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1.
S. Bourg-Garros N. Razafindramboa A. A. Pavia 《Journal of the American Oil Chemists' Society》1997,74(11):1471-1475
(Z)-3-Hexen-1-yl butyrate is an important flavor and fragrance compound as it represents the model of a natural herbaceous (green)
note. Two immobilized lipases from Mucor miehei (Lipozym IM) and from Candida antarctica (Novozym 435) were investigated for their use in the synthesis of (Z)-3-hexen-1-yl butyrate by direct esterification in n-hexane. To determine optimal conditions for esterification, we examined the following parameters: temperature, amount of
lipase, acid/alcohol ratio, and absence of solvent. In n-hexane, bioconversion yields reached 95 (after 4 h) and 92% (after 6 h) for, respectively, Lipozym IM [17 (w/w reactants)]
and Novozym 435 [2% (w/w reactants)]. In the absence of solvent, at 60°C, Novozym 435-catalyzed esterification afforded the
title compound in 80% yield. Up to 250 g (in hexane) and 160 g (without solvent) of ester were easily prepared, in a single
operation, at a laboratory scale, in few hours, using 2% (w/w reactants) lipase. 相似文献
2.
Pseudomonas sp. lipase (PS) was immobilized by adsorption technique onto glass beads and tested for its ability to synthesize geranyl
acetate by transesterification with acetic anhydride as the acyl donor. Reactions were carried out inn-hexane containing 0.1 M geraniol, 0.1 M acetic anhydride, and 200 units of lipase PS. Enzyme load, effect of substrate concentration,
added water, temperature, time course, organic solvent, pH memory, and enzyme reuse were studied. Yields of up to 96% were
obtained with 200 units (approximately 11% w/w of reactants) of enzyme. Increasing amounts of geraniol inhibited lipase activity,
while excess acyl donor concentration enhanced ester production. Yields as high as 97% were obtained at 50°C, 24 h incubation,
with no added water. Solvents with logP values ≥3.0 showed the highest conversion yields. Solvent-free samples also performed well. The pH range of 4–9 gave good
yields (92–98.4%). Enzyme reuse studies showed the lipase remained active after 15 runs. 相似文献
3.
Enzymatic modification of trilinolein: Incorporation of n-3 polyunsaturated fatty acids 总被引:2,自引:0,他引:2
Casimir C. Akoh Brenda H. Jennings Dorris A. Lillard 《Journal of the American Oil Chemists' Society》1995,72(11):1317-1321
Two immobilized lipases, IM60 fromMucor miehei and SP435 fromCandida antarctica, were used as biocatalysts for the modification of trilinolein with n-3 polyunsaturated fatty acids (PUFA), such as eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA), by using their ethyl esters as acyl donors (EEPA and EDHA, respectively). Transesterification
(ester-ester interchange) reactions were carried out in organic solvent. The products were analyzed according to their equivalent
carbon number and polarity by reverse-phase high-performance liquid chromatography, and the fatty acid profiles were determined
by gas-liquid chromatography. Modified triacylglycerol products contained 1 or 2 molecules of n-3 PUFA. With EEPA as the acyl
donor, the total EPA product yields with IM60 and SP435 as biocatalysts were 79.6 and 81.4%, respectively. However, with EDHA
as the acyl donor and IM60 and SP435 as biocatalysts, the total DHA product yields were 70.5 and 79.7%, respectively. Effects
of reaction parameters, such as type of solvent, enzyme load, time course, and molar ratio of substrates on the n-3 PUFA incorporation,
were followed with SP435 as the biocatalyst. High yields were obtained, even in the absence of organic solvent. These lipids
do hold promise for specialty nutrition and other therapeutic uses. 相似文献
4.
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
5.
