Green Synthesis and Physical and Chemical Characterization of Chitosans with a High Degree of Deacetylation, Produced by a Binary Enzyme System

Chitosan is a biopolymer obtained from chitin, where the N-acetylglucosamine monomer is in its deacetylated form; this polymer is useful for a wide variety of industrial applications. The properties and uses of chitosan depend on its physical and chemical characteristics, which result from the treatments used for its production. In this study, we report the preparation and characterization ofchitosan oligosaccharides by a green synthesis from crystalline shrimp chitin, using a sequential enzyme treatment by chitinase and chitin deacetylase. Chitinases were purified from grapes and used to rupture the crystalline shrimp chitin structure, modifying the crystallinity index from 57.6% to 15.9%. The resultant polymers were deacetylated using a recombinant chitin deacetylase from Saccharomyces cerevisiae, which was cloned and expressed in Pichia pastoris. The chitosans produced showed an estimated DA （degree of acetylation） of approximately 20%, and the molecular weights ranged from -7,600 to -3,700 after treatment in pH 3.0 and pH 6.0 for 10 min and 40 min, respectively. Physical and chemical characterization of the products indicated that enzyme fragmentation of chitin probably makes the acetamide groups more accessible to deacetylation, forming homogeneous polymers that are free of hazardous sub-products, have defined low molecular weights, and are highly deacetylated.

Methods of <i>N</i>-acetylated chitosan scaffolds and its <i>In-vitro</i>biodegradation by lysozyme

Generally, the lysozyme degradation on chitosan (CTS) is slower than that of chitin (CT). The CTS can be fabricated in scaffold form but it is difficult to fabricate CT scaffold under mild conditions. The method for the preparation of scaffold from N-acetylated CTS (N-CTS) was investigated in this research. By using this method, the scaffolds could be fabricated chitosan to chitin with the degree of acetylation (DA) 18% - 70%. Among these scaffolds, the highest degradation of scaffold by lysozyme was observed on the N-CTS scaffold with DA 60%, which determined by examination of the reducing end contents in the degradation media and by measuring the weight loss of scaffolds. Moreover, the best condition for the degradation of N-CTS scaffold with DA70% by lysozyme was also investigated. The maximum degradation rate of the scaffold was observed on the treatment with lysozyme 500 mg/l of acetate buffer at pH 4.5, 37°C, 100 rpm and for 7 days.

Effects of Partially N-acetylated Chitosans to Elicit Resistance Reaction on Brassica napus L.

The effects to elicit resistance reaction on oilseed rape (Brassica napus L. cv Xinongchangjiao ) by four partially N-acetylated chitosan 7B, 8B, 9B and 10B (Degree of acetylation (D. A.) is 30% , 20% , 10%, 0%, respectively) and Glycol chitosan (GC, D.A. is 0%) were investigated and compared. Results showed that chitosan were similar to salicylic acid (SA), and could induce resistance reaction, but the reaction was influenced by the degree of acetylation of chitosan. Fully deacetylated chitosans, 10B and GC, elicited chitinase activity, but partially acetylated chitosan, 7B, 8B and 9B, inhibited chitinase activity. Phenyalanine ammonia-lyase (PAL) was also elicited. Elicitor activity increased with on increasing degree of acetylation, 7B induced highest PAL activity among all chitosans. All chitosans induced peroxidase (POD) in a similar level. After elicited by glycol chitosan, like SA treatment, the seedlings increased disease resistance to Sclerotinia sclerotiorum significantly.

Preparation and Surface Modification of High-Density Chitosan/Functionalized Multi-walled Carbon Nanotubes Hollow Fibers

Functionalized multi-walled carbon nanotubes( fMWNTs) were prepared with chitosan via controlled surface deposition and crosslinking process and scanning electron microscopy( SEM),Fourier translation infrared spectroscopy( FT-IR) and Xray diffraction( XRD) are used to character properties. A novel high-density chitosan( HCS) was dissolved in f-MWNTs dispersed dilute acetic acid with a maximal concentration of 5. 8%. The hollow fibers can be made by extruding the solution into a dilute alkali solution through a wet-spinning process and the tensile properties of the materials were evaluated by universal tester. The surface property of fibers,pretreated by Helium( He) and the following grafted with gelatin was evaluated with X-ray photoelectron spectroscopy( XPS).As the hollow fibers were intended for neural tissue engineering,its suitability was evaluated in vitro using rat Schwann cells( RSC96) as model cells. The cells attachment,proliferation and morphology,were studied by various microscopic techniques. Based on the results,the gelatin grafted HCS / f-MWNTs hollow fibers could be used as a potential cell carrier in neural tissue engineering.

