磁性聚丙烯酰胺-丙烯酸共聚纳米粒子固定脂肪酶的研究

用沉淀聚合制备了P(Am-co-Aa)-Gd(Ⅲ)磁性高分子纳米微球,在此基础上通过共价键合固定脂肪酶。结果表明:固定脂肪酶后的磁性纳米微球具有优异的磁分离能力;钆离子对固定化酶有明显的激活作用,当钆离子质量分数为0.8%时,偶联率和活力回收率分别提高57%和60%;脂肪酶被固定化后其pH稳定性,操作稳定性均比自由酶明显提高。     

冰胶印迹聚合物固定化脂肪酶的制备及催化性能

利用冰冻凝胶(cryogel,简称冰胶)印迹聚合物实现了脂肪酶的固定化.在脂肪酶存在的条件下,以过硫酸铵/亚硫酸氢钠为引发剂,由丙烯酰胺、N,N-亚甲基双丙烯酰胺、丙烯酸、烯丙胺共聚而得到印迹聚合物固定化酶.通过催化三油酸甘油酯与甲醇的酯交换反应,发现冰胶固定化脂肪酶、常规凝胶固定化脂肪酶、游离脂肪酶具有相似的催化性能.冰胶固定化酶与相应的凝胶固定化酶显示出类似的稳定性,而传质方面则优于常规凝胶固定化酶,因此冰胶印迹聚合物固定化有望成为一种具有吸引力的酶固定化方法.     

核壳结构磁性树枝状纤维形有机硅固定化脂肪酶制备及其应用

为了提升脂肪酶的稳定性并构建新型固定化酶催化体系,利用改进的Winsor Ⅲ微乳液双连续相体系合成了超顺磁性Fe₃O₄内核和树枝状纤维形氧化硅外壳的核壳结构磁性有机硅纳米粒子（MMOSNs）,用于固定化南极假丝酵母脂肪酶B（CALB）。优化条件后CALB负载量为177.49 mg/g,比水解活性为27390 U/g。磁性有机硅通过与CLAB分子之间疏水相互作用及表面孔道结构,可有效激活CALB的界面活性并保护活性构象免受破坏,比游离酶和磁性无机硅固定化酶表现出更好的活性和稳定性。除此之外,将CALB@MMOSNs用于催化乙酰丙酸与十二醇的酯化反应最高转化率为85.05%,重复使用9次后仍保留68.94%转化率,而商业化N435只保留29.83%。证明疏水性磁性核壳结构有机硅是固定化CALB的良好载体,可有效扩展脂肪酶的工业应用。     

Microwave preparation and adsorption properties of EDTA‐modified cross‐linked chitosan

A novel chitosan‐based adsorbent (CCTE) was synthesized by the reaction between epichlorohydrin O‐cross‐linked chitosan and EDTA dianhydride under microwave irradiation (MW). The chemical structure of this new polymer was characterized by infrared spectra analysis, thermogravimetric analysis, and X‐ray diffraction analysis. The results were in agreement with the expectations. The static adsorption properties of the polymer for Pb²⁺, Cu²⁺, Cd²⁺, Ni²⁺, and Co²⁺ were investigated. Experimental results demonstrated that the CCTE had higher adsorption capacity for the same metal ion than the parent chitosan and cross‐linked chitosan. In particular, the adsorption capacities for Pb²⁺ and Cd²⁺ were 1.28 mmol/g and 1.29 mmol/g, respectively, in contrast to only 0.372 mmol/g for Pb²⁺ and 0.503 mmol/g for Cd²⁺ on chitosan. Kinetic experiments indicated that the adsorption of CCTE for the above metal ions achieved the equilibrium within 4 h. The desorption efficiencies of the metal ions on CCTE were over 93%. Therefore, CCTE is an effective adsorbent for the removal and recovery of heavy metal ions from industrial waste solutions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Solvent‐free preparation of phytosteryl esters with fatty acids from butterfat in equimolecular conditions in the presence of a lipase from Candida rugosa

BACKGROUND: Enzymatic esterification of phytosterols with fatty acids from butterfat in equimolecular conditions to produce phytosteryl esters was performed in solvent‐free medium. Commercial and immobilized Candida rugosa lipases were used as biocatalysts for the reaction. RESULTS: By this methodology, under simple and mild reaction conditions (without solvents, 50 °C and short reaction times), 94% and 99% (w/w) of phystosteroyl esters were obtained in 48 h and 9 h with the commercial and the immobilized lipase, respectively. The effects of temperature, fatty acid specificity, enzyme amount and residual activity of each lipase were also evaluated. CONCLUSIONS: The phytosteryl esters from butterfat produced in this study are expected to have lower melting point, improved oil and fat solubility and bioavailability compared to that of their corresponding free phytosterols. Copyright © 2008 Society of Chemical Industry     

