用于叶黄素/玉米黄质高效萃取分离的离子液体-生物柴油两相体系构筑及其识别机制研究

Lutein and zeaxanthin with high purity are expensive and widely used to produce the high-end eye health care products. So it will be of great economic efficiency to extract lutein and zeaxanthin from DDGS (Distillers Dried Grains with Solubles), the cheap byproduct of dry-grind corn ethanol process. As isomers, lutein and zeaxanthin have the similar molecular structure and the only difference between them is the different position of a C=C double bond in the carbon ring. So the selective separation of lutein and zeaxanthin becomes a hotspot in the field chemical engineering. In this project, the ionic liquid-biodiesel biphasic system was used to separate the lutein and zeaxanthin. First, the ionic liquids with high solubility of lutein and zeaxanthin were selected by constructing the weak force between the ionic liquid and the target product, such as hydrogen bonding, polar force and π-π effect. Then, the ionic liquid-biodiesel biphasic system with low intersolubility was constructed by regulating the polar difference of ionic liquid and fatty acid methyl esters in biodiesel. Finally, the extraction mechanism of ionic liquids can be investigated with the help of microcosmic regulation of weak force, as well as the macroscopic liquid-liquid extraction process. This project proposed to provide the theoretical basis for large scale application of ionic liquid assisted extractive separation of lutein and zeaxanthin from DDGS.

高纯度的叶黄素和玉米黄质价格昂贵，是高端护眼保健品行业的宠儿。从玉米燃料乙醇廉价固废酒糟饲料DDGS中分离叶黄素和玉米黄质，能够有效利用玉米资源，提高产业利润。作为同分异构体，叶黄素和玉米黄质在分子结构上的差别只在于一个C=C双键的位置不同，将其高选择性分离是化工学科中的难点和热点。本项目采用离子液体-生物柴油两相体系作为液液萃取媒介，首先通过在离子液体与目标产物之间建立弱相互作用（氢键作用、极性作用和π-π作用），提高目标产物在离子液体中的溶解度，从而筛选得到高萃取容量的离子液体；然后通过调控离子液体与原料相生物柴油中脂肪酸甲酯的极性差异，构筑低互溶度的液-液两相体系；最后通过微观调控离子液体与目标产物之间弱键作用的大小差异，实现叶黄素和玉米黄质的高选择性分离，并结合宏观的多级液液萃取性能，探索其构效关系和萃取机理，为离子液体在萃取分离叶黄素和玉米黄质的大规模应用提供理论依。

叶黄素(Lutein)是一种高附加值的类胡萝卜素，其与同分异构体玉米黄质(Zeaxanthin)均为视网膜黄斑色素的主要组成部分，可以通过去除自由基、滤除蓝光而起到保护视力的作用。而相比于叶黄素，玉米黄质由于多含一个共轭双键，其抗氧化性能更高，疗效更好。本文介绍了采用化学工程中广泛使用的液液萃取工艺，通过引入物理化学性质可调的两亲性离子液体和生物柴油（长链脂肪酸酯）和水这三种绿色溶剂作为基体媒介，构筑液-液两相萃取体系。最后通过离子液体阴阳离子结构的改变，调控萃取剂与目标产物的弱相互作用力差异（比如氢键、极性作用、π-π作用等），从而实现从玉米黄色素中对叶黄素和玉米黄质进行高选择性分离。实验结果表明，调控离子液体阴离子的氢键碱性以及阳离子的极性对于提高分离性能效果显著，在离子液体1-辛基-3-甲基咪唑醋酸盐体系中，叶黄素和玉米黄质的分配系数分别为4.3781/9.7866，选择性系数达到了2.2349，具有很好的应用前景。