Effects of Surface Characteristics and Xanthan Polymers on the Immobilization of Xanthomonas campestris to Fibrous Matrices

ABSTRACT: The production of xanthan gum, an industrially important microbial exopolysaccharide, was enhanced by using Xanthomonas campestris cells adsorbed to cotton fibers. However, the function of xanthan polymers during cell adsorption has not been elucidated. Polyethylenimine (PEI), a cationic polyelectrolyte, was employed to investigate respective effects of fiber surface properties and xanthan polymers during cell adsorption. Adsorption of X. campestris cells to fiber was independent of fiber roughness and hairiness, and the effect of electrostatic interactions between cells and fiber was insignificant. Fiber hydrophilicity was critical in initiating cell-fiber contacts, whereas xanthan polymers enhanced retention of cells on fiber surface. The untreated cotton showed the highest immobilization efficiency and xanthan production.     

荆树皮栲胶/纤维素-聚乙烯亚胺气凝胶吸附阿散酸的研究

以纤维素为原料,采用NaOH/尿素/水混合溶液溶解纤维素,通过溶胶-凝胶法将荆树皮栲胶（BWT）和聚乙烯亚胺（PEI）接枝到纤维素上以制备荆树皮栲胶/纤维素-聚乙烯亚胺气凝胶（（Cell/BWT）@PEI）,通过扫描电子显微镜（SEM）、比表面积（BET）分析、热分析（TG-DTG）等手段对其进行结构表征和性能分析,并且研究了其对阿散酸（p-ASA）的吸附性能。结果表明,（Cell/BWT）@PEI比表面积为190.5 m2/g,孔径为15.2 nm,具有较好的热稳定性;当p-ASA初始质量浓度为100 mg/L、溶液pH值为5.0、吸附时间为360 min、吸附温度为25℃、（Cell/BWT）@PEI投加量为0.4 g/L时,（Cell/BWT）@PEI对p-ASA的平衡吸附容量（Qe）为163.3 mg/g,去除率为65.3%;(Cell/BWT)@PEI对p-ASA的吸附为化学吸附,Freundlich等温吸附方程更适于描述（Cell/BWT）@PEI对p-ASA的吸附,且吸附过程自发进行;吸附再生实验结果表明,循环再生5次后,（Cell/BWT）@PEI对p-ASA的Qe为1...     

Development of water‐based polymeric dye and its application as a colorant for waterborne polyurethane

In this project, an eco‐friendly aqueous synthesis method of water‐based polymeric dye (WPD) was developed and its potential as a colorant for waterborne polyurethane (WPU) was tested. The WPD was produced by reacting polyethylenimine with commercial reactive dye in the warm alkaline solution. The colored polyurethane membrane was then produced via solution blending of WPD and WPU, followed by air‐drying. The results showed that WPD with a wide variety of colors can be easily synthesized by selecting different precursory reactive dyes and can be easily blended with WPU via moderate stirring. The colored PU membranes have good transparency and the logo under them can be clearly observed. Compared with the pure polyurethane membrane, the absorbance of colored polyurethane membrane at the wavelength of maximum absorption increases at least 20.2% even if the content of WPD within the colored polyurethane membrane is as low as 0.16%, implying that our WPD has excellent color strength. Finally, the colored polyurethane membranes have very high colorfastness to water and can be stored in deionized water for 2 weeks without dissolution of WPD. As a result, our developed WPD is a promising and cost‐effective colorant for WPU. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44710.     

Simultaneous Recovery of Nickel and Cobalt from Aqueous Solutions using Complexation-Ultrafiltration Process

Simultaneous recovery of nickel and cobalt from aqueous solutions by complexation-ultrafiltration process with polyethylenimine (PEI) was studied. Experiments were performed as a function of polymer/metal ratio (P/M), solution pH, and ionic strength. Effects of concentration time on metal rejection and membrane flux were also studied. At optimum experimental conditions of pH 6.0 and P/M 5.0, the nickel removal efficiency reaches at 99.9% and cobalt removal efficiency goes to 96.4%. Both nickel and cobalt removal efficiencies decreased as the adding salt concentration increases. During 12 h of the ultrafiltration process, the decline of membrane flux was less than 16% and the removal efficiencies for both nickel and cobalt were kept almost constant. Diafiltration was further performed to regenerate PEI. The removal efficiencies for both metals using recycled PEI were found to be close to those with the original PEI. Results from the two-step process of complexation-UF and decomplexation-UF separation showed that it could be a promising method for simultaneous recovery of nickel and cobalt from aqueous solutions.     

