Trypsin purification using magnetic particles of azocasein-iron composite

•Ferromagnetic particles of azocasein composite (mAzo) were synthesized.•Crude extract from intestines of fish Nile tilapia (Oreochromis niloticus) was exposed mAzo, washed to remove unbound proteins by magnetic field and trypsin was leached off under high ionic strength.•Preparation was achieved containing specific activity about 60 times higher than that of the crude extract.•SDS-PAGE showed protein with molecular weight (24 kDa) similar to reported Nile tilapia trypsin.•mAzo can be reused and applied to purify trypsin from other sources.

This work presents an inexpensive, simple and fast procedure to purify trypsin based on affinity binding with ferromagnetic particles of azocasein composite (mAzo). Crude extract was obtained from intestines of fish Nile tilapia (Oreochromis niloticus) homogenized in buffer (01 g tissue/ml). This extract was exposed to 100 mg of mAzo and washed to remove unbound proteins by magnetic field. Trypsin was leached off under high ionic strength (3 M NaCl). Preparation was achieved containing specific activity about 60 times higher than that of the crude extract. SDS-PAGE showed that the purified protein had molecular weight (24 kDa) in concordance with the literature for the Nile tilapia trypsin. The mAzo composite can be reused and applied to purify trypsin from other sources.