Physicochemical characterization and antioxidant activity of quercetin‐loaded chitosan nanoparticles

Quercetin is an abundant flavonoid in food plants with numerous biological activities and widely used as a potent antioxidant. Being sparingly soluble in water and subject to degradation in aqueous intestinal fluids, the absorption of quercetin is limited upon oral administration. In the present study, chitosan nanoparticles and quercetin‐loaded nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions. The encapsulation of quercetin in the chitosan nanoparticles were confirmed by differential scanning calorimetry, X‐ray powder diffractometry, Fourier transformed infrared spectroscopy, ultraviolet‐visible spectrum, and fluorescence spectrum. The morphology of the nanoparticles was characterized by atomic force microscopy. The antioxidant activity of the quercetin‐nanoparticles was also evaluated in vitro by two different methods (free radical scavenging activity test and reducing power test), which indicates that inclusion of quercetin in chitosan nanopaticles may be useful in improving the bioavailabilty of quercetin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Pervaporation of tertiary butanol/water mixtures through chitosan membranes cross‐linked with toluylene diisocyanate

Membranes made from 84% deacetylated chitosan biopolymer were cross‐linked by a novel method using 2,4‐toluylene diisocyanate (TDI) and tested for the separation of t‐butanol/water mixtures by pervaporation. The unmodified and cross‐linked membranes were characterized by Fourier transform infra red (FTIR) spectroscopy, X‐ray diffraction (XRD) studies and sorption studies in order to understand the polymer–liquid interactions and separation mechanisms. Thermal stability was analyzed by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA) while tensile strength measurement was carried out to assess mechanical strength. The membrane appears to have good potential for breaking the aqueous azeotrope of 88.2 wt% t‐butanol by giving a high selectivity of 620 and substantial water flux (0.38 kg m^?2 hr^?1). The effects of operating parameters such as feed composition, membrane thickness and permeate pressure on membrane performance were evaluated. Copyright © 2005 Society of Chemical Industry     

Preparation and evaluation of chitosan/β‐cyclodextrin magnetic nanoparticles as a photodegradable and hydrophobic drug delivery carrier

In this study, novel tumor targeting nanocarriers comprised of chitosan (CS)/β‐cyclodextrin (β‐CD) magnetic nanoparticles were prepared to improve the photodegradable stability and bioavailability of hydrophobic drug. Resveratrol (Res) with photodegradable and hydrophobic properties was selected as a model drug. The photodegradation rate of Res in Fe₃O₄ nanoparticles solution was 7.8 times lower than that in the ethanol solution_. In addition, the value of the saturation magnetization of CS/β‐CD nanoparticles was found to be 19.56 emu/g with characteristic of superparamagnetism. Approximately 90% Res was entrapped into the CS/β‐CD magnetic nanoparticles with the size distribution ranging from 200 to 359 nm, and the nanoparticles were spherical in shape with high zeta potentials. Furthermore, the formation of CS/β‐CD nanoparticles showed a sustained release in vitro. These results indicated that the obtained CS/β‐CD magnetic nanoparticles were a promising magnetic targeting carrier for photodegradable and hydrophobic drugs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45076.     

Preparation and characterization of hyaluronan/chitosan scaffold cross‐ linked by 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide

A novel biocompatible scaffold was prepared by cross‐linking hyaluronan (HA) and chitosan (CS). The carboxyl groups of HA were activated by 1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide (EDC) and then cross‐linked with amino groups of CS by forming amide bonds. The HA/CS scaffold thus prepared was characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and differential scanning calorimetry. FTIR spectra showed that the absorbance of the amide (1550 cm^?1) and carbonyl (1633 cm^?1) bond in the cross‐linked scaffold was stronger than that in HA or CS. SEM micrographs showed that the cross‐linked scaffold produced at low EDC concentration had an intertwisted ribbon‐like microstructure, while the product prepared at higher EDC concentration had a porous structure. The concentration of EDC in the reaction system greatly affected the structure and properties of the HA/CS scaffold. The prepared scaffold could strongly resist degradation by hyaluronidase, free radicals in vitro and stress. Copyright © 2007 Society of Chemical Industry     

Porcine pancreatic lipase immobilized on polysiloxane–polyvinyl alcohol hybrid matrix: catalytic properties and feasibility to mediate synthesis of surfactants and biodiesel

