分子筛固定氨基酰化酶I的研究

以Y型分子筛为载体,分别采用吸附法、吸附-戊二醛交联法、偶联法和偶联-重氮法4种方法对氨基酰化酶I进行固定化。 研究发现偶联法获得的分子筛固定化酶的活性最高,达0.258 IUmg-1,并对分子筛固定化酶最适pH值、最适反应温度、重复使用性和米氏常数进行了测定;结果表明该载体适合氨基酰化酶I的固定,可以获得较高的酶活力,分子筛固定化酶的最适pH值、最适反应温度都有所拓宽。     

分子筛固定氨基酰化酶Ⅰ的研究

以Y型分子筛为载体,分别采用吸附法、吸附-戊二醛交联法、偶联法和偶联-重氮法4种方法对氨基酰化酶I进行固定化。 研究发现偶联法获得的分子筛固定化酶的活性最高,达0.258 IUmg-1,并对分子筛固定化酶最适pH值、最适反应温度、重复使用性和米氏常数进行了测定;结果表明该载体适合氨基酰化酶I的固定,可以获得较高的酶活力,分子筛固定化酶的最适pH值、最适反应温度都有所拓宽。     

固定酶法催化合成生物柴油Ⅰ.大孔树脂固定化脂肪酶的制备

研究了用于生物柴油酶催化的大孔树脂固定化脂肪酶的制备过程,考察和优化了脂肪酶固定化方法及条件。结果表明,采用大孔树脂D3520作载体,以载体涂布法固定化脂肪酶的最适固定化条件为:酶用量为酶∶树脂=0.16∶1(质量比),吸附时间1~3 h,pH值范围为9.0~9.4,固定化温度40℃。酶活力可达91.49 U/g,酶活回收率约为54%。     

AS1.398中性蛋白酶的固定化研究

利用壳聚糖为载体，戊二醛为交联剂，对AS1．398中性蛋白酶进行了固定化研究，固定化反应的最佳条件是采用1％的戊二醛浓度，壳聚糖和戊二醛的交联反应时间为4h，加入酶固定化反应12h，固定化酶的最适温度35℃，最适pH值8．0。得到的固定化酶的活力回收平均为82．5％，固定化酶的稳定性能好于游离酶。     

磁性聚乙烯醇缩丁醛微球固定化α-淀粉酶

制备出磁性聚乙烯醇缩丁醛微球,并用该微球做载体,采用共价交联法固定α 淀粉酶。最佳固定化工艺条件为:pH=6 07,激活和交联时戊二醛的质量分数分别为4%和0 025%。在最佳固定化条件下所制磁性固定化酶的活力为25426 3U/g微球,蛋白载量为187 2mg/g微球,比活为135 8U/mg蛋白,活性回收率为36 9%。磁性固定化酶的理化性质为:磁性固定化酶的最适温度(60℃)比自由酶(50℃)高,最适pH(6 97)与自由酶相同,磁性固定化酶Km(米氏常数)值(5 7×10-4kg/L)较自由酶Km值(5 0×10-4kg/L)大,热稳定性、pH稳定性及操作稳定性均比自由酶有所提高。     

固定化黄孢原毛平革菌木素过氧化物酶的研究

用大孔吸附树脂进行黄孢原毛平革菌来源的木素过氧化物酶固定化试验,筛选出固定化效果较好的XAD7HP大孔树脂,研究了其固定化条件。结果表明,当树脂1.0g,酶液pH4.5,加酶量87.2U,吸附温度25℃,吸附4h,戊二醛质量分数0.2%,戊二醛处理时间120min,可获得最佳的固定化效果,固定化酶活力可达到16U/g(对载体)。     

弱碱性大孔树脂固定化氨基酰化酶的性能研究

对以弱碱性大孔阴离子树脂二乙胺基乙基羟乙酯(DEAE-E/H)为载体制备得到的固定化氨基酰化酶的性质进行系统研究。结果表明,DEAE-E/H固定化氨基酰化酶具有很好的热稳定性。与自由酶相比,固定化酶的最适反应温度分别由47℃变为57℃,pH值由7.0变为6.5,并且最适反应条件范围明显变宽。Co2+对固定化酶活力具有较强的激活作用,其最佳浓度为1×10-3mol/L。分别对其在间歇和连续操作过程巾的反应进行研究,结果表明,固定化酶具有较高的操作稳定性。     

固定化L-天门冬酰胺酶的性质及其填充床反应器的研究

利用海藻酸钙包埋、戊二醛交联的方法对L-天门冬酰胺酶进行固定化。研究了固定化L-天门冬酰胺酶的最适pH、最适温度、米氏常数、半衰期等酶学性质,并考察了影响固定化酶柱式填充床反应器转化率的因素。结果表明:固定化酶最适pH值为8.5,最适温度为67°C,固定化酶的米氏常数Km增大,固定化酶半衰期随着温度的增加而逐渐减小;温度、反应柱内径、底物溶液浓度、流速等因素对填充床反应器转化率均有显著影响。     

