Antioxidant and anti-freezing peptides from salmon collagen hydrolysate prepared by bacterial extracellular protease.

Extracted salmon skin collagen was hydrolysed with the free or immobilized extracellular protease of Vibrio sp. SQS2-3. The hydrolysate exhibited anti-freezing activity (>3 kDa) and antioxidant activity (<3000 Da) after ultrafiltration. The antioxidant peptide was further purified by size-exclusion chromatography and found to scavenge DPPH (73.29 ± 1.03%), OH (72.73 ± 3.34%,), and intracellular ROS in HUVECs; protect DNA against oxidation-induced damage; and have an ORAC of 2.78 ± 0.28 mmol TE/g. The antioxidant peptide fraction was identified using mass spectrometry, and nineteen salmon collagen-sourced peptides were obtained. Of these, the peptide Pro-Met-Arg-Gly-Gly-Gly-Gly-Tyr-His-Tyr is a novel sequence and was the major component; this peptide was shown to have antioxidant activity via the ORAC assay (2.51 ± 0.14 mmol TE/g). These results suggested that the protease from Vibrio sp. SQS2-3 is suitable for preparation of anti-freezing peptides and antioxidant peptides in a single step and represents a comprehensive use of fish skin collagen.