SUSTAINABLE EXPLOITATION OF DISCARDED FISHERIES RESOURCES AND DEVELOPMENT OF ADDED VALUE BIOPRODUCTS

Marine collagen is a precious resource that in recent years has been gaining great success in the cosmetic, food, and biomedical industries thanks to its extreme versatility, bioactive properties, and cytocompatibility with human tissues. Derived mainly from fishing by-products, such as skins, scales, and bones, or from marine organisms obtained from by-catches, such as jellyfish, it represents a safe and sustainable alternative to mammalian collagen. Collagen is the most abundant protein in nature, playing a fundamental role as a mechanical and structural support to tissues. During the PhD, the jellyfish Rhizostoma pulmo collected during a bloom in the Mediterranean Sea was used for collagen extraction using innovative mechanical pre- treatments (e.g., sonication, freeze-drying, and homogenization) to improve yield and reduce the use of chemical solvents. The results showed that sonication significantly increased collagen yield, especially in R. pulmo oral arms, with an increase of up to 10- fold compared to traditional methods. On the contrary, freeze-drying and homogenization had no effect. Moreover, the extracted collagen was subsequently characterized by ATR- FTIR and SDS-PAGE, confirming its structure and purity. This study highlighted the effectiveness of sonication as an adjuvant mechanical treatment in improving eco- friendly extraction processes with potential applications in biotechnology. Moreover, collagen extracted from the jellyfish R. pulmo was also used to create membranes based on marine collagen and methacrylated chitosan for liver tissue engineering applications. The analyses showed that the addition of marine collagen improves the membranes mechanical properties, hydrophilicity, and porosity, promoting the engraftment of liver cells. Another study performed during the PhD focused on the extraction, by the classical method, of acid-soluble collagen from sea bass (Dicentrarchus labrax) skin, and its use in the development of biocompatible scaffolds based on marine collagen/chitosan, for biomedical applications. The incorporation of marine collagen into the scaffolds improved the mechanical properties, and showed a greater porosity of the scaffolds compared to the scaffolds based on chitosan alone. Also, in vitro cytotoxicity tests confirmed a high cytocompatibility for the murine fibroblast L929 cell line. On the other hand, marine peptides and hydrolysates also represent an important category of high added value biomolecules derived from fishery by-products and by-catch, such as jellyfish or starfish. In a further study, the bioactive potential of soluble and hydrolysed proteins from the freeze-dried jellyfish Cotylorhiza tuberculata collected in the 2 Mediterranean Sea was explored. Soluble proteins were extracted from the umbrella and oral arms using phosphate-buffered saline, then the insoluble portion was subjected to sequential enzymatic hydrolysis with pepsin and collagenase to obtain hydrolysed proteins. The obtained fractions were fractionated based on the molecular weight through membrane filters with different cut-offs. The fractions were analyzed for their antioxidant, antiproliferative, and anti-inflammatory activities. The ABTS assay revealed strong antioxidant properties in all samples, especially in the collagenase hydrolysed fractions. In vitro cell viability tests on A2058 melanoma and HaCaT cell lines indicated that some fractions showed good antiproliferative activity and low cytotoxic activity. Furthermore, a simulated gastrointestinal digestion model demonstrated that acetic acid hydrolysis of the umbrella fractions reduced IL-6 levels, suggesting anti-inflammatory effects. This study highlighted how peptides from the jellyfish C. tuberculata could be used as nutraceutical bioactive ingredients. Similarly, fractions extracted from the digestion of the starfish Asterias rubens, performed by three different enzymes, Food Pro PNL, Corolase 8000, and Corolase 7089, were analyzed for their properties. The hydrolysates were produced from raw starfish, deproteinized starfish, and demineralized starfish. The protein purity of the hydrolysates prepared from the deproteinized samples was higher than those prepared from whole starfish, even showing a lower yield. Also in this case, results showed good antioxidant and antiproliferative activity of the hydrolysates, suggesting that starfish could be effectively utilized for nutraceutical and pharmaceutical applications.