有机相中微生物脂肪酶合成短链脂肪酸酯的研究

用微生物脂肪酶在溶剂相中合成短链脂肪酸酯的研究表明：脂肪酶在正庚烷中催化合成短链脂肪酯转化率比水相中有明显的优势。在１０个不同来源的商品脂肪酶中，来自Ｍｕｃｏｒｍｉｅｈｅｉ，Ｃａｎｄｉｄａｒｕｇｏｓａ和Ｐｏｒｃｉｎｅｐａｎｃｒｅａｓ的脂肪酶合成酯转化率较高，其中Ｍｕｃｏｒｍｉｅｈｅｉ脂肪酶对己酸乙酯４８ｈ合成转化率达９４％，己酸乙酯产量３３．８４ｇ／Ｌ．同时就底物酸和醇的碳链长度对酯转化率的影响进行了研究。     

微生物脂肪酶及其催化合成芳香酯研究进展

微生物脂肪酶可以催化酯类化合物的分解、合成和酯交换，因而被广泛应用于食品、精细化工和医药等工业中，近年来，随着界面酶学、有机相催化以及固化技术的不断深入和发展，微生物脂肪酶的诸多新特性正在被发现，其应用领域也在不断拓展。国内外的研究结果表明，用微生物脂肪酶可以催化合成多种芳香酯，并且在有机相中微生物脂肪酶的催化活性和稳定性较水溶液中明显提高；用微生物脂肪酶催化合成芳香酯可以克服用化学方法合成带来的问题，是一种芳香酯合成的有效方法。     

脂肪酶对白酒四大酯的可逆合成与分解

为了探究白酒中四大酯的可逆合成与分解规律,用固定化南极假丝酵母脂肪酶B(Novozym 435),分别在水相和有机相(正己烷)中,进行酯化反应。结果显示,4种酯在水相中有利于分解,分解转化率为乙酸乙酯>丁酸乙酯>乳酸乙酯>己酸乙酯,在有机相(正己烷)中有利于合成,合成转化率为己酸乙酯>丁酸乙酯>乳酸乙酯>乙酸乙酯。同时重点比较了酯在水相中的合成能力,测得酯在水相中5 h内的最高合成转化率分别为乙酸乙酯8.9%、丁酸乙酯29.1%、己酸乙酯16.7%、乳酸乙酯5.7%,低于水相中的水解转化率和有机相中的合成转化率。研究结果对白酒风味酯的形成原理以及生产合成具有参考价值。     

黑曲霉脂肪酶在反胶束体系中的光学特性及其催化合成己酸乙酯

研究黑曲霉脂肪酶在反胶束体系中的紫外-可见吸收光谱和荧光光谱特性,并优化黑曲霉脂肪酶在反胶束中催化合成己酸乙酯的反应条件,最后分离和鉴定产物。结果表明：在反胶束体系中黑曲霉脂肪酶的结构发生了变化,芳香族氨基酸暴露更多。黑曲霉脂肪酶催化合成己酸乙酯的反应条件为：在含有异辛烷-正己醇-水的体积比为60:4:1,十六烷基三甲基溴化铵(CTAB)添加量100mmol/L的反胶束体系中,脂肪酶质量浓度为0.003g/L,己酸浓度为0.3mol/L,酸醇物质的量比为1:0.9,反应温度为35℃,摇床转速为120r/min条件下16h时己酸乙酯的合成量达到最大,己酸的转化率达到(88.92±1.00)%。     

响应面法优化无溶剂体系酶法合成己酸乙酯

目的：探讨无溶剂体系酶法合成己酸乙酯的最佳工艺条件。方法：在单因素试验的基础上,以脂肪酶添加量、底物(己酸/乙醇)物质的量比、反应时间为影响因素,应用二次回归中心组合试验法进行三因素五水平试验,以己酸乙酯产率为评价指标,进行响应面分析。结果：无溶剂体系酶法合成己酸乙酯的最佳工艺条件为脂肪酶添加量0.5%、酸醇物质的量比1:1.3、反应时间12.2h、反应温度30℃,转速150r/min。在此条件下,己酸乙酯产率实际值为81.6%,与预测值相近。结论：采用中心组合试验设计--响应面法对无溶剂体系酶法合成己酸乙酯工艺条件进行优化合理可行。     

