酯交换法合成共轭亚油酸三甘酯

采用酯交换反应,以共轭亚油酸乙酯、甘油为原料,脂肪酸钾为均相化试剂,无水K2CO3为催化剂,在压力～1 0kPa下反应制得共轭亚油酸三甘酯。合成工艺条件:n(共轭亚油酸乙酯)∶n(甘油)=6∶1;酯化反应温度140℃;反应时间～1 5h;无水K2CO3用量为共轭亚油酸乙酯质量的0 5%～1%;按统计平均值,产物三甘酯脂肪酸侧链中w(共轭亚油酸)>80%;产率(以甘油计)60%～65%。     

高纯度单月桂酸甘油酯的酶催化合成

采用脂肪酶Novozyme 435催化月桂酸甲酯与甘油进行酯交换反应制备单月桂酸甘油酯。以反应体系中单月桂酸甘油酯的质量分数为考察指标,通过单因素实验和正交实验对酶催化合成工艺进行优化,得到最佳的工艺条件为:底物摩尔比n(月桂酸甲酯)∶n(甘油)=1∶5,底物质量分数为20%(即月桂酸甲酯与叔丁醇的质量百分数,下同),反应温度为55℃,酶添加量为7%(即酶与月桂酸甲酯的质量百分数,下同),初始含水量为20%(以月桂酸甲酯质量计,下同),转速为100 r/min,反应时间为1 h,在该条件下,体系中单月桂酸甘油酯的质量分数为71.86%。经提纯后终产物中单月桂酸甘油酯的质量分数高于95%,最高可达98.76%,而双月桂酸甘油酯的质量分数低于5%。酶重复使用6次,单月桂酸甘油酯的质量分数从71.75%降至68.36%,其催化性能无显著降低。     

共轭亚油酸乙酯的合成

采用间歇式反应 ,以硫酸、磷酸、对甲苯磺酸为催化剂对共轭亚油酸乙酯进行了合成 ,并采用正交实验设计研究了物料比、反应温度、反应时间、催化剂用量对产品收率和品质的影响。硫酸、对甲苯磺酸催化活性佳 ,磷酸催化活性差。得到了如下合成工艺条件 :硫酸催化 ;n(共轭亚油酸 )∶n(无水乙醇 ) =1∶6;酯化反应温度 76℃ ;反应时间 1h ;催化剂用量为共轭亚油酸质量的 2 5 % ,收率可达 75 % ,产品w(共轭亚油酸乙酯 ) =77%～ 82 %。     

共轭亚油酸甘油酯的合成研究概况

共轭亚油酸甘油酯具有优良的生理和营养功能,性质稳定,并有优异的亲脂性,受到人们的日益重视。共轭亚油酸甘油酯叙述了共轭亚油酸甘油酯的合成技术研究概况,主要通过酯化反应、酯交换反应制得。认为目前应用固定化脂肪酶合成共轭亚油酸甘油酯的研究较少．开发一种具有位置专一性、结构专一性的高活性的固定化脂肪酶是今后合成共轭亚油酸低级甘油酯的研究方向。     

偏铁酸钠催化合成共轭亚油酸

以红花菜籽油中亚油酸为原料,偏铁酸钠为催化剂,在单因素试验的基础上,选取反应温度、反应时间、催化剂用量为考察因素,以异构化产物共轭亚油酸(CLA)转化率为响应值,通过响应面分析法对异构化反应进行优化,并建立相应的回归模型,试验结果表明,红花菜籽油中亚油酸异构化为CLA的最佳工艺为:反应温度195℃、反应时间4.7 h、...     

响应面法优化月桂酸单甘油酯的酶催化合成工艺

以月桂酸三甘油酯和甘油为原料,脂肪酶催化甘油解反应合成月桂酸单甘油酯。在单因素试验的基础上,采用响应面分析法进行合成工艺优化。结果表明,含水量(相对于甘油的质量)对月桂酸单甘油酯产率的影响最为显著,且较优合成条件为:恒温振荡器转速100 r/min,酶添加质量分数(相对于底物)5%,n(甘油)∶n(月桂酸三甘油酯)=6∶1,底物质量分数(相对于整个反应体系)51.9%,温度65℃,含水量4.23%,反应时间5 h。在此条件下,月桂酸单甘油酯产率的预测值和实验值分别为81.68%和81.32%,说明二次多项回归模型具有良好的预测性。     

