The valorization of Atlantic cod (Gadus morhua) frames from a filleting industry was investigated using subcritical water extraction and hydrolysis (SBW) at different temperatures (90, 140, 190 and 250 °C) and 100 bar to obtain extracts rich in proteins, peptides and amino acids. Up to 57.7 g of extract per 100 g of codfish frames were obtained, with nearly total recovery of the protein fraction. At each temperature, protein extracts of decreasing molecular weight were obtained, according to SEC-GPC results. Most of the protein present in the raw material and extracts was collagen and collagen fragments, as suggested by the amino acid profile. Codfish SBW extracts did not show cytotoxicity in the range of concentrations tested and the protein extract obtained at the lowest temperature (90 °C) showed the highest anti-inflammatory potential in human intestinal epithelium cell model. The mineralized residue left after SBW treatment of cod frames was identified as practically pure, crystalline, hydroxyapatite, that may find applications in biomedical field and hard-tissue engineering. This study shows the possible valorization of cod frames using green extraction methods such as SBW process to obtain protein extracts for food and nutraceutical applications.

The fishery industry generates large amounts of waste (20–75% (w/w) of the total caught fish weight). The recovery of bioactive compounds from residues and their incorporation in cosmetics represents a promising market opportunity and may contribute to a sustainable valorisation of the sector. In this work, protein-rich extracts obtained by high-pressure technologies (supercritical CO₂ and subcritical water) from sardine (Sardina pilchardus) waste and codfish (Gadus morhua) frames were characterized regarding their cosmeceutical potential. Antioxidant, anti-inflammatory and antibacterial activities were evaluated through chemical (ORAC assay), enzymatic (inhibition of elastase and tyrosinase), antimicrobial susceptibility (Klebsiella pneumoniae, Staphylococcus aureus and Cutibacterium acnes) and cell-based (in keratinocytes-HaCaT) assays. Sardine extracts presented the highest antibacterial activity, and the extract obtained using higher extraction temperatures (250 °C) and without the defatting step demonstrated the lowest minimum inhibitory concentration (MIC) values (1.17; 4.6; 0.59 mg/mL for K. pneumoniae, S. aureus and C. acnes, respectively). Codfish samples extracted at lower temperatures (90 °C) were the most effective anti-inflammatory agents (a concentration of 0.75 mg/mL reduced IL-8 and IL-6 levels by 58% and 47%, respectively, relative to the positive control). Threonine, valine, leucine, arginine and total protein content in the extracts were highlighted to present a high correlation with the reported bioactivities (R² ≥ 0.7). These results support the potential application of extracts obtained from fishery industry wastes in cosmeceutical products with bioactive activities.