Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida.
Department of Microbiology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan.
J Basic Microbiol. 2020 Jul;60(7):600-612. doi: 10.1002/jobm.202000077. Epub 2020 May 4.
Industrial applications require enzymes to be highly stable and economically viable in terms of reusability. Enzyme immobilization is an exciting alternative to improve the stability of enzymatic processes. Immobilization of β-1,4-xylanase produced by Bacillus licheniformis S3 is performed by using two polymer supports (agar-agar and calcium alginate). The maximum enzyme immobilization yield was achieved at a concentration of 3% agar, whereas a combination of sodium alginate, 4%, and calcium chloride, 0.3 M, was used for the formation of immobilized beads. The immobilization process increased the optimum reaction time from 10 min to 35 and 40 min for agar and calcium alginate, respectively, and the incubation temperature increased from 55°C to 60°C for agar, but it remained unchanged for calcium alginate. The pH profile of free and immobilized xylanase was quite similar in both cases. Both the techniques altered the kinetic parameters of immobilized β-1,4-xylanase as compared with the free enzyme. The diffusion limit of high molecular weight xylan caused a decline in V of the immobilized enzyme, whereas there was an increase in the K value. However, calcium alginate-immobilized enzyme displayed broad thermal stability as compared with agar-agar-immobilized enzyme and retained 57.1% of its initial activity at 80°C up to 150 min. Biotechnological characterization showed that the reusability of enzymes was the most striking finding, particularly of immobilized xylanase using agar-agar as immobilization carrier, which after six cycles retained 23% activity.
工业应用要求酶在可重复使用方面具有高度稳定性和经济可行性。酶固定化是提高酶法工艺稳定性的一种很有前途的方法。通过使用两种聚合物载体（琼脂和海藻酸钠）对地衣芽孢杆菌 S3 产生的β-1,4-木聚糖酶进行固定化。在琼脂浓度为 3%时，达到了最大的酶固定化产率，而海藻酸钠 4%和氯化钙 0.3 M 的组合用于形成固定化珠。固定化过程将最佳反应时间分别从 10 分钟延长到琼脂和海藻酸钠的 35 分钟和 40 分钟，并且琼脂的孵育温度从 55°C升高到 60°C，而海藻酸钠的孵育温度保持不变。游离和固定化木聚糖酶的 pH 曲线在两种情况下都非常相似。与游离酶相比，这两种技术都改变了固定化β-1,4-木聚糖酶的动力学参数。高分子量木聚糖的扩散限制导致固定化酶的 V 值下降，而 K 值增加。然而，与琼脂-琼脂固定化酶相比，海藻酸钠固定化酶显示出更宽的热稳定性，在 80°C 下保持 57.1%的初始活性，直至 150 分钟。生物技术特性表明，酶的可重复使用性是最显著的发现，特别是使用琼脂作为固定化载体的固定化木聚糖酶，在经过六个循环后仍保留 23%的活性。
