Lipase-catalyzed transesterification of trilinolein or trilinolenin with selected phenolic acids

The enzymatic transesterification of selected phenolic acids with TAG, including trilinolein (TLA) and trillinolenin (TLNA), was investigated in an organic solvent medium. Maximal bioconversion of 66% was obtained with a dihydrocaffeic acid (DHCA) to TLA ratio of 1∶2 after 5 d of reaction. Similarly, the highest bioconversion of 62% was obtained with a DHCA to TLNA ratio of 1∶2, but after 12 d of reaction. However, a ratio of 1∶4 DHCA/TLA decreased the bioconversion to 53%. Transesterification reactions of ferulic acid with both TAG, using a ratio of 1∶2, resulted in low bioconversion of 16 and 14% with TLA and TLNA, respectively. The overall results indicated that bioconversion of phenolic MAG was higher than that of phenolic DAG. The structures of mono- and dilinoleyl dihydrocaffeate as well as those of mono- and dilinolenyl dihydrocaffeate were confirmed by LC-MS analyses. The phenolic lipids demonstrated moderate radical-scavenging activity.     

Lipase-catalyzed preparation of palmitic and stearic acid-rich phosphatidylcholine

Saturated FA enhance the oxidative stability of phospholipids. In the present study phosphatidylcholine (PC) rich in palmitic and stearic acids was prepared using lipase-catalyzed transesterification from PC isolated from egg and soybean lecithins. Two different lipases, namely, Novozym 435 and Lipozyme TL IM, were used for the transesterification. The reaction conditions were optimized by varying the lipase dosage, molar ratio of PC to FA, and reaction period. Palmitic acid could be incorporated up to 58.6 and 57.1% using Lipozyme TL IM and 56 and 61% using Novozym 435 in egg and soybean PC from an initial content of 37.4 and 16.8%, respectively. Similarly, stearic acid incorporation was up to 44.7 and 46.3% using Lipozyme TL IM and 37.2 and 55.8% using Novozym 435 in egg and soybean PC from an initial content of 8.6 and 2.1%, respectively.     

Effect of phospholipids on enzyme-catalyzed transesterification of oils

The effect of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI) on the activity of an immobilized lipase, Lipozyme, during transesterification of oils has been studied. PC concentrations less than 0.05% did not affect the initial rate of transesterification. Higher concentrations of PC as well as PE and PI-rich phospholipids at the 0.5% level caused a reduction in the initial reaction rate, but after ten hours transesterification had progressed to the same extent as the control sample. Reuse of Lipozyme for ten batch reactions showed that a PC content of less than 0.05% did not cause significant inactivation of the enzyme, but PC contents above this level caused progressive inactivation of the enzyme and the inactivation increased with PC content. The ability of phospholipids to inactivate the Lipozyme was in the order PE>PC>PI. Variation in the acyl groups of PC did not significantly affect inactivation of the enzyme. It is concluded that the phospholipid content of edible oils should be reduced below 200 ppm by degumming if unacceptable inactivation of Lipozyme is to be avoided.     

Lipase-catalyzed glycerolysis of soybean oil in supercritical carbon dioxide

The transesterification of soybean oil with glycerol, 1,2-propanediol, and methanol by an immobilized lipase in flowing supercritical carbon dioxide for the synthesis of monoglycerides is described. A lipase from Candida antarctica was used to catalyze the reaction of soybean oil with glycerol, 1,2-propanediol, ethylene glycol, and methanol. Reactions were performed in supercritical carbon dioxide at a density of 0.72 g/L and at a flow rate of 6 μL/min (expanded gas). The substrates were added at flows ranging from 2.5 to 100 μL/min. Monoglycerides were obtained at up to 87 wt%, and fatty acid methyl esters at nearly 100 wt%. The reactivity of the alcohols paralleled the solubility of the substrate in liquid carbon dioxide. Glycerol has the slowest reaction rate, only 2% of that of methanol.     