Polysiloxane–polyvinyl alcohol hybrid matrix was prepared by a sol–gel technique and its capacity to bind porcine pancreatic lipase investigated. The loading of 250 units g^?1 support was shown to be effective, resulting in an immobilized lipase with high catalytic activity. Both free and immobilized lipases were characterized by determining the activity profile as a function of pH, temperature, substrate concentration and thermal stability. Application of the immobilized lipase in non‐conventional biocatalysis for the synthesis of surfactants and biodiesel was also analyzed. Production of sugar fatty acid esters was found to be dependent on the carbohydrate and the highest molar conversion (50% in 3–4 h of reaction) was achieved for substrates containing fructose and lauric or oleic acids. Biodiesel synthesis from babassu oil and ethanol, propanol or butanol was feasible and regardless of the kind of alcohols, results revealed that the immobilized PPL could efficiently convert triglycerides to fatty acid alkyl esters attaining yields varying from 75 to 95%. Copyright © 2007 Society of Chemical Industry     

Extraction of Candida rugosa lipase from aqueous solutions into organic solvents by forming an ion‐paired complex with AOT

Candida rugosa lipase was extracted from aqueous solutions into organic solvents by forming an ion‐paired complex with sodium bis(2‐ethylhexyl)sulfosuccinate (AOT). The optimal aqueous pH for lipase recovery was 4.5 and the optimal CaCl₂ concentration was 10 mmol dm^?3. The lipase recovery decreased with increasing aqueous enzyme concentration but increased with increasing AOT concentration in the organic phase. The presence of polar co‐solvents in the aqueous phase did not obviously improve the lipase recovery, which was also little influenced by the type of hydrophobic organic solvent used for solubilising AOT. Surprisingly, no detectable activity of the ion‐paired C. rugosa lipase was observed for both the esterification of lauric acid with 1‐propanol in isooctane and the hydrolysis of olive oil in isooctane containing an appropriate amount of water. The ion‐paired C. rugosa lipase mediated the enantioselective crystallisation of racemic ketoprofen in isooctane, indicating the feasibility of using it as a chiral mediator for the enantioseparation of hydrophobic racemic compounds in organic systems. Copyright © 2006 Society of Chemical Industry     

Acid‐sensitive magnetic nanoparticles as potential drug depots

Superparamagnetic magnetic nanoparticles were successfully functionalized with poly(methacrylic acid) via atom transfer radical polymerization, followed by conjugation to doxorubicin (Dox). Because of pH‐sensitive hydrazone linkages, the rate and extent of Dox release from the particles was higher at a lower pH and/or a higher temperature than at physiological conditions. Appropriate changes to the pH and temperature can increase the drug release from the particles. Because of the released drug, the particles were found to be cytotoxic to human breast cancer cells in vitro. Such magnetic nanoparticles, with the potential to retain drug under physiological conditions and release the drug in conditions where the pH is lower or temperature is higher, may be useful in magnetic drug targeting by reducing the side effects of the drug caused to healthy tissues. In addition, they may serve as hyperthermia agents where the high temperatures used in hyperthermia can trigger further drug release. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Esterification of n‐butyric acid with n‐butyl alcohol and transesterification of (R, S)‐phenylethanol by lipase immobilized on cellulose acetate–TiO2 gel fibre

Lipase (EC 3.1.1.3) was immobilized on cellulose acetate–TiO₂ gel fibre by the sol–gel method. The immobilized lipases were used for esterification of n‐butyric acid with n‐butyl alcohol and enantioselective acylation of (R, S)‐phenylethanol using vinyl acetate as an acyl donor. Compared with native lipase, the activity of the immobilized lipase was stable and relatively unaffected by the water content of the solvent and the substrate concentration. The data indicate that the lipases are immobilized on the fibre surface and that enzyme activity is influenced by bound water. However, the thermal reactivity and enantioselectivity of the immobilized lipase were less than those of native lipase. This may not reflect thermal inactivation of the enzyme but rather significant thermal contraction of the gel fibre by cellulose crystallization, resulting in liberation of bound water and a decrease in the amount of enzyme which is available for the reaction. Copyright © 2001 Society of Chemical Industry     

Characterization of Candida rugosa Lipase Immobilized on Poly(N‐methylolacrylamide) and Its Application in Butyl Butyrate Synthesis

Candida rugosa lipase was immobilized on poly(N‐methylolacrylamide) by physical adsorption. The biocatalyst performance (immobilized lipase) was evaluated in both aqueous (hydrolysis) and organic (butyl butyrate synthesis) media. In the first case, a comparative study between free and immobilized derivatives was provided in terms of pH, temperature and thermal stability following the olive oil hydrolysis, establishing new optimum values. In the second case, the influence of temperature, biocatalyst concentration and acid/alcohol molar ratio was simultaneously studied according to a 2³ full experimental design. The highest molar conversion (96 %), volumetric productivity (1.73 g L^–1 h^–1) and specific esterification activity (1.00 μM mg^–1 min^–1) were obtained when working at the lowest level of temperature and butyric acid in excess. Under these conditions, repeated batch use of the immobilized enzyme was performed and half‐life time (t_1/2) was found to be 145 h.