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1.
A comparative study was made of lipase‐catalyzed acylation of konjac glucomannan (KGM) with vinyl acetate as the acyl donor in five ionic liquids (ILs) and also in the presence of the organic solvent tert‐butanol (t‐BuOH). An obvious enhancement in enzyme activity and stability was observed using ILs as the reaction media when compared with t‐BuOH. The maximum degree of substitution (DS) of the modified KGM in ILs and t‐BuOH under the conditions employed is 0.71 and 0.54, respectively. The water activity (aw) of the reaction system affected the acylation of KGM to some extent. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate (C4MIm.BF4) was the best IL medium for the reaction, and an aw of 0.75 was optimum. It was also found that the nature of both the cation and the anion of ILs had an effect on the reaction. Candida antarctica lipase B immobilized on an acrylic resin (Novozym 435) displayed no acylation activity to KGM in 1‐butyl‐3‐methylimidazolium chloride (C4MIm.Cl). The optimum reaction temperature for enzymatic acylation in ILs was shown to be 45‐55 °C. Enzymatic acylation of KGM in IL‐t‐BuOH co‐solvent systems was also investigated. When an appropriate amount of t‐BuOH was added to ILs, the DS of the modified KGM was enhanced. Additionally, the enzymatic acylation of KGM in all the media examined was shown to be regioselective, with acylation occurring predominantly at the C‐6‐OH. Copyright © 2006 Society of Chemical Industry  相似文献   

2.
Under certain reaction conditions, the acidolysis of tripalmitin with oleic acid using immobilized lipase from Rhizomucor miehei resulted in a higher level of monosubstituted oleoyldipalmitoyl (OPP) triglycerides than had been predicted according to kinetic modeling. The reaction products were subjected to chiral analysis by high-performance liquid chromatography (HPLC), which indicated that the enzyme was more active at the sn-1 position of the triglyceride than at the sn-3 position, resulting in synthesis of the chiral triglyceride 1-oleoyl-2,3-dipalmitoyl-sn-glycerol. A kinetic model was developed and was correlated with the HPLC method to provide a simple means to predict the stereoselectivity of lipase-catalyzed reactions. By using the model, the stereoselectivity of immobilized Rhizomucor miehei lipase was found to depend strongly on the initial water activity (a w) of the reaction mixture, with greater selectivity occurring at lower a w. The sn-1 selectivity was essentially maintained using various solvents, or without solvent, when a w was kept constantly low. Variation in the fatty acid composition of the triglyceride indicated that shorter-chain fatty acids result in greater stereoselectivity, while variation of the chainlength of the free fatty acid indicated an enhancement by the longest chainlength. The stereoselectivity of this lipase was confirmed using a new 13C nuclear magnetic resonance method. By using immobilized R. miehei lipase at low a w approximately 80% of the chiral triglyceride found in the reaction mixture was the sn-1 enantiomer, at high reaction conversion.  相似文献   

3.
Enzymatic synthesis of fatty acid glucose esters from different fatty acyl donors are performed via enzymatic catalysis in the presence of Candida antarctica lipase B (CALB), using acetonitrile as the solvent. The acyl donor nature (fatty acid or fatty acid vinyl ester) and structure are varied. Lower reaction rates and lower conversions are obtained with fatty acids in comparison to their corresponding vinyl esters. Moreover, the acyl donor with the longest chain length gives the highest conversions. The presence of unsaturation on the acyl donor chain is also shown to be detrimental to the conversion. Practical Applications: The practical applications of the present work are related to the production of gluco‐esters that could be used as nonionic surfactants as detergents, cosmetics and food emulsifiers, emollients or conservatives, respectively. In this study, it is shown that in order to get high production yields, each reaction parameter has to be tuned properly.  相似文献   

