Microwave-Assisted Facile and Rapid Esterification of Amino Acids I: Esterification of L-Leucine from Batch to Flow Processes and Scale-Up

We herein report our studies into the effects of microwave irradiation on the solvent-free esterification of L-leucine with alcohols. In the absence of solvent, microwave irradiation accelerated the reaction compared to conventional oil bath heating. Measurement of the dielectric properties under the reaction conditions revealed that the high dielectric loss factor of the reaction mixture containing L-leucine, n-butanol, and a p-toluene sulfonic acid catalyst could be attributed to the acceleration of the reaction. The depth of microwave penetration into the reaction mixture as derived from the in-situ measurement of the dielectric properties was ~13 mm, which suggested that a thinner reaction vessel was favorable for the esterification of L-leucine. In addition to the batch reaction using a desktop microwave reactor, two types of flow reaction were also performed using a desktop tubular reactor and a semi-bench-scale tubular reactor. These flow reactions also exhibited high performances, thus allowing the scale-up of this reaction system for industrial use.

Application of Microwave Heating Technique to Esterification

Introduction Although the application of microwave technique has been reported as a new type of energy source chemically, it is only in recent years that this technique has been used as the energy source for organic synthesis. In 1986, R. Gedye, et al., published the report of the benzoate synthesis from the respective reactions between benzene carboxylic acid and methanol, propanol or butanol under microwave heating and the catalysis of H;SO;.

Influence of Microwave Irradiation on Hydrolysis Reaction of Sunflower Oil in Aqueous Emulsion

Microwave irradiation (MW) has been widely applied as heating in chemical processing. It offers a clean, convenient and inexpensive method of heating which often results in higher yields and shorter reaction times. Here, we study the microwave heating influence on the hydrolysis of the triglyceride (sunflower oil) in aqueous emulsion catalyzed by using 4-dodecylbenzenesulfonic acid (DBSA). The progress of the hydrolysis reaction was determined by Fourier Transform Infrared spectroscopy (FTIR). The effects of temperature, reaction time and the catalyst nature and concentration on the hydrolysis reaction were investigated. The hydrolysis was carried out at temperatures ranging between 90°C and 150°C. The polarity of the reaction medium accelerated this reaction.

Effective of Microwave-KOH Pretreatment on Enzymatic Hydrolysis of Bamboo

Bamboo, with its advantages of fast growth, short renovation, easy propagation and rich in cellulose and hemicellulose, is a potential feedstock for bioethanol or other biofuels production. The objective of this study was to examine the feasibility of microwave assistant KOH pretreatments to enhance enzymatic hydrolysis of bamboo. Pretreatment was carried out by immersing the bamboo in KOH (12% and 8% w/w bamboo) solutions and exposing the slurry to microwave radiation power of 400 W for 30min. Chemical composition of the pretreated substrates and spent liquor was analyzed. Pretreated substrates were enzymatic hydrolyzed, and glucose and xylose in the hydrolysate were analyzed. The results showed that the pretreated substrate with microwave assisted KOH had significantly higher sugar yield than the untreated samples. The fermentation inhibitors formic acid, furfural, HMF and levulinic acid were much lower than acid pretreatment reported.

Preparation of κ-carra-Oligosaccharides with Microwave Assisted Acid Hydrolysis Method

A rapid method of microwave assisted acid hydrolysis was established to prepare κ-carra-oligosaccharides. The optimal hydrolysis condition was determined by an orthogonal test. The degree of polymerization(DP) of oligosaccharides was detected by high performance thin layer chromatography(HPTLC) and polyacrylamide gel electrophoresis(PAGE). Considering the results of HPTLC and PAGE, the optimum condition of microwave assisted acid hydrolysis was determined. The concentration of κ-carrageenan was 5 mg m L-1; the reaction solution was adjusted to p H 3 with diluted hydrochloric acid; the solution was hydrolyzed under microwave irradiation at 100 for 15℃ min. Oligosaccharides were separated by a Superdex 30 column(2.6 cm × 90 cm) using AKTA Purifier UPC100 and detected with an online refractive index detector. Each fraction was characterized by electrospray ionization mass spectrometry(ESI-MS). The data showed that odd-numbered κ-carra-oligosaccharides with DP ranging from 3 to 21 could be obtained with this method, and the structures of the oligosaccharides were consistent with those obtained by traditional mild acid hydrolysis. The new method was more convenient, efficient and environment-friendly than traditional mild acid hydrolysis. Our results provided a useful reference for the preparation of oligosaccharides from other polysaccharides.

