生物可降解聚酯PBS的合成工艺研究

目的:为了提高1,4-丁二醇的附加值和开发新型的生物可降解材料.方法:以钛酸四丁酯为催化剂通过酯化缩聚合成了聚丁二酸丁二醇酯(PBS).考察了醇酸摩尔比、催化剂用量、反应温度、反应时间等因素对酯化率的影响.结果:醇酸物质的量比为1∶1.2,催化剂用量为0.6%(质量百分含量),反应温度220℃,反应时间6h,酯化率可达98.7%,平均分子量和分子量分布分别为:Mn=182197,Mw/Mn=1.626406.利用红外谱(IR)、凝胶渗透色谱(GPC)对产物进行了表征确认.     

大孔树脂共吸附固定葡聚糖-脂肪酶催化合成香茅酯

以大孔树脂为载体对脂肪酶和葡聚糖进行共吸附固定,考察葡聚糖的共吸附对脂肪酶固定化效果的影响,并应用所得固定化酶在无溶剂体系催化合成月桂酸香茅酯。结果表明:在固定化过程中添加终质量浓度为0.75mg/m L的葡聚糖可提高固定化酶酶活回收率,使用该固定化酶在无溶剂体系催化月桂酸与香茅醇酯化,酶的催化效率及操作稳定性均有提高。在底物月桂酸与香茅醇物质的量的比为1∶1,加入1 U的固定化脂肪酶,在50℃时无溶剂体系中反应10 h,反应的酯化率达95.3%。添加终质量浓度为0.75 mg/m L的T-20及T-40(葡聚糖相对分子质量为2×10~4和4×10~4)制备的固定化酶可将到达95%酯化率的反应时间缩短至6 h,其中添加T-40的固定化酶经10次连续催化后,仍保持75%以上的催化活性。     

微波辐射一步法合成香料富马酸二苄酯的研究

目的:在微波辐射下,以顺丁烯二酸酐和苄醇为原料,在复合催化剂对甲苯磺酸-硫脲存在下以甲苯为带水剂一步合成了富马酸二苄酯.方法:通过熔点测定和红外光谱分析对产物进行了结构表征.采用正交试验法研究了反应物的摩尔比、催化剂用量、反应温度、辐射反应时间等对产物收率的影响.结果:实验结果表明,在微波功率为700W,n(顺丁烯二酸酸酐):n(苄醇)=1:5,复合催化剂用量为总投料量的7%,甲苯20mL,一酯化、转化、二酯化的温度分别为140℃、145℃、135℃,回流分水90min的条件下,富马酸二苄酯的收率可达92.50%.结论:采用微波辐射法复合催化合成富马酸二苄酯具有操作简便、反应时间短、产物收率高等特点.     

硫酸酯化银耳多糖的制备及抗氧化性活性研究

采用氯磺酸-吡啶法化学合成硫酸酯化银耳多糖,对硫酸酯化反应的吡啶与氯磺酸的体积比进行优化,氯化钡-明胶比浊法测定硫酸酯化银耳多糖的取代度,并对不同取代度的硫酸酯化银耳多糖进行体外抗氧化实验。结果表明:硫酸酯化银耳多糖取代度随吡啶与氯磺酸体积比的提高而增加;当吡啶与氯磺酸体积比为4∶1,反应温度60℃,反应时间3 h时,产物的取代度为1.32,在0.8～2.0 mg/mL浓度范围内对Fenton反应产生的羟基自由基体外清除率相对于银耳多糖具有明显优势。     

响应面分析应用于抗病毒药物香菇多糖酯化工艺的优化

目的:应用响应面分析法(RSM)优化香菇多糖酯化的工艺,确定最佳酯化条件.方法:利用Design Expert软件的中心组合设计法对香菇多糖酯化条件进行了优化,并利用响应面分析法对主要影响因素进行了回归分析,主要考察脂肪酶添加量,反应时间和反应温度对酯化效果的影响.结果:得到了各因素的最佳水平值,即酶加量为0.069g,反应时间为11.92h,反应温度为40.4℃,在模拟优化的条件下,酯化后滴定所消耗NaOH量为36.60ml.结论:将在此条件下酯化的香菇多糖测定红外光谱,证实有酯键生成.     