脂肪酶非水相转化失水山梨醇油酸酯

失水山梨醇单油酸酯（Ｓｐａｎ８０）可在非水相中用脂肪酶酶促转化合成．比较不同来源的脂肪酶和不同的非水相系统后发现：来源于假丝酵母的脂肪酶Ｎｏｖｏｚｙｍ４３５在无溶剂系统中有较高合成Ｓｐａｎ８０的能力．同时考察了水分对酯化反应的影响,并对酯化反应的条件如底物摩尔比、用酶量等进行了研究．与化学合成的产品比较,各项指标基本接近,但酶法合成的产品单酯含量较高,达８０％以上     

根霉脂肪酶有机相合成己酸乙酯条件的研究

用根霉ZM-10脂肪酶为催化剂,在有机相中催化合成己酸乙酯。文中研究了温度、底物浓度、酸醇比、溶剂、吸水方法等对己酸乙酯合成转化率的影响。结果表明,以环己烷为溶剂,以摩尔比为1∶1.3的己酸和乙醇为底物,己酸浓度为0.2 mol/L,在40℃条件下振荡反应14h,合成己酸乙酯的的转化率可达到91.5%。     

固定化脂肪酶催化己酸乙酯的研究

利用固定化脂肪酶在溶剂相中催化己酸和乙醇的合成反应。研究了反应体系中的含水量、溶剂、反应温度、加酶量、加入分子筛等因素对催化己酸乙酯反应的影响规律，在含水量在0.4%、酶粉湿度8％、温度30℃、加酶量0.1g/15ml，在环己迷溶剂中，经过8h的反应，加入1克分子筛，己酸乙酯的合成转化率可达82.69%。     

非水介质中脂肪酶催化反应在食品中的应用

综述近10年来非水介质中脂肪酶催化反应在芳香酯、乳化剂合成、脂质改性、多不饱和脂肪酸强化等食品领域的应用，并相信脂肪酶将在食品生产中得到更大的发展。     

固定化脂肪酶催化己酸乙酯的研究

利用固定化脂肪酶在溶剂相中催化己酸和乙醇的合成反应。研究了反应体系中的含水量、溶剂、反应温度、加酶量、加入分子筛等因素对催化己酸乙酯反应的影响规律。在含水量在 0 .4%、酶粉湿度 8%、温度 3 0℃、加酶量 0 .1g/ 15ml,在环己烷溶剂中 ,经过 8h的反应 ,加入 1克分子筛 ,己酸乙酯的合成转化率可达 82 .69%。     

Enzymatic synthesis of ethyl hexanoate by transesterification

Summary Enzymatic synthesis of ethyl hexanoate by means of an acyl transfer reaction has been studied by using an immobilized Rhizomucor miehei lipase (RML). The effect of reaction parameters on ester synthesis has been investigated. Rhizomucor miehei lipase showed more specificity than other lipases when ethyl hexanoate was synthesized in n‐hexane. Maximum ester synthesis was obtained by using a 0.5 m substrate concentration (equimolar ratio). Temperatures in the range of 45–55 °C were found to be optimum and at higher temperatures (>60 °C) deactivation of enzyme was observed. Higher molar concentrations of hexanoic acid inhibited RML, but no inhibitory effect of ethyl caprate, even at higher molar concentrations, was observed. Apparent kinetic parameters have been determined. The values are as follows: K_M (ester), 0.0135 m ; K_M (acid), 0.08466; K_i (ester), 3.07 m ; K_i (acid), 0.550 m ; V_max, 1.861 µmol min^?1 mg^?1 enzyme.     

Lipase Mediated Synthesis of Low Molecular Weight Flavor Esters

Screening 27 commercial lipases showed that enzymes from Candida cylindracea, Pseudomonas fluorescens and Mucor miehei (immobilized) promoted synthesis of selected low molecular weight esters in nonaqueous systems. Maximum production after 24 hr incubation was obtained with substrate concentrations of 0.05 mol/L for isopentyl acetate, 0.2 mol/L for ethyl butyrate and 0.3 mol/L for isopentyl butyrate. Yield of butyl butryate was almost 100% at acid substrate greater than 0.2 mol/L. Substrate inhibition was observed with P. fluorescens lipase but not with C. cylindracea or M. miehei lipases, up to 1 mol/L. Hexane, octane and decane could be used as reaction media except for ethyl butyrate synthesis where hexane was the medium of choice. Poor synthesis was achieved when methylene chloride was used.     