Determination of Amino Acids in Panax notoginseng by Microwave Hydrolysis and Derivatization Coupled with Capillary Zone Electrophoresis Detection

The microwave hydrolysis and derivatization coupled with capillary electrophoresis detection were developed for the separation and determination of the amino acids in Panax notoginseng. The experimental conditions for the microwave hydrolysis and derivatization were examined and optimized. Several parameters of capillary electrophoresis, such as pH value of background electrolyte, borate concentration and applied voltage were optimized Under the selected conditions, 11 amino acids were completely separated. The real sample was analyzed and the results were satisfactory. Compared with that of conventional heat hydrolysis and derivatization, the analytical time of this method was significantly shortened.

Microwave-assisted catalyst-free hydrolysis of fibrous cellulose for deriving sugars and biochemicals

Microwave(MW)assisted catalyst-free hydrolysis of fibrous cellulose(FC,cellulolysis)at 200℃promoted a cellulose conversion o f ca.37.2%and quantitative production o f valuable C5/C6 sugars(e.g.,glucose)and the according platform biochemicals(e.g.,5-hydroxymethylfurfliral),corresponding to an overall selectivity o f 96.5%.Conversely,conventional hydrothermal cellulolysis under similar conditions was not effective,even after 24 h,carbonising the FC.Based on the systematic study of MW-assisted cellulolysis,the specific interaction between water molecules and macroscopic FC under the MW irradiation was proposed,accounting for the interpretation o f the experimental observation.The kinetic energy o f water molecules under the MW irradiation facilitated the C-C(in the non-hindered surface-CH2OH groups)and C-O-C bond breaking(inside the cellulose cavities)in FC,producing primary cellulolysis products of xylose,glucose and cellobiose.

Amide Hydrolysis Reaction Catalyzed by KF/Al2O3 under Microwave Irradiation and Solvent Free Conditions

A microwave-enhanced hydrolysis of amides utilizing KF/Al2O3 in the absence of solvents has been developed. Amines are produced in excellent yields along with the corresponding carboxylic acids.

ResearchonS202一／Zr02solidsuperacidinsynthesisofn—amylacetateundermicrowaveradiation

采用沉淀一浸渍法制得S2O62 8-／ZrO2固体超强酸，在微波辐射下催化合成乙酸正戊酯。通过单因素实验和正交实验优化了合成的反应条件；采用Hammett指示剂法、BET法、红外光谱、电子透镜技术和x_射线衍射对其进行了表征。实验结果表明，采用最佳制备条件下得到的催化剂在微波辐射下催化合成乙酸正戊酯的最优合成条件为：醇酸摩尔比1．9：1，反应温度135℃，反应时间25min，催化剂用量1．2g，功率500W，收率为97．8％。该工艺具有绿色、安全、操作简单和收率高等优点。

Ultra-fast and high-efficient synthesis of caffeic acid phenethyl ester by microwave assistant ionic liquids catalysis

Caffeic acid phenethyl ester (CAPE), a natural and rare ingredient with several biological activities, was successfully synthesized from caffeic acid (CA) and phenylethanol (PE) by microwave assistant coupled with ionic liquids (ILs) catalysis. Four ILs, acted as both solvent and catalyst in this chemical synthesis, were optimized. Among them, [Bmim] [PF6] was the best with the highest CA conversion. 95% conversion was achieved under substrate molar ratio 4:1 (PE/CA, n/n), IL content 7:1 (IL/CA, w/w), microwave power 200 W, at 135 oC for 7 min. This study might be attributed to developing new chemical reaction system to produce caffeic acid derived esters.