Lipase-catalyzed transesterification of ethyl ferulate with triolein in solvent-free medium

The lipase-catalyzed transesterification of ethyl ferulate with triolein in a solvent-free medium was investigated. Transesterification was catalyzed by immobilized lipase from Candida antarctica (Novozym 435), to form ferulyl oleins, a mixture of ferulyl diolein and ferulyl monoolein. These ferulated esters can be widely used as natural antioxidant in both lipid containing food and cosmetic applications. External mass transfer limitations were lowest, when the agitation speed was higher than 180 rpm. A linear relationship between the initial reaction rate and enzyme load up to 10% demonstrated that the internal diffusion limitations could be minimized. The effects of various parameters on yields and rates of reaction were studied in the absence of mass transfer limitations. The initial reaction rate increased when the reaction temperature was raised in the range of 45-65 °C, further increase to 70 °C decreased the final yield to 48.9%. The value of activation energy was calculated as 65.04 kJ/mol based on the Arrhenius law. Under the most favorable conditions, a kinetic model based on the ping-pong bi-bi mechanism with triolein inhibition was found to fit the initial reaction rate data very well and the kinetic parameters were evaluated by non-linear regression analysis.     

Lipase-catalyzed synthesis of lysophosphatidylcholine using organic cosolvent for in situ water activity control

Lysophosphatidylcholines (LPC) were synthesized from l-α-glycerophosphatidylcholine (GPC) by lipase-catalyzed esterification in a solvent-free system. Adding small amounts of a water-mimicking solvent such as dimethylformamide (DMF) to the reaction media significantly enhanced the reaction rate and the product yield. The role of solvent was studied with regard to changes in substrate solubility, the water activity of the reaction system, and the water content of the enzyme. Whereas the solubility of GPC was virtually unaffected by the addition of DMF at controlled water activity, it was considerably affected by water activity. DMF itself lowered the water activity of the system and deprived Lipozyme IM of water. The LPC production was also controlled by varying the initial water content of the enzyme. When two kinds of controls were employed together, a synergistic effect was observed and a 90% conversion was achieved. As a result, an operating window was suggested for LPC production, including water activity of Lipozyme IM and concentration of DMF as two parameters.     

Lipase-catalyzed transesterification of rapeseed oil and 2-ethyl-1-hexanol

Lipase-catalyzed transesterification (alcoholysis) of lowerucic acid rapeseed oil and 2-ethyl-1-hexanol without an additional organic solvent was studied in stirred batch reactors. Of a number of commercially available enzymes investigated, the best results were obtained with aCandida rugosa lipase. The optimal transesterification conditions were an oil/alcohol molar ratio of 1∶2.8, a minimum of 1.0% (w/w) added water, and with a temperature of 37–55°C. Under the optimal conditions, a nearly complete conversion was obtained in one hour with 14.6% (w/w) lipase, whereas 0.3% (w/w) lipase required 10 h for similar results. The enzyme was inactivated at 60°C.     

Influence of ionic liquids under controlled water activity and low halide content on lipase activity

Room-temperature ionic liquids (ILs) can be used as reaction media for nonaqueous biocatalysis. However, the purity of ILs should be considered to understand the influence of ILs on enzyme activity. The major impurities in ILs are water and halide. In the transesterification of benzyl alcohol with vinyl acetate, the optimal water activities for lipases in [Omim][Tf₂N] were similar to those in organic solvents. The chloride impurity in [Omim][Tf₂N] seriously influenced the activity of lipase. In this work, the effect of ILs on lipase activity was investigated under controlled initial water activity and low halide content. The activity of lipase was highly dependent upon the anion structure of ILs. The initial reaction rate of lipases followed the order [Tf₂N]⁻>[PF6]⁻>[TfO]⁻>[SbF₆]⁻≈[BF₄]⁻. All tested lipases showed the highest activities in ILs containing [Tf₂N] anion. Particularly, [AAIM][Tf₂N] was shown as a suitable reaction medium for biocatalysis. Lipozyme IM showed the highest activity in this IL among tested ILs. Thermal stability of lipase was also investigated. The higher thermal stability of Novozym 435 was obtained in hydrophobic and water-immiscible ILs such as [Bmim][Tf₂N], [Edmim][Tf₂N], and [Bmim][PF₆].     

