Acid and enzymatic extraction of collagen from Atlantic cod (Gadus Morhua) swim bladders envisaging health-related applications

Atlantic cod is processed industrially for food purposes, with several by-products being directed to animal feed and other ends. Looking particularly into swim bladders, the extraction of collagen can be a valuable strategy for by-product valorization, explored in the present work for the first time. Collagen was extracted using acetic acid (ASCsb) and pepsin (PSCsb) with yields of 5.72% (w/w) and 11.14% (w/w), respectively. SDS-PAGE profile showed that the extracts were compatible with type I collagen. FTIR, CD and XRD results suggest that the PSCsb structure underwent partial denaturation, with microDSC showing a band at 54 ºC probably corresponding to a melting process, while ASCsb structure remained intact, with preserved triple helix and a denaturation temperature of 29.6 ºC. Amino acid composition indicates that the total content of proline-like amino acids was 148/1000 residues for ASCsb and 141/1000 residues for PSCsb, with a hydroxylation degree of about 37%. The extracts exhibited a typical shear thinning behavior, interesting property regarding their further processing toward the development of biomaterials. In this regard, assessment of metabolic activity of human fibroblast cells cultured in the presence of collagen extracts with concentrations up to 3mg/mL revealed the absence of cytotoxic behavior. Collagen extracts obtained from Atlantic cod swim bladders shown attractive properties regarding their use in cosmetic or biomedical applications.The authors would like to acknowledge to European Union for the financial support under the scope of European Regional Development Fund (ERDF) through the Structured Project NORTE-01-0145-FEDER-000021 (Norte2020) and under the scope of the European Union Seventh Framework Programme (FP7/2007-2013) through grant agreement ERC-2012-ADG 20120216-321266 (ERC Advanced Grant ComplexiTE). The Portuguese Foundation for Science and Technology is also acknowledged for the PhD grant of A. L. A under Doctoral Programme Do ~ Mar (PD/BD/127995/2016), as well as Norte2020 Regional Programme for the PhD grant of C. O. (Norte-08-5369-000037)