Lipase-catalyzed modification of borage oil: Incorporation of capric and eicosapentaenoic acids to form structured lipids 总被引:2,自引:0,他引:2
Casimir C. Akoh Charment O. Moussata 《Journal of the American Oil Chemists' Society》1998,75(6):697-701
Two immobilized lipases, nonspecific SP435 from Candida antarctica and sn-1,3 specific IM60 from Rhizomucor miehei, were used as biocatalysts for the restructuring of borage oil (Borago officinalis L.) to incorporate capric acid (10:0, medium-chain fatty acid) and eicosapentaenoic acid (20:5n-3) with the free fatty acids
as acyl donors. Transesterification (acidolysis) reactions were carried out in hexane, and the products were analyzed by gas-liquid
chromatography. The fatty acid profiles of the modified borage oil were different from that of unmodified borage oil. Higher
incorporation of 20:5n-3 (10.2%) and 10:0 (26.3%) was obtained with IM60 lipase, compared to 8.8 and 15.5%, respectively,
with SP435 lipase. However, SP435 lipase was able to incorporate both 10:0 and 20:5n-3 fatty acids at the sn-2 position, but the IM60 lipase did not. Solvents with log P values between 3.5 and 4.5 supported the acidolysis reaction better than those with log P values between −0.33 and 3.0. 相似文献
6.
Lisa N. Yee Casimir C. Akoh Robert S. Phillips 《Journal of the American Oil Chemists' Society》1997,74(3):255-260
Pseudomonas sp. lipase PS was immobilized by adsorption and tested for its ability to catalyze the synthesis of citronellyl butyrate
and geranyl caproate by transesterification in n-hexane. The reaction parameters investigated were: enzyme load, effect of substrate concentration, added water, temperature,
time course, organic solvent, pH memory, and enzyme reuse. Yields as high as 96 and 99% were obtained for citronellyl butyrate
and geranyl caproate, respectively, with 300 units (approx. 15% w/w of reactants) of lipase PS. Increasing amounts of terpene
alcohol inhibited lipase activity, while excess acyl donor (triacylglycerol) concentration enhanced ester production. Optimal
yields were obtained at temperatures from 30–50°C after 24-h incubation time. Yields of 90 and 99% were obtained for citronellyl
and geranyl esters, respectively, with 2% added water. Solvents with log P values ≥ 2.5 showed the highest conversion yields. pH 7 and 6–8 seemed to be ideal for citronellyl butyrate and geraniol
caproate, respectively. The lipase remained active after reusing 12 times. 相似文献
7.
S. Bradoo R. K. Saxena R. Gupta 《Journal of the American Oil Chemists' Society》1999,76(11):1291-1295
High yields of ascorbyl palmitate (6-O-palmitoyl-l-ascorbic acid) were obtained by lipase-mediated esterification using Bacillus stearothermophilus SB 1 lipase. The final yield was greatly influenced by the initial water content of the system, quantity of enzyme, and molar
ratio of palmitic acid to l-ascorbic acid. Reaction rates increased directly with temperature from 40 to 100°C. Maximum conversion (97%) was achieved
after 30 min at 100°C (solvent-free), 1 h at 80°C (solvent-free), and 2 h at 60°C (solvent/hexane). The synthesis was scaled
up to 1-l volume with 95% conversion using 50 mmoles of ascorbic acid and 250 mmoles of palmitic acid in hexane. Similar yields of
ester were obtained in five repetitive cycles using 5 g enzyme immobilized on Accurel. The present B. stearothermophilus SB 1 lipase was a more efficient catalyst for the synthesis of ascorbyl palmitate than other commercial lipases. 相似文献
8.
Structured lipids: Lipase-catalyzed interesterification of tricaproin and trilinolein 总被引:2,自引:0,他引:2
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
9.
Two systems were investigated and compared as models for making margarine-type fats. Two immobilized lipases, IM60 from Rhizomucor miehei and SP435 from Candida antarctica, were used to catalyze the transesterification of triolein with stearic acid and stearic acid methyl ester, respectively,
in n-hexane. The optimal reaction temperature for both enzymes was 55°C at a mole ratio of triolein to acyl donor of 1:2. Equilibria
were reached at 18 h for IM60 and 24 h for SP435. Analysis of the overall yield and incorporation of fatty acid at the sn-2 position indicated that the triacylglycerol products contained 38.4 and 16.2% 18:0 for acidolysis and 34.2 and 11.3% for
interesterification reactions, respectively, at the 2-position. With SP435, the softest fat was produced after 18 h of incubation,
and the hardest after 30 h. For IM60 system, 18 h of incubation gave the most plastic fat. 相似文献
10.
