不同虾壳部位中的甲壳素和壳聚糖

用EDTA的方法分别从虾壳的不同部位:虾头、虾身、虾足和虾头内容物三部分制备甲壳素和壳聚糖,对三组试样的性能参数如脱乙酰度和相对分子量等进行分析研究。得出结论:由虾壳不同部位所制得的甲壳素和壳聚糖结构基本一致,但其脱乙酰度和相对分子量有较大差别,其物化性质也有所不同。在三组试样中,以从虾头壳制备的甲壳素和壳聚糖的相对分子质量为最大;而脱乙酰度则以从虾足和虾头内容物中制得试样较高。     

制备条件对脱乙酰甲壳素性能的影响

我们研究了甲壳素及脱乙酰甲壳素的制备方法,测定了脱乙酰甲壳素的分子量、脱乙酰度及粘度。对不同条件下及用不同原材料制得的脱乙酰甲壳素的性能进行了比较。结果表明,提高反应温度、碱液浓度和延长反应时间,可以提高脱乙酰度,但其分子量和粘度均相应降低。在脱乙酰度基本相同的情况下,由虾壳制得的脱乙酰甲壳素,其分子量和粘度都大于由蟹壳制得的产品。实验表明,脱乙酰甲壳素不适于在极性介质中吸附弱极性物质。     

壳聚糖脱乙酰度的实验研究

以虾壳为原料制取甲壳素 ,甲壳素脱乙酰基制备壳聚糖。讨论了影响壳聚糖脱乙酰度的因素。通过正交实验得出了制备壳聚糖的最佳工艺条件为氢氧化钠浓度 4 0 % ,反应温度 90℃ ,反应时间 14h。通过分段碱制得脱乙酰度高达 98.14 %的壳聚糖     

克氏螯虾制备甲壳素及壳聚糠的研究

以克氏螯虾(Procambarus clarkii)壳为原料,通过脱脂、脱蛋白及脱钙得到甲壳素,甲壳素继续脱乙酰基制得壳聚糖。研究了HCl质量分数、酸浸时间对甲壳素脱钙的影响及NaOH质量分数、反应时间对壳聚糖脱乙酰度和黏度的影响。得到较佳的工艺为:wHCl=5%,酸浸时间2 h;wNaOH=45%,脱乙酰反应时间4 h。制得甲壳素中灰分0.9%,壳聚糖脱乙酰度81%,黏度440 mPa.s。另外,在甲壳素制备中,通过原料粉碎、添加复合脱脂剂等工艺的改进来提高效率,降低酸、碱消耗,产品质量也得到提高。     

红螯螯虾壳制备壳聚糖的研究

以红螯螯虾壳为原料提取甲壳素,得到白色片状产品,收率为18%。甲壳素通过脱乙酰化制备壳聚糖,脱乙酰度可达83%。考察了浸酸时间、浸酸温度和NaOH浓度对产品质量的影响。结果表明,采用红螯螯虾壳制备壳聚糖是可行的。     

微波辐射制备壳聚糖

用质量分数34％的NaOH在微波辐射下对甲壳素进行非均相脱乙酰以快速制备壳聚糖，并测定了不同条件下制得的壳聚糖的相对分子质量和脱乙酰度，该反应时间短，重复性好，产品质量易控制。     

高脱乙酰度壳聚糖的制备及结构与性能研究

本文系统地研究了从虾壳制备高脱乙酰度、高分子量壳聚糖的方法。在一定条件下可得到脱乙酰度达97％,分子量达5×10~5左右的壳聚糖。用IR、NMR、DTA、TGA等分析技术对壳聚糖的结构与性能进行了研究。     

壳聚糖的微波干燥行为的研究

本文对壳聚糖在微波和烘箱技术条件下的干燥行为进行了研究。并对其脱乙酰度、粘度、分子量及红外光谱进行了测定。结果表明，用微波干燥处理壳聚糖所用的时间是用烘箱处理所需要的十分之一；而其脱乙酰度、粘度、分子量及红外光谱在两种条件下测得的结果几乎一致。实验还发现，在相同条件下，由虾壳制得的壳聚糖，其分子量和粘度都大于由蟹壳制得的产品。     

微波法制备壳聚糖絮凝剂的研究

以虾壳作为原料制得甲壳素后,用NaOH溶液浸润然后在微波作用脱去乙酰基和蛋白质制备壳聚糖;研究了影响壳聚糖脱乙酰度及粘均分子质量的因素;选择c（NaOH）=45%～50%,微波功率400 W,一次微波法反应时间10 min,可得脱乙酰度75%、分子质量（3.5～4） 万的壳聚糖;二次微波法每次反应时间分别为5 min,可得脱乙酰度90%的壳聚糖;与传统方法相比,缩短了反应时间,节约了能耗;将实验制得的壳聚糖作为絮凝剂用于含磷废水,絮凝效果明显,除磷率可达90%.     

