超声酶促合成氯乙酸对硝基苄酯研究

以氯乙酸和对硝基苄醇为原料,超声辅助固定化脂肪酶催化合成氯乙酸对硝基苄酯,并对超声酶促合成条件进行了优化。实验结果表明:20 Hz的超声声强为0.5 W·cm-2,温度为35℃,固定化酶的浓度为2 g·L-1时,反应6 h,对硝基苄醇的转化率最高可达89.7%。     

超声酶促维生素A棕榈酸酯反应的动力学

考察超声辐照下影响合成维生素A棕榈酸酯反应的因素(溶剂、底物摩尔比、底物浓度、反应时间、酶量和超声功率),并优化了反应条件:在10 mL的正己烷溶剂中,0.164 g维生素A醋酸酯和0.32 g棕榈酸,在酶与维生素A醋酸酯的质量比为1∶4的固定化脂肪酶Novozym 435催化下,超声功率为90 W,反应6 h,酯化率可达82%。并对其动力学进行了研究,由非线性拟合得到动力学参数:最大反应初速率(rmax)为0.522 mmol/(min.g);维生素A醋酸酯的米氏常数为0.404 mmol/L;棕榈酸的米氏常数为0.034 mmol/L。     

有机相中脂肪酶催化转酯化反应动力学拆分左旋帕罗醇

研究了在有机相中脂肪酶催化转酯化反应动力学拆分左旋帕罗醇,考察了酶种类、溶剂、酰基供体、温度、底物与酰基供体摩尔比等因素对反应的影响。结果表明:以Novozym 435为催化剂,在30℃下,以乙腈为反应溶剂,乙酸乙烯酯为酰基供体,底物浓度40mmol/L及其与酰基供体摩尔比为1:8时,反应8h后,底物转化率为48.1%,ee_s为53.3%,E值为6.20。     

固定化脂肪酶合成3-TBDMSO戊二酸甲酯

脂肪酶主要催化醇、酸、内酯的酯化反应,脂肪酶催化反应可在非水溶剂中进行,并且反应条件温和,被认为是制备单一对映异构体的有效方法。文中利用固定化脂肪酶Novozym 435催化3-TBDMSO戊二酸酐不对称醇解制备3-TBDMSO戊二酸甲酯,通过高效液相色谱考察了不同反应条件对底物转化率、产物选择性的影响规律。实验研究了四氢呋喃、乙酸乙酯、乙醚、甲基叔丁基醚和甲苯5种溶剂对酶催化反应的影响,结果表明:在甲基叔丁基醚溶剂中,Novozym 435的催化效果最好。最优反应条件:温度25℃,酶质量浓度30 mg/mL,醇与3-TBDMSO戊二酸酐摩尔比1.0,酸酐浓度100 mmol/L,pH值为6.5,水活度0.66,反应时间6 h。实验采用萃取的方法分离出反应产物,通过结晶纯化得到无色晶体,利用核磁氢谱证明产物为3-TBDMSO戊二酸甲酯,通过圆二色光谱说明合成产物为对映体过剩产品。     

非水相脂肪酶催化阿魏酸淀粉酯合成

以玉米淀粉和阿魏酸乙酯为原料,利用脂肪酶催化合成阿魏酸淀粉酯。对反应介质和脂肪酶进行了筛选,同时对影响合成阿魏酸淀粉酯反应的因素进行了探究,主要考察了底物摩尔比、酶添加量、反应时间及反应温度等参数对该反应的影响。采用紫外分光光度计对取代度进行测定,并以取代度为考察指标,确定了最佳反应条件：Novozym435脂肪酶为催化剂、异辛烷为反应介质、底物摩尔比为3:1、酶添加量为10%、反应时间18 h、反应温度65 ℃,在此条件下,产物的最大取代度可达0.031. 并通过FT-IR以及1H NMR对产物进行表征。     

非水相脂肪酶催化阿魏酸淀粉酯的合成

以玉米淀粉和阿魏酸乙酯为原料,利用脂肪酶催化合成了阿魏酸淀粉酯,对反应介质和脂肪酶进行了筛选,同时对影响合成阿魏酸淀粉酯反应的因素进行了探究,主要考察了底物摩尔比、酶添加量、反应时间及反应温度对反应的影响。采用紫外分光光度计对取代度进行测定,并以取代度为考察指标,确定了最佳反应条件:Novozym435脂肪酶为催化剂、异辛烷为反应介质、底物摩尔比n(阿魏酸乙酯)∶n(活化淀粉)=3∶1、酶添加量为10%(以活化淀粉质量计)、反应时间18 h、反应温度65℃,在该条件下,产物的最大取代度可达0.031,并通过FTIR以及1HNMR对产物结构进行了表征。     