非水相酶促合成己酸乙酯的研究

用Pseudomonas sp.脂肪酶在烷烃溶剂中催化合成已酸乙酯,研究了反应温度,时间,加水量,加酶量,底物浓度,溶剂种类以及原料摩尔比对乙酸转化率的影响。最佳反应条件为：反应温度36℃,已酸浓度0.4mol/L,己酸与乙醇的摩尔比为1：1．1。辛烷作为溶剂,加酶量为1000u/g己酸,反应时间24h,已酸转化率达92．3％。     

酸浓度和pH值对浓香型大曲酯化酶催化活力的影响

研究了己酸、乳酸、丁酸、乙酸的浓度以及pH值对浓香型大曲酯化酶催化合成四种酯（己酸乙酯、乳酸乙酯、丁酸乙酯、乙酸乙酯）的影响。结果表明,大曲酯化酶催化合成四种酯的最适酸质量浓度分别为己酸8 g/L,乳酸1 g/L,丁酸9 g/L,乙酸12 g/L;在同一酸浓度条件下,大曲酯化酶催化合成己酸乙酯、丁酸乙酯、乙酸乙酯最适pH值均为4.5,乳酸乙酯最适pH值为6.0;大曲酯化酶催化相同物质的量浓度混合酸的试验结果表明,己酸乙酯的合成以酯化酶催化反应为主,而乳酸乙酯和丁酸乙酯的合成以化学反应为主。     

气相色谱法测定脂肪酶催化反应体系中的己酸乙酯

建立测定脂肪酶催化合成的己酸乙酯含量的毛细管气相色谱方法。以乙酸正戊酯为内标物,采用AT.PEG-20M(30m×0.25mm×0.33μm)的极性石英毛细管柱,程序升温:起始柱温55℃,恒温1min,以10℃/min升温至70℃,恒温2min,再以20℃/min升温至180℃,保持5min;进样口温度200℃;采用氢焰离子化检测器,在温度220℃条件下进行测定。己酸乙酯的最低检测限为2.774μg/mL,相对标准偏差为0.97%,平均加标回收率为97.44%。该方法快速、准确、灵敏,可用于检测脂肪酶催化反应体系中己酸乙酯的含量。     

Lipase-catalysed synthesis of natural aroma-active 2-phenylethyl esters in coconut cream

The aim of this research was to study the feasibility of biosynthesising natural aroma-active 2-phenylethyl esters in coconut cream via biocatalysis. Five commercial fungal lipases (Palatase 20 000L, Lipase AYS “Amano”, Lipase A “Amano” 12, Piccantase A and Piccantase AN) were screened for their ability to produce 2-phenylethyl hexanoate and 2-phenylethyl octanoate from coconut cream supplemented with natural 2-phenylethanol. Palatase 20 000L and Lipase AYS “Amano” showed the greatest potential for the synthesis of 2-phenylethyl esters. The biosynthetic reaction by the lipase Palatase 20 000L was further studied under different temperature, pH, enzyme and substrate concentrations, with maximum ester synthesis obtained at 9% v/v 2-phenylethanol and 2.15–8.60 mg enzyme protein/100 ml of reaction mixture. A temperature range of 30–53 °C and a pH range of 5.2–8.5 had little effect on the lipase Palatase activity, respectively. The ester-synthesising reaction appeared to proceed by both alcoholysis and esterification.     

Transesterification of conjugated linoleic acid and tricaprylin by lipases in organic solvents

Lipase-catalyzed transesterification of tricaprylin with conjugated linoleic acid (CLA) ethyl ester was performed to produce triacylglycerols containing conjugated linoleic acid. Six commercially available lipases, and seven solvents were screened for their ability to incorporate CLA into tricaprylin. The transesterification reaction was performed by incubating a 1:2 mole ratio of tricaprylin and CLA ethyl ester in 3 ml solvents at 55°C, and the products were analyzed by gas chromatography. Three lipases, Novozym 435, Lipozym IM and lipase PS-C were chosen to allow a comparison of transesterification activity in our model reaction. The highest CLA incorporation with Novozym 435 and Lipozym IM was achieved in hexane while isooctane produced the highest CLA incorporation with lipase PS-C. Lipase PS-C gave higher CLA incorporation into tricaprylin when fatty acid was used as the acyl donor than other lipases did. Lipozym IM and lipase PS-C had not restrict specificity to sn-1, 3 positions, even though they had high specificity at sn-1, 3 positions. Novozym 435 among lipases tested was the most effective on the incorporation of CLA into tricaprylin.