Study of the poly (butylene adipate-co-terephthalate)/poly (vinyl alcohol) coated recycled Fe ₃ O ₄ magnetic particle carriers for immobilization penicillin G acylase

In this work, the process began by coating a layer of poly (butylene adipate-co-terephthalate) (PBAT)/poly (vinyl alcohol) (PVA) on the surface of magnetic Fe₃O₄ particles (MPs) obtained from the nickel slag. Then, it was grafted by glutaraldehyde (GA) to obtain Fe₃O₄@PBAT/PVA-g-GA MPs, which were used as a carrier. Finally, the immobilized PGA was achieved by forming a covalent bond through the Schiff base reaction. To confirm each stage, employed Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibration sample magnetometer (VSM), scanning electron microscope-energy spectroscopy of dispersive x-rays (SEM-EDS), inductively coupled plasma mass spectrometry (ICP-MS), and x-ray photoelectron spectrophotometry (XPS). The immobilization conditions were studied and optimized to improve immobilized PGA stability and catalytic activity. The immobilization of PGA demonstrated its optimal performance under the process conditions. The results were achieved using a 2.5 vol.% enzyme solution concentration, a pH of 8.0, an immobilization time of 24 h, and an immobilization temperature of 37 °C. Under these conditions, the immobilized PGA exhibited an enzyme activity recovery (<i>EAR</i>) of 93.71%, an enzyme activity (<i>EA</i>) of 31,367 U/g, and an enzyme loading capacity (<i>EL</i>C) of 111 mg/g. The operating stability, reusability, and storage stability of Fe₃O₄@PBAT/PVA-g-GA-PGA MPs were investigated. Comparatively, immobilized PGA exhibited superior operational and storage stability compared to free PGA. Even after 11 repeated uses, the immobilized PGA retained 58% of its initial activity, while the carrier recovery (<i>Re</i>) reached 82%. This indicated that the immobilized PGA MPs offer improved longevity and efficiency, making them a promising choice for practical applications.