为26.0,分子质量约为2.9×104。采用黏度法测定壳聚糖的分子质量具有原料处理简单,仪器易于清洗,实验数据重现性好等特点。     

糖化酶/H2O2二步法降解壳聚糖的研究

研究糖化酶/H2O2二步法降解壳聚糖的工艺条件。以降解产物壳寡糖的相对分子质量和收率为指标,采用单因素和正交试验确定壳聚糖降解的优化工艺条件为酶底质量比0.008,酶解温度62℃,酶解时间33h,H2O2的添加量12.6%,该条件下可以将相对分子质量为2.5×105的壳聚糖降解为分子量为470～1 102的壳聚糖,收率为83.3%。二步法可以更好地降解高分子量的壳聚糖,为壳聚糖的综合利用提供了新途径。     

Simultaneous depolymerization and decolorization of chitosan by ozone treatment

ABSTRACT:  Currently, depolymerization and decolorization of chitosan are achieved by chemical or enzymatic methods, which are time consuming and expensive. Ozone has been shown to be able to degrade macromolecules and remove pigments due to its high oxidation potential. In this study, the effects of ozone treatment on depolymerization and decolorization of chitosan were investigated. Crawfish chitosan was ozonated in water and acetic acid solution for 0, 5, 10, 15, and 20 min at room temperature with 12 wt% gas. In this study, the effects of ozone treatment on depolymerization and decolorization of chitosan were investigated by measuring the molecular weight, viscosity, and color of chitosan. The color of ozone-treated chitosan was analyzed using a Minolta spectrophotometer. The degree of deacetylation was determined by a colloid titration method. Molecular weight of ozone-treated chitosan in acetic acid solution decreased appreciably as the ozone treatment duration increased. Ozonation for 20 min reduced the molecular weight of the chitosan by 92% (104 kDa) compared to the untreated chitosan (1333 kDa) with a decrease in viscosity of the chitosan solution. Ozonation for 5 min markedly increased the whiteness of chitosan with a molecular weight of 432 kDa; however, further ozonation resulted in development of yellowness. In the case of the ozonation in water, there were no significant differences in the molecular weight and color between ozone-treated chitosans. This study showed that ozone can be used to modify molecular weight and remove pigments of chitosan without chemical use in a shorter time and with less cost.     

Influences of solution plasma conditions on degradation rate and properties of chitosan

In this work, the effects of solution plasma conditions on the degradation rate and properties of chitosan are investigated. Various types of electrodes including tungsten (W), copper (Cu), and iron (Fe) were used. The treatment time and the applied pulse frequency of the bipolar supply varied from 0 to 210 min and 15 to 30 kHz, respectively. The plasma-treated chitosan was characterized by GPC, XRD, FT-IR, and fractionation analysis. The results showed that after plasma treatment for 210 min, the molecular weight of chitosan decreased remarkably, when compared to those of untreated samples. The plasma treatment of chitosan using Fe electrode and high pulse frequency strongly promoted the degradation rate of chitosan. The XRD analysis showed that the crystallinity of plasma-treated chitosan was destroyed. FT-IR analysis revealed that the chemical structure of chitosan was not changed by solution plasma treatment. Solution plasma treatment of chitosan using an Fe electrode provided the highest %yield of water-soluble chitosan.Industrial RelevanceIn this study, the solution plasma process is introduced to treat chitosan in order to prepare low-molecular-weight chitosan. According to our finding, the solution plasma could be a potential method for the preparation of low-molecular-weight chitosan and chitooligosaccharides. Since the solution plasma is generated under mild conditions (i.e., the reaction proceeds at room temperature and ambient pressure), therefore, it is very attractive for the degradation of polysaccharide polymer and applicable to industrial materials process such as medicine, food, chemical industry, and cosmetics. In addition, we expected that plasma technology could be used instead of conventional enzymatic treatment and chemical treatment which was high cost and contamination process.