豆甾醇与琥珀酸酐单酯化反应工艺及动力学研究

研究了甲苯为溶剂,吡啶为催化剂,豆甾醇与琥珀酸酐的酯化反应工艺和反应动力学。探讨了反应温度、催化剂吡啶用量、反应物的摩尔配比和反应时间对酯化反应结果的影响。实验结果表明:豆甾醇与琥珀酸酐的反应产物为豆甾醇琥珀酸单酯;当吡啶的体积分数为1.5%,反应物的摩尔比为1.0∶1.6,回流下反应20 h后,豆甾醇的酯化率大于97%,反应后的溶液经蒸发回收溶剂甲苯,固体产物分别经乙醇和水洗涤除杂,所得固体在60℃下真空干燥至恒重,得到的豆甾醇琥珀酸单酯的单程收率大于86%。单酯化反应满足二级不可逆反应动力学规律,反应的活化能为85 kJ/mol。     

嗜麦芽黄单胞菌游离细胞催化合成α-熊果苷

研究了利用嗜麦芽黄单胞菌BT-112(Xanthomonas maltophilia BT-112)游离细胞生物催化合成α-熊果苷,系统探讨了温度、对苯二酚浓度、对苯二酚与蔗糖摩尔比、反应时间、转速、细胞浓度、磷酸缓冲溶液pH值和浓度对反应转化率的影响。最佳反应条件为:反应温度为25℃,菌体对对苯二酚的最大耐受度为30mmol/L,蔗糖和对苯二酚的摩尔比为20∶1,反应时间为45h,摇床转速为160r/min,细胞浓度为85g/L,磷酸缓冲溶液浓度为25mmol/L、pH值为8.0。在此条件下α-熊果苷转化率高达86.7%(以对苯二酚计算)。     

双氧水介导制备对硝基苯甲酸乙酯的初步研究

目的:探讨双氧水催化合成对硝基苯甲酸乙酯的可行性,并考察了反应物的摩尔比、催化剂用量、反应温度及反应时间对产物收率的影响.方法:分别采用单因素设计实验与正交设计实验,分析比较这两种方法的最佳反应条件.采用数字熔点仪测定样品的熔点:用GC112A型气相色谱仪测定了产物的纯度;用傅里叶变换红外光谱仪测定产物的结构.结果:双氧水可以作为合成对硝基苯甲酸乙酯的催化剂.综合分析可知:当无水乙醇和对硝基苯甲酸的摩尔比为4:1,催化剂含量为10%,反应温度为80℃,反应时间为2.5-3h时酯化产率可达到最高值.结论:双氧水催化对硝基苯甲酸、无水乙醇合成对硝基苯甲酸乙酯的效率较高,产品纯度高,环境污染小,不失为一种新的合成方法.     

非水溶剂中Rhizopus arrhizus脂肪酶催化合成三种酯的最佳条件(英文)

以少根根霉 (Rhizopusarrhizus)脂肪酶为催化剂 ,有机溶剂为反应介质 ,合成了 3种短链脂肪酸酯 .研究了反应温度、溶剂、底物浓度、底物摩尔比、吸水剂用量等因素对酯化反应的影响 .确定了3种酯的最佳合成条件 :(1)己酸乙酯 :反应温度为 4 0℃ ,环己烷为溶剂 ,0 2 5mol L底物浓度 ,酸醇摩尔比为 1∶1 2 ;(2 )乙酸异丙酯 :5 0℃ ,环己烷为溶剂 ,0 15mol L底物浓度 ,摩尔比为 1∶1;(3)乙酸异戊酯 :5 0℃ ,异辛烷为溶剂 ,0 2 0mol L底物浓度 ,摩尔比为 1∶1.三种酯合成时均需 0 12 5g ml的0 5nm分子筛为吸水剂 ,在 8h后 ,合成酯转化率达到 97%～ 99% .     

