载脂肪酶壳聚糖/海藻酸钙微胶囊的制备

针对固定化脂肪酶的研究背景,以壳聚糖、海藻酸钠为微载体制备材料,采用脉冲电场液滴工艺制备壳聚糖/海藻酸钙微胶囊。以脂肪酶为生物模型,系统考察了制备条件对载脂肪酶壳聚糖/海藻酸钙微胶囊酶活力的影响。结果表明:海藻酸钠质量浓度和酶与海藻酸钠载体配比是影响固定化酶活力的主要因素,载酶量为15mg/mL,海藻酸钠质量浓度为10mg/mL时载酶微胶囊酶活力最高,球形度好。通过改变壳聚糖质量浓度和相对分子质量,可以调控微胶囊膜的厚密程度进而影响固定化酶活力。成膜液pH值依次影响壳聚糖与海藻酸盐分子中官能团的电离状态、成膜反应静电络合程度、酶蛋白包封率,最终影响固定化酶活力。在载酶量为15mg/mL,海藻酸钠质量浓度为10mg/mL,壳聚糖相对分子质量、质量浓度和pH值依次为50kDa、1mg/mL和3.0的条件下,固定化酶活力为187IU/g。     

三维有序大孔硅材料载体固定化脂肪酶研究

以聚苯乙烯胶体晶体为模板制备三维有序大孔硅材料(3DOM-SiO_2),以其作为载体来固定脂肪酶。分别考察了脂肪酶加入量、反应体系pH、固定反应时间对固定化效果的影响。结果表明,3DOM-SiO_2材料固定脂肪酶的最佳酶液加入量为200 mL/g,固定化最适宜pH为7.0,最佳反应时间为5 h。固定化的脂肪酶在催化性能上与游离脂肪酶相比优势明显,最适宜反应温度提高到40℃左右,并且酶活随温度变化率低,热稳定性明显提高;脂肪酶固定化后对pH的敏感度降低,适应范围更宽,催化反应的最适pH为8.0;固定化脂肪酶重复使用8次后,相对酶活保持在62%。由此可见,3DOMSiO_2材料是固定脂肪酶的优良载体,在酶固定化领域应用前景广阔。     

脂肪酶固定化载体材料研究进展

脂肪酶的不稳定性和高昂的价格是限制其广泛应用的主要原因。对脂肪酶进行固定化是增强其稳定性和重复利用性的一种关键技术。固定化材料的选择和开发是改进脂肪酶固定化工艺的一个重要方面。本文围绕酶的固定化载体,对无机、有机、复合载体等固定化材料进行了归纳,综述这些方面近年来的研究进展。对固定化所用材料的发展前景予以展望。     

仿生膜吸附-絮凝组合固定化脂肪酶及其应用

研究了猪胰脂肪酶的仿生膜、吸附-絮凝组合固定化新工艺,考察了该组合固定化脂肪酶体系用于橄榄油水解的性能。最终试验结果表明：该组合固定化脂肪酶水解反应体系的反应转化率达到54.5％,固定化酶质量回收率86,7％,酶活回收率66．7％,远高于单一固定化方法。     

功能碳材料的制备及其固定化脂肪酶

以废弃玉米芯为原料,用稀硫酸处理,通过水热法制备表面含有丰富功能基团的碳基材料并测试其在固定化脂肪酶方面的性能。研究结果表明此方法制备的碳材料表面含有羟基(-OH)、羧基(-COOH)等功能基团,有利于脂肪酶的固定化;固定化后脂肪酶表现出良好的热稳定性、重复使用活性。     

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%。     

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.     

磁性纳米粒子的制备及脂肪酶的固定化

建立了以纳米级磁性粒子为载体固定化脂肪酶的方法,优化了脂肪酶的固定化条件,考察了固定化酶的性质. 制备的磁性载体平均粒径20 nm,具有超顺磁性,分散和再分散效果好. 固定化酶的最适吸附时间为60 min,酶用量:载体量为1:1,固定化酶的酶活达到718 U/g. 结果表明,经纳米磁性粒子固定化后,脂肪酶得到活化,固定化酶比活为游离酶的1.8倍. 同时,固定化脂肪酶的pH稳定性显著提高.     