Kuan-hsiang Huang Casimir C. Akoh 《Journal of the American Oil Chemists' Society》1994,71(11):1277-1280
The ability of immobilized lipases IM60 fromMucor miehei and SP435 fromCandida antarctica to modify the fatty acid composition of selected vegetable oils by incorporation of n−3 polyunsaturated fatty acids into
the vegetable oils was studied. The transesterification was carried out in organic solvent with free acid and ethyl esters
of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as acyl donors. With free EPA as acyl donor, IM60 gave higher
incorporation of EPA than SP435. However, when ethyl esters of EPA and DHA were the acyl donors, SP435 gave higher incorporation
of EPA and DHA than IM60. When IM60 and free acid were used, the addition of 5 μL water increased EPA incorporation into soybean
oil by 4.9%. With ethyl ester of EPA as acyl donor, addition of 2 μL water increased EPA incorporation by 3.9%. For SP435,
addition of water up to 2μL resulted in increased EPA incorporation, but the incorporation declined when the added water exceeded
this amount. The addition of water increased the EPA incorporation into Trisun 90 after 24 h reaction but not the reaction
rate at early stages of the reaction. 相似文献
11.
Roxana Irimescu Kiyomi Furihata Kazuhiko Hata Yugo Iwasaki Tsuneo Yamane 《Journal of the American Oil Chemists' Society》2001,78(3):285-290
A highly efficient enzymatic method for the synthesis of regioisomerically pure 1,3-dicapryloyl-2-docosahexaenoyl glycerol
(CDC) in two steps was established. 2-Monoglyceride (2-MG) formation by ethanolysis of tridocosahexaenoylglycerol (DDD) with
immobilized Candida antarctica lipase (Novozym 435) as catalyst was the key step of the synthesis. CDC was finally obtained by reesterification of 2-MG
with ethylcaprylate (EtC) catalyzed by Rhizomucor miehei lipase (Lipozyme IM). The regiospecificity of Novozym 435 depended on the type of reaction and the initial composition of
the reaction medium. It displayed strict 1,3-regiospecificity for ethanolysis at a high excess of ethanol in the reaction
mixture although it displayed no regiospecificity in transesterification and esterification reactions. The highest yield of
CDC (85.4%) was obtained by ethanolysis at a 4∶1 weight ratio of ethanol/DDD for 6 h followed by reesterification at a 20∶1
molar ratio of EtC/initial DDD for 1.5 h. The regioisomeric purity of CDC was 100%. Good results were obtained also for the
synthesis of 1,3-dicapryloyl-eicosapentaenoylglycerol (CEC) by the same method: 84.2% yield and 99.8% regioisomeric purity
at the same reactant ratios as above. The yield of the reesterification step and the regioisomeric purity of the product were
influenced by the molar ratio of the reactants for both CDC and CEC syntheses: higher excess of EtC favored higher yields
and regioisomeric purity of the products. 相似文献
12.
Lipase biocatalysis in the production of esters 总被引:2,自引:0,他引:2
Y. -Y. Linko M. Lämsä A. Huhtala O. Rantanen 《Journal of the American Oil Chemists' Society》1995,72(11):1293-1299
Lipase biocatalysis was investigated as a tool for the production of butyl oleate and rapeseed oil 2-ethyl-1-hexyl ester by
esterification and transesterification, respectively. We screened 25 commercially available lipases and found that butyl oleate
was produced at high yields from oleic acid and 1-butanol by lipases fromCandida rugosa, Chromobacterium viscosum, Rhizomucor miehei, and Pseudomonas fluorescens. The initial water content of the system, lipase quantity, and the molar ratio of 1-butanol to oleic acid were important
factors in influencing the ester yield. In general, no ester was formed without the addition of water. The exception wasCh. viscosum lipase, which yielded 98% of ester in 12 h with 1-butanol excess without additional water. The addition of 3.2% water increased
the initial rate of reaction. With an oleic acid excess and only 0.3% lipase,C. rugosa andR. miehei lipases yielded 94 and 100% esters with initial water contents of 3.2 and 14%, respectively. Lipase-catalyzed alcoholysis
of low-erucic acid rapeseed oil and 2-ethyl-1-hexanol without additional organic solvent also was studied in stirred batch
reactors. In this case,C. rugosa lipase was the best biocatalyst with an optimal 2-ethyl-1-hexanol to rapeseed oil molar ratio of 2.8, a minimum of 1.0% added
water, and 37°C. An increase in temperature up to 55°C increased the rate of reaction but did not affect the final ester yield.
