Application of magnetic immobilized papain on passivated rice bran lipase

Magnetically immobilized papain is prepared by magnetic Fe₃O₄/P (GMA-EDGMA-St) composite carrier with the addition of 12.0 mg/mL papain, 5.0% glutaraldehyde and 4 hour reaction time. The characteristic absorption peaks of each functional group were shown by infrared light. The X-diffraction pattern showed six main diffraction peaks with a magnetization value of 37.60 emu/g. TEM and SEM showed that free papain was immobilized on the magnetic carrier with an average particle size of 196 nm. The concentration of the enzyme was 122.25 mg/g, enzyme activity recovery was 55,263 U/g, compared with the free enzyme, the magnetically immobilized papain indicated higher acid-base tolerance and thermal stability, pH tolerance increased from 7.0 to 8.0, temperature tolerance increased from 60 °C to 65 °C. The magnetically immobilized papain was added to the rice bran under the condition that every gram of rice bran is submerged in 6 g of phosphate buffer solution. The magnetically immobilized papain was 0.36 mg/g, and the passivation time was 120 min. The relative activity of lipase in rice bran was 19.93%. After repeated use eight times, the relative activity of magnetically immobilized papain remained above 72%.