Pig Liver Esterase-catalyzed Hydrolysis of Three Diesters of meso-Bicyclic Dicarboxylic Acid and Three Tetraesters of Tetrahydrofuran -2,3,4,5-tetracarboxylic Acid

Three diesters of exo- syn-meso-oxabicyclo (2, 2, 1 ) -hept- 5- ene- 2, 3- dicarboxylic acid and three tetraesters of tetrahydrofuran-2, 3, 4, 5-tetracarboxylic acid were synthesized and tested with enantioselective hydrolysis catalyzed by pig liver esterase(PLE). The results of the PLEcatalyzed hydrolysis were discussed.

3-甲基-6-氨甲基-喹喔啉-2-甲酸衍生物的合成

通过在3,4-二氨基苯甲腈原有的结构中引入两个活性基团(—NH 2、—COOH),合成新型3-甲基-6-氨甲基-喹喔啉-2-甲酸衍生物,使之与载体蛋白进行偶联,在有机药物中间体方面具有更好的潜在价值。以3,4-二氨基苯甲腈、乙酰乙酸乙酯和N-溴代琥珀酰亚胺(NBS)为原料,通过亲核加成再消除、加氢还原和氢氧化钠水解3步反应,设计并合成了一种3-甲基-6-氨甲基-喹喔啉-2-甲酸衍生物,其结构经^(1)H NMR,^(13)C NMR和MS(ESI)表征,并对关键合成工艺(最佳物质的量之比、加氢还原中溶剂种类、水解试剂种类以及最佳试剂用量)进行优化。结果表明:当3,4-二氨基苯甲腈与乙酰乙酸乙酯的投料比为1∶1时(物质的量之比),反应收率为56%。加氢还原反应中,溶剂为乙醇时收率最高,为44%。在酯化水解为羧酸反应中,当水解催化剂为氢氧化钠,且氢氧化钠与原料的物质的量之比为3∶1时,反应效果最好,产品收率为97%。

脂肪酶法制备富含DHA甘油酯的研究

本文对目前国内关于脂肪酶制备富含DHA甘油酯的研究进行了阐述,总结了几种优化方法:反应条件的优化、催化方法的优化以及与其他技术的联用。本文旨在为脂肪酶制备富含DHA甘油酯的研究提供参考,为以后的深入研究提供新思路。

Hydroesterification of <i>Nannochloropsis oculata</i>microalga’s biomass to biodiesel on Al₂O₃supported Nb₂O₅catalyst

Hydroesterification process has been presented biodiesel production from oil the green microalga Nannochloropsis oculata raw materials. Biodiesel studied in this work is the main product got from the hydroesterification of biomass the Nannochloropsis oculata and was obtained from esterification of fatty acid (product of a hydrolysis reaction) with methanol. It was used as catalyst the niobic acid pure and supported on δ-aluminum. The product was evaluated by gas chromatography and other analyses. The optimum conditions found in the conversion (%) for the hydrolysis reactions of the biomass (92.3%). Better results were observed in the algae concentration 20%, lead at 300?C with 20% of catalyst. For esterification of fatty acids of Nannochloropsis oculata (92.24%), were observed the molar ratio methanol: fat acid 3, lead at 200°C with 20% of catalyst supported.

三种核桃花粉破壁方法比较

比较了温差破壁、微波-酶解破壁、超声波破壁对核桃花粉的破壁率、VC含量、抗氧化总能力的影响,结果表明:微波-酶解所得的花粉有较高破壁率、V_(C)含量、较大抗氧化总能力。

