Enzymatic preparation and antioxidative activity of hydrolysate from Rice bran protein

As a protein-rich resource, rice bran protein has not been developed and utilized effectively. In this study, the optimal condition to prepare hydrolysate from rice bran protein was determined by screening protease and conducting single factor experiments along with response surface methodology. Optimal hydrolysate was prepared to further investigate its chemical (DPPH, ABTS, Fe2+) and cellular antioxidative activity. Finally, its amino acid composition was explored. In the results, alcalase was selected and other parameters were: pH 8.5, enzyme-to-substrate ratio 0.38%, and substrate concentration 6%. It was proved that the hydrolysate was an excellent DPPH (EC50 = 5.647) and ABTS (EC50 = 0.195) scavenger as well as good Fe2+(EC50 = 1.765) chelator, showing directly proportional relationships with dose. In cellular antioxidant activity (CAA) assay, the CAA value reached 31.76% at the concentration of 1 mg/mL and the increasing use of rice bran protein hydrolysate significantly improved CAA. Amino acid composition analysis showed that the hydrolysate was rich in glutamic acid (13.02%), aspartic acid (6.68%), arginine (3.34%) and many kinds of hydrophobic amino acids which contribute to the antioxidant property. This research revealed the potential application of rice bran protein hydrolysate in natural antioxidants.