微波间歇法快速制备高粘均分子量和高脱乙酰度的壳聚糖

使用微波间歇法可快速制备高脱乙酰度和高粘均分子量的壳聚糖. 单因素实验确定的工艺条件为微波功率800 W,将45%(w)的氢氧化钠溶液与250~380 mm的20 g甲壳素粉以8:1的体积比混合,在100℃下反应10 min,洗涤、微波干燥后在相同条件下再反应1次,共20 min,可制得脱乙酰度为94.5%、粘均分子量1.48×106的白色壳聚糖粉末. 其他制备条件相同,使用电加热法间歇处理甲壳素粉3次,反应共5 h,可以得到脱乙酰度为96.2%、粘均分子量为3.8×105的褐色壳聚糖粉末. 微波间歇法所制壳聚糖的结晶度高,内部有规整的有序结构,用它制备的膜致密,性能优于用电加热法所制壳聚糖制备的膜.     

Variation in Properties of Chitosan Prepared at Different Alkali Concentrations from Squid Pen and Shrimp Shell

Chitin from squid pen (Loligo sp.) and kiddi shrimp shell (Parapenaeopsis stylifera) were treated at room temperature (30 ± 2°C) with four different concentrations of sodium hydroxide: 20, 30, 40, and 50% w/w. With 50% sodium hydroxide solution, within 108 h, the chitin from squid pen was deacetylated to give chitosan. But it required 126 h at 40% and 144 h at 30% concentration of sodium hydroxide. In the case of chitin from Parapenaeopsis stylifera, complete deacetylation took place after 120 h and 168 h at 50 and 40% concentrations of sodium hydroxide, respectively. But shrimp shell on treatment with 20 and 30% sodium hydroxide solutions and squid pen kept at 20% sodium hydroxide were not sufficiently deacetylated even after 480 h. Properties like degree of deacetylation, viscosity and molecular weight of the prepared chitosan samples were studied. Minimum alkali concentration required for the formation of chitosan at room temperature was found to be 30% for squid chitin and 40% for shrimp chitin. With the increase in the time of deacetylation, decreases in molecular weight and viscosity were observed in chitosan from both sources. Maximum viscosity was recorded by chitosan prepared from squid pen using 30% sodium hydroxide solution at room temperature.     

A new approach for the preparation of chitosan from γ‐irradiation of prawn shell: effects of radiation on the characteristics of chitosan

Chitosan is a biodegradable polymer composed of randomly distributed β‐(1,4)‐linked D ‐glucosamine (deacetylated unit) and N‐acetyl‐D ‐glucosamine (acetylated unit). It is produced commercially by deacetylation of chitin, which is the structural element in the exoskeleton of crustaceans (such as crabs and shrimps) and the cell walls of fungi. In the work reported, we developed a facile technique for the preparation of chitosan by irradiating prawn shell at various intensities from 2 to 50 kGy. It was observed that γ‐irradiation of prawn shell increased the degree of deacetylation (DD) of chitin at a relatively low alkali concentration during the deacetylation process. Among the various irradiation doses applied to prawn shell, a dose of 50 kGy and 4 h heating in 50% NaOH solution yielded 84.56% DD while the chitosan obtained from non‐irradiated prawn shell with the same reaction conditions had only 74.70% DD. In order to evaluate the effect of γ‐irradiation on the various physicochemical, thermomechanical and morphological properties, the chitosan samples were again irradiated (2–100 kGy) with γ‐radiation. Molecular weight, DD, thermal properties with differential scanning calorimetry and thermogravimetric analysis, particle morphology by scanning electron microscopy, water binding capacity (WBC), fat binding capacity (FBC) and antimicrobial activity were determined and the effects of various γ‐radiation doses were assessed. The DD, WBC, FBC and antimicrobial activity of the chitosan were found to improve on irradiation. It was obvious that irradiation caused a decrease of molecular weight from 187 128 to 64 972 g mol^?1 after applying a radiation dose of 100 kGy which occurred due to the chain scission of chitosan molecules at glycosidic linkages. The decrease of molecular weight increased the water solubility of the chitosan, the extent of which was explored for biomedical applications. Copyright © 2012 Society of Chemical Industry     

