Preparation of temperature-sensitive magnetic microspheres for separation and purification of bromelain

The core–shell temperature-responsive Fe 3 O 4 @P(GMA- co -NIPAM)/IDA/Ni 2+ magnetic microspheres were prepared by distillation precipitation polymerization. The morphology, structure, and magnetic property of the magnetic microspheres were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). The obtained microspheres show remarkable affinity to bromelain with the maximum adsorption capacity was 117   mg/g. The magnetic microspheres had the capability of thermal protection to the bromelain. UV–vis, FT-IR and circular dichroism (CD) spectra were determined to demonstrate that the process of adsorption and elution had no negative effect on the structure of bromelain. Finally, the microspheres were applied to purification of bromelain from the crude extract of pineapple peel with satisfactory results.