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1.
Kojic acid is an inhibitor of bacteria, viruses, and fungi. It is used for inhibiting the browning effect of tyrosinase in
the food and cosmetic industries. To improve its lipophilic properties, Pseudomonas cepacia lipase and Penicillium camembertii lipase were used for catalyzing the esterification of kojic acid to synthesize kojic acid monolaurate and kojic acid monooleate.
These products showed a 69.5% inhibitory effect on tyrosinase in hydrophobic organic solvent. The yields of kojic acid esters
were affected by enzymes, substrates, organic solvent, and temperature. Lauric and oleic acids were the best substrates for
esterification among various fatty acids tested. CaCl2 and MnCl2 stimulate Pseudomonas cepacia lipasecatalyzed esterification by 7.0%. On the contrary, MgCl2, SrCl2, and ZnCl2 inhibited the reaction. The best pH of buffer for lipase pretreatment was pH 6.0. Pseudomonas and Penicillium lipases can be reused for the synthesis of kojic acid esters. After reaction at 40°C for 10 d, the Penicillium and Pseudomonas lipases still retained 57.0% and 92.0% of their initial activities, respectively. 相似文献
2.
Michiaki Matsumoto Koji Kida Kazuo Kondo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2001,76(10):1070-1073
The catalytic activities of lipases derived from Pseudomonas sp and pretreated with various organic solvents were investigated. The activity of the solvent‐pretreated lipase was greater than that of native lipase in both the esterification reaction in an organic medium and the hydrolysis reaction in an aqueous medium. With esterification calalysed by pretreated lipase, the product, benzyl octanoate, was detected without time‐lag. Conversions at equilibrium state were correlated with the hydrophobicities of the solvents used. In the hydrolysis reaction, most pretreated lipases yielded increased acid production compared with native lipase. A linear correlation was observed between the solvent hydrophobicity and the relative initial reaction rate of the hydrolysis reaction when using pretreated lipases. © 2001 Society of Chemical Industry 相似文献
3.
以L-氨基酸和醇为原料,酸性离子液体辅以少量强酸性阳离子交换树脂作催化剂,直接酯化合成了8种游离的L-氨基酸酯,并用1HNMR对产物进行了表征。通过L-苯丙氨酸正丁酯的合成对离子液体的活性进行了考察,结果表明,所选用的11种离子液体在反应过程中均起到了一定的催化作用和助溶作用。其中,[Hmim][HSO4]效果较好,在重复使用后,显示了较好的稳定性,是氨基酸酯化反应理想的催化剂和助溶剂。 相似文献
4.
以L-丙氨酸乙酯盐酸盐、甘氨酸乙酯盐酸盐、L-蛋氨酸甲酯盐酸盐、L-亮氨酸乙酯盐酸盐和L-酪氨酸甲酯盐酸盐在1-乙基-(3-二甲基氨基丙基)碳酰二亚胺盐酸盐和1-羟基苯并三唑(HOBt)的作用下分别与油酸进行反应,生成了5种油酸的氨基酸衍生物;将L-丙氨酸乙酯盐酸盐和甘氨酸乙酯盐酸盐分别与十二烷二酸进行反应,生成了两种十二烷二酸的氨基酸衍生物,7种产物的收率均≥75%。利用FTIR、TGA、1HNMR和LC-MS对产物进行了表征,测试了产物的水油分散性,考察了产物对金黄色葡萄球菌和大肠杆菌的抑菌性。结果表明,所合成的脂肪酰氨基酸酯均能在水油体系中分散,且具有较强的生物抗菌性,其中,0.01 mg油酸酰亮氨酸乙酯能有效地抑制金黄色葡萄球菌(菌数由2.0×109 CFU/mL降至1.4×107 CFU/mL),而相同质量油酸酰酪氨酸甲酯则能抑制大肠杆菌(菌数由2.0×109 CFU/mL降至1.8×107 CFU/mL)。 相似文献
5.
Enzymatic phosphatidylcholine hydrolysis in organic solvents: An examination of selected commercially available lipases 总被引:1,自引:0,他引:1
M. J. Haas K. Scott W. Jun G. Janssen 《Journal of the American Oil Chemists' Society》1994,71(5):483-490
Eight commercial lipase preparations were examined for the ability to hydrolyze phosphatidylcholine (PC) in hexane solutions.
