Al-Harbi Sami A, Almulaiky Yaaser Q
Department of Chemistry, University College in Al-Jamoum, Umm Al-Qura University, Makkah, Saudi Arabia.
Department of Chemistry, Collage of Science and Arts at Khulis, University of Jeddah, Jeddah, Saudi Arabia.
Heliyon. 2024 Mar 19;10(6):e28396. doi: 10.1016/j.heliyon.2024.e28396. eCollection 2024 Mar 30.
Copper-based metal-organic frameworks (BDC-Cu MOFs) were synthesized via a casting approach using 1,4-benzene dicarboxylic (BDC) as organic ligand and their properties characterized. The obtained materials were then utilized to immobilize the α-amylase enzyme. The chemical composition and functional components of the synthesized support (BDC-Cu MOFs) were investigated with Fourier transform infrared spectroscopy (FTIR), the surface morphology was determined with scanning electron microscopy (SEM), and the elemental composition was established with energy dispersive X-ray (EDX) analyses. X-ray diffraction (XRD) was employed to analyze the crystallinity of the synthesized DBC-Cu MOFs. The zeta potentials of DBC-Cu MOFs and DBC-Cu MOFs@α-amylase were determined. The immobilized α-amylase demonstrated improved catalytic activity and reusability compared to the free form. Covalent attachment of the α-amylase to BDC-Cu provided an immobilization yield (IY%) of 81% and an activity yield (AY%) of 89%. The immobilized α-amylase showed high catalytic activity and 81% retention even after ten cycles. Storage at 4 °C for eight weeks resulted in a 78% activity retention rate for DBC-Cu MOFs@α-amylase and 49% retention for the free α-amylase. The optimum activity occurred at 60 °C for the immobilized form, whereas the free form showed optimal activity at 50 °C. The free and immobilized α-amylase demonstrated peak catalytic activities at pH 6.0. The maximum reaction velocities (Vmax) values were 0.61 U/mg of protein for free α-amylase and 0.37 U/mg of protein for BDC-Cu MOFs@α-amylase, while the Michaelis‒Menten affinity constants (Km) value was lower for the immobilized form (5.46 mM) than for the free form (11.67 mM). Treatments of maize flour and finger millet samples with free and immobilized α-amylase resulted in increased total phenolic contents. The enhanced antioxidant activities of the treated samples were demonstrated with decreased IC values in ABTS and DPPH assays. Overall, immobilization of α-amylase on BDC-Cu MOFs provided improved stability and catalytic activity and enhanced the antioxidant potentials of maize flour and finger millet.
通过浇铸法合成了以1,4 - 苯二甲酸（BDC）为有机配体的铜基金属有机框架材料（BDC - Cu MOFs），并对其性能进行了表征。然后将所得材料用于固定α - 淀粉酶。采用傅里叶变换红外光谱（FTIR）研究了合成载体（BDC - Cu MOFs）的化学成分和功能成分，用扫描电子显微镜（SEM）测定了表面形态，并用能量色散X射线（EDX）分析确定了元素组成。采用X射线衍射（XRD）分析合成的DBC - Cu MOFs的结晶度。测定了DBC - Cu MOFs和DBC - Cu MOFs@α - 淀粉酶的zeta电位。与游离形式相比，固定化α - 淀粉酶表现出更高的催化活性和可重复使用性。α - 淀粉酶与BDC - Cu的共价连接提供了81%的固定化产率（IY%）和89%的活性产率（AY%）。固定化α - 淀粉酶即使在十个循环后仍表现出高催化活性和81%的保留率。在4℃下储存八周后，DBC - Cu MOFs@α - 淀粉酶的活性保留率为78%，游离α - 淀粉酶的活性保留率为49%。固定化形式在60℃时出现最佳活性，而游离形式在50℃时表现出最佳活性。游离和固定化α - 淀粉酶在pH 6.0时表现出峰值催化活性。游离α - 淀粉酶的最大反应速度（Vmax）值为0.61 U/mg蛋白质，BDC - Cu MOFs@α - 淀粉酶的最大反应速度（Vmax）值为0.37 U/mg蛋白质，而固定化形式的米氏亲和常数（Km）值（5.46 mM）低于游离形式（11.67 mM）。用游离和固定化α - 淀粉酶处理玉米粉和龙爪稷样品导致总酚含量增加。在ABTS和DPPH测定中，处理后样品的IC值降低，表明其抗氧化活性增强。总体而言，将α - 淀粉酶固定在BDC - Cu MOFs上提高了稳定性和催化活性，并增强了玉米粉和龙爪稷的抗氧化潜力。