4.
The lipase/acyltransferase from Candida parapsilosis is an original biocatalyst that preferentially catalyses alcoholysis over hydrolysis in biphasic aqueous/organic media. In this study, the performance of the immobilised biocatalyst in the interesterification in solvent‐free media of fat blends rich in n‐3 polyunsaturated fatty acids (n‐3 PUFA) was investigated. The interesterification activity of this biocatalyst at a water activity (aw) of 0.97 was similar to that of commercial immobilised lipases at aw values lower than 0.5. Thus, the biocatalyst was further used at an aw of 0.97. Response surface modelling of interesterification was carried out as a function of medium formulation, reaction temperature (55–75 °C) and time (30–120 min). Reaction media were blends of palm stearin (PS), palm kernel oil and triacylglycerols (TAG) rich in n‐3 PUFA (“EPAX 4510TG”; EPAX AS, Norway). The best results in terms of decrease in solid fat content were observed for longer reaction time (>80 min), lower temperature (55–65 °C), higher “EPAX 4510TG” content and lower PS concentration. Reactions at higher temperature led to final interesterified fat blends with lower free fatty acid contents. TAG with high equivalent carbon number (ECN) were consumed while acylglycerols of lower ECN were produced.  相似文献   

5.
The esterification of cinnamic acid (CA) and oleyl alcohol (OA) in organic solvent media by immobilized lipase Novozym 435 was optimized in terms of selected parameters, including the logarithm of the 1‐octanol/water partition coefficient of the organic solvent (log P, 0.29–4.5), initial water activity (aw, 0.05–0.75), agitation speed (0–200 rpm), temperature (35–65 °C) and ratio of substrates (CA/OA, 1.0:0.5–1.0:6.0). The results showed that the more hydrophobic solvent mixtures and lower initial aw values resulted in a higher enzymatic activity and bioconversion yield. The most appropriate solvent medium and initial aw value was the mixture of iso‐octane/2‐butanone (85:15, v/v) and 0.05, respectively. The results also showed that an agitation speed of 150 rpm and a reaction temperature of 55 °C were optimal for the reaction system. The activation energy (Ea) of the esterification reaction was calculated as 43.6 kJ mol?1. The optimal ratio of CA to OA was 1.0:6.0, with the absence of any inhibition by OA. Using the optimized conditions, the maximum enzymatic activity was 390.3 nmol g?1 min?1, with a bioconversion yield of 100% after 12 days of reaction. In addition, the electrospray ionization‐mass spectroscopy analysis confirmed that the major end product of the esterification reaction was oleyl cinnamate. Copyright © 2005 Society of Chemical Industry  相似文献   

6.
Ethanol‐soluble (ES) lecithin mainly contains phosphatidylcholine (PC). The incorporation of caprylic acid into PC using immobilized phospholipase A2 (PLA2) and lipase was investigated. The Rhizomucor meihei lipase and the porcine pancreatic PLA2 were immobilized on the hydrophobic resin Diaion HP‐20 and the modification was carried out in hexane as solvent. HPTLC with densitometer technique was successfully used for monitoring the production of structured phospholipids (PL) (ML‐type PC, MM‐type PC, and lysophosphatidylcholine; L: long‐chain fatty acid, M: medium‐chain fatty acid). The various parameters such as the effects of reaction temperature, enzyme loading, and the effect of molar proportion of substrate were studied in order to determine the optimum reaction conditions for the acidolysis reaction. The optimal operating conditions for the PLA2‐catalyzed reaction were obtained as 50°C temperature, 50% (wt/wt of substrate) enzyme loading, and a 1:12 molar proportion of PC/caprylic acid. For the lipase‐catalyzed reaction, the optimized temperature was the same as for PLA2, but the enzyme loading and molar proportion were slightly lower, i.e., 40 % w/w of substrate and 1:9 PC/caprylic acid, respectively. The effects of these parameters on the production of structured PL were compared. Under these optimal conditions, the ML‐type PC content was higher in the PLA2‐catalyzed reaction, i.e., 45.29 mol%, and in the lipase‐catalyzed reaction it was 38.74 mol%.  相似文献   

