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21.
Combined biosynthesis and product separation has been successfully performed for the first time using a zonal centrifugal bioreactor–separator. The biosynthesis of dextran polymer from sucrose using the dextransucrase enzyme was investigated in order to evaluate bioreactor performance. The bioreactor consisted of a bowl, fitted with a Reorienting gradient rotor which facilitated substrate and enzyme loading and the reproducible unloading of solutions from the system. This allowed the distribution of substrate, enzyme and product materials in the bowl at the end of each trial to be accurately determined. Studies have indicated that combined bioreaction–separation is possible using this system. However, viscosity build-up in the bioreactor must be minimised in order to increase the yield of polymer product per unit time and improve product separation.  相似文献   
22.
通过改变分散剂的种类和用量,引发剂的用量及聚合反应时间等实验条件,在能获得轴向流型的聚合反应釜中,烯丙基葡聚糖与N,N‘-亚甲基双丙烯酰胺可以悬浮聚合,形成分布较窄的珠状亲水层析凝胶。  相似文献   
23.
Solid polymer electrolytes (SPEs) play a pivotal role in advancing electrochemical devices, such as proton batteries and supercapacitors, owing to their potential for enhancing safety and flexibility. In this work, employs a solution casting technique to prepare SPEs, utilizing chitosan-dextran blends as the polymer matrix. Ammonium thiocyanate (NH4SCN) is incorporated as a charge carrier, while honey is introduced as a plasticizer. The interaction between these materials is confirmed through Fourier transform infrared (FTIR) analysis. X-ray diffraction (XRD) analysis reveals that the addition of 10 wt.% honey (H10) to the polymer blend results in the lowest degree of crystallinity (15.24%), emphasizing the pivotal role of plasticizers in modulating the structural properties of SPEs. Furthermore, by incorporating 40 wt.% NH4SCN (SN40) into the plasticizer-polymer host (H10), the ambient temperature conductivity obtains its maximum value of (1.08 ± 0.19 × 10−3 S cm−1) with the lowest degree of crystallinity of 10.44%, verify it is the most amorphous electrolyte. The observed trend in conductivity is influenced by the diffusion coefficient (D), ion density (n), and mobility of the ions (μ). Complementing these findings, field emission scanning electron microscopy (FESEM) is employed to investigate the surface morphology and cross section of the SPEs, providing a comprehensive understanding of their structural characteristics. From linear sweep voltammetry (LSV), SN40 is electrochemically stable up to 2.2 V and the tion is 0.97 indicating that the ions are the dominant charge carriers.  相似文献   
24.
Physiological effects of the polymeric cryoprotectant dextran on an ion-transporting epithelium were investigated. In the isolated rabbit pancreas, dextran caused inhibition of fluid secretion and an increase of the concentrations of Na+, K+ and Cl? in the secreted fluid. Dextran did not affect the basal or pancreozymin-stimulated enzyme secretion. These effects of dextran can partially be explained by the fact that it is osmotically active and does not permeate through the epithelium. The effect of dextran on water transport can be compensated by lowering the ion concentrations in the solvent of the cryoprotectant. It is concluded that in cryoprotected ion-transporting epithelia the absolute ion concentration values obtained by X-ray microanalysis of frozen-hydrated specimens may not be completely correct, but that valid conclusions about intracellular ion distribution may still be drawn.  相似文献   
25.
合成右旋糖酐菌体固定化研究   总被引:2,自引:0,他引:2  
为了将微生物固定化技术用于合成右旋糖酐,对肠膜明串珠菌20074固定化载体和固定化条件进行了研究。活性炭固定肠膜明串珠菌20074的效果较好,以活性炭为载体,获得肠膜明串珠菌20074的固定化条件为:培养基初始pH值为7.10,接种量10%,固定化时间10~13 h,摇床转速150 r/min,温度25℃,右旋糖酐产率为81.6%。用高效凝胶渗透色谱法测定合成的右旋糖酐相对分子质量大于40万,红外光谱表征产品结构中的特征基团与标准品相符。  相似文献   
26.
研究了电渗析法除右旋糖酐铁原液中氯化钠新工艺的可行性及电渗析装置的设计模型,探讨了电渗析法除盐对产品质量的影响,并对比2种除盐工艺的经济性.  相似文献   
27.
Natural polysaccharides like chitosan and dextran have garnered considerable interest in biomedical applications due to their biocompatibility, biodegradability, and nontoxicity. Nonetheless, the development of a reproducible class of medical devices from these materials is challenging and has had limited success. Chitosan and dextran are inherently variable and synthesis using these materials is prone to inconsistencies. In this study, we put forward a robust product development regimen that allows these natural materials to be developed into a reproducible class of biomaterials. First, an array of validated characterization methods (Proton Nuclear Magnetic Resonance, titrations, Ultraviolet spectroscopy, Size Exclusion Chromatography—Multi-Angle Light Scattering, Size Exclusion Chromatography—Refractive Index, and proprietary methods) were developed that allowed rigorous specifications to be set for unprocessed chitosan and dextran, chitosan and dextran intermediates, and chemically modified materials—acrylated chitosan (aCHN) and oxidized dextran (oDEX). Second, a robust and reproducible synthesis scheme involving various in-process controls was developed to chemically modify the unprocessed polysaccharides. Third, purification methods to remove byproducts and low-molecular-weight impurities for both aCHN and oDEX were developed. The study presents a viable strategy for converting variable, natural materials into a reproducible class of biomaterials that can be applied in various biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48454.  相似文献   
28.
As drug delivery systems, stimuli‐responsive polymer micelles hold great potential in cancer chemotherapeutics to improve therapeutic efficiency and eliminate organism adverse effects. Here, pH‐sensitive polymeric micelles based on dextrang‐benzimidazole were designed and used for intracellular anticancer drug delivery. The anticancer drug doxorubicin (DOX) was effectively loaded into the micelles via hydrophobic interactions. In vitro release studies demonstrated that the release of loaded DOX was greater and faster under acid conditions such as in carcinomatous areas (pH < 6.8) than in physiological conditions (pH 7.4). MTT assays and flow cytometric analyses showed that DOX‐loaded micelles had higher cellular proliferation inhibition towards HeLa and HepG2 cells than pH‐insensitive controls. These pH‐sensitive micelles with significant efficiency for intracellular drug release will be beneficial to the future of in vivo biomedical applications. © 2014 Society of Chemical Industry  相似文献   
29.
30.
Wyn Brown  Peter Stilbs 《Polymer》1983,24(2):188-192
Transport in ternary polymer1, polymer2, solvent systems has been investigated using an n.m.r. spin-echo technique. The dependence of the self-diffusion coefficient of poly(ethylene oxide) polymers on the concentration and molecular size of dextran in aqueous solution has been measured. Monodisperse poly(ethylene oxide) fractions (M?w=7.3×104, 2.8·105 and 1.2·106) and dextrans (M?w=2·104, 1·105 and 5·105) have been employed over a range of concentration up to the miscibility limit in each system. It is found that when the molecular size of the diffusant is commensurate with or exceeds that of the matrix polymer, a relationship of the form: (DD0)PEO=exp?k(C[η]) is applicable, where C[η] refers to the dextran component and is considered to describe the extent of coil overlap in concentrated solution. (DD0) is independent of the molecular size of the poly(ethylene oxide), at least in the range studied (Mw<300 000).  相似文献   
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