Bio/sonochemical conversion of fish backbones into bioactive nanospheres

•The valorization of salmon co-streams into cosmetic ingredients is proposed.•An enzymatic treatment was applied to produce anti-ageing and antioxidant biopeptides.•The biopeptides were unstable in aqueous medium and prone to microbial contamination.•Stable biopeptide-shell and tea tree oil-core nanospheres were generated.•The nanospheres presented improved antioxidant and antimicrobial properties.

Salmon backbones, co-streams of salmon processing industry, were transformed into stable, odour-free ingredients for cosmetics. First, the backbones were hydrolysed using commercial proteases (Bromelain + Papain, Trypsin, Corolase® 7089 and Protamex®) in order to accomplish the release of fish protein hydrolysates (FPH), which showed antioxidant activity and aptitude to inhibit skin-degrading and inflammatory enzymes. However, due to the FPH instability in aqueous solution and propensity for microbial contamination, their bioactive properties were entirely lost only after 24 h. To overcome the low stability and prevent the effect loss, a sonochemical technology was then employed to transform the FPH into stable tea tree oil-filled bioactive peptide-shell nanospheres (NS). Such transformation boosted the FPH antioxidant potential, which was further reflected in protection of fibroblasts from UV damage. In the form of NSs, the FPH resisted microbial contamination for more than 6 months and presented antimicrobial activity against Escherichia coli and Staphylococcus aureus. In addition, the fish odour was eliminated after the NSs processing, thus addressing this important challenge for using fish raw materials in cosmetics. This work suggests an alternative high value use of the fishery co-streams and expands their application potential beyond their current use as fish or animal feed.

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