高纯卵磷脂的分离方法

卵磷脂是一种天然的表面活性剂，在食品、医药、化妆品等方面有重要的应用。本文详细介绍了卵磷脂分离提纯方面的研究成果，总结了溶剂法、层析法、超临界萃取等六种分离纯化卵磷脂方法的进展。     

酯交换法合成碳酸二苯酯的反应工艺

简要介绍了酯交换法合成碳酸二苯酯的反应原理。对碳酸二苯酯合成及碳酸二甲酯/苯酚分离法、分区反应法、连续法、反应精馏法和偶联法5种酯交换法合成碳酸二苯酯的反应工艺进行了详细讨论。其中反应精馏法及偶联法是创新的工艺,其反应工艺简单,原料利用率高,碳酸二苯酯的产率和选择性均很高。     

酯交换法在生物柴油制备中的研究进展

介绍了国内外生物柴油制备方法的研究进展,主要阐述了非均相催化、均相催化、生物催化和超临界催化技术等酯交换法的研究进展。阐明了各种催化法的优缺点,指出了目前酯交换法研究的热点和未来发展的方向。     

酯交换法合成碳酸二甲酯研究进展

从催化剂体系和反应条件等方面,综述了酯交换法合成碳酸二甲酯的研究新进展。介绍了硫酸二甲酯法、环烷基碳酸酯法和甲醇、环氧烷、CO2一步合成法,并评价所用催化剂的性能,分析了这些合成方法的优缺点。     

无溶剂体系脂肪酶催化制阿魏酸双油酸甘油酯

在无溶剂体系中以分散在硅藻土上的褶皱假丝酵母脂肪酶为催化剂,以阿魏酸乙酯与油酸甘油酯为原料,一步合成阿魏酸双油酸甘油酯。通过质谱和红外光谱对薄层层析分离纯化后的产物结构进行了表征。定量分析表明,当反应温度为50℃,n(阿魏酸乙酯)/n(油酸甘油酯)=1时,阿魏酸双油酸甘油酯的质量占生成物总质量分数较高。在1 mmoL阿魏酸乙酯,1 mmoL油酸甘油酯和70 mg脂肪酶组成的无溶剂反应体系中,50℃空气浴振荡120 h,总产率可达63.32%,其中阿魏酸双油酸甘油酯质量占生成物总质量的63.37%。     

Lipase-catalyzed synthesis of aliphatic polyesters via copolymerization of lactide with diesters and diols

Aliphatic lactate-bearing copolyesters were successfully synthesized via copolymerization of L-lactide (LLA) with diesters and diols using Candida antarctica lipase B (CALB) as the catalyst. The resultant copolymers had a M_w up to 38,000 Da with M_w/M_n between 1.5 and 2.0, and contained L-lactate units (up to 53 mol%), C₆–C₁₂ diester units, and C₄–C₆ alkylene units in the polymer chains. The lactate repeat units were present primarily as lactate–lactate diads in the polymers. The LLA-diester-diol copolymers were purified in good yield (70–85%) and all purified copolymers were optically active. Hydrolytic degradation study shows that LLA-diethyl adipate-1,6-hexanediol (LLA-DEA-HD) copolymers are degradable polymers as the molecular weight (M_w) of the copolymer with 53% lactate units decreased by ∼70% upon incubation in PBS solution under physiological conditions (37 °C, pH of 7.4) for 80 days. The LLA-diester-diol copolymers are thermally stable up to at least 300 °C with the temperature of maximum degradation rate ranging from 380 to 410 °C. The copolymers exhibit a wide range of physical properties (e.g., from white solid to wax and liquid) depending on their structure and composition. In particular, the LLA-DEA-HD and LLA-DEA-1,4-butanediol copolymers with ∼50 mol% lactate units are colorless, viscous liquids at ambient temperature. Biodegradable liquid polymers are potentially useful biomaterials for drug delivery to treat ocular ailments because of their good compatibility with sensitive soft tissues.     