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     

Chitosan and modified chitosan membranes I. Preparation and characterisation

Chitosan has been prepared from prawn shell and crab shell chitin. The molecular weight of the material derived from prawn shells is higher than that obtained from crab shell. The molecular weight, tensile strength, elongation at the break, and hydrophilic properties of chitosan are extremely dependent on the degree of deacetylation achieved when chitin is hydrolyzed to chitosan. Graft copolymers have been prepared with chitosan and a series of vinyl monomers using both heterogeneous and homogeneous reaction conditions. The hydrophilic properties of chitosan can be modified by blending with poly(vinyl alcohol).     

低分子量壳聚糖的制备

利用H2O2的强氧化性制备低分子量分布的壳聚糖是将虾皮用HC l浸泡去除碳酸钙盐;再用稀碱除去蛋白质得甲壳素;然后浓碱在50℃与其反应,并控制反应时间,分别制备出脱乙酰度为85%,93%,99%的壳聚糖,最后用H2O2氧化不同脱乙酰化壳聚糖,得到不同低分子量的壳聚糖。其中,脱乙酰度为85%壳聚糖用不同浓度的H2O2降解,得到了4.7×105,3.5×105,2.5×105,1.2×105,8×105等5个不同分子量段的壳聚糖产品。H2O2浓度越大,降解所得壳聚糖的分子量就越小。     

Valorization of chitins extracted from North Morocco shrimps: Comparison of chitin reactivity and characteristics

Huge quantities of waste discharged by the gray and pink shrimp decortication units in the North of Morocco can be valorized by producing about 950 tons of pure chitin, which can be transformed into 700 tons of highly to totally deacetylated chitosan. During the preparation of chitin and chitosan from gray and pink shrimps, differences in reaction behavior were observed even though these are taxonomically close species. The presented results concern several chitinous sources, and they show that the progress in the N-deacetylation reactions of chitin would be linked to the crystallinity index of the starting chitin. Following the kinetic study of the polymer hydrolysis during N-deacetylation, the difference in the molecular weights of the chitosan samples obtained under identical reaction conditions was related to the differences between molecular weights of the native chitin, 478 000 g.mol⁻¹ for pink shrimp and 562 000 for gray shrimp. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47804.     

不同来源甲壳素和壳聚糖的吸湿性与保湿性

对虾、蟹、蝇蛹和蝉子虫为原普的甲壳素和壳聚糖的吸湿性和保湿性进行了研究，结果表明，蝉子虫甲壳素和壳聚糖有较高的吸湿性和保湿性。     

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     

Production of Well-Dispersed Aqueous Cross-Linked Chitosan-Based Nanomaterials as Alternative Antimicrobial Approach

In the current study, chitosan was extracted by deacetylation of chitin, which is extracted from shrimp shell. chitosan nanoparticles (CSNPs) were prepared by ionotropic gelation technique. chitosan/tripolyphosphate ratio (CS:TPP) was kept at 3:1 to prepare CSNPs. chitosan/silver nanocomposite (CS/AgNCs) were prepared by incorporating silver nanoparticles into CSNPs. The quality of the prepared nanocomposite was evaluated by infrared spectroscopy, UV–Vis spectroscopy, transmission electron microscopy, and antibacterial activity. Results showed that chitosan/silver nanocomposite in which, both chitosan and silver are in nanoscale was successfully prepared for the first time in a well-dispersed aqueous form. Whereas CSNPs act as a host material to form the nanocomposite unlike the previously prepared forms of chitosan–silver nanocomposites, that used chitosan bulk as host materials and the dispersion medium was slightly acidic. Moreover, results revealed that the antibacterial activity of CSNPs was significantly enhanced after incorporating trace amount of silver nanoparticles (0.535% w/w AgNPs/CSNPs).