Production, purification and activity evaluation of three novel antioxidant peptides obtained from grass carp (Ctenopharyngodon idella) scale waste by microbial protease BaApr1 hydrolysis

In this study, an alkaline protease BaApr1 from the Bacillus altitudinis W3 was chosen to hydrolysis grass carp (Ctenopharyngodon idella) scales. The hydrolysate of alkaline protease BaApr1 exhibited the best antioxidant activity compared to other protease hydrolysates. The optimal hydrolysis conditions for BaApr1 were an enzyme dosage of 1250 U/g, a hydrolysis time of 7 h, a pH of 9.5 and a temperature of 50 °C. Three novel peptides were purified using ultrafiltration, anion exchange chromatography, gel filtration chromatography and ultra-performance liquid chromatography, and their sequences were identified as Tyr-Val-Gln-Ala-Gly-Ala-Ala-Gly-Ala-Ala-Ala-His (SHP2), Val-Lys-Leu-Tyr-Val-Leu-Leu-Val-Pro (SHP4), and Val-Gln-Val-Leu-Ala-Gly-Pro-Val-Val-Lys-Leu-Tyr (SHP5) with molecular weights of 1086.53 Da, 1043.69 Da and 1285.79 Da, respectively. Among them, SHP2 exhibited the highest scavenging activity on DPPH· (EC50 4.08 mg/mL), ABTS+· (EC50 0.23 mg/mL) and HO· (EC50 2.78 mg/mL), and the strongest reducing power. Additionally, SHP5 can significantly inhibit lipid peroxidation in the linoleic acid system. In conclusion, three peptides isolated from scales of hydrolysate of grass carp showed great antioxidant activity and might be used as potential food ingredients and pharmaceuticals.