固定化脂肪酶催化合成癸二酸二(2-乙基己基)酯

在有机溶剂中,分别采用固定化脂肪酶Lipozyme TL IM,Lipozyme RM IM和Novozym 435催化癸二酸和2-乙基己醇合成癸二酸二(2-乙基己基)酯,考察了溶剂、反应温度、反应时间、酶量和底物比等对产率的影响.结果表明:反应温度40℃,癸二酸400 mg,2-乙基己醇0.96 mL(2-乙基己醇和癸二酸物质的量之比3),环己烷15 mL,在600 PLU固定化脂肪酶催化条件下反应24 h,Lipozyme TL IM催化产率可达96.94％,Lipozyme RM IM 催化产率可达96.23％,Novozym 435催化产率可达84.65％.在上述反应条件下,使用6次后,这3种固定化脂肪酶仍保持较高的催化活性.     

有机相酶促合成阿魏酸糖酯

利用酶促方法合成阿魏酸葡糖酯,对酶和有机溶剂进行了比较和筛选,并对影响阿魏酸葡糖酯产率的因素(酶量、反应时间、反应温度、底物比)进行了研究。结果表明,葡萄糖和阿魏酸乙烯酯(摩尔比4∶1)分别加入到体积比2∶1的无水吡啶和叔丁醇中,20 g/L Novozym 435脂肪酶,在220 r/min的空气振荡器中50℃反应72 h,产率能达到80.9%。     

单体碳数对脂肪酶N435催化合成直链聚酯的影响

通过多级催化法用脂肪酶N435催化不同碳数脂肪族二醇与二酯反应,合成直链聚酯。结果表明:短链二醇与短链二酯难以被脂肪酶催化发生反应,长链二醇与二酯易被催化发生反应。采用脂肪酶N435催化己二酸二乙酯与1,4-丁二醇反应可以获得重均分子量为24 816,相对分子质量分布为1.09的聚酯。脂肪酶催化二醇、二酯与甘油共聚合可以获得重均分子量较高、相对分子质量分布窄的共聚物。     

毕赤酵母表面展示脂肪酶催化合成肉豆蔻酸糖酯

研究了毕赤酵母表面展示脂肪酶(CALB)全细胞催化剂的较佳活性条件,结果显示,适宜的反应温度为50~60℃。以CALB为催化剂,比较了不同底物对糖酯合成的影响。以1,2-O-异亚丙基-D-呋喃葡萄糖(Ip Glc)为酰基受体,肉豆蔻酸为酰基供体,考察了有机溶剂种类、CALB的添加量、底物摩尔比、分子筛的添加量、初始水活度对合成6-O-肉豆蔻基-1,2-O-异亚丙基-α-D-呋喃型葡萄糖酯(Ip Glc-C14)的影响,得到较佳的合成条件为:丙酮5 m L、CALB(干粉)0.3 g、n(Ip Glc)∶n(肉豆蔻酸)=1∶3(其中Ip Glc 0.5 mmol)、4A分子筛0 g、初始水活度a_w=0.11、反应温度50℃、200 r/min反应72 h。在此条件下,Ip Glc-C14的收率为91.25%。比较了CALB和固定化脂肪酶Novozym 435对Ip Glc-C14合成的反应进程的影响,结果显示使用Novozym 435的反应速率快,而CALB的最终收率较高。     

Lipase-catalyzed esterification of lactic acid with straight-chain alcohols

Enzymatic synthesis of esters of lactic acid and straight-chain alcohols with different chain lengths (C₆–C₁₈) were investigated in batch reactions with hexadecanol (C₁₆) as the model alcohol. Cyclohexane was the best solvent for higher ester yields, and the best biocatalyst was the immobilized Candida antarctica lipase B (Novozym 435) as well as the textile-immobilized Candida sp. lipase. A method was established to obtain ester yields in the range of 71 to 82% for the different alcohols, and the most favorable conditions for the esterification reaction using Novozym 435 were an equimolar ratio of lactic acid to alcohol, each at a concentration of 120 mM each; a 50°C reaction temperature; 190 rpm shaking speed; and the addition of 100 mg molecular sieves (4 Å) for drying. The ester yield increased with increasing lipase load, and a yield of 79.2% could be obtained after 24 h of reaction at 20 wt% of Novozym 435. The immobilized Candida sp. lipase prepared in the laboratory also could be used to produce esters of lactic acid and straight-chain alcohols, but it had a much lower activity than Novozym 435 with a temperature optimum of 40°C.     