脂肪酸甘油酯磺酸盐的合成

以α-磺酸脂肪酸甲酯和甘油为原料,经酯交换及中和反应合成了脂肪酸甘油酯磺酸盐。得到较佳的反应条件为:四氯化碳作溶剂,n(α-磺酸脂肪酸甲酯)∶n(甘油)=1∶5,75℃反应4 h,高效液相色谱分析α-磺酸脂肪酸甲酯的转化率可达66.33%。采用红外光谱和质谱确证了脂肪酸甘油酯磺酸盐的结构,结果表明,反应产物中除了含有单脂肪酸甘油酯磺酸盐外,还含有脂肪酸甲酯磺酸盐和二脂肪酸甘油酯磺酸盐。     

固定化脂肪酶催化合成生物基增塑剂2,5-呋喃二甲酸正丁酯

以固定化脂肪酶Novozym435为催化剂,在甲苯中催化2,5-呋喃二甲酸二甲酯与正丁醇转酯化反应制备2,5-呋喃二甲酸正丁酯(DBF),对酶促合成DBF的工艺进行优化,探讨了糖类物质和吸附剂作为添加剂对DBF收率的影响。结果表明,在n(2,5-呋喃二甲酸二甲酯)∶n(正丁醇)=1∶5,其中,2,5-呋喃二甲酸二甲酯的物质的量为1 mmol,固定化脂肪酶Novozym435添加量为925 U的10 mL甲苯中,45℃、150 r/min反应28 h后,DBF的收率达到最大。4A分子筛的加入能明显促进DBF的生成,海藻糖的加入也增强了反应体系中脂肪酶的催化能力,在反应体系中加入0.2 kg/L 4A分子筛和固定化脂肪酶质量15%的海藻糖,45℃反应14 h,DBF的收率达到了87.25%,固定化脂肪酶Novozym435在DBF的最优合成体系中连续使用10次后,DBF的收率仍然能保持在47.68%。     

高纯度EPA/DHA甘油三酯的酶法合成

利用脂肪酶分别催化游离型EPA和DHA与甘油发生酯化反应生成甘油三酯,考察了合成的影响因素. 结果表明,正己烷6 mL,甘油/EPA(DHA)摩尔比为1:3(以0.4 mmol甘油为基准),Novozym 435添加量为100 mg,反应温度40℃,振荡频率150 r/min,反应24 h后添加1 g分子筛,反应时间48 h,EPA甘油三酯与DHA甘油三酯的得率分别可达88.64%和88.07%,EPA与DHA酯化度分别可达95.0%和94.5%. 分析结果表明,所得产物为EPA甘油三酯和DHA甘油三酯.     

KF/γ-Al2O3催化甘油酯交换合成碳酸甘油酯

采用等体积浸渍法制备了一系列氧化铝负载碱金属氟化物固体碱催化剂,用于甘油(丙三醇)与碳酸二甲酯酯交换反应合成碳酸甘油酯,其中KF/γ-Al2O3催化剂能够更好地促进碳酸甘油酯的生成。进一步考察了KF/γ-Al2O3催化剂的制备条件、反应条件对甘油与碳酸二甲酯酯交换反应的影响。当KF负载在γ-Al2O3的负载量为15%(质量分数,下同),于400℃焙烧5 h后制得固体碱催化剂,在n(碳酸二甲酯)∶n(甘油)=3∶1,反应温度80℃,反应时间1.5 h的条件下,甘油的转化率达96.1%,碳酸甘油酯选择性和收率分别达98.1%和94.3%。     

玉米油酶法合成甘油二酯工艺优化研究

以玉米油、甘油为原料,在无溶剂体系中用固定化脂肪酶Lipozyme TL IM催化合成甘油二酯,通过单因素试验和响应面试验研究底物摩尔比(亚油酸/甘油)、反应温度、反应时间、酶质量分数和初始水质量分数等因素对亚油酸转化率的影响。得出:反应温度、底物摩尔比、反应时间、酶质量分数对亚油酸转化率影响较大;影响酯化反应中亚油酸转化率的主次因素依次为反应温度、底物摩尔比、反应时间、酶质量分数;最佳工艺条件为亚油酸和甘油的摩尔比为2.10∶1,反应温度为61.16℃,反应时间为12.17 h,酶质量分数为20.09%,亚油酸转化率达到75.69%。Lipozyme TL IM连续反应3批次,其相对酶活仍有65.7%。     

Continuous synthesis of glycerides by lipase in a microporous membrane bioreactor

