Arica M Y, Hasirci V, Alaeddinoğlu N G
Department of Biology, Faculty of Science, Kirikkale University, Turkey.
Biomaterials. 1995 Jul;16(10):761-8. doi: 10.1016/0142-9612(95)99638-3.
Microspheres of poly(2-hydroxyethyl methacrylate) with and without cross-linker were prepared by suspension polymerization. As the amount of cross-linker increased, the equilibrium water content, enzyme loading, immobilization efficiency and recovered activity were all adversely affected. Enzyme alpha-amylase was immobilized onto the microspheres after activation with epichlorohydrin. The Km value for the immobilized enzyme (0.90% w/v) was much greater than that of the free enzyme (0.53% w/v). It was found that the inactivation constant (ki) increased from 2.23 x 10(-8) min-1 at 20 degrees C to 1.45 x 10(-4) min-1 at 60 degrees C. Since the enzyme activity increased as the temperature increased, the temperature profile yielded a peak at 50 degrees C. For free enzyme this is at 45 degrees C. The residence time was proportional to the percentage hydrolysis until a residence time of 12 min was reached. Beyond this the activity increase could not match the increase in residence time. The pH profile yielded a broadening upon immobilization in addition to a small shift to higher pH (from 5.5 to 6.0). The continuous run at 30 degrees C, 1.0% w/v starch concentration and flow rate of 40 cm3 h-1 led to only 20% loss in activity after a 120 h operation.
通过悬浮聚合制备了含交联剂和不含交联剂的聚甲基丙烯酸2-羟乙酯微球。随着交联剂用量的增加，平衡含水量、酶负载量、固定化效率和回收活性均受到不利影响。用环氧氯丙烷活化后，将α-淀粉酶固定在微球上。固定化酶（0.90% w/v）的Km值远大于游离酶（0.53% w/v）的Km值。发现失活常数（ki）从20℃时的2.23×10⁻⁸ min⁻¹增加到60℃时的1.45×10⁻⁴ min⁻¹。由于酶活性随温度升高而增加，温度曲线在50℃时出现峰值。对于游离酶，该峰值在45℃。停留时间与水解百分比成正比，直至达到12分钟的停留时间。超过此时间，活性增加无法与停留时间的增加相匹配。固定化后pH曲线除了向较高pH值（从5.5到6.0）有小的偏移外，还变宽。在30℃、1.0% w/v淀粉浓度和40 cm³ h⁻¹流速下连续运行120小时后，活性仅损失20%。
