Abstract: The epoxy-modified Fe3O4 magnetic microspheres prepared in our laboratory were used as the carrier to immobilize phospholipase A1 (PLA1). Response surface methodology was used to optimize the immobilization conditions. Furthermore, the properties of the immobilized enzyme were studied. The results showed that the optimal immobilization conditions were determined as follows: buffer pH 4.0, reaction time 1.9 h and enzyme dosage 3.6 mL/g. The activity of the immobilized enzyme obtained under these conditions was 3 675 U/g with an immobilization efficiency of 61.1%. Compared with the free enzyme, the optimal reaction pH was shifted to alkaline pH of 1.0 and the optimal reaction temperature of the immobilized enzyme was increased by 5?℃. The storage stability of the immobilized enzyme was increased as well. And the immobilized enzyme retained about 81.1% of the initial activity after the 8th use for rapeseed oil degumming. Moreover, modern analytical methods such as X-ray diffraction (XRD), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the carrier. The results showed that the nano-sized microspheres were successfully prepared with epoxy-modified surfaces.

Key words: epoxy, Fe3O4 magnetic microspheres, phospholipase A1 (PLA1), immobilization