微波辐射合成小檗红碱的工艺研究

首次以DMF为反应介质,微波法快速合成小檗红碱。通过单因素法,考察了反应功率、液料比、反应时间对产率的影响,并采用析晶的方法纯化产物,产品纯度和结构经HPLC、UV、IR、ESI-MS、1H NMR、13C NMR确定,得出最佳合成工艺条件:微波功率400 W、微波时间15 min、小檗碱与DMF料液比为1∶25(g∶mLL),析晶纯化,纯度98%,收率93%。并与传统的真空热解法相比,微波辅助合成可使产率提高近15%,反应时间缩短近4倍;且反应物纯度高(≥95%),可直接析晶纯化,方法经济简便。     

Multiple synthesis by the multipin method as a methodological tool

The multipin method of peptide synthesis is demonstrated as a potent methodological tool, where large numbers of comparative studies can be performed concurrently. Two studies are presented. In each study, the test peptides were simultaneously synthesized, and the products examined by high throughput ion spray mass spectrometry and reverse-phase HPLC. In the first study, comprising 24 experiments, peptides 1 (AELFSTHYLAFKEDYSQ-NH₂) and 2 (LKDFRVYFREGRDQLWKGPG-NH₂) were prepared using Fmoc-Axx/BOP/HOBt/NMM (100: 100: 100: 150 mM ) and Fmoc-Axx/HATU/HOAt/NMM (100: 100: 100: 150 mM ) with 60.90 and 120 min coupling times. The two reagent combinations were found to give comparable results. The second study compared the N-terminal coupling of Fmoc-Asn-OH, Fmoc-Asn(Mbh)-OH, Fmoc-Asn(Mtt)-OH, Fmoc-Asn(Tmob)-OH and Fmoc-Asn(Trt)-OH in the synthesis of seven test peptides: 3 , NVQAAIDYIG-cyclo(Kp); 4 , NTVQAAIDYIG-cyclo(KF); 5 , NRVYVHPFNL; 6 , NRVYVHPFHL: 7 , NEAYVHDAPVRSLN: 8 , NQLVVPSEGLYLIYSQVLFK. 9 , NPNANPNANPNA. A total of 33 experiments were performed. Peptides 3 and 4 were selected to highlight the effect of steric bulk of each Asn derivative on coupling efficiency. Reagent efficiency, as measured by target peptide purity, was as follows: Fmoc-Asn(Tmob)-OH > Fmoc-Asn-OH > Fmoc-Asn(Mtt)-OH = Fmoc-Asn(Trt)-OH > Fmoc-Asn(Mbh)-OH.     

2-Chlorotrityl chloride resin. Studies on anchoring of Fmoc-amino acids and peptide cleavage

The esterification of 2-chlorotrityl chloride resin with Fmoc-amino acids in the presence of DIEA is studied under various conditions. High esterification yields are obtained using 0.6 equiv. Fmoc-amino acid/mmol resin in DCM or DCE, in 25 min, at room temperature. The reaction proceeds without by product formation even in the case of Fmoc-Asn and Fmoc-Gln. The quantitative and easy cleavage of amino acids and peptides from 2-chlorotrityl resin, by using AcOH/TFE/DCM mixtures, is accomplished within 15-60 min at room temperature, while t-butyl type protecting groups remain unaffected. Under these exceptionally mild conditions 2-chlorotrityl cations generated during the cleavage of amino acids and peptides from resin do not attack the nucleophilic side chains of Trp, Met, and Tyr.     

Effect of alcohol chain length on the optimum conditions for lipase-catalyzed synthesis of adipate esters

Immobilized Candida antarctica lipase B, Novozym® 435, was used in the esterification of adipic acid and alcohols with different chain lengths (C₁–C₁₈). Optimum conditions for the synthesis of adipate esters were obtained using response surface methodology (RSM) with respect to important reaction parameters including time, temperature, substrate molar ratio and amount of enzyme. Alcohol chain length specificity of the enzyme in the synthesis of adipate esters was also determined. Minimum reaction time (215 min) for achieving maximum ester yield was obtained for butyl alcohol. Methanol required an increased time (358 min) and enzyme amount (10.2%, w/w) for attaining maximum yield. The maximum required temperature and time of 65°C and 523 min, respectively, were obtained for the synthesis of dioctadecyl adipate. The results demonstrate that alcohol chain length is a determining parameter in optimization of the lipase-catalyzed synthesis of adipate esters. Reactions under optimized conditions yielded a high percentage of esterification (>97%). The optimum conditions can be used to scale up the process.     