填料塔中酯交换合成碳酸二甲酯工艺研究

以甲醇和碳酸丙烯酯为原料,研究了在填料塔中通过酯交换反应合成碳酸二甲酯的工艺,考察了原料配比、催化剂种类和用量、回流比等因素对碳酸二甲酯产率的影响。结果表明,较好的反应条件为甲醇和碳酸丙烯酯摩尔比为5∶1,加入催化剂NaOH的量为原料总质量的2%,在70℃时反应1 h,回流比为5,DMC产率可达43.6%;产物分离阶段,以正己烷为共沸剂,共沸精馏分离了甲醇和碳酸二甲酯共沸物,当正己烷用量为甲醇体积的350%、回流比为5时,DMC分离纯度高达95.78%。     

酯交换法合成对苯二甲酸二环己酯

研究了以无水碳酸钾、自制的钛酸酯等化合物为催化剂,对苯二甲酸二甲酯和环己醇为原料,进行酯交换反应制取对苯二甲酸二环己酯,考察了催化剂用量、反应温度、反应时间、反应物摩尔配比等因素的影响.适宜的操作条件为:环己醇与对苯二甲酸二甲酯的摩尔配比为3:1、反应温度160～190℃、反应时间7 h、催化剂用茸为1.0%.此时,对苯二甲酸二甲酯转化率达93%以上,对苯二甲酸二环己酯的收率达92%以上.     

用棉籽油制备生物柴油

采用棉籽油为原料连续化生产生物柴油,研究了工艺及设备的设计。由棉籽油与甲醇在催化剂NaOH存在下由酯交换反应制得生物柴油。在优化条件下反应50 min,转化率达到99%。生产的生物柴油,各项指标与天然柴油相似。其各项燃烧指标优于或与普通柴油相仿,满足欧洲Ⅱ排放标准。     

酯交换法制备生物柴油的反应动力学研究进展

掌握制备生物柴油的反应动力学对优化生物柴油的生产工艺、降低成本有重要作用。主要论述了目前国内酯交换反应制取生物柴油的反应动力学研究的现状,分析并总结了各自的特点。     

Variables affecting the in situ transesterification of microalgae lipids

This paper describes the effect of important reaction variables on the production of biodiesel from non-edible microalgae lipids, using the acid-catalysed in situ transesterification process. The specific gravity of the biodiesel product was used to monitor the conversion progress. The results indicate that increasing the reacting alcohol volume and the temperature lead to improved fatty acid methyl ester (FAME) conversions. With the exception of in situ transesterification carried out at room temperature (23 °C), the equilibrium FAME conversions appear to approach asymptotic limits for reaction times greater than 8 h for all temperatures investigated. Stirring the reaction vessel had a significant positive influence on the rate of biodiesel formation. Increasing the moisture content of the microalgae biomass had a strong negative influence on the equilibrium FAME yield, and in situ transesterification was inhibited when the biomass water content was greater than 115% w/w (based on oil weight).     

三油酸甘油酯与甲醇酯交换反应热力学分析

为了揭示酯交换反应的热力学特性,并为动力学研究和生物柴油的工业化生产提供基础数据,采用Benson基团贡献法和其他经验公式计算了三油酸甘油酯与甲醇之间发生的3步连续可逆酯交换反应的焓变、Gibbs自由能变及平衡常数的值,以及在303—338K各值随温度的变化关系。结果表明,在该温度范围内,反应焓接近于0,Gibbs自由能为正值,平衡常数接近于1。说明三油酸甘油酯与甲醇酯交换反应体系的反应热较小,温度对平衡的影响不大。