Evaluation of silver carp (Hypophthalmichthys molitrix) skin collagen characteristics recovered by the isoelectric precipitation method

The aim of this study was using the silver carp skin wastes as a potential source of collagen and recovering the soluble collagen in acid and enzyme solution by isoelectric precipitation method. The physicochemical properties of produced collagen investigated as well. Hence, collagen was extracted from the skin of silver carp by acidic and enzymatic methods. Then, soluble collagens were recovered using isoelectric precipitation (Isoelectric-Acid-soluble collagen (I-ASC) and Isoelectric-Pepsin-soluble collagen (I-PSC)) and salting-out (Acid-soluble collagen (ASC) and Pepsin-soluble collagen (PSC) methods. The results showed that the extraction yield and total protein content of ASC and PSC samples were higher than I-ASC and I-PSC samples. But the production yield was the same in all the samples. The high purity of I-ASC and I-PSC collagens represented different total protein content and extraction yield, however similar production yield. The SDS-PAGE pattern confirmed the structure of I-ASC and I-PSC as type I collagen. In addition, the amino acid composition showed high amino acid content for I-PSC. It was estimated that the thermal denaturation temperatures for I-ASC and I-PSC samples laying at 28.70°C and 29.99°C, respectively. Finally, the investigation of collagen solubility at different pH levels and concentrations of NaCl showed that the solubility decreases with increasing ion concentration of the solution, and increases at the pH above and below the isoelectric point. Overall, the results showed that the isoelectric precipitation of soluble collagen produces a high-purity collagen protein that could be an alternative source to replace mammalian collagens.
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