The enzyme was inactivated at 60°C. Under optimal conditions, the ester yield increased from 88% in 7 h to nearly complete
conversion in 1 h when the lipase content was increased from 0.3 to 14.6%. In a 2-kg small pilot scale, up to 90% conversion
(97% of theoretical) was obtained in 8 h at 37°C with 3.4% lipase in the presence of Amberlite XAD-7 resin with 3% added water. 相似文献
13.
Studies on the enzymatic synthesis of lipophilic derivatives of natural antioxidants 总被引:7,自引:0,他引:7
H. Stamatis V. Sereti F. N. Kolisis 《Journal of the American Oil Chemists' Society》1999,76(12):1505-1510
The esterification of some natural antioxidants such as cinnamic acid derivatives and ascorbic acid in non-aqueous media,
catalyzed by immobilized lipases from Candida antarctica and Rhizomucor miehei, was investigated. The alcohol chain length affected the rate of esterification of cinnamic acids by both lipases. Higher
reaction rates were observed when the esterification was carried out with medium- or long-chain alcohols. The rate also depended
on aromatic acid structure. The reactivity of the carboxylic function of the cinnamic acids was affected by electron-donating
substituents in the aromatic ring. Higher yields were observed for the esterification of p-hydroxyphenylacetic acid (97%) catalyzed by C. antarctica lipase and for the esterification of cinnamic acid (59%) catalyzed by R. miehei lipase. Candida antarctica lipase was more suitable for producing ascorbic acid fatty esters, catalyzing with a relatively high yield (up to 65% within
24 h) the regioselective esterification of ascorbic acid with various fatty acids in 2-methyl-2-propanol. The reaction rate
and yield depended on the fatty acid chain length and on the molar ratio of reactants. All ascorbic acid fatty esters produced
by this procedure exhibited a significant antioxidant activity in a micellar substrate composed of linoleic acid. 相似文献
14.
Effects of selected substrate forms on the synthesis of structured lipids by two immobilized lipases
Two immobilized lipases, IM 60 from Rhizomucor miehei and SP 435 from Candida antarctica, were used to synthesize structured lipids (SL). Tricaprin and trilinolein were interesterified to produce SL that contained
one linoleic acid per triacylglycerol molecule (SL1) and SL with two linoleic acids (SL2). SL1 and SL2 were separated by silver
nitrate thin-layer chromatography according to their unsaturation, and the fatty acid at the sn-2 position was determined after pancreatic lipasecatalyzed hydrolysis of SL1 and SL2. With IM 60, 57.7 mol% capric acid and
42.3 mol% linoleic acid were found at the sn-2 position of SL1, while 43.3 mol% capric acid and 56.7 mol% linoleic acid were at the sn-2 position of SL2. The fatty acid at the sn-2 position of SL1 with SP 435 as biocatalyst was 43.6 mol% capric acid and 56.4 mol% linoleic acid, while SL2 contained 56.6
mol% capric acid and 43.4 mol% linoleic acid. Different structural forms of the capric acid-containing substrate (triacylglycerol
vs. ethyl ester) and different chainlengths of triacylglycerol were selected to study the substrate selectivity of lipases.
