A Novel Temperature-Controlled Ionic Liquid as the Medium for Phenylethyl Acetate Synthesis Catalyzed by Lipase

Three 1,3-dipentylimidazolium hexafluorophosphate ionic liquid isomers, 1,3-di-n-pentylimidazolium hexafluorophosphate ([D(n-C5)Im]PF6), 1,3-di-isopentylimidazolium hexafluorophosphate ([D(i-C5)Im]PF6), and 1,3-di(2-methylbutyl)imidazolium hexafluoro-phosphate ([D(2-mb)Im]PF6), were designed and synthesized. They were used as media for the synthesis of phenylethyl acetate catalyzed by Pseudomonas cepacial lipase. The activity and reactivity of the lipase in [D(2-mb)Im]PF6 is obviously higher than that in organic solvent hexane. Based on the temperature-controlled characteristics of [D(2-mb)Im]PF6, we designed a new route to synthesize phenylethyl acetate catalyzed by lipase, in which the reaction and the separation of the product were carried out under a relatively high and low temperature, respectively. By investigating the influence of various factors on the yield of product, optimal conditions for the synthesis of phenylethyl acetate were obtained, i.e., the amount of lipase 30 mg, the ionic liquid 1.0 g, water content 2%, reaction temperature 35 °C, and reaction time 48 h. Under the optimal conditions, the yield of phenylethyl acetate was up to 92.3%. Also, the stability of the lipase in the [D(2-mb)Im]PF6 medium was 7.4-fold that in hexane. The lipase in [D(2-mb)Im]PF6 was recycled 10 times without substantial diminution in activity. Moreover, circular dichroism and fluorescence spectroscopy were used to follow the changes of enzyme structure in different solvents. The results showed that the lipase in the ionic liquid has excellent secondary structure stability and slightly big exposure level of amino-acid residues.

摘要设计合成了三种同分异构离子液体䜕1,3-二正戊基咪唑六氟磷酸盐䜕([D(n-C5)Im]PF6)、1,3-二异戊基咪唑六氟磷酸盐䜕([D(i-C5)Im]PF6)䜕和䜕1,3-二䜕(2-甲基丁基)䜕咪唑六氟磷酸盐䜕([D(2-mb)Im]PF6).䜕䜕以假单胞菌脂肪酶䜕Pseudomonas cepacial 䜕催化合成乙酸苯乙酯为模型反应,䜕分别考察了反应介质对酶行为的影响.䜕䜕结果发现,䜕酶在离子液体[D(2-mb)Im]PF6䜕中的活性及反应性能明显高于有机溶剂正己烷.䜕䜕基于[D(2-mb)Im]PF6䜕离子液体的温控特点,䜕提出了一种高温反应与低温分离相结合的乙酸苯乙酯合成路线.䜕䜕通过优化实验,䜕得到合成乙酸苯乙酯的最佳反应条件为䜕䜕䜕mg䜕酶,䜕1.0䜕g䜕离子液体,䜕2%䜕含水量,䜕反应温度䜕35䜕°C,䜕反应时间䜕48䜕h.䜕䜕此时,䜕乙酸苯乙酯产率达䜕92.3%.䜕䜕脂肪酶在[D(2-mb)Im]PF6䜕中的稳定性是在正己烷中的䜕7.4䜕倍,䜕且重复使用䜕10䜕次后催化活性没有明显降低.䜕䜕此外,䜕采用圆二色谱和内源荧光光谱法研究了不同介质中脂肪酶结构的变化.䜕䜕结果表明,䜕脂肪酶在[D(2-mb)Im]PF6䜕中有较大的氨基酸残基裸露程度和良好的二级结构稳定性.䜕

The study presents a new route for biosynthesis of phenylethyl acetate, in which the novel ionic liquid offers an excellent microenvironment for lipase. The enzyme activity, stability, and reuse are remarkably better than that in hexane.Figure optionsDownload as PowerPoint slide