7.
Oxidative stability of lipids is one of the most important parameters affecting their quality. Lipase‐catalyzed lipophilic tyrosyl esters with an equivalent carbon alkyl chain but different degrees of unsaturation (C18:0 to C18:4n3) were prepared, characterized, and used as antioxidants. Free fatty acids and fatty acid ethyl esters (substrate molar ratio tyrosol: acyl donor, 1:10) were used as acyl donors and immobilized lipase from Candida antarctica was the biocatalyst (10 %). The phenolipids were isolated and characterized using ESI–MS, 1H‐NMR, and 13C‐NMR. Peroxide value (PV) and para‐anisidine value (p‐AV) were measured to evaluate their antioxidant activities in bulk oil structured lipid (SL) and in an oil‐in‐water emulsion (SL‐based infant formula). No significant difference was found in yield and reaction time between the two types of acyl donors. However, as the unsaturation of the fatty acids increased the reaction time also increased. In SL, tyrosyl esters exhibited lower antioxidant activity than tyrosol whereas the addition of an alkyl chain enhanced the antioxidant efficiency of tyrosol in infant formula. Tyrosyl oleate was the most efficient antioxidant in the emulsion system followed by tyrosyl stearate and tyrosyl linoleate. These results suggest that the synthesized phenolipids may be used as potential antioxidants in lipid‐based products.  相似文献   

8.
The syntheses of geranyl acetate and citronellyl acetate by alcoholysis reaction catalyzed by immobilized lipase from Mucor miehei was studied for the first time in a solvent-free system. Reactions were carried out at a terpene alcohol/acyl donor molar ratio of 1:5 with Lipozyme at 10% of the total weight of the reactants in a solvent-free system. Incubations were carried out at 55 to 60°C for ethyl and butyl acetates as acyl donors, whereas for methyl acetate the incubation temperature was 40 to 45°C. Excess concentration of acyl donor increases the percentage of geranyl acetate and citronellyl acetate, while excess of terpene alcohol concentration decreases the same. Yields from 75 to 77% molar conversion (90 to 98% conversion, w/w) were obtained after 8 to 28 h of reaction time.  相似文献   

9.
The regioselective acylation of pyridoxine catalyzed by immobilized lipase (Candida Antarctica) in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6) has been investigated, and compared with that in acetonitrile (ACN). The acetylation of pyridoxine using acetic anhydride in [BMIM]PF6 gave comparable conversion of pyridoxine to 5-monoacetyl pyridoxine with considerably higher regioselectivity (93%–95%) than that in ACN (70%–73%). Among the tested parameters, water activity (a w) and temperature have profound effects on the reaction performances in either [BMIM]PF6 or ACN. For the reaction in [BMIM] PF6, higher temperature (50°C–55°C) and lower a w (<0.01) are preferable conditions to obtain better conversion and regioselectivity. Mass transfer limitation and intrinsic kinetic from the ionic nature of ionic liquids (ILs) may account for a different rate-temperature profile and a lower velocity at lower temperature in [BMIM]PF6-mediated reaction. Moreover, consecutive batch reactions for enzyme reuse also show that lipase exhibited a much higher thermal stability and better reusability in [BMIM]PF6 than in ACN, which represents another advantage of ILs as an alternative to traditional solvents beyond green technology.  相似文献   

10.
This work deals with the resolution of DL ‐menthol with propionic acid by Candida cylindracea lipase (Ccl) in organic solvent reaction systems and a reverse micelles system of sodium 1,4‐bis (2‐ethylhexyl) sulfosuccinate (AOT). The activity and stability as well as enantioselectivity of the lipase in two systems were studied. The results indicate that the lipase showed higher stability in reverse micelles than in organic solvent, which proved that the reverse micelles system has potential application for maintaining the activity of the enzyme for a long time. This is because lipase molecules can be entrapped in water‐containing micro‐drops of reverse micelles, avoiding direct‐contract with unfavorable organic medium. The enantioselectivity (E > 30, eep = 92.5) in the two systems is relatively high, although the conversion is moderate. The influence of the characteristic parameters of the two systems, such as pH, temperature, w0 (molar ratio of water to AOT in reverse micelles systems) and water content (organic solvent) on the conversion of DL ‐menthol was also investigated. Copyright © 2005 Society of Chemical Industry  相似文献   

