Unveiling an innovative sustainable blue resource-ecofriendly extraction technique towards a circular economy: Optimization of natural deep eutectic solvent and ultrasonication synergistic pathways for type-I collagen refined recovery from discarded fish scales.

A vast sum of fish waste is being annually discarded by marine fishing industries imposing serious environmental pollution concerns. However, these aquatic discarded matters are captivating sources of collagen, a fibrous protein with eminent social and economic relevance. Collagen is conventionally recovered using outdated complex processes requiring many reagents, multiple steps, and extended periods. Hereupon, the current project is the first work on the isolation of Seabass fish scales (FSC) type-I collagen, with preserved secondary and triple helical structures of the native collagen, developing a simple, green, cost-effective, and eco-friendly methodology, utilizing sustainable natural deep eutectic solvents (NADES)-assisted ultrasonication (US) technical route. The operational conditions were optimized based on the one-factor-at-a-time modeling to maximize the yield with no alteration of collagen integrity. Recorded data confirmed type-I collagen with preserved triple helix integrity and thermal stability, improved bio-functionalities, in vitro fibril formation, and functional performances. Finally, the in vitro hemolysis and cytotoxicity tests confirmed the extracted collagens biocompatibility, demonstrating the feasibility of Seabass FSC waste and a NADES-coupled US brief process (20 min) to establish a more sustainable eco-friendly pathway to isolate high-quality type I-collagen, as an attempt to rise industries awareness about wastes valorization within the scheme of circular economy.