Extraction, purification and characterization of collagen peptide prepared from skin hydrolysate of sturgeon fish

Abstract Collagen peptides from marine organisms have drawn great attention in food, cosmetics and medicine owing to their multiple functions including antioxidant, anticancer, cardioprotection, skin protection, and wound healing effects. Recent reports have revealed that a large amount of solid waste is discarded from fisheries that could be used for producing high value-added products. This study aims to extract and purify collagens and peptides from sturgeon fish skin, a by-product obtained during the processing of sturgeon fish. A high yield of acid-soluble collagen was obtained by using acetic acid for extraction followed by sonication, while a high yield of pepsin-soluble collagen (PSC) was shown by acetic acid and sonication followed by adding acetic acid and pepsin to the residue for extraction and then sonication. Two-stage hydrolysis with pepsin first followed by flavourzyme was necessary to produce high yield of PSC peptide. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis analysis revealed the presence of type I collagen and the structural integrity was confirmed by Fourier transform infrared spectroscopy analysis. Flavourzyme was more effective in hydrolyzing PSC into peptides with low molecular weight (MW) than pepsin, papain, alcalase, and trypsin. Purification of PSC hydrolysate with a Sephadex G-10 column to exclude peptide with MW>700 Da or ultrafiltration with a dialysis membrane with MW cutoff of 500 Da produced PSC peptides with MW<700 Da and MW<728 Da accounting, respectively, accounting for 40% or 52% of all the fragments based on low resolution-matrix assisted laser desorption/ionization-mass spectrometry (LR-MALDI-MS). In conclusion, with sturgeon fish skin as raw material and flavourzyme level of 5%, the highest degree of hydrolysis and yield of PSC peptides with low MW was obtained by controlling the pH at 8, temperature at 50 °C, ratio of PSC to deionized water at 1:40 (mass concentration), hydrolysis time at 4 h, and ultrafiltration with dialyzing membrane MW cutoff of 500 Da.