Abstract: In this investigation, Fe3O4-SiO2 magnetic nanoparticles were used as a carrier to study the effects of different operating conditions on the immobilization of phospholipase A1. The optimal conditions determined using response surface methodology were as follows: pH 6.7, temperature 30 ℃, immobilization time 7.9 h, glutaraldehyde concentration 8.3%, and amount of enzyme 8.2 mL/50 mg. Under these conditions, the recovery of enzymatic activity was as high as 63.6% and the percentage of protein immobilization was 68%. The chemical composition, morphological structure and particle size of the immobilized phospholipase were characterized. The results showed that the efficiency of phospholipase immobilization was good; uniform particle size distribution was observed with a mean particle size of about 200 nm. The thermal, pH and storage stability of the immobilized enzyme were enhanced relative to the free one. The optimum reaction temperature for the immobilized enzyme was 50 ℃ and optimum pH 6.0. Over 60% of the enzymatic activity remained after tenth repeated use.

Key words: phospholipase A1, magnetic nanoparticles, immobilization