Results indicated that SP 435 had some degree of preference for the triacylglycerol form (tricaprin), and IM 60 produced SL
more rapidly and reached steady state faster with tricaprin as substrate than with capric acid ethyl ester. For chainlength
selectivity, mol% of synthesized SL from tricaprin + trilinolein and tristearin + trilinolein were compared. SP 435 exhibited
no apparent preference for either tricaprin or tristearin. However, IM 60 showed a more rapid reaction with tricaprin than
with tristearin. 相似文献
15.
Enzyme,medium, and reaction engineering to design a low-cost,selective production method for mono- and dioleoylglycerols 总被引:3,自引:0,他引:3
The selective enzymic production of mono- and diolein (MO, DO) was optimized at high yields. A comparative study of the following
distinct enzymic reactions was conducted: ethyl oleate glycerolysis, triolein (TO) glycerolysis, and direct esterification
Solvent-free systems were compared with media that contained different solvents. Native, modified (with polyethylene glycol),
and immobilized lipases were used. Mechanical resistance, the support effect on enzyme and glycerol dispersion and on process
reproducibility, and hydrophilicity of the support were considered in the process optimization. We report the use of an immobilized
lipase on an inorganic support (Celite), which has high activities in both solid-phase glycerolysis (99% reaction conversion)
and esterification (100% conversion). The optimum conditions for the distinct reactions were compared by considering their
selectivities, conversions, yields, and cost of the substrates. We found less costly and more selective processes in the absence
of solvents for glycerolysis of triolein and direct esterification. Although glycerolysis was the most interesting process
to produce diolein, esterification was better for monoolein preparation with this biocatalyst. The esterification reaction
yielded 93 wt% of MO, in the absence of either TO or oleic acid (OA), at low cost because of the 100% reaction conversion.
Similar costs of the substrates (10.6 and 10.1 $/g) were necessary to obtain 67 and 80 wt% of DO in esterification and glycerolysis,
respectively. The glycerolysis conversion was 96%. In esterification, the product mixture was impure, with a high amount of
residual OA due to the low conversion (59%). The high activity of PSL-Celite in these solid-phase reactions has an advantage
over the reactions with nonimmobilized lipases due to the ease of enzyme recovery. The absence of organic solvents reduces
the need for solvent removal from the reaction mixtures. 相似文献
16.
Lipase B (GCB) produced by the fungus Geotrichum candidum CMICC 335426 is known for its high specificity towards cis-Δ9 unsaturated fatty acids. The wild-type lipase (not genetically modified) as well as the lipase obtained by heterologous
expression of the corresponding gene in Pichia pastoris (genetically modified) were studied in a process aiming to produce an oil containing very little saturated fatty acids (SAFA).
The approach described in this paper is based on the selective hydrolysis of sunflower oil (12% SAFA) using the G. candidum type B (GCB) lipases. Depending on the lipase input, up to 60% w/w degree of hydrolysis was obtained within 6–8 h. Because
of the high specificity of the GCB lipases (specificity factor ∼30), the level of unsaturates in the free fatty acid fraction
was >99% w/w. In contrast with literature data, no loss of specificity was observed, even at the highest degree of hydrolysis
obtained. Though both GCB lipases are stable at 30°C, the rate of hydrolysis decreased considerably during the process. Product
inhibition as well as time-dependent deactivation (half-life ≈2 h) were shown to be involved. After separation of the oil
phase, the unsaturated free fatty acids were recovered from the mixture by evaporation and reconverted to triglycerides by
enzymatic esterification with glycerol. Because the GCB lipases have a very low efficiency for esterification, this reaction
was carried out with immobilized Rhizomucor miehei lipase. Under continuous removal of the water generated during the process, >95% triglycerides were obtained in less than
24 h. Standard deodorization resulted in an odorless, colorless, and tasteless oil with less than 1% SAFA. 相似文献
17.