Enzymatic synthesis of betulinic acid ester as an anticancer agent: Optimization study

Abstract

Immobilized Candida antarctica lipase, Novozym 435, was used to catalyze the esterification reaction between betulinic acid and phthalic anhydride to synthesize 3-O-phthalyl betulinic acid in n-hexane/chloroform. Response surface methodology based on a five-level, four-variable central composite rotatable design was employed to evaluate the effects of synthesis parameters such as reaction time, reaction temperature, enzyme amount and substrate molar ratio on the yield of ester. Based on the response surface model, the optimal enzymatic synthesis conditions were predicted to be: reaction time 20.3 h, reaction temperature 53.9°C, enzyme amount 145.6 mg, betulinic acid to phthalic anhydride molar ratio 1:1.11. The predicted yield was 65.8% and the actual yield was 64.7%.     

L-酪氨酸苄酯的合成及其影响因素研究

以L-酪氨酸和苯甲醇为原料合成一种新型的L-酪氨酸衍生物——L-酪氨酸苄酯。首先用苯甲醇与氯化亚砜反应生成氯化亚硫酸酯,合成物再与L-酪氨酸发生酯化反应得到L-酪氨酸苄酯,其结构经质谱(MS)分析法确证。在此基础上研究了影响该合成工艺的主要因素,即原料配比、反应温度、反应时间、pH值。结果显示合成L-酪氨酸苄酯的较佳工艺条件为:物料摩尔比mol(SOCl2)∶mol(L-酪氨酸)=1.3∶1.0,室温下反应3h,120℃下反应2h,后处理溶液pH为7.5。本工艺适宜于工业化大规模生产。     

Synthesis of monoacylglycerol containing pinolenic acid via stepwise esterification using a cold active lipase

High purity monoacylglycerol (MAG) containing pinolenic acid was synthesized via stepwise esterification of glycerol and fatty acids from pine nut oil using a cold active lipase from Penicillium camembertii as a biocatalyst. Effects of temperature, molar ratio, water content, enzyme loading, and vacuum on the synthesis of MAG by lipase‐catalyzed esterification of glycerol and fatty acid from pine nut oil were investigated. Diacylglycerol (DAG) as well as MAG increased significantly when temperature was increased from 20 to 40°C. At a molar ratio of 1:1, MAG content decreased because of the significant increase in DAG content. Water has a profound influence on both MAG and DAG content through the entire course of reaction. The reaction rate increased significantly as enzyme loading increased up to 600 units. Vacuum was an effective method to reduce DAG content. The optimum temperature, molar ratio, water content, enzyme loading, vacuum, and reaction time were 20°C, 1:5 (fatty acid to glycerol), 2%, 600 units, 5 torr, and 24 h, respectively. MAG content further increased via lipase‐catalyzed second step esterification at subzero temperature. P. camembertii lipase exhibited esterification activity up to ?30°C. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012     

Optimized enzymatic synthesis of ascorbyl esters from lard using Novozym 435 in co-solvent mixtures

A mild and efficient method for the conversion of fatty acid methyl esters from lard into ascorbyl esters via lipase-catalyzed transesterification in co-solvent mixture is described. A solvent engineering strategy was firstly applied to improve fatty acid ascorbyl esters production. The co-solvent mixture of 30% t-pentanol:70% isooctane (v/v) was optimal. Response surface methodology (RSM) and central composite design (CCD) were employed to estimate the effects of reaction parameters, such as reaction time (12–36 h), temperature (45–65 °C), enzyme amount (10–20%, w/w, of fat acid methyl esters), and substrate molar ratio of fatty acid methyl esters to ascorbic acid (8:1–12:1) for the synthesis of fatty acid ascorbyl esters in co-solvent mixture. Based on the RSM analysis, the optimal reaction conditions were determined as follows: reaction time 34.32 h, temperature 54.6 °C, enzyme amount 12.5%, substrate molar ratio 10.22:1 and the maximum conversion of fatty acid ascorbyl esters was 69.18%. The method proved to be applicable for the synthesis of ascorbyl esters using Novozym 435 in solvent.     