功能化磁性纳米颗粒固定化脂肪酶研究

用葡萄糖酸对Fe3O4磁性纳米颗粒表面进行修饰,然后用水溶性碳化二亚胺（EDC）作偶联剂,对脂肪酶进行固定化。考察了偶联剂浓度、给酶量和反应时间对脂肪酶固定化过程的影响。结果表明,制备功能化磁性颗粒固定化酶的最佳条件为：偶联剂浓度为12．5mg／mL磷酸缓冲液（PBS）,给酶量为2．5mg／mLPBS,反应时间为24h。固定化脂肪酶表现出优异的热稳定性,60℃时酶活为游离酶的6倍。重复使用10次后,酶促活力依然保持80％以上。     

固定化脂肪酶的新技术及在食品领域中的应用

综述了近年来研究日益广泛的脂肪酶固定化新技术,讨论了每种固定化技术中影响固定化脂肪酶活性的重要因素,并阐述了固定化脂肪酶在食品领域中的应用,最后展望了脂肪酶固定化技术的发展趋势。     

聚氨酯泡沫固定化重组枯草杆菌三段培养生产青霉素酰化酶

引　言青霉素G酰化酶 (penicillinGacylase ,EC3 5 1 11,PGA)是 β 内酰胺类抗生素工业中的关键酶之一 .目前主要采用大肠杆菌和巨大芽孢杆菌进行工业化生产 ,但由于产酶水平较低、变温发酵和需要苯乙酸诱导等缺点 ,国内外研究者尝试采用各种基因重组技术 ,以期大幅度提高产酶     

Influence of folate conjugation on the cellular uptake degree of poly(allylamine hydrochloride) microcapsules

The microcapsules in drug delivery systems can prevent degradation of drugs and help to control the release rate. To enhance the targeted delivery effect of the microcapsules to cancer cells, some specific ligands such as folic acid (FA) are necessarily further conjugated. Herein, covalent poly(allylamine hydrochloride) (PAH) multilayers were fabricated on CaCO₃ microparticles under the cross‐linking of glutaraldehyde, which were further immobilized with different amount of FA molecules via the spacer of diamino terminated poly(ethylene glycol) (PEG). As a comparison study, four types of microcapsules, i.e., the PAH capsules, the PAH capsules grafted with PEG, and the PAH capsules conjugated with two different amount of FA via the PEG spacer were prepared. Their chemical and physical structures were confirmed by infrared spectroscopy, UV–vis spectroscopy and scanning electron microscopy. In vitro cell culture found that the cellular uptake of the PAH capsules grafted with PEG was reduced significantly compared with that of the pure PAH capsules. The FA‐modified microcapsules could be selectively delivered into HepG2 tumor cells which overexpress FA receptors but not into the endothelial cells. The number of HepG2 cells which ingested the FA‐conjugated capsules showed a positive correlation with FA amount. The results indicate that these FA conjugated capsules have a high selectivity to be delivered to tumor cells, endowing them with a larger opportunity functioning as targeted delivery vehicle for anticancer drugs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Lipase‐catalyzed synthesis of butyl esters by direct esterification in solvent‐free system

BACKGROUND: Reactions performed under solvent‐free conditions give processes that are environmentally friendly, since most solvents are polluting agents. In this work, the performance of Candida rugosa lipae (CRL) immobilized on styrene‐divinylbenzene (STY‐DVB) or controlled pore silica (CPS), and the commercial lipase Novozym 435, was evaluated for the synthesis of butyl esters in solvent–free systems (SFS). A 2² full factorial design was used to study the influence of the organic acid chain length and the biocatalyst concentration on the esterification performance. RESULTS: When CRL on STY‐DVB was used, the ester formation was influenced by both variables and their interaction. The reaction conversion was higher (63%) using 10% of immobilized system and lauric acid, corresponding to a productivity of 3.62 g L^?1 h^?1 For CRL on CPS, only the effect of biocatalyst concentration was significant, and the highest yield was attained using 20% of immobilized system and caprilic acid. In the case of Novozym 435, the highest yield (49%) was obtained using butyric acid as acyl donor at 15% of immobilized lipase. CONCLUSION: The results allowed better understanding of the influence of important parameters in this environmentally friendly process, which also has the process advantage of a higher volumetric productivity when compared with a solvent system. Copyright © 2007 Society of Chemical Industry     

Lipase-Catalyzed Solid Phase Synthesis of Sugar Esters

Lipase-catalyzed synthesis of sugar fatty acid esters was performed in a heterogeneous reaction system in the presence of an organic solvent serving as adjuvant. Although the sugar is almost insoluble in such a system, high conversions to the corresponding sugar esters were achieved, due to crystallization of the product. Acylation occurred regioselectively at the primary hydroxyl group and subsequent diacylation was observed only in the case of caprylic acid (2–5%). Best conditions were found for solvents having low log P values and low product solubility such as acetone, using immobilized lipase from Candida antarctica (CAL-B, Novo SP435) and fatty acids with chain lengths from C₁₂ to C₈ as acyl donors. The esterification of β-D(+)-glucose with stearic acid resulted in up to 100% conversion after 48 hours equal to a productivity of 0.4 mmol sugar ester per gram lipase and hour.     