磁性中性蛋白酶的固定化研究

为了克服游离酶在实际工业生产中稳定性不好、活性易丧失、不易回收、重复利用率较低的缺点,对中性蛋白酶进行了固定化研究。将具有磁性的二氧化硅包覆的Fe_3O_4(Fe_3O_4@SiO_2)材料作为载体进行中性蛋白酶固定化实验。考察了交联剂戊二醛的质量分数、交联时间、给酶量、固定化时间、温度和酸碱度对于固定化酶活力的影响,筛选出最佳固定化条件。结果表明,在交联剂质量分数为3%,交联时间为2 h,给酶量为0.20 g/g,固定化时间为3 h的条件下,固定化中性蛋白酶的活性最好。固定化酶的最适温度为50℃,固定化酶的最适pH为7.5,而且一定范围内其热稳定性和pH稳定性都比游离酶有所提高。     

磁性SiO2纳米粒子的制备及其用于漆酶固定化

以氨基修饰的磁性SiO2纳米粒子为载体,通过交联剂戊二醛固定漆酶,对固定化条件进行了优化,比较了固定化酶与游离酶的酶学性质. 结果表明,漆酶固定化的最佳条件为戊二醛浓度8%(w),固定化时间6 h,缓冲液pH值7.0,初始酶液浓度0.15 g/L. 固定化的漆酶的最适pH为4.0,最适温度为20℃. 在60℃条件下保温4 h,固定化漆酶仍能保持酶活力60.9%,在连续10次操作后,酶活力仍能保持55%以上,其热稳定性和操作稳定性均比游离酶高.     

AS1.398中性蛋白酶制备水解明胶(Ⅱ)--酶的固定化研究

以壳聚糖为载体、戊二醛为交联剂 ,探讨了影响AS1 398中性蛋白酶的固定的因素。确定了固定化酶制备的适宜条件 :温度为 30℃～ 45℃ ,pH值为 6 5 ,时间为1 0h ,戊二醛含量为 0 1 2 % (质量分数 )和固定化酶中的酶的含量为 2 % (质量分数 )。     

生物温敏性水凝胶的研究

采用明胶（Gel）和N－异丙基丙烯酰胺（NIPAM）为原料，制备交联结构不同的Gel-PNIPAM水凝胶，研究不同的pH值、温度对它们的溶胀度和溶胀速度的影响，进而了解明胶的交联结构对水凝胶的温敏性、pH敏感性的影响。结果表明：不同交联结构的Gel-PNIPAM水凝胶对pH值的响应取决于明胶部分，Gelx-PNIPAM水凝胶的温敏性最明显，温度大于LCST（最低临界溶液温度），Gel-PNIPAMx与Gelx-PNIPAMx,Gelx-PNIPAM相比，呈现更高的溶胀度及溶胀速度，其控制过程分别符合Case-Ⅱ和Fick定律。     

新型水再湿胶的研制

以水为反应介质,在过硫酸铵的引发下,合成了糊精(?)丙烯酰胺接枝共聚物,对单体浓度,引发剂浓度,反应温度和反应时间对接枝率的影响进行了研究。然后加入甲醛作为交联剂,研究了交联剂的浓度,pH 值,温度和时间对交联程度的影响。最后在上述已交联的接枝共聚物中加入各种改性剂,合成了新型再湿胶,经测试各种性能优异,有很好的应用价值。     

酸性脲酶的固定化研究

以明胶为包埋材料,戊二醛为交联剂固定化粪产碱菌所产的酸性脲酶。对酸性脲酶的固定化条件(包括明胶含量、戊二醛浓度、吸附时间、交联时间和粗酶液用量)及酶学性质(温度和pH值)进行了研究。结果表明,固定化酶的最适宜条件为：明胶的质量分数15％,戊二醛质量分数0.3％,吸附时间4 h,交联时间20 min,粗酶液用量4 mL。...     

Cellulose fiber networks reinforced with glutaraldehyde–chitosan complexes

In this study, glutaraldehyde–chitosan complexes (GA–chitosan) were prepared and were used as functional additives to enhance the strength properties of cellulose fiber networks. The adsorption and distribution of GA–chitosan on the surface of cellulose fiber were characterized by scanning electron microscopy, X‐ray photoelectron spectroscopy and time‐of‐flight secondary ion mass spectrometry. The effects of glutaraldehyde dosage and GA–chitosan to fiber ratio on the strength properties, including wet‐strength, wet‐web strength, and dry strength, were investigated. GA–chitosan did not require high temperature curing and had good cross‐linking rates at room temperature. Samples treated with GA–chitosan exhibited significant improvements in their mechanical properties. Wet tensile index and wet‐web tensile index (both at 50% solids), and dry tensile index, were increased by about 1300, 190, and 115%, respectively. The GA–chitosan additive developed in this study provides a useful approach to prepare high‐performance value‐added specialty wood‐fiber based products. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42375.     

