Department of Chemistry of Natural and Microbial Products, National Research Center, El-Behooth St., Dokki, Giza, Egypt; Centre of Scientific Excellence-Group of Encapsulation and Nanobiotechnology, National Research Center, El-Behooth St., Dokki, Giza, Egypt.
Int J Biol Macromol. 2017 Dec;105(Pt 1):894-904. doi: 10.1016/j.ijbiomac.2017.07.102. Epub 2017 Jul 18.
Porous chitosan beads of superior mechanical properties were produced via a two stepped treatment process. First, the chitosan ionotropic gelation solution was supplemented with NaCO, which acted as a porogen. Afterwards, the beads were chemically cross-linked with glutaraldehyde. This treatment also caused the produced porous chitosan beads to acquire higher observed activities of immobilized β-d-galactosidase (β-gal). The observed activities of the β-gal immobilized onto the 0.2M and the 0.35M NaCO treated beads were 1.63 and 1.91 fold respectively, higher than the activity offered by the control beads. Nevertheless, both the control beads and the 0.2M NaCO beads caused the optimum pH range of β-gal to shift from 4.6-5.1 to ∼2.7-5. The enzyme's optimum temperature shifted from 55 to 60°C after its immobilization onto the control chitosan beads whereas the β-gal immobilized onto the 0.2M NaCO chitosan beads exhibited a temperature optimum of 55-60°C. The reusability study revealed the superiority of the 0.2M NaCO treated beads which retained 59.1% of their initial activity during the 13th enzymatic cycle. On the other hand, the control chitosan beads were fragmented and lost their activity after only four enzymatic cycles.
通过两步处理工艺制备了具有优异力学性能的多孔壳聚糖珠。首先，壳聚糖离子凝胶溶液中添加了 NaCO，它作为致孔剂。然后，用戊二醛对珠粒进行化学交联。这种处理还使制备的多孔壳聚糖珠获得了更高的固定化β-半乳糖苷酶（β-gal）的观察活性。固定在 0.2M 和 0.35M NaCO 处理珠上的β-gal 的观察活性分别比对照珠高 1.63 和 1.91 倍。然而，无论是对照珠还是 0.2M NaCO 珠都导致β-gal 的最佳 pH 范围从 4.6-5.1 转移到∼2.7-5。β-gal 固定在对照壳聚糖珠上后，其最适温度从 55°C 转移到 60°C，而固定在 0.2M NaCO 壳聚糖珠上的β-gal 的最适温度为 55-60°C。重复使用研究表明，0.2M NaCO 处理珠具有优越性，在第 13 个酶循环期间保留了初始活性的 59.1%。另一方面，对照壳聚糖珠在仅四个酶循环后就碎裂并失去了活性。