Improved Preparation Method of Polyethylenimine-Hydroxyapatite and Its Chromatographic Properties

Previously, we developed polyethylenimine-coated hydroxyapatite as a chromatography medium. This report describes a simple, safe, productive, and improved preparation method and reports further chromatographic properties. The improved polyethylenimine-coated hydroxyapatite was prepared by use of a rotary evaporator with neither decantation, cross-linking agent, nor organic solvent. In chromatography, ovalbumin (a phosphoprotein) was separated from other proteins. Furthermore, ovalbumin derivatives or nucleotides could be separated on the basis of the number of phosphate residues. This method yielded high-quality and -quantity polyethylenimine-coated hydroxyapatite.     

Efficient mAb production in CHO cells incorporating PEI‐mediated transfection,mild hypothermia and the co‐expression of XBP‐1

BACKGROUND: Transient gene expression (TGE) provides a rapid way to generate recombinant protein biologics for pre‐clinical assessment. Human embryonic kidney (HEK293) cells have traditionally been used for TGE; however, there is demand from industry for efficient, high‐producing TGE systems that utilize Chinese hamster ovary (CHO) cells. A polyethyleneimine (PEI) ‐based TGE process has been developed for CHO cells using an episomal expression system to generate enhanced recombinant protein titers. RESULTS: A five‐fold improvement in monoclonal antibody (mAb) volumetric productivity was achieved by examining key parameters including transfection medium, cell density, transfection reagent, DNA:reagent ratio, the time of transfer to mild hypothermia and feeding strategy post‐transfection. The Epi‐CHO system allowed for a six‐fold expansion in culture volume post‐transfection without significantly affecting specific productivity. This system generates 400% more mAb per µg of plasmid DNA when compared with a non‐episomal system. In addition, the use of X‐box binding protein 1 to enhance secretion capacity and provide further improvements in mAb production with TGE was investigated. CONCLUSION: Through optimization of key parameters, our results demonstrate the development of a low‐cost, high‐yielding, episomal TGE system that may be adopted during pre‐clinical biologic drug development. Copyright © 2011 Society of Chemical Industry     

Immobilization of alcohol dehydrogenase on the surface of polyethylene membrane

Using polyacrylic acid (PAA) modified polyethylene (PE) membrane as a carrier, two immobilization routes of alcohol dehydrogenase (ADH) were studied, and the catalytic performance of immobilized enzyme was investigated using formaldehyde as a substrate. In the first route, PAA-PE membrane was further modified by polyethyleneimine (PEI) and then ADH was covalently linked by glutaraldehyde (GA) to the surface of PEI/PAA-PE. The results show that the optimal immobilization pH was 6.0, immobilization temperature was 5—15℃, ADH and GA concentrations were 1.0mg/ml and 0.01%(mass). For immobilized enzyme, the optimal reaction pH was 6.5, temperature was 15—30℃, and the highest reaction rate was 9.6 μmol/(L·min), the remaining activity was 47.3% after 10 use cycles. In the second route, ADH was immobilized on PAA-PE membrane with 1-(3-dimethylaminopropyl)-2-ethylcarbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) as activators. The results show that the optimal molar ratio of EDC and NHS was 1∶0.5, and the immobilization time was 24 h. For immobilized enzyme, the optimal reaction pH was 6.5, temperature was 20—37℃, and the highest reaction rate was 15.58 μmol/(L·min), 53.8% activity was remained after 10 cycles.     

高分子季铵盐型抗菌材料的制备

通过γ-氯丙基三甲氧基硅烷的偶联,将水溶性聚乙烯亚胺(PEI)接枝在纳米SiO2表面,随后分别用1-溴己烷和碘甲烷对接枝的PEI进行N-烷基化修饰,使PEI中的部分氨基转变成季铵盐,得到水不溶性QPEI/SiO2微粒。通过测定PEI/SiO2上PEI的接枝量,考察了各种反应条件对QPEI/SiO2微粒制备的影响规律。研究结果表明,纳米SiO2表面接枝PEI的适宜条件为:反应溶剂为DMF,反应温度90~100℃,反应时间8 h,氯丙基化SiO2与PEI质量比为4∶1,在此条件下制备的QPEI/SiO2微粒中PEI接枝量为14.8%。QPEI/SiO2微粒经甲基化修饰后,季铵盐含量由0.96%增加到3.37%,其抗菌性能显著增强。