Covalent immobilization of naringinase for the transformation of a flavonoid

Naringinase (EC 3.2.1.40) from Penicillium sp was immobilized by covalent binding to woodchips to improve its catalytic activity. The immobilization of naringinase on glutaraldehyde‐coated woodchips (600 mg woodchips, 10 U naringinase, 45 °C, pH 4.0 and 12h) through 1% glutaraldehyde cross‐linking was optimized. The pH–activity curve of the immobilized enzyme shifted toward a lower pH compared with that of the soluble enzyme. The immobilization caused a marked increase in thermal stability of the enzyme. The immobilized naringinase was stable during storage at 4 °C. No loss of activity was observed when the immobilized enzyme was used for seven consecutive cycles of operations. The efficiency of immobilization was 120%, while soluble naringinase afforded 82% efficacy for the hydrolysis of standard naringin under optimal conditions. Its applicability for debittering kinnow mandarin juice afforded 76% debittering efficiency. Copyright © 2005 Society of Chemical Industry     

Investigation of mechanical properties,antibacterial features,and water vapor permeability of polyvinyl alcohol thin films reinforced by glutaraldehyde and multiwalled carbon nanotube

Polyvinyl alcohol (PVA) thin films were reinforced by glutaraldehyde and multiwalled carbon nanotubes (MWCNTs) and then mechanical, water solubility, water swelling, water uptake, water vapor permeability, and antibacterial properties of the films were examined. Cross‐linking by glutaraldehyde or incorporation of MWCNT caused a significant increase in tensile strength, decrease in elongation at break, and increase in Young's modulus of the PVA films, while MWCNTs were more effective rather than that of glutaraldehyde. Cross‐linking by glutaraldehyde or incorporation of MWCNT caused a significant decrease in water solubility, water swelling and water uptake, with a similar manner. Cross‐linking by glutaraldehyde or incorporation of MWCNT caused a significant increase in the light absorbance, while maximum absorbance was at 400 nm. Only PVA/MWCNT films but no PVA/glutaraldehyde showed significant antibacterial activities in a dose‐dependent manner against both Gram‐positive and Gram‐negative bacteria. Thus, noncovalent improvement by MWCNT was more effective on the PVA thin films rather than covalent cross‐linking by glutaraldehyde. Our results suggest that the PVA/MWCNT composites films could be used as a very attractive alternative to traditional materials for different biomedical and food applications. POLYM. COMPOS., 35:1736–1743, 2014. © 2013 Society of Plastics Engineers     

High‐temperature‐resistant polymer gel system with metal–organic mixed cross‐linking agents

A high‐temperature (200°C)‐resistant polymer gel system was developed from partially hydrolyzed polyacrylamide (HPAM), chromium lactate (CrL), and water‐soluble phenol/formaldehyde resin (WPF) mixed cross‐linkers. Rheological measurements indicated that the gelation process of the gel system could be divided into four successive steps: induction, first cross‐linking with metal cross‐linker, secondary cross‐linking with organic cross‐linker, and stabilization. Effects of various parameters that affect the gelation time and gel strength including polymer concentration, cross‐linker concentration, salinity, pH, and the gelation temperature were evaluated. Gelant formulated with 0.5 wt % HPAM, 0.1 wt % CrL, and 0.9 wt % WPF and treated at 80°C for 48 h showed sufficient gelation time, high rigidity, and good thermal stability. Morphology observation by scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed that the gel had compact network microstructure. A cross‐linking mechanism for the gel system was proposed based on the gelation process and experimental results. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42261.     

Effect of cross‐linking time on the thermal and mechanical properties and pervaporation performance of poly(vinyl alcohol) membrane cross‐linked with fumaric acid used for dehydration of isopropanol

Cross‐linked poly (vinyl alcohol) membranes were prepared using fumaric acid as the cross‐linking agent and were used for the pervaporation separation of water/isopropanol mixtures. Cross‐linking process was carried out at 150°C at three different times of 10, 30, and 60 min. The membranes were characterized by different known methods of FT‐IR, TGA, XRD as well as tensile test. The effects of cross‐linking time on the thermal and mechanical properties of the membranes and also their pervaporation performance were investigated. Formation of more ester groups by increasing the cross‐linking time was confirmed by the FT‐IR results. TGA analyses showed that thermal stability of the membranes is improved by prolonging the duration of cross‐linking process. This was due to the formation of more compact structure in the membranes. The XRD results revealed that the crystalline regions of the membranes were relatively diminished with an increase in the cross‐linking time. No specific trend was observed for the variation of tensile strength at break with the cross‐linking time. The PVA membrane cross‐linked for 60 min showed high selectivity of 1492 for water permeation for the feed mixture containing 10 wt % water. The temperature dependency of the permeation flux was investigated using Arrhenius relationship, and the activation energy values were calculated for total permeation (E_p), water (E_pw), and IPA (E_pIPA) fluxes. Lower value of E_pw in comparison with E_pIPA supported excellent dehydration performance of the cross‐linked membranes. Despite large increase in activation energy of water with prolonged cross‐linking time, the selectivity was improved. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2013