Synthesis of trimethylolpropane esters of oleic acid by Lipoprime 50T

The ability of the commercial lipolytic enzyme Lipoprime 50T to catalyze the biotechnologically important synthesis of the biodegradable and environmentally acceptable trimethylolpropane (2-ethyl-2-(hydroxymethyl)-1,3-propanediol) ester of oleic acid was investigated. Simple and accurate thin-layer chromatography and computer analysis methods were used that enable one to follow changes of all reaction mixture components simultaneously. The processes of transesterification and esterification were compared. The effects of the molar ratio of the substrates, reaction temperature, time, and medium on the composition of the reaction mixture were analyzed. Esterification was determined to be more preferable than transesterification in both studied solvents. Under the optimal conditions identified (15% w/w water, temperature 60°C, trimethylolpropane to oleic acid molar ratio 1:3.5, and reaction time 72 h), the highest trimethylolpropane trioleate yield of around 62% and trimethylolpropane mono-, di-, and trioleate overall yield of about 83% were obtained. Although the yields are not high enough for industrial application, the process shows the potential to be optimized for higher yields in the near future as the conversions were obtained at ambient pressure, whereas many other processes described in the literature are conducted under vacuum at a specific pressure.     

Assessment of process variables on 2-ethylhexyl palmitate production using Novozym 435 as catalyst in a solvent-free system

This work reports the optimization of 2-ethylhexyl palmitate production by esterification reaction in a solvent-free system using a commercial lipase as catalyst. For this, a sequential strategy was performed applying three experimental designs. An empirical model was built so as to assess the effects of process variables on the reaction conversion. Afterward, the operating conditions that optimized 2-ethylhexyl palmitate production were determined to be acid to alcohol molar ratio of 1:5.5, 70 °C, 150 rpm and 10.5 wt% of enzyme, leading to a reaction conversion as high as 93%. From this point, a kinetic study was carried out evaluating the influence of acid to alcohol molar ratio, enzyme concentration and temperature on product yield. Results obtained in this step allow to conclude that an excess of alcohol (acid to alcohol molar ratio of 1:6), relatively low enzyme concentration (10 wt%) and temperature of 70 °C led to nearly complete reaction conversion.     

Optimisation and Characterisation of Lipase-Catalysed Synthesis of a Kojic Monooleate Ester in a Solvent-Free System by Response Surface Methodology

Kojic acid is widely used to inhibit the browning effect of tyrosinase in cosmetic and food industries. In this work, synthesis of kojic monooleate ester (KMO) was carried out using lipase-catalysed esterification of kojic acid and oleic acid in a solvent-free system. Response Surface Methodology (RSM) based on central composite rotatable design (CCRD) was used to optimise the main important reaction variables, such as enzyme amount, reaction temperature, substrate molar ratio, and reaction time along with immobilised lipase from Candida Antarctica (Novozym 435) as a biocatalyst. The RSM data indicated that the reaction temperature was less significant in comparison to other factors for the production of a KMO ester. By using this statistical analysis, a quadratic model was developed in order to correlate the preparation variable to the response (reaction yield). The optimum conditions for the enzymatic synthesis of KMO were as follows: an enzyme amount of 2.0 wt%, reaction temperature of 83.69°C, substrate molar ratio of 1:2.37 (mmole kojic acid:oleic acid) and a reaction time of 300.0 min. Under these conditions, the actual yield percentage obtained was 42.09%, which is comparably well with the maximum predicted value of 44.46%. Under the optimal conditions, Novozym 435 could be reused for 5 cycles for KMO production percentage yield of at least 40%. The results demonstrated that statistical analysis using RSM can be used efficiently to optimise the production of a KMO ester. Moreover, the optimum conditions obtained can be applied to scale-up the process and minimise the cost.