Enhancing Biological Wastewater Treatment with Chitosan

Chitin and chitosan have been applied to biological wastewater treatment.From a number of parallel comparison experiments,it can be concluded that the application of chitin and chitosan can both enhance the biological treatment,besides which chitosan is more efficient than chitin.The study on the enhancement mechanism reveals the difference between the two additives:chitosan improves the sludge structure and settlibility,while chitin acts as a kind of carrier for microorganism in the biological treatment system.

Seed treatment and inhibition of plantpathology by chitosan

0. 1% solution of chitosan was studied as seed soaking agent for cotton and maize.Chitosan will help stimulate the seeds of cotton and maize for sprouting. It can also restrain thefosanum oxysporin and verticillium. then inhibit the cotton wilt and maize smut. The annual out-put of cotton and maize increased by 11.80% and ,0.4%, respectively.

Research of the Mechanism of Enhancing Biological Treatment by Chitosan

Chitosan of different molecular weight （M. W. ） was added into SBR bioreactor to treat domestic wastewater. From comparison of treatment efficiency, sludge activity, sludge structure etc., we revealed the mechanism that chitosan enhanced the biological treatment function of activated sludge. The results proved that, chitosan is certain to restrain the reaction of activated sludge, but it do improve the structure of sludge floes and increase the treatment efficiency of activated sludge. The bigger the M. W. of chitosan is, the better the efficiency of enhancing biological treatment can be.

Adsorption and Desorption Behaviors of Bovine Serum Albumin on Gelatin/Chitosan Sponge

Gelatin (Gel) and chitosan (CTS) have several biomedical applications because of their biodegradability and biocompatibility. Crosslinking of Gel and Gel/CTS systems was evaluated using N-acetyl-D-glucosamine (GlcNAc) formed into sponges by lyophilization. The prepared sponges were used to study the adsorption and desorption of fluorescein isothiocyanate (FITC) labeled bovine serum albumin (BSA) as a model instead of a growth factor. The effect of FITC-BSA concentration and temperature on the adsorption behavior of Gel/CTS sponges was investigated. The Langmuir adsorption isotherm model was used on the basis of the assumption that monolayer adsorption occurs on the surface;the results fit with the experiment data. The adsorption constants were 5.77 and 9.68 mL/mg for Gel and Gel/CTS sponges, respectively. The adsorption thermodynamic constants were found;adsorption onto sponges was an exothermic reaction. In particular, Gibbs free energy (ΔG) exhibited negative values in the range of 283 - 343 K for both Gel and Gel/CTS sponges, demonstrating the spontaneous nature of adsorption reaction. In addition, desorption behavior was evaluated for different concentrations and pH values of the FITC-BSA solution. The high adsorbed amounts of FITC-BSA on sponge resulted in high desorbed amounts in sponge, up to 55% from 3.5 mg/mL adsorbed concentration (around 1.5 mg from 3 mg adsorb amount). Desorption decreased following the buffer solution pH decrease, from 7.4 to 4 and 2 in Gel and Gel/CTS sponges, respectively. Based on the results of this preliminary study, these composite sponges could have significant application in biomedical materials.

Composites on Base of the Ultradispersed Polytetrafluoroethylene and Chitosan Salts

Composites based on ultradispersed polytetrafluoroethylene and chitosan salts (nitrate, perchlorate and dodecahydro-closo-dodecaborate) and methods of their fabrication have been developed. For this purpose, the ultrasonic effect on the mixture of the aqueous gels of chitosan salts with dry UPTHE or UPTFE ethanol dispersion with propeller agitators. Introduction of ultradispersed polytetrafluoroethylene improving their functioning properties, namely high combustion efficiency and resistance to air moisture.

Immobilized chitosan as a selective absorbent for the nickel removal in water sample

Method for preparation of chitosan immobilized on silica gel(CTS silica) was described. The CTS silica was used as absorbent for the absorption of nickel in water. The results showed that this absorbent had relatively high selectivity and strong affinity to nickel. The maximum absorption capacity for nickel can reach 667 mg/g of chitosan. Factors that affect the absorption capacity, such as pH, ion strength and the presence of calcium, EDTA and the mechanism of absorption were discussed in detail. The absorbent can be regenerated with acid and reused for several times. The recovery rate for nickel can reach 99 99%. This absorbent filled in a column can be used in nickel removal from wastewater and drinking water.

