聚脲多孔材料的简单制备及在酶固定和手性拆分中的应用

以甲苯二异氰酸酯(TDI)为单体,在水与丙酮混合溶剂中通过沉淀聚合一步法制备了富含胺基的聚脲多孔材料(PPU),通过扫描电镜和压汞法对其表面形貌和孔结构进行了表征.PPU经戊二醛(GA)活化后用于荧光假单胞菌脂肪酶(PFL)的固定,考察了GA活化过程中GA浓度对酶固定量及固定酶活性的影响.结果表明,PPU是一种粒子尺寸分布在30~50μm范围的形状不规则的多孔粒子,孔径在2 nm~100μm之间呈连续分布.在pH=8.0的缓冲溶液中用0.17 mol/L的GA对PPU进行改性,将改性后的PPU用于PFL的固定,当酶溶液浓度为2.56 mg/m L时,得到酶的最大固定量为95.2 mg/g,固定酶的活性为375 U/mg,相对活性为76%.将此固定酶作为催化剂,用于1-苯乙醇外消旋化合物的手性拆分,并与游离酶催化的结果相比较.结果表明,固定酶的反应活性和立体选择性都明显优于游离酶.通过沉淀聚合制备的聚脲多孔材料在酶固定及手性分子拆分方面具有应用前景.

Easy Synthesis of Porous Polyurea and Its Application in Enzyme Immobilization and Kinetic Resolution of Racemic Phenylethanol

Porous polyurea (PPU) was prepared through one step precipitation polymerization in a mixed solvent of water-acetone with toluene diisocyanate (TDI) as the only monomer through step polymerization of TDI with its amine derivatives in-situ produced by TDI reaction with water.The morphology,pore size and size distribution of the PPU were characterized by scanning electron microscope and mercury intrusion.The results demonstrate that PPU is of irregular and granular form with the size of the granules varied from 30 μm to 50 μm.PPU is featured by a continuous pore size distribution from 2 nm to 100 μm with two main regions of pore size distribution,one from 2 nm to 100 nm and another from 5 pμm to 100 μm.Amine groups on PPU surface are converted to aldehyde via a treatment with glutaraldehyde,followed by immobilization of lipase from pseudomonasfluorescens(PFL) onto the surface of activated PPU by covalent bonding of the aldehyde groups with the primary amine of the enzyme.Impact of GA and PFL concentration in the process was studied.It is found that the optimized results are obtained when PPU is activated by GA at pH =8 with a concentration of 0.17 mol/L followed by PFL immobilization with PFL concentration of 2.56 mg/mL.Under the optimized conditions,a maximal PFL immobilization of 95.2 mg/g was observed with a high activity of the immobilized PFL of 375 U/mg and the relative activity of 76％ relative to free PFL.The immobilized PFL is then used as the catalyst in the kinetic resolution of 1-phenylethanol,the reactivity and the enantioselectivity compared with the free PFL.The results reveal that the activity and the enantioselectivity of the immobilized PFL are greatly enhanced in comparison with the free enzyme.The kinetic resolution of the racemic PEOH is achieved with pure enantiomers.Therefore,this PPU material prepared through simple precipitation is a good potential candidate for enzyme immobilization,the immobilized enzyme is efficient for kinetic resolution of racemic molecules.