A membrane bioreactor was developed for continuous synthesis of glycerides by lipase to overcome the drawbacks associated with the usual operation in an emulsion system. One unit (total area: 726 cm²) of flat, plate-type dialyzer was used as the membrane bioreactor at 40 C. The glycerol solution, containing bacterial lipase and water, was supplied continuously to 1 side of a sheet of microporous polypropylene membrane (strongly hydrophobic) and the effluent was recycled, while undiluted liquid fatty acid (oleic or linoleic) was fed continuously to the opposite side of the membrane and came in contact with a glycerol-water-lipase solution to cause the reaction. The product, glycerides, was obtained at the outlet, in a pure state, with no other phase. Highest conversion (ca. 90%) was obtained when the water content of the glycerol solution was 3–4%. As the accumulation of water produced by the reaction lowered the conversion, molecular sieves in a column that the glycerol solution passed through were used for optimal water content. The reaction could be continued at least for 1 month, yielding a conversion above 70% when 1% CaCl₂ was added in the glycerol solution. The main component of glycerides formed was almost equimolar amounts of mono-and diglycerides.     

Characterisation of acylglycerol synthesis in aqueous foams by lipases

Low water systems have become important for organic synthetic reactions catalysed by enzymes. Esterification reactions could be catalysed by lipase in multiphasic reaction media, such as foams, containing excess water. The esterification of glycerol with oleic acid catalysed by lipase in aqueous foams has been characterised. More than 80% of the oleic acid was converted to glycerides within 10 h. Preliminary characterisation of the reaction with respect to time, pH and temperature indicate that acylglycerol synthesis in foam media as similar to hydrolysis by the same lipase. The observed high K_m of glycerol for the esterification reaction may be due to poor surface active properties of glycerol. The unique advantages of foam as a medium to conduct lipase reactions are discussed. © 1999 Society of Chemical Industry     

Triglyceride composition of tobacco seed oil

Fatty acid and triglyceride compositions of Indian tobacco seed oil (Nicotiana rustica) have been determined by combination of the techniques of systematic crystallization at low temperatures, pancreatic lipase hydrolysis, and gas liquid chromatography of methyl esters. The percentages of individual fatty acids were found to be linoleic 71.2, oleic 15.7, palmitic 8.4, and stearic 3.8. The special characteristic of the tobacco seed oil is its content of 37.4, 22.8, 4.9, 19.7, 9.3, and 3.3% of trilinolein, dilinoleoolein, dioleolinolein, dilinoleosaturated, linoleooleosaturated, and linoleodisaturated glycerides, respectively. In the present investigation, preference of linoleic acid over oleic acid for the 2-position of glycerol moiety was not observed.     

Synthesis of CLA‐enriched TAG by Candida antarctica lipase under vacuum

Conjugated linoleic acid (CLA)‐enriched triacylglycerol (TAG) of 90 wt% was successfully synthesized in 10 h by direct esterification of glycerol and CLA using an immobilized lipase from Candida antarctica under vacuum. The best operating conditions for the synthesis of TAG were investigated according to the three parameters of temperature, enzyme loading, and vacuum. The synthesis of TAG increased with increasing temperature but it did not significantly change above 60°C (p>0.05). The increase of enzyme loading lead to an enhanced conversion of TAG, but enzyme loading of more than 10% (based on the total weight of the substrates) was not effective. Moreover, when vacuum increased, the conversion of TAG increased, but the conversion rate decreased when the vacuum level was too high. The best combination of temperature, enzyme loading, and vacuum level were 60°C, 10% of the total weight of the substrates, and 0.4 kPa, respectively. During the initial 6 h of reaction, Candida antarctica lipase had more selectivity for 10t,12c‐CLA than 9c,11t‐CLA onto the glycerol backbone, and a preference for the incorporation at the sn‐1,3 positions of glycerol rather than at the sn‐2 position.     

Stability of Immobilized Candida sp. 99–125 Lipase for Biodiesel Production

The stability of the immobilized lipase from Candida sp. 99–125 during biodiesel production was investigated. The lipase was separately incubated in the presence of various reaction components such as soybean oil, oleic acid methyl ester, n‐hexane, water, methanol, and glycerol, or the lipase was stored at 60, 80, 100 and 120 °C. Thereafter the residual lipase activity was determined by methanolysis reaction. The results showed that the lipase was rather stable in the reaction media, except for methanol and glycerol. The stability study performed in a reciprocal shaker indicated that enzyme desorption from the immobilized lipase mainly contributed to the lipase inactivation in the water system. So the methanol and glycerol contents should be controlled more precisely to avoid lipase inactivation, and the immobilization method should be improved with regard to lipase desorption.     

