Copper-based metal-organic frameworks (BDC-Cu MOFs) as supporters for α-amylase: Stability, reusability, and antioxidant potential

Sami A Al-Harbi; Yaaser Q Almulaiky

doi:10.1016/j.heliyon.2024.e28396

Copper-based metal-organic frameworks (BDC-Cu MOFs) as supporters for α-amylase: Stability, reusability, and antioxidant potential

Heliyon. 2024 Mar 19;10(6):e28396. doi: 10.1016/j.heliyon.2024.e28396. eCollection 2024 Mar 30.

Authors

Sami A Al-Harbi¹, Yaaser Q Almulaiky^{2

3}

Affiliations

¹ Department of Chemistry, University College in Al-Jamoum, Umm Al-Qura University, Makkah, Saudi Arabia.
² Department of Chemistry, Collage of Science and Arts at Khulis, University of Jeddah, Jeddah, Saudi Arabia.
³ Chemistry Department, Faculty of Applied Science, Taiz University, Taiz, Yemen.

Abstract

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 IC₅₀ 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.

Keywords: Antioxidant activity; Immobilization; Metal-organic frameworks; α-Amylase.