Lipase-catalyzed synthesis of kojic acid esters in organic solvents

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.     

Enhanced activities of lipase pretreated with organic solvents

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     

离子液体协同催化合成游离氨基酸酯

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。     

油酸和十二烷二酸的氨基酸酯的合成及其生物抗菌性

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)。     

Enzymatic phosphatidylcholine hydrolysis in organic solvents: An examination of selected commercially available lipases

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.     

有机相酶法不对称水解乳酸乙酯

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 r•min^-1、水含量（水与底物的质量比）1∶5、乳酸乙酯浓度0.27 g•ml^-1、酶浓0.8 g•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。     

Characterization of potentially bioreactive soil organic carbon and nitrogen by acid hydrolysis

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.     

Crystallization of amorphous poly(lactic acid) induced by organic solvents

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     

Synthesis of propylene glycol monoesters of docosahexaenoic acid and eicosapentaenoic acid by lipase-catalyzed esterification in organic solvents

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.     

Synthesis of magnesium sulfate from seawater using alkaline industrial wastes,sulfuric acid,and organic solvents

ABSTRACT

In 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.     

酶催化手性拆分旋光异构体

将酶催化拆分反应的国内外新进展归纳为水解反应、氧化-还原反应、转移-裂合反应以及非水介质中的合成反应等类型,并列举了其中一些具有重要理论意义或应用价值的实例。探讨了介质工程、预处理酶及添加剂等因素对对映体选择性和产率的影响。指出酶催化手性拆分在不对称合成领域的发展方向将是新的适用反应类型的开发、酶的固定化及重复利用技术,以及大规模制备手性产品的专用反应器的设计等。     

Production of propylene glycol fatty acid monoesters by lipase-catalyzed reactions in organic solvents

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.     

扁桃酸的酶促光学拆分

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.     

Enzymic hydrolysis of animal fats in organic solvents at temperatures below their melting points

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.     

The hydrolysis of phosphatidylcholine by an immobilized lipase: Optimization of hydrolysis in organic solvents

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.     

表面活性剂包衣酶在有机溶剂中拆分对映异构体

天然酶经表面活性剂包衣后在有机溶剂中的活性和对映选择性有显著提高 ,稳定性也大为改善。目前研究涉及的大多为酯化或酯交换反应 ,使用最多的为脂肪酶 ,底物的分子结构对包衣酶的对映选择性有显著影响。指出可以借助膜反应器来实现包衣酶的截留和反复利用及产物的分离 ,通过改良表面活性剂或改进包衣酶的制备过程可望进一步提高包衣酶的收率和活性 ,包衣酶催化反应的机理及动力学也有待深入研究。     

Novel amino acid ionic liquids prepared via one-step lactam hydrolysis for the highly efficient capture of CO2

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.     

D-(-)-苯甘氨酸衍生物拆分DL-扁桃酸的研究

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。     

以动物羽毛为原料制备饲用氨基酸的进展

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。     

高效液相色谱测定氨基酸衍生物的对映纯度

利用酒石酸型手性固定相正相模式下拆分了一氨基酸衍生物,讨论了流动相中极性添加剂的种类及含量对手性拆分效果的影响。结合拆分过程对应的热力学参数对手性识别机理进行了探讨。该法具有分析时间多,分离效果好,重现性好等优点。