Optimization of the methods for extraction of chitin in crab shell and preparation of chitosan

A combination of both acid and alkali treatments was used to extract chitin from crab shell in this study. Then, a three factors (NaOH solution concentration, reaction time, reaction temperature) and three levels (35, 45, 55; 2, 6, 10; 70, 105, 140) L 9(3 4) orthogonal experiment design is further adopted to conduct a de acetyl treatment to prepare chitosan by considering the viscosity and de acetyl degree of the chitosan as the main performance indexes. Determination of de acetyl degree of chitin complys with the procedures given by the reference and the viscosity meter was used for determination of viscosity of chitosan. The results show that the extraction of chitin shall use pulverized crab shell as the raw material and such raw material shall be immersed in 10% HCl solution for 6 hours and washed with water for one time in every 2 hours, then heated in boiled water for 2 hours by the use of 10% thin NaOH solution. Afterwards, the said material shall be washed with water to become a neutral solution and dried over a stove. When chitin is mixed with 55% NaOH solution in a proportion of 1∶10 (W/V, g/mL) and the reaction takes place at a temperature of 105℃ for 6 hours, chitosan having a de acetyl percentage of 94% and viscosity of >200 cps can be available.

Preparation of magnetic chitosan microspheres and its applications in wastewater treatment

The methods of preparation of magnetic chitosan microspheres have been introduced. In addition, their applications in the wastewater treatment, based on different kinds of wastewater, have been reviewed, and their mechanisms have been discussed.

Preparation of Spherical Silica-supported Biosorbent for Copper Ions Removal in Wastewater Based on Sol-gel Reaction and Simple Treatment with Sodium Hydroxide

A new and effective strategy was proposed for preparing new organic-inorganic composite biosorbent with spherical silica as supporting core and chitosan（CS）-based hybrid layer as shell based on sol-gel reaction and simple treatment with sodium hydroxide（NaOH）. The coating layer was covalently bound on the supporting silica through polysaccharide incorporated sol-gel process starting from CS and inorganic precursor γ-glycidoxypropyltrimethoxysiloxane（GPTMS）. GPTMS had epoxide groups and cross-linked amine groups of CS to avoid its acidic solubilization. The composite biosorbent had coarse surface due to the wet phase-inversion by treating in NaOH solution. The prepared biosorbent could be used in treating electric plating wastewater.

脱支玉米淀粉-壳聚糖复合物的制备及结构表征

为了探究脱支处理对玉米淀粉-壳聚糖复合物理化性质和流变特性的影响,以玉米淀粉(MS)为原料,用普鲁兰酶酶解脱支,将脱支淀粉(DBS)与壳聚糖(CS)溶液混合制备脱支玉米淀粉-壳聚糖复合物(DBS-CS),测定复合物的微观结构、粒径分布、结晶结构、分子短程有序结构、流变学特性。结果表明:脱支玉米淀粉-壳聚糖复合物的颗粒表面附着壳聚糖越多,颗粒间的结合力越紧密且复合物的平均粒径越大,热稳定性提高。脱支后的DBS和DBS-CS的结晶度降低,结晶结构由A型转变为B型。红外光谱和核磁共振氢谱表明淀粉与壳聚糖能够形成复合物且脱支后的玉米淀粉与壳聚糖复合效果更好。脱支淀粉-壳聚糖复合物具有典型的弱凝胶动态流变行为和假塑性剪切变稀行为。本研究结果为获得一种新型绿色的复合改性淀粉提供了理论依据。

静电纺壳聚糖基纳米纤维的制备及其在水处理中应用研究进展

为提高壳聚糖的可纺性,改善壳聚糖基纳米纤维的物理形态和力学性能,对国内外利用静电纺丝技术制备壳聚糖基纳米纤维的相关研究进行了综述。介绍了壳聚糖静电纺丝液的配制要求以及不同纺丝参数对纤维形态的影响;在此基础上,详细综述了壳聚糖化学改性纳米纤维和壳聚糖共混改性纳米纤维的研究进展;最后,对应用壳聚糖基纳米纤维处理废水中重金属离子、染料和其它污染物的研究现状进行总结。研究发现:不同纺丝参数最终均是通过影响射流拉伸的难易程度来改变纤维形态,且通过化学改性和共混改性的方法不仅可提高壳聚糖的可纺性,还可增强壳聚糖基纳米纤维的耐酸性、热稳定性、抗菌性和吸附性;同时指出探寻新的溶剂、共混剂和功能材料以及与选择性分离技术结合来增强对水中污染物的吸附能力是壳聚糖基纳米纤维的未来发展趋势。