液相色谱-串联质谱法测定畜禽肉和鸡蛋中氨基酸含量

建立了微波水解技术和液相色谱-串联质谱技术测定畜禽肉和鸡蛋中17种氨基酸含量的方法。以传统酸水解技术为对照,比较分析微波水解和高压水解技术的不同。以0.1%(体积分数)甲酸水溶液+10 mmol/L乙酸铵溶液和甲醇为流动相,梯度洗脱,串联质谱正离子模式进行监测,外标法定量。结果表明,与传统的氨基酸分析仪相比,微波水解-液相色谱-串联质谱技术法无需进行样品的衍生可直接测定,缩短了样品的检测时间。该检测方法的线性范围为5~375μg/L,相关系数R^(2)≥0.993,检出限为0.025~0.250μg/kg,加标回收率为85%~96%,精密度为0.01%~0.71%。该方法缩短了蛋白质的水解时间,快速简便、灵敏度较高、数据准确可靠,可用于畜禽肉和鸡蛋中17种氨基酸的测定。

微波辅助酸水解-HPLC测定紫肉甘薯中矢车菊素和芍药素的含量

目的建立微波水解-高效液相色谱(HPLC)法同时测定紫肉甘薯中矢车菊素和芍药素两个花青素成分含量的方法。方法样品经盐酸甲醇(3→10)微波水解后,采用Agilent Eclipse XDB-C_(18)(250 mm×4.6 mm,5μm)色谱柱,以乙腈-0.1%三氟乙酸水溶液(80:20)为流动相,流速1.0 ml/min,检测波长538 nm,柱温25℃,进样量10μl。结果矢车菊素和芍药素进样量分别在0.045~0.225μg(r=0.9998)和0.102~0.510μg(r=0.9997)范围内线性关系良好。两者平均回收率分别为98.6%,RSD=0.88%(n=6)和98.8%,RSD=1.2%(n=6)。结论该方法简便、准确可靠、重复性强,可作为同时测定紫肉甘薯中矢车菊素和芍药素含量的方法。

超声波-微波预处理辅助酶解制备大豆降糖肽及其稳定性分析

以大豆分离蛋白为原料,进行超声波-微波预处理辅助酶解改性,研究超声波功率、微波功率、超声波-微波预处理温度以及超声波-微波预处理时间对大豆降糖肽α-葡萄糖苷酶抑制率的影响。根据α-葡萄糖苷酶抑制率确定制备大豆降糖肽的最优工艺条件,并测定大豆分离蛋白和大豆降糖肽的环境稳定性。结果表明,当超声波功率200 W、微波功率400 W、超声波-微波预处理温度45℃、超声波-微波预处理时间20 min、加酶量7 000 U·g^(-1)、底物浓度3%、酶解时间60 min时,大豆降糖肽的α-葡萄糖苷酶抑制率为(81.46±0.31)%。经过超声波-微波预处理后,获得的大豆降糖肽储存稳定性、热稳定性和冻融稳定性显著增强。本实验为制备具有降血糖活性和稳定性较好的大豆降糖肽提供理论依据。

微波-超声波辅助酶解提取香菇中的呈味氨基酸

呈味氨基酸是香菇滋味的主要物质之一,但大部分呈味成分被纤维素包裹难以释放,限制了香菇呈味物质的利用。以香菇为原料,通过微波、超声波辅助酶法进行香菇中呈味氨基酸的提取工艺研究。分析超声波处理时间、微波时间、料液比、酶解温度和酶解时间等因素对实验结果的影响。在此基础上,通过正交实验对呈味氨基酸的提取工艺进行优化。结果显示,在料液比为1:25、超声波处理时间为60 min、微波时间为10 s、酶解时间为1.5 h、酶解温度为45℃的条件下,呈味氨基酸的提取率是11.61 mg·g^(-1)。

微波辅助制备硬脂酸微孔红薯淀粉酯

以微孔红薯淀粉为原料,采用微波辅助制备硬脂酸微孔红薯淀粉酯。通过单因素试验和正交试验优化硬脂酸微孔红薯淀粉酯的制备工艺。结果表明:最佳制备工艺为硬脂酸添加量2%、盐酸添加量0.07%、微波时间4.0 min、微波功率480 W,在此条件下制得的硬脂酸微孔红薯淀粉酯吸油率为67.38%、取代度为0.0712。