11.
Structured lipids were synthesized by interesterification of trilinolein and tricaproin with sn-1,3-specific (IM 60) and nonspecific (SP 435) lipases. The interesterification reaction was performed by incubating a 1:2 mole ratio of trilinolein and tricaproin in 3 mL hexane at 45°C for the IM 60 lipase from Rhizomucor miehei, and at 55°C for the SP 435 lipase from Candida antarctica. Reaction products were analyzed by reverse-phase high-performance liquid chromatography with an evaporative light-scattering detector. The fatty acids at the sn-2 position were identified after pancreatic lipase hydrolysis and analysis with a gas chromatograph. IM 60 lipase produced 53,5 mol% dicaproyllinolein (total carbon number = C33) and 22.2% monocaproyldilinolein (C45). SP 435 lipase produced 41% C33 and 18% C45. When caproic acid was used in place of tricaproin as the acyl donor, the IM 60 lipase produced 62.9% C33. The effects of variation in mole ratio, temperature, added water, solvent polarity, and time course on the interesterification reaction were also investigated. In the absence of organic solvent, IM 60 lipase produced 52.3% C33.  相似文献   

12.
BACKGROUND: The enantiomers of N‐hydroxymethyl vince lactam are important intermediates during the synthesis of chiral drugs. The preparation of its single enantiomer can be performed through enzymatic resolution. The aim of this work is to obtain (1S, 4R)‐N‐hydroxymethyl vince lactam with high enantiomeric purity via lipase‐catalyzed enantioselective transesterification in organic solvents. To achieve this, effects of various reaction conditions (including lipase sources, acyl donor, substrate molar ratio, organic solvent, temperature, and water activity) on the enzyme activity as well as enantioselectivity were investigated. RESULTS: The results of the study showed that the enantiopreference for all the selected enzymes was (4S, 1R)‐N‐hydroxymethyl vince lactam in enantioselective transesterification of racemic N‐hydroxymethyl vince lactam. Under the selected optimum conditions, the highest enantioselectivity (E = 33.8) was obtained with a higher enzyme activity (20.3 µmol g?1 min?1) for Mucor miehei lipase (MML) when vinyl valerate was used as the acyl donor. Besides, the remained (1S, 4R)‐N‐hydroxymethyl vince lactam with high enantiomeric purity (ee > 99%) was obtained when the conversion was about 60%. CONCLUSION: The results obtained clearly demonstrated potential for industrial application of lipase in resolution of N‐hydroxymethyl vince lactam through enantioselective transesterification. © 2012 Society of Chemical Industry  相似文献   

13.
Rhamnolipids are becoming an important class of glycolipid biosurfactants. Herein, we describe for the first time the enzymatic synthesis of rhamnose fatty acid esters by the transesterification of rhamnose with fatty acid vinyl esters, using lipase from Pseudomonas stutzeri as a biocatalyst. The use of this lipase allows excellent catalytic activity in the synthesis of 4-O-acylrhamnose (99% conversion and full regioselectivity) after 3 h of reaction using tetrahydrofuran (THF) as the reaction media and an excess of vinyl laurate as the acyl donor. The role of reaction conditions, such as temperature, the substrates molar ratio, organic reaction medium and acyl donor chain-length, was studied. Optimum conditions were found using 35 °C, a molar ratio of 1:3 (rhamnose:acyldonor), solvents with a low logP value, and fatty acids with chain lengths from C4 to C18 as acyl donors. In hydrophilic solvents such as THF and acetone, conversions of up to 99–92% were achieved after 3 h of reaction. In a more sustainable solvent such as 2-methyl-THF (2-MeTHF), high conversions were also obtained (86%). Short and medium chain acyl donors (C4–C10) allowed maximum conversions after 3 h, and long chain acyl donors (C12–C18) required longer reactions (5 h) to get 99% conversions. Furthermore, scaled up reactions are feasible without losing catalytic action and regioselectivity. In order to explain enzyme regioselectivity and its ability to accommodate ester chains of different lengths, homology modelling, docking studies and molecular dynamic simulations were performed to explain the behaviour observed.  相似文献   