叔戊醇体系酶促大豆油制备生物柴油

叔戊醇作为反应介质,固定化脂肪酶Novozym 435催化大豆油与甲醇的转酯反应制备生物柴油。叔戊醇消除了反应底物甲醇及反应副产物甘油对酶活的负面影响。定量分析表明,叔戊醇与油脂的体积比为1,甲醇与油脂的摩尔比为3,2%脂肪酶,反应体系含水量2%,40 ℃、180 r/min条件下反应15 h,生物柴油得率可达97%。在最适条件下反应进行160批次,酶仍保持了较高的活性和良好的稳定性。     

Effect of methanol content on enzymatic production of biodiesel from waste frying oil

The enzymatic production of biodiesel from waste frying oil with methanol has been studied using immobilized lipase Novozym 435 as catalyst. The effects of methanol to oil molar ratio, dosage of enzyme and reaction time were investigated. The optimum reaction conditions were methanol to oil molar ratio of 25:1, 10% of Novozym 435 based on oil weight and reaction period of 4 h at 50 °C obtaining a biodiesel yield of 89.1%. Moreover, the reusability of the lipase over repeated cycles was also investigated under standard conditions.     

维生素C乳酸酯酶催化合成的响应曲面分析

以脂肪酶Novozym 435催化维生素C和乳酸乙酯转酯合成维生素C乳酸酯。采用基于四因素五水平的中心组合设计实验的响应曲面法,分析了温度(30~70℃)、酶量(10~30 mg)、维生素C质量浓度(9.36~28.07g/L)和反应时间(24~72 h)以及它们的交互作用对维生素C乳酸酯产率的影响。获得的最佳实验条件为:温度50℃,维生素C的质量浓度18.71 g/L,脂肪酶质量20 mg和反应时间48 h。在最佳条件下,维生素C乳酸酯的预计产率为71.20%,与实际产率71.12%符合较好。     

Modeling and optimization of lipase‐catalyzed synthesis of dilauryl adipate ester by response surface methodology

BACKGROUND: Adipate esters are used as low‐temperature and low‐viscosity plasticizers for polyvinyl chloride and its copolymers. In this work, optimization of lipase‐catalyzed production of dilauryl adipate was carried out using response surface methodology (RSM) based on a four‐factor‐five‐level central composite rotatable design (CCRD). Immobilized lipase from Candida antarctica (Novozym 435) was used as catalyst in this reaction. Various reaction parameters affecting the synthesis of adipate ester, including alcohol/acid molar ratio, amount of enzyme, temperature and reaction time, were investigated. RESULTS: Statistical analysis showed that the amount of enzyme was less significant than the other three factors. The optimal conditions for the enzymatic reaction were obtained at 5.7:1 substrate molar ratio using 0.18 g of enzyme at 53.1 °C for 282.2 min. Under these conditions the esterification percentage was 96.0%. CONCLUSIONS: The results demonstrated that response surface methodology can be applied effectively to optimize the lipase‐catalyzed synthesis of adipate ester. The optimum conditions can obtained be used to scale up the process. Copyright © 2008 Society of Chemical Industry     

Lipase catalyzed synthesis of oleyl oleate: Optimization by response surface methodology

Lipase catalyzed production of oleyl oleate, which is an analogue of jojoba oil, was carried out using oleic acid and oleyl alcohol in the solvent-free system. Novozym 435, immobilized Candida antarctica lipase, was used as a biocatalyst. Response surface methodology (RSM) based on five-level, four-variable central composite rotatable design was used to evaluate the effects of important parameters on the production of oleyl oleate. Acid/alcohol molar ratio (0.5-1.5), enzyme quantity (2-10% w/w of substrates), reaction temperature (40-60°C), and reaction time (30-90 min) were chosen as process variables for the optimization. Among these parameters, enzyme quantity and acid/alcohol molar ratio have significant effects compared with temperature and time on the production of oleyl oleate. Optimum conditions were found to be a acid/alcohol molar ratio of 1, enzyme quantity of 7% (w/w), reaction temperature of 51°C, and reaction time of 75 min. The coefficient of determination (R 2 ) for the model is 0.97. Probability value is 2.9 ‐ 10 m 9 (P-value<0.01). This P-value demonstrates a very high significance for the regression model. The maximum oleyl oleate concentration predicted by the equation (737 g/L) agrees well with the experimentalvalue (734 g/L) obtained from the experimental verification at the optimum values.     

