低聚水溶性壳聚糖的制备方法及研究进展

低聚水溶性壳聚糖的制备是目前非常热门的一个研究课题,本文对壳聚糖降解以制备低聚水溶性壳聚糖的各种方法及目前的研究进展情况进行了综述。     

壳聚糖及低聚壳聚糖在日用化妆品中的应用

随着壳聚糖及其衍生物、低聚壳聚糖研究的迅速发展，其研究内容和应用范围越来越广泛，从壳聚糖及低聚壳聚糖在护发、护肤、美容等方面对其在日用化妆品中的应用进行了综述，并对其发展前景进行了简要评述。     

低聚壳聚糖的制备与应用研究

壳聚糖经过降解后达到较小分子量（Mw1000—100000）范围的低聚壳聚糖因具有特殊的生物活性和功能性质而日益受到研究者们的重视与关注。本文概要综述了国内外低聚壳聚糖的研究进展，包括低聚壳聚糖的制备方法，如酶降解法、酸水解法、氧化降解法、物理法等，以及低聚壳聚糖在医药、抗菌、化妆品、农业、食品等方面的应用。     

利用纤维素酶催化水解壳聚糖的研究

利用纤维素酶催化降解壳聚糖，分别研究了pH值、温度、酶／糖及反应时间等因素对壳聚糖相对分子质量的影响，得到的最佳反应条件为：pH为5．6、n（酶）／n（糖）为0．1／1．0、反应温度为50℃、反应时间为6h。用纤维素酶催化降解壳聚糖只能得到最低平均相对分子质量为18000的低聚壳聚糖。为了得到更低相对分子质量的壳聚糖，在壳聚糖酶降解后加入一定量双氧水继续降解。研究了双氯水加入量及加入时间的影响，最终可得到平均相对分子质量为1500的低聚壳聚糖。     

HAc/H_2O_2协同氧化制备水溶性壳聚糖的实验研究

壳聚糖在 HAc介质中被氧化剂 H2 O2 解聚 ,解聚速度与壳聚糖浓度、H2 O2 的用量、介质的浓度、温度及反应时间有关。通过正交实验 ,得出了水溶性低聚壳聚糖的制备条件为 n(氧化剂 )∶n(壳聚糖 ) =1 .5、θ=80°C、t=6h、CHAc=1 %(质量分数 )、Cchi=5 %(质量分数 )。     

O-季铵化低聚壳聚糖芳香醛席夫碱衍生物的制备及其抑菌活性

以低聚壳聚糖为对象,苯甲醛、水杨醛、香草醛为改性试剂,设计合成了一系列O-季铵盐低聚壳聚糖芳香醛席夫碱衍生物。产物元素分析发现其席夫碱取代度接近100%,电位滴定确定产物的季铵盐接枝率在35%左右。抑菌活性研究表明,合成的各种O-季铵盐低聚壳聚糖芳香醛席夫碱衍生物抑菌活性明显增强,活性大小依次为香草醛改性物水杨醛改性物苯甲醛改性物低聚壳聚糖。抑菌活性构效关系分析表明,低聚壳聚糖通过芳香醛席夫碱改性引入了酚羟基抑菌活性中心,但酚羟基的抑菌活性受空间位阻影响较大。     

低聚壳聚糖的制备及应用研究进展

从壳聚糖降解得到的低聚壳聚糖具有特殊的生理活性而日益受到人们的关注。综述了近年来壳聚糖降解制备低聚壳聚糖的方法,包括化学降解法、酶降解法、物理作用帮助下的降解法以及复合降解法。重点介绍了这些方法的降解机理、影响因素和对产品质量的影响以及低分子质量壳聚糖在化妆品、食品、医药、农业、抗菌等方面的应用。     

Mn(Ⅱ)对壳聚糖降解制备低聚壳聚糖的影响

将壳聚糖进行液态均相配合反应制得壳聚糖锰配合物，IR、元素分析及热分析等检测证实了壳聚糖锰配合物中配位键的存在，且显示壳聚糖锰配合物存在有利于壳聚糖高分子链断裂的弱势结构。以H2O2对壳聚糖．Mn(Ⅱ)配合物及壳聚糖进行氧化降解，考察降解过程中粘度的变化及降解产物分子量分布，在相同的降解条件下，壳聚糖锰配合物的降解速度明显高于壳聚糖，且降解产物分子量分布较壳聚糖直接降解窄。对壳聚糖锰配合物降解反应动力学研究表明壳聚糖锰配合物对H2O2分解不存在催化作用，其降解反应与壳聚糖的差异只与其结构有关。对降解产物进行脱金属处理，所得低聚壳聚糖含锰量为0。     

低聚壳聚糖锆配合物的制备及其性能

以低聚壳聚糖(L-CTS)和硝酸锆为原料合成了低聚壳聚糖锆配合物[L-CTS-Zr(Ⅳ)]。利用红外光谱、紫外光谱、核磁、X-粉末衍射对配合物进行了表征。探讨了配合物的抑菌性,结果表明:低聚壳聚糖锆配合物的抑菌性强于低聚壳聚糖。     

