A clean enzymatic process for producing flavour esters by direct esterification in switchable ionic liquid/solid phases
作者:Pedro Lozano、Juana M. Bernal、Alicia Navarro
DOI:10.1039/c2gc36081k
日期:——
A clean biocatalytic approach for producing flavour esters using switchable ionic liquid/solid phases as reaction/separation media has been developed. The phase behaviour of different IL/flavour acetyl ester (geranyl acetate, citronellyl acetate, neryl acetate and isoamyl acetate) mixtures was studied at several concentrations, resulting for all cases in fully homogeneous liquid media at 50 °C, and solid systems at room temperature. By using an iterative centrifugation protocol on the solid IL/flavour ester mixtures at controlled temperatures, the solid IL phase and the liquid flavour ester phase can be easily separated. The excellent suitability of an immobilized Candida antarctica lipase B (Novozym 435) catalyst in the esterification reaction between an aliphatic carboxylic acid (acetic, propionic, butyric or valeric) and a flavour alcohol (isoamyl alcohol, nerol, citronellol or geraniol) in N,N′,N′′,N′′′-hexadecyltrimethyl-ammonium bis(trifluoromethylsulfonyl)imide ([C16tma][NTf2])IL has been demonstrated, the product yield being improved up to 100% under appropriate reaction conditions (enzyme amount, dehydrating molecular sieves, etc.) at 50 °C. The enzymatic synthesis of sixteen different flavour esters was carried out in [C16tma][NTf2] by means of this approach, providing products of up to 0.757 g mL−1 concentration after IL separation. The residual activity of the enzyme/IL system during seven consecutive operation cycles was shown to be practically unchanged after reuse.
开发了一种清洁的生物催化方法,利用可切换的离子液体/固体相作为反应/分离介质来生产香味酯。研究了不同离子液体与香味乙酰酯(香叶醇乙酸酯、香茅醇乙酸酯、奈缬醇乙酸酯和异戊醇乙酸酯)混合物的相行为,在多个浓度下进行研究,结果发现所有情况下在50°C时均为完全均匀的液态介质,而在室温下则为固态系统。通过在控制温度下对固体离子液体/香味酯混合物采用迭代离心分离协议,可以轻松分离出固态离子液体相和液态香味酯相。已证明,在N,N′,N′′,N′′′-十六烷基三甲基铵双(全氟甲基磺酰)亚胺([C16tma][NTf2])离子液体中,固定化的南极酵母脂肪酶B(Novozym 435)催化剂在脂肪族羧酸(醋酸、丙酸、丁酸或戊酸)与香味醇(异戊醇、香叶醇、香茅醇或香茅醇)之间的酯化反应中极为适合,在适当的反应条件(酶量、脱水分子筛等)下,产率提高至100%。通过这种方法在[C16tma][NTf2]中合成了十六种不同的香味酯,离子液体分离后产品浓度达到0.757 g mL−1。在七个连续操作周期中,酶/离子液体系统的残余活性在重复使用后几乎没有变化。