Immobilized lipase-catalysed esterification and transesterification reactions in non-aqueous media for the synthesis of tetrahydrofurfuryl butyrate: comparison and kinetic modeling

Immobilized lipase-catalyzed synthesis of tetrahydrofurfuryl butyrate is reported in this paper. Esterification and transesterification of tetrahydrofurfuryl alcohol (THFA) with butyric acid (BA) and transesterification with ethyl butyrate (EB) to prepare tetrahydrofurfuryl butyrate (THFB) were studied systematically including kinetic modeling. A series of immobilized lipases such as Novozym 435, Lipozyme IM 20, Pseudomonas species lipase on toyonite (PSL/Toyo), Candida rugosa lipase (CRL) on polypropylene, CRL on egg shells and CRL on celite were screened to establish that Novozym 435 was the best catalyst for both esterification and transesterification at 30°C. The effects of various parameters on reaction rates were studied in detail for both reactions with Novozym 435. The ping-pong bi-bi mechanism with inhibition by the substrate THFA fits the data for esterification whereas the ping-pong bi-bi mechanism with inhibition by both the reactants (THFA and EB) and both the products (THFB and ethanol) is valid for the transesterification reaction. The kinetic parameters deduced from these models were used to simulate the conversions, which are in good agreement with the experimental values. Since transesterification suffers inhibition by both the substrates and products, esterification is a better method compared to transesterification.     

Synergism of microwave irradiation and enzyme catalysis in synthesis of isoniazid

Isoniazid is a useful antitubercular drug widely employed in combination therapy with rifampicin. The synthesis of isoniazid from ethyl isonicotinate and hydrazine hydrate was studied in non‐aqueous media via lipase‐catalyzed hydrazinolysis under both conventional heating and microwave irradiation by using different supported lipases. Among three different commercial lipases used, namely Novozym 435 (Candida antarctica lipase), Lipozyme RM IM (Rhizomucor miehei lipase) and Lipozyme TL IM (Thermomyces lanuginosus lipase), Novozym 435 was found to be the most effective, with conversion of 54% for equimolar concentrations at 50 °C in 4 h. The rate of reaction as well as final conversion increased synergistically under microwave irradiation in comparison with conventional heating, which showed 36.4% conversion, even after 24 h, for the control experiment. Effects of various process parameters such as speed of agitation, catalyst loading, substrate concentration, product concentration and temperature were studied. A kinetic model is also described. Copyright © 2007 Society of Chemical Industry     

Optimization of the enzymatic production of isoamyl acetate with novozym 435 from candida antarctica

In this study the production of isoamyl acetate by esterification of isoamyl alcohol and acetic acid was carried out using immobilized C . antarctica lipase (Novozym 435) as a catalyst without any organic solvent. The esterification yield was optimized with response surface methodology. This method was used with four parameters to evaluate the effects of important variables on the esterification yield. The parameters are acid/alcohol mole ratio (0.2-0.8), enzyme amount (4-12%, w/w), temperature (30-50 °C), and reaction time (4-8 hr). It was found that the most effective parameter was acid/alcohol mole ratio. As acid/alcohol mole ratio increased at any given reaction time and amount of enzyme, ester concentration, C p (mmol ester/g mixture), increased up to an acid/alcohol mole ratio of 0.7 and thereafter decreased. The model indicated the optimum conditions for maximum esterification (3.45 mmol ester/g mixture) in the acid/alcohol mole ratio of 0.52 for 8.15% enzyme at 43.2 °C and after 5.27 hr, which were in good agreement with the experimental value (3.5 mmol ester/g mixture).     

Synthesis of (Z)-3-hexen-1-yl butyrate in hexane and solvent-free medium using Mucor miehei and Candida antarctica lipases

(Z)-3-Hexen-1-yl butyrate is an important flavor and fragrance compound as it represents the model of a natural herbaceous (green) note. Two immobilized lipases from Mucor miehei (Lipozym IM) and from Candida antarctica (Novozym 435) were investigated for their use in the synthesis of (Z)-3-hexen-1-yl butyrate by direct esterification in n-hexane. To determine optimal conditions for esterification, we examined the following parameters: temperature, amount of lipase, acid/alcohol ratio, and absence of solvent. In n-hexane, bioconversion yields reached 95 (after 4 h) and 92% (after 6 h) for, respectively, Lipozym IM [17 (w/w reactants)] and Novozym 435 [2% (w/w reactants)]. In the absence of solvent, at 60°C, Novozym 435-catalyzed esterification afforded the title compound in 80% yield. Up to 250 g (in hexane) and 160 g (without solvent) of ester were easily prepared, in a single operation, at a laboratory scale, in few hours, using 2% (w/w reactants) lipase.