纤维素酶降解结合膜法制备低聚壳聚糖

研究纤维素酶降解结合膜法制备低聚壳聚糖。采用正交设计优选酶降解的最佳工艺条件及分析超滤产品的平均相对分子质量和收率。纤维素酶对壳聚糖降解的最佳条件为:温度50℃,酶糖质量比为0.1,pH=4.6。纤维素酶催化降解结合膜法制备低聚壳聚糖。在5 h内即可获得收率超过75%,平均相对分子质量在5000左右的优质低聚壳聚糖产品。该工艺简单可行,运行时间短,产品相对平均分子质量小而且分布窄,收率较高。     

壳聚糖的化学改性(Ⅱ)

概述了近十年来壳聚糖化学改性方面取得的其它一些研究进展,主要包括酶改性、脱氧胆酸改性和树枝状高分子杂化改性等,并且对改性壳聚糖的生物降解性能进行了讨论。改性壳聚糖可广泛应用于食品、农业、医药及环保等领域。     

Aggregation of hydrophobically modified chitosan in solution and at the air–water interface

Oleoyl‐chitosans (O‐chitosans), with three degrees of substitution (DS), were synthesized by reacting chitosan with oleoyl chloride. The chemical structures of these polymers were characterized by ¹H NMR and FTIR. The results suggested the formation of an amide linkage between amino groups of chitosan and carboxyl groups of oleic acid. These O‐chitosans exhibited poor solubility in aqueous acidic solution. The solubility of O‐chitosans decreased as the DS values increased. The transmittance of O‐chitosans (2 g/L) with DS 5%, 11%, 27% in 1% (v/v) HCl solution were 69.5%, 62.7%, 48.6%, respectively. These O‐chitosans were not soluble at neutral or alkali pH. Formation of self‐aggregation was observed using pyrene as a fluorescent probe in the O‐chitosans aqueous solution. The increase of DS of O‐chitosans resulted in significant decrease of critical aggregation concentration (CAC). The CAC of the O‐chitosans with DS 5%, 11%, 27% were 79.43, 31.6, 10 mg/L, respectively. The surface tension of solution could be reduced slightly by all of the O‐chitosans. The surface tension of O‐chitosans solution decreased with the increase of DS values. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1968–1973, 2006     

酶载体壳聚糖制备的研究

本文分别采用电热法、连续微波法和问歇微波法制备了几种性能不同的壳聚糖,并对产品的脱乙酰度和分子量进行了比较.结果表明,间歇微波法制备的壳聚糖具有制备时间短、产品脱乙酰度高和分子量大等特点,能更好地满足酶载体的要求.     

不同相对分子质量壳聚糖絮凝性能

壳聚糖作为天然高分子絮凝剂具有无毒、不存在2次污染、使用方便等优点;但生产和应用成本高,具有一定限制。而相对分子质量是壳聚糖的一个重要分子参数,不同相对分子质量的壳聚糖性质差异很大,研究了不同相对分子质量的壳聚糖对生活污水的絮凝性能,结果表明：高相对分子质量壳聚糖的絮凝效果较好,且随着壳聚糖用量的增加絮凝性能也随之增加,但是5×10^-6后絮凝下降,其在pH值为6.5时絮凝效果最佳。     

Effect of degree of deacetylation of chitosan on the kinetics of ultrasonic degradation of chitosan

The objective of the study was to explore the effect of the degree of deacetylation (DD) of the chitosan used on the degradation rate and rate constant during ultrasonic degradation. Chitin was extracted from red shrimp process waste. Four different DD chitosans were prepared from chitin by alkali deacetylation. Those chitosans were degraded by ultrasonic radiation to different molecular weights. Changes of the molecular weight were determined by light scattering, and data of molecular weight changes were used to calculate the degradation rate and rate constant. The results were as follows: The molecular weight of chitosans decreased with an increasing ultrasonication time. The curves of the molecular weight versus the ultrasonication time were broken at 1‐h treatment. The degradation rate and rate constant of sonolysis decreased with an increasing ultrasonication time. This may be because the chances of being attacked by the cavitation energy increased with an increasing molecular weight species and may be because smaller molecular weight species have shorter relaxation times and, thus, can alleviate the sonication stress easier. However, the degradation rate and rate constant of sonolysis increased with an increasing DD of the chitosan used. This may be because the flexibilitier molecules of higher DD chitosans are more susceptible to the shear force of elongation flow generated by the cavitation field or due to the bond energy difference of acetamido and β‐1,4‐glucoside linkage or hydrogen bonds. Breakage of the β‐1,4‐glucoside linkage will result in lower molecular weight and an increasing reaction rate and rate constant. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3526–3531, 2003     