Only the enzymes fromHumicola lanuginosa, Rhizopus delemar andCandida rugosa displayed appreciable activity. Solvent polarity was the largest single factor affecting activity. TheH. lanuginosa sample was most active in polar solvents. TheR. delemar preparation was most active in polar (2-hexamone) and nonpolar (decane) solvents and least active in solvents of intermediate
polarity (hexane). The solvent dependence of the activity of theC. rugosa enzyme varied with the ratio of substrate to enzyme. Different degrees of activity were retained by the three enzymes after
passive immobilization on Celite, controlled-pore glass, polypropylene and Amberlite XAD-7 resins. No single resin yielded
the best retained activity for all three preparations. When examined in 2-octanone, hexane and isooctane, the Celite-immobilizedR. delemar andH. lanuginosa enzymes exhibited highest activity in 2-octanone, while immobilizedC. rugosa was most active in isooctane. The water content at which maximum activity was observed was relatively independent of solvent
polarity and the amount of catalyst but was proportional to the amount of PC in the reaction. The retention of activity by
immobilizedRhizomucor miehei lipase (Lipozyme) during multiple hydrolytic cycles required a reduction in the water content of the system below that yielding
optimal activity in a single cycle. 相似文献
6.
探讨了在有机介质中酶催化外消旋乳酸乙酯不对称水解制备L-乳酸的可行性。 研究了反应介质、不同来源的酶、摇床转速、水含量、乳酸乙酯浓度及温度等因素对反应的影响。结果表明,N435的活性和选择性较高,叔丁醇和异辛烷的混合溶剂(体积比为1∶1)为最合适的反应介质,其余最适条件为:摇床转数200 r8226;min-1、水含量(水与底物的质量比)1∶5、乳酸乙酯浓度0.27 g8226;ml-1、酶浓0.8 g8226;mol-1、反应温度60℃,在此条件下反应16 h得产物ee值为90.02% ,产率为28.69%。 最后研究了乳酸乙酯不对称水解的动力学,结果表明反应符合米氏方程,属于双底物抑制的双乒乓机制,并考察了D-乳酸乙酯和D-乳酸在建立反应动力学模型时的影响。 相似文献
7.
J.M. Xu H.H. Cheng W.C. Koskinen J.A.E. Molina 《Nutrient Cycling in Agroecosystems》1997,49(1-3):267-271
Studies determined the potential of acid hydrolysis for estimating the bioreactive fraction of organic carbon in soils (SOC).
Three soils (clay loam, silt loam, and sandy loam) were hydrolyzed with 1 M or 6 M HCl under reflux for up to 24 h. Results
showed that 1.7 to 3.2 % of SOC could be liberated as CO2 from the acid hydrolysis of soil. This readily hydrolyzed fraction should be a part of the bioreactive SOC. Higher amounts
of soluble SOC and N as well as CO2 were released from all soils by 6 M HCl than by 1 M HCl. Soluble SOC and N contents in both 1 M HCl and 6 M HCl hydrolysates
of all soils increased rapidly during the initial 2 hours of hydrolysis, and then increased very gradually. The amounts of
CO2-C evolved correlated with the amounts of NH4-N released during the acid hydrolysis (r = > 0.88). The ratio of SOC to soluble N was lower in 6 M HCl hydrolysate than in
1 M HCl. Hydrolysis of soil by 1 M HCl for 4 h appeared to be a promising approach for estimating the more bioreactive pools
of SOC and N.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Naofumi Naga Yuji Yoshida Masaya Inui Keiichi Noguchi Shigemitsu Murase 《应用聚合物科学杂志》2011,119(4):2058-2064
Crystallization of amorphous poly(lactic acid) (PLA) was investigated in various organic solvents, such as acetone, ethylacetate, diethylether, tetrahydrofurane, methanol, hexane, toluene, xylene, and o‐dichlorobenene. Most of the solvents, except hexane, induced crystallization of amorphous PLA. Acetone was the most effective solvent to accelerate the crystallization among the solvents used. The crystallization was induced by permeation of acetone into the amorphous phase of PLA, and the permeation obeyed Fick type diffusion. The crystallization rate increased with increasing of conducting temperature. Crystallized PLA formed α crystalline structure. The permeated acetone in the crystallized PLA gradually evaporated as time passes, and the elimination of acetone affected thermal and mechanical properties of the crystallized PLA. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
9.
