Ahmed Samia A, Abdella Mohamed A A, El-Sherbiny Gamal M, Ibrahim Atef M, El-Shamy Aliaa R, Atalla Sherien M M, Hassan Mohamed E
Chemistry of Natural and Microbial Products Department, National Research Centre, Dokki, Cairo, Egypt.
Department of Botany and Microbiology, Faculty of Science (Boys), Al-Azhar University, Cairo, Egypt.
Biotechnol Rep (Amst). 2020 Feb 26;26:e00443. doi: 10.1016/j.btre.2020.e00443. eCollection 2020 Jun.
strain-MK1 α-amylase was successfully immobilized on Chitosan-magnetic nanoparticles (Ch-MNP) that had been modified with polyethyleneimine (PEI) and glutaraldehyde (GA). Optimization of Ch-MNP/PEI/GA beads modification by Central Composite design enhanced the immobilization yield (IY %) by 1.5-fold. Ch-MNP/PEI/GA was characterized before and after modification and immobilization by FTIR and SEM. Ch-MNP/PEI/GA/Enzyme showed the same pH optima of free enzyme, while an elevation 10 °C in temperature optima was observed after its immobilization. Ch-MNP/PEI/GA/Enzyme displayed higher and values (2.1 and 1.2-fold) and lower / ratio (1.7-fold), respectively than the free enzyme. Compared to the free enzyme, Ch-MNP/PEI/GA/Enzyme exhibited lower activation energy, lower deactivation constant rate, higher -values, higher half-life, and higher energy for denaturation. Immobilization of α-amylase increased enthalpy (4.2-fold), free energy (1.1-fold) and decreased entropy (4.6-fold) of thermal inactivation. A significant increase in pH stability of Ch-MNP/PEI/GA/Enzyme was observed especially at alkaline pH values. In addition, Ch-MNP/PEI/GA/Enzyme preserved 83.2 % of its initial activity after 15 consecutive cycles. When storing Ch-MNP/PEI/GA/Enzyme at 4 °C the residual activity was 100 and 86 %, respectively after 21 and 40 days. Finally, immobilization process improved the catalytic properties and stabilities, thus raising the suitability for industrial processes with lower cost and time.
菌株MK1α-淀粉酶成功固定在经聚乙烯亚胺（PEI）和戊二醛（GA）修饰的壳聚糖磁性纳米颗粒（Ch-MNP）上。通过中心复合设计对Ch-MNP/PEI/GA微珠修饰进行优化，使固定化产率（IY%）提高了1.5倍。通过傅里叶变换红外光谱（FTIR）和扫描电子显微镜（SEM）对修饰和固定前后的Ch-MNP/PEI/GA进行了表征。Ch-MNP/PEI/GA/酶显示出与游离酶相同的最适pH值，而固定化后观察到最适温度升高了10°C。Ch-MNP/PEI/GA/酶的 值和 值分别比游离酶高（2.1倍和1.2倍），而 / 比值比游离酶低（1.7倍）。与游离酶相比，Ch-MNP/PEI/GA/酶表现出更低的活化能、更低的失活常数速率、更高的 值、更长的半衰期和更高的变性能量。α-淀粉酶的固定化增加了热失活的焓（4.2倍）、自由能（1.1倍）并降低了熵（4.6倍）。观察到Ch-MNP/PEI/GA/酶的pH稳定性显著增加，尤其是在碱性pH值下。此外，Ch-MNP/PEI/GA/酶在连续15个循环后保留了其初始活性的83.2%。当将Ch-MNP/PEI/GA/酶储存在4°C时，在21天和40天后残余活性分别为100%和86%。最后，固定化过程改善了催化性能和稳定性，从而提高了其在工业过程中的适用性，降低了成本和时间。