铜基氮碳微球对废水中盐酸四环素的吸附性能

以水溶性低相对分子质量壳聚糖(0.1000 g)为碳源和氮源,Cu(NO_(3))_(2)·3H_(2)O(0.2174、0.2899、0.6522 g)为铜源,采用一步水热法制备了3种铜基氮碳微球Cu-x/NC(x=1、2、3),通过SEM、FTIR、XRD、Raman光谱和BET对Cu-x/NC进行了表征,通过静态吸附实验考察了Cu-x/NC对盐酸四环素(TC)的吸附性能,并测定了吸附动力学、吸附等温线和吸附热力学参数,测试了Cu-x/NC抗离子干扰、pH稳定性和循环吸附性能。结果表明,Cu-x/NC呈规整的球形结构,表面有含氧和含氮基团,并均匀分布着Cu元素;在25℃吸附温度和24h吸附时间的条件下,Cu-2/NC(5 mg)表现出吸附TC的最大平衡吸附容量(1993.42 mg/g);Cu-2/NC吸附TC符合Langmuir等温线模型和准二级动力学模型,吸附过程是自发、吸热过程;TC溶液中存在NaCl不会降低Cu-2/NC吸附TC的平衡吸附容量,TC溶液在p H=5.5时对吸附最有利;7次循环吸附测试中,Cu-2/NC对TC表现出较为稳定的去除率(95.84%~86.67%);Cu-2/NC吸附TC依靠的主要作用力有氢键、Cu阳离子桥、电子供体-受体相互作用以及静电作用。

Natural Polysaccharide:Modification and Application

Natural polysaccharides are synthetic macromolecules located in the cell wall and intracellular,intercellular,and secretory cells.These are essential components of life activities.Cellulose and its derivatives,chitosan,alginic acid,starch,and other natural polymer materials that exist in nature are polysaccharides.This article briefly reviews the structure and sources of several natural polysaccharides,focusing on the modification design strategies of polysaccharides such as graft polymerization,oxidation,etherification,and esterification on cellulose(mainly cellulose nanocrystals,CNC),chitosan(CTS),and other polysaccharides and derivatives in the fields of biomass energy,composite materials,wastewater treatment,and biomedicine.Based on the theory of modification and application of polysaccharides at the present stage,future research goals and modification strategy design are prospected.

西兰花采后霉变控制技术研究

西兰花花球采后贮运过程中易出现真菌霉变现象,严重影响其商品品质。为降低贮运过程中西兰花真菌霉变发生情况,本研究采用不同温度、乙醇浓度、壳聚糖涂膜浓度等对西兰花进行处理。单因素试验结果表明,45℃热激处理效果最佳,3 d病斑面积为6%;最适的乙醇处理浓度为30%,处理3 d后病斑面积仅为3.4%;壳聚糖涂膜浓度1.5%和2%均有很好的抑菌效果,3 d后病斑面积分别为7.3%和4.5%,且无显著差异,综合考虑采用1.5%的壳聚糖浓度处理最为适宜。45℃热激+1.5%壳聚糖和30%乙醇+45℃热激处理西兰花的霉变病害控制效果表明,两个组合处理均能有效控制病害发生;30%乙醇+45℃热激处理组,能降低乙醇残留,更加绿色安全,且保绿抗霉变效果更好。

PNIPAm@CMCS生物基水凝胶吸附染料研究

针对目前皮革废水处理剂难回收问题,以羧甲基壳聚糖(CMCS)和聚N-异丙基丙烯酰胺(PNIPAm)为原料,合成一种兼具优异吸附性和可重复利用且易回收的生物基水凝胶(PNIPAm@CMCS),并对该水凝胶的抗疲、亲水、溶胀、吸附及抗菌等性能进行了研究。结果表明,所制备的生物基水凝胶具有出色的抗疲性(耐循环压缩15次)、溶胀率(2034%)、吸附性(伊红Y=587 mg/g,罗丹明=444 mg/g,甲基橙=621 mg/g)和抗菌性能(抗菌率=100%)。该生物基水凝胶作为一类高效、环保的染料废水处理剂,展现了广阔的应用前景,有望为制革工业处理含染料污水提供新的思路。

功能化壳聚糖基材料处理有机废水研究进展

壳聚糖具有优良的生物降解性、生物相容性和可再生性,在医药、食品、化妆品、废水处理等领域拥有广阔的应用前景和独特的优势。介绍了壳聚糖的功能化改性方法,如交联改性、接枝聚合、金属螯合、分子印迹、磁化改性,对比了不同改性方法的优缺点,综述了功能化壳聚糖基材料对酚类、抗生素类、有机染料类及其他有机废水处理的研究进展。