Propylene glycol monoesters (PGM) of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are potentially health-beneficial
water-in-oil emulsifiers useful in the food industry. These esters were synthesized enzymatically to overcome the problems
associated with chemical processes. The products were analyzed by gas chromatography. The immobilizedMucor miehei lipase was found to be the best enzyme for the synthesis of both propylene glycol monoesters of EPA and DHA among nine lipases
tested. The anhydrous enzyme and hydrophobic organic solvents were favored for the production of both monoesters. The yields
of monoesters were also affected by temperature, pH memory, fatty acid/propylene glycol ratio, and reaction time. The yields
of PGMDHA and PGMEPA with 50 mM fatty acid and 225 mM propylene glycol as substrates in 1 mL solvent mixture (hexane/t-butyl alcohol=9:1), catalyzed by Lipozyme IM-20 (50 mg) at 40°C for 24 h, were 47 and 49 mM, respectively. The enzyme still
retained over 60% of its original activity after 10 d of batch-type operation (1 d per cycle) at 40°C for the synthesis of
both PGMDHA and PGMEPA. 相似文献
10.
《分离科学与技术》2012,47(16):2749-2757
ABSTRACTIn this study, we used three processes to synthesize magnesium sulfate from seawater. First, alkaline industrial wastes, cement kiln dust and paper sludge ash, were injected to the seawater to precipitate magnesium in the form of magnesium hydroxide (Mg(OH)2). Then, magnesium was eluted with a small amount of H2SO4 to make a high concentration magnesium solution. Finally, an organic solvent was added to precipitate magnesium sulfate (MgSO4). Over 90% of magnesium was recovered through the three processes. It is expected that 11.3 kg of magnesium sulfate (based on MgSO4 · 6H2O) can be synthesized from 1 ton of seawater. 相似文献
11.
12.
Fatty acid monoesters of propylene glycol (1,2-propanediol) are good water-in-oil emulsifiers. These esters were synthesized
enzymatically to overcome the problems associated with chemical processes. APseudomonas lipase was added to reaction mixtures containing propylene glycol and various acyl donors (fatty acids, fatty acid ethyl
esters, fatty acid anhydrides and triglycerides) in organic solvents, and the mixtures were shaken at 30°C. The products were
analyzed by gas chromatography. The yield of monoesters was affected by the acyl donors, organic solvents, temperature, water
content, pH memory and reaction time. The anhydrous (lyophilized) enzyme and fatty acid anhydrides were best for monoester
production. The optimum pH ranges were 4–5 and 8–10. The yields of propylene glycol monolaurate, monomyristate, monopalmitate,
monostearate and monooleate with 50 mM fatty acid anhydrides as acyl donors were 97.2, 79.6, 83.7, 89.7 and 93.4 mM, respectively;
those with 50 mM fatty acids as acyl donors were 37.3, 28.7, 28.7, 35.3 and 36.2 mM, respectively. The yields of propylene
glycol monopalmitate, monostearate and monooleate with 50 mM triglycerides as acyl donors were 87.4, 65.1 and 83.2 mM, respectively. 相似文献
13.
对在非水体系中,利用脂肪酶催化水解扁桃酸乙酯外消旋混合物拆分R(-)-扁桃酸进行了初步的研究.筛选出脂肪酶N435作为催化剂,叔丁醇作为溶剂.确定了最适的反应条件:脂肪酶N435浓度为2.5 g·L-1,RS-扁桃酸乙酯浓度为0.25 mol·L-1,水∶RS-扁桃酸乙酯的摩尔比为5∶1,反应温度为40℃,摇床转速为200 r·min-1,反应时间为24 h.在此条件下,R(-)-扁桃酸乙酯的转化率为41.6%,对映体过量百分率达84.0%.考察了底物R(-)-扁桃酸乙酯和产物R(-)-扁桃酸对反应的抑制作用,在此基础上运用顺序机制和拟稳态法,建立了反应的动力学模型,模拟计算结果和实验结果吻合较好. 相似文献
14.
