The differences in the IC₅₀(g GAE) between DPPH and ABTS assays of date cultivars.

In this study, a new support has been developed by immobilization of α-amylase onto modified magnetic Fe₃O₄-nanoparticles. The characterization of soluble and immobilized α-amylases with regards to kinetic parameters, pH, thermal stability and reusability was studied. The effect of polypyrrole/silver nanocomposite (PPyAgNp) percentage on weight of Fe₃O₄ and pH on the immobilization of α-amylase was studied. The highest immobilization efficiency (75%) was detected at 10% PPyAgNp/Fe₃O₄-nanocomposite and pH 7.0. Immobilization of α-amylase on PPyAgNp/Fe₃O₄-nanocomposite was characterized by FT-IR spectroscopy and scanning electron microscopy. The reusability of the immobilized enzyme activity was 80% of its initial activity after 10 reuses. The immobilized enzyme was more stable towards pH, temperature and metal ions compared with soluble enzyme. The kinetic study appeared higher affinity of immobilized enzyme (K_m 2.5 mg starch) compared with soluble enzyme (K_m 3.5 mg starch). In conclusion, the immobilization of α-amylase on PPyAgNp/Fe₃O₄-nanocomposite could successfully be used in industrial and medical applications.