The structural composition and thermal properties of the products of enzymatic interesterification of triolein and tristearin
were investigated. The biocatalyst for the reaction was an immobilized Candida antarctica lipase, SP435. Enzyme load of 10% (w/w reactants) produced 72% of desired total products. Oleoyl-distearoyl triglycerides
(SSO, OSS) had higher melting points than dioleoyl-stearoyl triglycerides (OOS, SOO) because the sample contained larger amounts
of stearic acid than oleic acid residues. SOS and OSO were hardly produced (0.2 to 1.2%), which indicates that SP435 acted
as a nonspecific lipase when catalyzing the interesterification of triolein and tristearin. The maximal yield of OSS and SSO
(46.9%) was achieved with a 1.2 mole ratio of triolein to tristearin. As the proportion of tristearin was increased, the production
of SOO and OOS decreased, the melting profile of the interesterified triglycerides shifted toward higher melting forms, and
the solid fat content increased, indicating formation of hard fats. 相似文献
18.
Raimund Multzsch Wolfram Lokotsch Beate Steffen Siegmund Lang Jürgen O. Metzger Hans J. Schäfer Siegfried Warwel Fritz Wagner 《Journal of the American Oil Chemists' Society》1994,71(7):721-725
Wax esters from fatty alcohols and uncommon fatty acids were synthesized in yields up to 90% when commercially available microbial
lipases fromRhizomucor miehei (Lipozyme™) andCandida antarctica (SP 435) were used with limited water content in nonpolar solvents under mild conditions. The corresponding fatty acids were
prepared by chemical conversion of naturally occurring resources (agricultural surpluses). Also, when phenylboronic acid was
added as solubilizing agent in a nonpolar solvent, the direct enzymatic monoacylation of glycerol with uncommon fatty acids
was successful. The measurement of π/A-isotherms by means of a Langmuir film balance indicated medium film pressures, medium
or large molecular areas, and interesting phase behavior. The monolayer of a wax ester at the air/water interface could be
directly visualized by Brewster angle microscopy. 相似文献
19.
Enzymatic synthesis of structured lipids: Transesterification of triolein and caprylic acid ethyl ester 总被引:4,自引:0,他引:4
Structured lipids were successfully synthesized by lipase-catalyzed transesterification (ester interchange) of caprylic acid
ethyl ester and triolein. The transesterification reaction was carried out in organic solvent as reaction media. Eight commercially-available
lipases (10% w/w substrates) were screened for their ability to synthesize structured lipid by incubating with 100 mg triolein
and 78.0 mg caprylic acid ethyl ester in 3 mL hexane at 45°C for 24 h. The products were analyzed by reverse-phase high-performance
liquid chromatography with evaporative light-scattering detector. Immobilized lipase IM60 fromRhizomucor miehei converted most triolein into structured lipids (41.7% dicapryloolein, 46.0% monocapryloolein, and 12.3% unreacted triolein).
However, lipase SP435 fromCandida antarctica had a higher activity at higher temperature. The reaction catalyzed by lipase SP435 yielded 62.0% dicapryloolein, 33.5% monocapryloolein,
and 4.5% unreacted triolein at 55°C. Time course, incubation media, added water, and substrate concentration were also investigated
in this study. The results suggest that lipase-catalyzed transesterification of long-chain triglycerides and medium-chain
fatty acid ethyl ester is feasible to synthesize structured lipids. 相似文献
20.
《Chemical Engineering Communications》2012,199(2):177-184
AbstractButyl acetate is a versatile chemical due to its excellent solvency for polymers, resins, and oils. In this work, the butyl acetate synthesis was studied by the esterification of n-butanol with acetic acid using the commercial immobilized lipase Novozym® 435. The acetic acid and n-butanol concentrations have to be limited in the enzymatic synthesis of this ester due to the deleterious effects caused by these reagents on the enzyme. Three methods of acetic acid addition (single, stepwise and continuous addition) were investigated to minimize the acid concentration. A significant drop on acid conversion was observed in the presence of a higher concentration of the reagents when single or stepwise acid addition was used. However, a solvent-free system using a continuous addition of acetic acid favored butyl acetate synthesis, reaching a conversion of 84% at 60?°C, employing 5?wt% of enzyme and n-butanol/acetic acid final molar ratio equal to 1/1. 相似文献