14.
An alcoholysis reaction between triolein and oleyl alcohol catalyzed by Lipozyme and Novozyme was carried out to produce oleyl oleate, a wax ester. The effects of various reaction parameters such as time, reaction temperature, amount of enzyme, molar ratio of substrates (oleyl alcohol/triolein), various organic solvents used and the initial water activity, aw of the reaction system were studied. The best conditions tested to produce wax ester were respectively, incubation time, 5 h; temperature, 50 °C for Lipozyme and 60 °C for Novozyme; weight of enzyme, 0.30 g and molar ratio of oleyl alcohol to triolein, 6:1. The use of organic solvents greatly influenced the activity of lipase. Generally, the activity of lipase was high in nonpolar solvents with log P values greater than 2.50. Heptane and hexane were the best solvents tested. The enzymatic synthesis of oleyl oleate was best carried out at aw 0.32. Analysis of the yield of the products of the reaction at optimized reaction condition using Lipozyme showed that 75.66% oleyl oleate was produced. © 2001 Society of Chemical Industry  相似文献   

15.
BACKGROUND: Optically pure amines are used in the fine chemical industry as resolving agents, chiral auxiliaries, and chiral synthetic building blocks for pharmaceuticals as well as agrochemicals. Lipase‐catalyzed kinetic resolution of ( ± )‐1‐phenylethylamine with ethyl acetate as an acyl donor was achieved using immobilized lipase (Novozyme 435) as a biocatalyst under microwave irradiation. RESULTS: Response surface methodology was employed with a four‐factor‐three‐level Box‐Behnken design to evaluate the effect of synthesis parameters (speed of agitation, enzyme loading, temperature and acyl donor:amine molar ratio) on conversion, enantiomeric excess, enantioselectivity and initial rate. The optimum reaction conditions obtained were mole ratio of acyl donor:amine 1:1, temperature 49.86 °C, 0.03 g of catalyst loading and 345 rpm speed of agitation, giving 49.12% conversion, 78.83% enantiomeric excess and an enantioselectivity of 38.21. R‐stereopreference of lipase was analyzed in detail from the aspects of enzymatic kinetic mechanism and reaction activation energy of both enantiomers. CONCLUSION: Novozyme 435 was found to be the most active chiral catalyst for resolution of ( ± )‐1‐phenylethylamine under microwave irradiation. Statistical analysis was satisfactorily used to determine the optimum reaction conditions. It was found that lipase has R‐stereopreference and the reaction matches the Ping Pong Bi Bi mechanism with dead‐end inhibition of 1‐phenylethylamine. Copyright © 2011 Society of Chemical Industry  相似文献   

16.
Lipase from Candida rugosa was immobilized on poly(N‐vinyl‐2‐pyrrolidone‐co‐styrene) hydrogel (poly‐(VP‐co‐ST)) with ethylene dimethacrylate and α,α'‐azoisobutyronitrile, which act as crosslinker and initiator, respectively. Three different compositions of monomers were used, namely VP(%):ST(%), 10:90, 50:50, and 70:30 (wt(%)/wt(%)). The immobilized lipases were used in the enantioselective esterification of (R,S)‐2‐(4‐chlorophenoxy)‐propanoic acid with n‐tetradecanol. The optimum reaction condition of the enantioselective esterification for the native lipase and the poly(VP‐co‐ST) hydrogel immobilized lipases was determined with respect to temperature, solvents, and initial water activity (aw). The optimum temperature obtained was 40°C, with the poly(VP‐co‐ST) hydrogel immobilized lipase VP(%)/ST(%):10:90 showing the highest enantiomeric excess. In the solvent effect studies, the best solvents for high enantioselectivity were chloroform and carbon tetrachloride. In the aw studies, optimum αw for NL, VP(%):ST(%), 10:90, and 50:50 was 0.328, while for VP(%):ST(%), 70:30, it was 0.55. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3381–3386, 2004  相似文献   

