Chemistry of Natural and Microbial Products Department, National Research Centre, El Behouth Street, Cairo, 12622, Egypt.
Chemistry of Natural and Microbial Products Department, National Research Centre, El Behouth Street, Cairo, 12622, Egypt; Department of Biology, Collage of Science, University of Hafr Al Batin, P.O. Box 1803, Hafr Al Batin, Saudi Arabia.
Int J Biol Macromol. 2019 Nov 1;140:1284-1295. doi: 10.1016/j.ijbiomac.2019.08.211. Epub 2019 Aug 26.
Alginate- polyethyleneimine gel beads modified by using 0.3 M Na were used for covalent immobilization of Aspergillus flavus xylanase. SEM images showed distorted structure with addition of Na that impaired the egg-box structure formation offered much covalent binding with xylanase. Immobilization onto (Alg+PEI/Na) showed an enhancement in the operational stability, immobilization efficiency as well as immobilization yield. Covalent immobilization of xylanase onto (Alg+PEI/Na) enhanced xylanase activity over a wide range of pHs (4-5.5) comparable to its free formula. As well as an increase in reaction temperature up to 60°C. However, immobilized formula of enzyme showed abroad thermal stability that it retained 79.0% of its initial activity at 70°C up to 30 min whereas, free formula completely lost its activity at this temperature. Thermodynamics studies showed an enhancement in thermal stability at high temperature for the immobilized xylanase. i.e. At 70°C the t and D-value for free formula of enzyme increased from 24 to165 min and from 79.95to 548.23 min, respectively. Moreover, the enzyme stability enhancement for immobilized formula of xylanase was proved with a remarkable increase in enthalpy and free energy. 93% of the immobilized xylanase activity was retained over 6 weeks of storage at -4°C.
用 0.3M Na 改性的海藻酸钠-聚乙烯亚胺凝胶珠用于共价固定化黄曲霉木聚糖酶。SEM 图像显示，加入 Na 后结构扭曲，破坏了提供与木聚糖酶大量共价结合的蛋盒结构的形成。固定在（Alg+PEI/Na）上显示出操作稳定性、固定化效率和固定化产率的提高。木聚糖酶通过共价固定化到（Alg+PEI/Na）上，在较宽的 pH 范围内（4-5.5）提高了木聚糖酶的活性，与游离形式相当。以及反应温度提高到 60°C。然而，酶的固定化形式表现出较宽的热稳定性，在 70°C 下保持 79.0%的初始活性长达 30 分钟，而游离形式在该温度下完全失去活性。热力学研究表明，固定化木聚糖酶在高温下的热稳定性得到增强。即在 70°C 时，游离酶的 t 和 D 值分别从 24 增加到 165 分钟和从 79.95 增加到 548.23 分钟。此外，固定化木聚糖酶的酶稳定性增强得到了证明，焓和自由能显著增加。在-4°C 下储存 6 周，93%的固定化木聚糖酶活性得以保留。