Transesterification of soy lecithin by lipase and phospholipase

Soy lecithin was modified by enzymatic transesterification in a solvent-free system. 1,3-SpecificRhizomucor miehei lipase was found to be efficient in the transesterification with lauric acid and oleic acid, where oleic acid was more incorporated into soy lecithin. Phospholipase A₂ incorporated lauric acid hardly at all, but it hydrolyzed lecithin efficiently. The mixture of lipase and phospholipase A₂ (1:1, w/w) incorporated lauric acid to the same extent as did 1,3-specific lipase alone at the same total enzyme concentration. The main fatty acids replaced were palmitic and linoleic acids by 1,3-specific lipase and its mixture with phospholipase A₂, and linoleic and linolenic acids by phospholipase A₂ alone, suggesting an improved oxidative stability of the resulting product. Hydrolysis could not be prevented, but it could be regulated by incubation time and by enzyme dosage. The minimal water content for significant incorporation of lauric acid into lecithin was below 0.5% of the weight of the reaction mixture.     

Synthesis of polyunsaturated fatty acid-enriched triglycerides by lipase-catalyzed esterification

This paper reports on the synthesis of triglycerides by enzymatic esterification of polyunsaturated fatty acids (PUFA) with glycerol. A PUFA concentrate obtained from cod liver oil was used to optimize the reaction to favor triglyceride synthesis with lipases. The type and amount of lipase and organic solvent, glycerol content, temperature, water content, and amount and time of addition of molecular sieves were studied. The optimal reaction mixture and conditions were: 9 mL hexane, 60°C, 0.5% (vol/vol) water, 1 g molecular sieves added after 24 h of reaction, glycerol/fatty acid molar ratio 1:3 and 100 mg of Novozym 435 (Novo Nordisk A/S) lipase. Under these conditions, an enriched triglyceride yiedl of 84.7% containing 27.4% eicosapentaenoic acid and 45.1% docosahexaenoic acid was obtained from a cod liver oil PUFA concentrate.     

Enzymatic Synthesis and Antioxidant Activity of 1‐Caffeoylglycerol Prepared from Alkyl Caffeates and Glycerol

Caffeic acid (CA) as a strong antioxidant has lower solubility in nonpolar media, which limits its application in the food industry. To increase the lipophilicity of CA, 1‐caffeoylglycerol (1‐CG) was synthesized by lipase‐catalyzed transesterification of alkyl caffeates in solvent‐free system and its antioxidant capacity was investigated. Methyl caffeate was screened as the appropriate substrate from tested alkyl caffeates with a yield of 90.63%. Ethyl acetate was used for extracting 1‐CG from enzymatic reactants and could be easily recycled. The produced 1‐CG had 2.5‐ and 10‐fold lower values of half maximal inhibitory concentration (IC₅₀) (10.86 and 3.99 μM) than butylated hydroxyanisole by 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging and β‐carotene‐linoleic acid assays, respectively. Thus, 1‐CG is an excellent antioxidant for application in the functional food industry. Using alkyl caffeates and glycerol as substrates to produce 1‐CG catalyzed by immobilized lipase in a solvent‐free system is a simple, selective, and safe bioprocess that can readily be achieved in the food industry, and the product 1‐CG could be widely applied in food, nutraceutical, and biotechnological products.     

Esterification of glycerol with conjugated linoleic acid and long-chain fatty acids from fish oil

Free fatty acids from fish oil were prepared by saponification of menhaden oil. The resulting mixture of fatty acids contained ca. 15% eicosapentaenoic acid (EPA) and 10% docosahexaenoic acid (DHA), together with other saturated and monounsaturated fatty acids. Four commercial lipases (PS from Pseudomonas cepacia, G from Penicillium camemberti, L2 from Candida antarctica fraction B, and L9 from Mucor miehei) were tested for their ability to catalyze the esterification of glycerol with a mixture of free fatty acids derived from saponified menhaden oil, to which 20% (w/w) conjugated linoleic acid had been added. The mixtures were incubated at 40°C for 48h. The ultimate extent of the esterification reaction (60%) was similar for three of the four lipases studied. Lipase PS produced triacylglycerols at the fastest rate. Lipase G differed from the other three lipases in terms of effecting a much slower reaction rate. In addition, the rate of incorporation of omega-3 fatty acids when mediated by lipase G was slower than the rates of incorporation of other fatty acids present in the reaction mixture. With respect to fatty acid specificities, lipases PS and L9 showed appreciable discrimination against esterification of EPA and DHA, respectively, while lipase L2 exhibited similar activity for all fatty acids present in the reaction mixture. The positional distribution of the various fatty acids between the sn-1,3 and sn-2 positions on the glycerol backbone was also determined.