静电纺丝制备苯乙烯马来酸酐共聚物纳米纤维及其固定化b-D-半乳糖苷酶

采用静电纺丝技术制备苯乙烯-马来酸酐共聚物纳米纤维，最佳电纺条件为：聚合物浓度0.35 g/mL、针尖到接收板距离25 cm、电纺液流量250 mL/h、电压21 kV. 该条件下获得了直径约300 nm且分布均一的纳米纤维. 利用该纳米纤维固定b-D-半乳糖苷酶，固定化反应的最适pH值为4.0，此时酶负载量为(15.1±0.5) mg/g. 固定化酶催化2-硝基苯酚-b-D-半乳吡喃糖苷水解反应的米氏常数Km=2.7 mmol/L，略大于游离酶的Km值(2.2 mmol/L)；最大反应速率Vmax为97.2 mmol/(min×mg)，为游离酶的47.8%. 固定化酶在37℃下重复操作21次后活性损失仅为15%. 在连续搅拌式反应器中将固定化酶用于催化乳糖的水解反应，连续使用17 d仍能稳定运行.

Preparation of Electrospun Poly(styrene-co-maleic anhydride) Nanofibers and Their Use in Immobilization of b-D-Galactosidase

Unique poly(styrene-co-maleic anhydride) nanofibers with a uniform diameter of about 300 nm were prepared by eletrospinning a solution containing 0.35 g/mL polymer, 25 cm gap between ejection needle tip and collector, flow rate of 250 L/h, and applied voltage of 21 kV. The electrospun nanofibers were applied subsequently for immobilization of b-D-galactosidase, an enzyme loading of (15.1±0.5) mg protein/g membrane was obtained. The immobilized enzyme demonstrated a Michealis constant (Km) of 2.7 mmol/L, slightly higher than that of the native enzyme (2.2 mmol/L). The maximum reaction velocity (Vmax) of the immobilized enzyme was found as 97.2 mol/(min×mg), 47.8% that of native enzyme. The immobilized enzyme showed an excellent reusability such that 21 reusing cycles only led to 15% loss of the enzyme activity. Furthermore, the immobilized b-D-galactosidase was suitable for hydrolysis of lactose in a continuous stirring tank reactor that was operated steadily for 17 d.