Large-scale immobilization of lipase fromPseudomonas fluorescens biotype I and an application for sardine oil hydrolysis

Large-scale production of thermostable lipase fromPseudomonas fluorescens biotype I was carried out in a fermenter with an antifoaming agent and physical deforming treatments. After cultivation, heat treatment was applied to kill the bacteria and to inactivate other enzmes. Large-scale immobilization of the lipase to a macroporous weak-anion exchange resin was performed with a lipase solution that had an ionic strength of less than 0.1 and an ethanol concentration of 50%. Almost all eicosapentaenoic acid and docosahexaenoic acid were liberated continuously from sardine oil by the immobilized lipase in a countercurrent fluidized-bed reactor. The cost of enzyme used in the reactor has been compared with a process in which soluble lipase fromCandida rugosa was used.     

Synthesis of Ascorbyl Palmitate with Immobilized Lipase from Pseudomonas stutzeri

Synthesis of ascorbyl palmitate by enzymatic esterification of palmitic acid and ascorbic acid was conducted in an organic medium with Pseudomonas stutzeri lipase TL immobilized in different supports and its performance was compared with commercial Novozym 435 lipase used as a reference. The enzyme was immobilized in different supports and the best catalyst was selected in terms of immobilization yield and mass specific activity to perform the reactions of synthesis. Synthesis of ascorbyl palmitate was optimized considering temperature, substrate molar ratio and enzyme to limiting substrate mass ratio as variables, and substrate conversion and specific productivity as evaluation parameters. The best reaction conditions for immobilized lipase TL were 55 °C, 1:5 ascorbic to palmitic acid molar ratio, and 1:10 lipase to ascorbic acid mass ratio, obtaining 57 % substrate conversion and a specific productivity of 0.013 [g ascorbic acid/(g enzyme × min)]; the best conditions for Novozym 435 were 70 °C, ascorbic to palmitic acid molar ratio 1:10, and 1:10 lipase to ascorbic acid mass ratio, obtaining 51 % substrate conversion and a specific productivity of 0.016 [g ascorbic acid/(g enzyme × min)].     

固定化假丝酵母脂肪酶合成棕榈酸异辛酯

开发了固定化假丝酵母脂肪酶99-125合成棕榈酸异辛酯的工艺.对反应温度、酶用量、底物摩尔比等酯化反应条件进行了研究.脂肪酶以吸附的形式固定在织物膜上,以1g棕榈酸、0.67g异辛醇、0.12g固定化脂肪酶和5ml石油醚组成的反应系统在40℃条件下反应24h,酯化率可达96.6%.固定化酶连续反应9批后酯化率仍维持在90%以上.     

固定化基因工程菌的培养和hEGF表达

引　言人表皮生长因子 (humanepidermalgrowthfactor,hEGF)是由 5 3个氨基酸残基组成、相对分子质量为 6 0 4 5的单链多肽[1] .hEGF具有多种生物活性 ,并在医药、化妆品工业中具有广泛用途 .国内外已有很多重组表达hEGF的报道[2 ,3] .但是 ,各种hEGF表达系统的质粒稳定性随培养     

大肠杆菌高水平表达脂肪酶BTL2及其催化油脂制备生物柴油

引言随着近年来石化能源的紧缺和日益严重的环境污染问题,作为绿色新型能源之一的生物柴油受到了越来越多的关注。生物柴油是动植物油脂与低碳醇(通常是甲醇或乙醇)发生转酯化反应后生成的脂肪酸低碳醇酯。生物柴油制备工艺按照其催化剂     

Enzymatic Interesterification of Palm Stearin and Coconut Oil by a Dual Lipase System

Enzymatic interesterification of palm stearin with coconut oil was conducted by applying a dual lipase system in comparison with individual lipase-catalyzed reactions. The results indicated that a synergistic effect occurred for many lipase combinations, but largely depending on the lipase species mixed and their ratios. The combination of Lipozyme TL IM and RM IM was found to generate a positive synergistic action at all test mixing ratios. Only equivalent amount mixtures of Lipozyme TL IM with Novozym 435 or Lipozyme RM IM with Novozym 435 produced a significant synergistic effect as well as the enhanced degree of interesterification. The interesterification catalyzed by Lipozyme TL IM mixed with thermally inactivated immobilized lipase preparations indicated that the carrier property may play an important role in affecting the interaction of two mixed lipases and the subsequent reactions. A dual enzyme system, consisting of immobilized lipases and a non-immobilized one (Lipase AK), in most cases apparently endows the free lipase with a considerably enhanced activity. 70% Lipase AK mixed with 30% immobilized lipase (Lipozyme TL IM, RM IM and Novozym 435) can achieve an increase in activity greater than 100% over the theoretical value when the reaction proceeds for 2 h. The co-immobilization action of the carrier of the immobilized lipases towards the free lipase was proposed as being one of the reasons leading to the synergistic effect and this has been experimentally verified by a reaction catalyzed by a Lipase AK-inactivated preparation. No apparently synergistic effect of the combinations of Lipozyme TL IM and RM IM was observed when the dual enzyme systems applied to the continuous reaction performed in a packed bed reactor. In brief, this work demonstrated the possibility of increasing the reaction rate or enhancing the degree of conversion by employing a dual lipase system as a biocatalyst.