17.
Tsujita T  Sumiyoshi M  Okuda H 《Lipids》1999,34(11):1159-1166
The synthesis/hydrolysis of wax esters was studied in an aqueous solution using purified rat pancreatic lipase, porcine pancreatic carboxylester lipase, and Pseudomonas fluorescens lipase. The equilibrium between wax ester synthesis and hydrolysis favored ester formation at neutral pH. The synthesizing activities were measured using free fatty acid or triacylglycerol as the acyl donor and an equimolar amount of long-chain alcohol as the acyl acceptor. When oleic acid and hexadecanol emulsified with gum arabic were incubated with these lipases, was ester was synthesized, in a dose- and time-dependent manner, and the apparent equilibrium ratio of palmityl oleate/free oleic acid was about 0.9/0.1. These lipases catalyzed the hydrolysis of palmityl oleate emulsified with gum arabic, and the apparent equilibrium ratio of palmityl oleate/free oleic acid was also about 0.9/0.1. The apparent equilibrium ratio of wax ester/free fatty acid catalyzed by lipase depended on incubation pH and fatty alcohol chain length. When equimolar amounts of trioleoylglycerol and fatty acyl alcohol were incubated with pancreatic lipase, carboxylester lipase, or P. fluorescens lipase, wax esters were synthesized dose-dependently. These results suggest that lipases can catalyze the synthesis of wax esters from free fatty acids or through degradation of triacylglycerol in an aqueous medium.  相似文献   

18.
Dihydroxystearic acid (DHSA) ester was synthesized enzymatically to overcome the problems associated with chemical processes. Immobilized enzyme, Lipozyme IM and Novozym 435, were employed as catalysts in the esterification reaction between DHSA and monohydric alcohol. Various factors that may affect the esterification reaction were studied, such as initial water content (a w ), organic solvent, substrate concentration and the influence of alcohol chain length. It was found that the percent conversion was higher in organic solvents with log P (the logarithm of the partition coefficient of solvent in octanol/water system) from 2.0 to 4.0. The reaction was not affected by a w from 0.09 to 0.96. Increasing the mole ratio of alcohol to acid above 2.0 did not increase the percent converions of ester. The ester was identified by Fourier transform infrared and 13C nuclear magnetic resonance spectroscopy.  相似文献   

19.
The hydrolysis of sunflower and soybean oil, catalyzed by two enzymes, non‐immobilized Candida rugosa and immobilized Candida antarctica lipase, was performed at atmospheric and high‐pressure. The results showed that at atmospheric pressure between 40 °C and 60 °C initial reaction rates were influenced by the temperature variation, as expected. Due to favorable physico‐chemical properties of dense gases as reaction media, hydrolysis of soybean oil was performed in non‐conventional solvents: in supercritical (SC) CO2 and near‐critical propane. In SC CO2 the activity of non‐immobilized Candida rugosa lipase decreased while the reaction rates of hydrolysis catalyzed by immobilized Candida antarctica lipase were 1.5‐fold higher than at atmospheric pressure. However, the reaction rates for the hydrolyses catalyzed by both lipases, were much higher in propane than at atmospheric pressure.  相似文献   

20.
We have examined the possibility of producing analogs of medium‐chain triglycerides (MCT) from copra oil, i.e. a triacylglycerol mixture with a high content of medium‐chain fatty acid moieties (C6–C10). A two‐step enzymatic process was used in which copra triacylglycerols were first split with papain lipase by alcoholysis with an alkyl alcohol and then subjected to interesterification with the alkyl esters recovered using papain lipase. Effects of temperature, water activity content, substrate ratio, biocatalyst amount, and alcohol chain length were also investigated. On the one hand, the sn‐3 stereoselectivity of the lipase in the alcoholysis of copra oil with butanol has permitted a direct enrichment of caproic, caprylic and capric moieties in the synthesized butyl esters. Thus, in the batch reactor, the reaction led to about 31% conversion of the oil after 24 h, and the content of C6–C10 acids in the synthesized esters increased from about 16% in the starting oil to almost 42%. A similar enzymatic alcoholysis in a packed‐bed column bioreactor gave 31% conversion of the oil after 120 min of reactor residence time. The reaction was also very selective because the C6–C10 fatty acyl groups represented about half of the newly formed butyl esters, whereas they accounted for only 16% of total fatty acids in the starting oil. On the other hand, the transesterification of the alkyl esters recovered (highly enriched in C6–C10 fatty acyl groups) with native copra oil directly led to an increase in the content of MCT in the oil, from 18 mol‐% at the beginning of the reaction to 61 mol‐% of MCT after a time period of 72 h in the batch reactor.  相似文献   

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