腈水合酶交联酶聚集体在生成烟酰胺体系中的应用

The application of nitrile hydratase cross-linked enzyme aggregates in the generated system of nicotinamide

采用交联酶聚集体(CLEAs)技术和球化酶技术对来自大肠杆菌的ES-NHT-118腈水合酶进行固定化.利用大分子葡聚糖醛作为交联剂交联腈水合酶,在优化了温度、p H、交联剂用量及交联时间后,腈水合酶CLEAs和球化酶的酶活回收率分别达到49.63%及52.88%.利用扫描电子显微镜对2种固定化酶进行了表征,将固定化酶用于催化3-腈基吡啶转化生成烟酰胺.同游离酶相比,腈水合酶CLEAs和球化酶显示了良好的p H稳定性和热稳定性,对高浓度底物的耐受性也有提升.酶活为4 U/m L,底物终浓度为50 mmol/L时,2种固定化酶在重复使用10次后分别保留了73.45%及61.26%的催化产率.

Cross-linked enzyme aggregates （CLEAs） and spherezymes ofnitrile hydratase （NHase） ES-NHT-118 from E.coli were prepared. Dextran polyaldehyde, a macromolecular cross-linker, was employed to cross-link NHase for the first time. After having optimized the temperature, pH, concentration of the cross-linker and the cross-linking time in the process of preparation, NHase CLEAs and spherezymes have obtained 49.63%, 52.88% of activity recovery, re- spectively. The morphology of CLEAs and spherezymes were analyzed by using scanning electron microscopy （SEM）. The immobilized enzymes were employed to catalyze 3-cyanopyridine converted to nicotinamide. The NHase CLEAs and spherezymes exhibited increased stability at varied pH and temperature conditions when compared with its free counterpart. When exposed to high concentrations ofacrylamide, immobilized enzymes also exhibited effective catalytic activity. When having reached the effect of 50 mmol/L 3-cyanopyridine, 4 U/mL NHase CLEAs and spherezymes kept respectively 74.37%, 63.95% of their original activity after being recycled ten times.