Peptide extraction from silver carp (Hypophthalmichthys molitrix) scales via enzymatic hydrolysis and membrane filtration

In this work, peptides were extracted from Silver carp (SC) scales via protease hydrolysis and separated using two membranes (M1 and M2). The results revealed that the water: SC scale ratios of 50.6 mL/g, alkaline protease 1 (AP1) dose of 2313.6 U/mL, and pH of 8.14 were the optimal hydrolysis conditions, and the peptide yield reached 88.77 +/- 0.32%. The optimal conditions of peptide separation were clarified: the operating pressure of the M1 (M2) was 0.25 (0.4) MPa, the liquid temperature was 30 degrees C, and the operation time was 65 min. In this case, the per-meability of the M1 (M2) reached 91.73 +/- 96% (79.83 +/- 7.23%), and the average molecular weight of the peptides was 758 Da (576 Da). Compared with M1 peptides, M2 peptides contained more acidic and aromatic amino acids exhibiting free-radical scavenging and tyrosinase inhibition properties. It might provide a way to utilize SC scales as a promising material to produce bioactive peptides.