M. D. Virto Jose Miguel Lascaray Rodolfo Solozabal Mertxe de Renobales 《Journal of the American Oil Chemists' Society》1991,68(5):324-327
Lipase fromCandida rugosa catalyzed the hydrolysis of inedible beef tallow and pork lard (edible and inedible) in the presence of organic solvents
at temperatures below the melting point of the fat. Reactions were carried out at 50% substrate with 180 lipase units per
gram of fat in a two-liter reactor. In the presence of isooctane (5-10%) beef tallow yielded 94% hydrolysis in 24 hr both
at 37° and 31°C. Edible pork lard yielded 97% hydrolysis under these conditions and at temperatures as low as 25°C, while
inedible lard gave hydrolysis intermediate between the other two fats. 相似文献
15.
The hydrolysis of phosphatidylcholine by an immobilized lipase: Optimization of hydrolysis in organic solvents 总被引:1,自引:0,他引:1
M. J. Haas D. J. Cichowicz J. Phillips R. Moreau 《Journal of the American Oil Chemists' Society》1993,70(2):111-117
The ability of a commercial immobilized lipase preparation (Lipozyme) to hydrolyze the fatty acyl ester bonds of soybean phosphatidylcholine
in organic media was investigated. Response surface methodology, based on a Modified Central Composite design, was employed
to examine the effects on hydrolysis of solvent polarity, water, pH, duration and temperature of incubation, and the amounts
of substrate and catalyst. A second-order regression model was developed, which allows evaluation of the effects of these
parameters, alone or in combination. Hydrolysis increased in a relatively straightforward manner in response to increases
in incubation time and the amount of catalyst and was approximately constant over the range of substrate amounts studied.
Solvent polarity had a profound effect on the degree of hydrolysis, and the qualitative and quantitative degrees of this effect
were dependent upon the values of the other parameters studied. Conditions were identified where enzyme activity was strong
in either nonpolar or polar solvents, with activity increasing as the polarity of the medium increased. Enzyme activity was
minimum at about 37°C, increasing below and above this temperature. Activity was not affected by the presence of acid or base
in the reactions. Increasing amounts of water stimulated enzyme activity in solvents more polar than hexane, while in less
polar solvents water inhibited activity. 相似文献
16.
17.
Shuyue Wen Tao Wang Xiaomin Zhang Weigao Xu Xingbang Hu Youting Wu 《American Institute of Chemical Engineers》2023,69(11):e18206
This article proposes for the first time the preparation of a series of amino acid ionic liquids (AAILs) via one-step hydrolysis of cheap lactams for the capture of CO2. The structures of the prepared AAILs are confirmed using NMR, FTIR, and ESI-MS, and their physical properties are also determined. It is found that these AAILs are reversible CO2 absorbents with very high absorption capacities (0.15 to 0.18 g·g−1 at 313.2 K and 1.0 bar), better than almost all task-specific ionic liquids reported in literatures. The absorption mechanism is also elucidated to be a combination of 1:1 and 2:1 stoichiometric reaction of AAILs with CO2 from NMR, FTIR, reaction equilibrium thermodynamical modeling and quantum calculations. The AAILs have the advantages of simple synthesis, high yield, and using available cheap raw materials. It is believed that this kind of AAILs have great potentials to be used as efficient CO2 absorbents. 相似文献
18.
D-(-)-苯甘氨酸衍生物拆分DL-扁桃酸的研究 总被引:1,自引:0,他引:1
描述了用D-(-)-苯甘氨酸丁酯及其盐酸盐为拆分剂,在水或醇的反应体系中,与扁桃酸反应,制备R-(-)-扁桃酸和S-(+)-扁桃酸的过程;其中R-(-)-扁桃酸有98.9%的收率和32%的光学纯度;而S-(+)-扁桃酸有90.1%的收率和66.73%的光学纯度。另外也描述了苯甘氨酸丁酯及其盐酸盐的一般合成方法。 相似文献
19.
以动物羽毛为原料制备饲用氨基酸的进展 总被引:7,自引:0,他引:7
综述了用酶和化学方法处理羽毛制备饲用氨基酸的进展及应用。羽毛的蛋白含量极高。是家畜的重要蛋白源。但是羽毛中含有大量的含胱氨酸的角蛋白,胱氨酸中含有二硫键。非反刍动物难以消化利用,因此,降解角蛋白为易消化吸收的氨基酸使其成为常规饲料,使废物充分利用,特别是合理利用蛋白质资源、开发角蛋白具有重要意义。 相似文献