壳聚糖的表面性能及分子量与脱乙酰度的影响

应用红外光谱法对四种壳聚糖样品进行了结构表征,同时估算了其脱乙酰度,并用粘度法测定了分子量。根据Washburn的浸渍理论和van Oss-Chaudhury-Good的组合理论,应用柱状灯芯技术,对壳聚糖的表面性能进行了测试。研究发现,壳聚糖的分子量和脱乙酰度都影响其表面性能。当脱乙酰度相同时,分子量与表面能γS及表面能分量γSLW、酸碱比值γS+/γS-成正比,而与其酸性力γS+和碱性力γS-以及极性率γAB/γs成反比;而分子量相近时,表面性能可能主要受脱乙酰度的影响。随着脱乙酰度的增加,壳聚糖的表面能γS及其分量γSLW、酸碱比值γS+/γS-都增大。实验所测得的壳聚糖的表面能数据得到文献的支持。     

壳聚糖的化学改性(Ⅰ)

壳聚糖是一种带阳离子的天然活性多糖,在一定条件下可以发生降解反应,其降解产物具有比壳聚糖更优良的功能特性,广泛应用于医药、食品、农业及环保等领域。壳聚糖与醛、酮可发生Schiff反应生成相应的醛亚胺或酮亚胺化合物,后者在氢硼化物作用下加氢进一步转化为各种N-烷基类衍生物。文章概述了近年来壳聚糖化学改性方面取得的某些研究进展,主要包括糖类改性,三甲基化、N-琥珀酰化、硫醇化和叠氮化改性,环状糊精改性,冠醚改性,化学接枝改性等。     

The effect of reaction time and temperature during heterogenous alkali deacetylation on degree of deacetylation and molecular weight of resulting chitosan

The objective of the study is to elucidate the effect of reaction time and temperature during heterogenous alkali reaction on degree of deacetylation (DD) and molecular weight (MW) of the resulting chitosans, and to establish the reaction conditions to obtain desired DD and MW chitosan products. Chitin was extracted from red shrimp process waste. DDs and MWs were determined by infrared spectroscopy (IR) and static light scattering, respectively. The results are as follow: The DD and MW of chitin obtained were 31.9% and 5637 kDa, respectively. The DD of the resulting chitosan increased along with reaction time and/or reaction temperature. The DDs of the resulting chitosan that were obtained from 140°C were higher than those reacted at 99°C. The highest DD of the resulting chitosans after alkali deacetylation at 99 and 140°C were 92.2 and 95.1%, respectively. The DDs of chitosans increased fast at the beginning of reaction process then slowed over time. The reaction rate and rate constant of the deacetylation reaction decreased with increasing DD of the reactant. The MWs of chitosans decreased along with the deacetylation time. MW of those chitosans reacted at 140°C are smaller than those at 99°C. The rate of chitosan degradation was above 43.6%/h in the initial stage, then decreased to about 20%/h. The degradation rate constants raised substantially in the late stage. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2917–2923, 2003     

Molecular weight effect on antimicrobial activity of chitosan treated cotton fabrics

The effect of the molecular weight of chitosan on antimicrobial activity was investigated using three chitosans of different molecular weights [1800 (water soluble), 100,000, and 210,000] and similar degrees of deacetylation (86–89%). Cotton fabrics were treated with chitosan by the pad–dry–cure method. The molecular weight dependence of the antimicrobial activity of chitosan was more pronounced at a low treatment concentration. Chitosans with molecular weight of 100,000 and 210,000 effectively inhibited Staphylococcus aureus at a 0.5% treatment concentration. Chitosan with a molecular weight of 1800 was effective against S. aureus at a 1.0% treatment concentration. Escherichia coli was effectively inhibited by chitosan with a molecular weight of 210,000 at a 0.3% treatment concentration and by chitosans with a molecular weight of 1800 and 100,000 at a 1.0% treatment concentration. Proteus vulgaris was effectively inhibited by chitosans with molecular weight of 100,000 and 210,000 at a 0.3% treatment concentration and by chitosan with a molecular weight of 1800 at a 0.5% treatment concentration. None of the chitosans significantly inhibited Klebsiella pneumoniae and Pseudomonas aeruginosa below a 1.0% treatment concentration. Chitosans with high molecular weights were more effective in inhibiting bacterial growth than chitosans with low molecular weights. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2495–2501, 2001     

溶剂对壳聚糖粘度及Mark-Houwink方程参数的影响

采用粘度法分析了不同溶剂对壳聚糖粘度的影响 ,用光散射法测定了超声波分级的壳聚糖的相对分子质量。实验结果表明 :四种溶剂体系分别溶解壳聚糖 ,其粘度行为不同 ,溶剂的离子强度越大 ,壳聚糖的比浓粘度越小。在 0 .3mol/ L乙酸 + 0 .3mol/ L乙酸钠溶剂的条件下 ,应用 Mark-Houwink方程测得 K=0 .1 81 cm3 / g、α=0 .62 ,说明离子强度越大 ,壳聚糖分子的聚集态越大 ,α越小。为了获得准确的 K、α值和壳聚糖的相对分子质量 ,必须选择合适的溶剂体系来消除这种聚集态的影响。