Sea Urchin Food Waste into Bioactives: Collagen and Polyhydroxynaphtoquinones from P. lividus and S. granularis

Approximately 75,000 tons of different sea urchin species are globally harvested for their
edible gonads. Applying a circular economy approach, we have recently demonstrated that non-
edible parts of the Mediterranean Sea urchin Paracentrotus lividus can be fully valorized into high-value
products: antioxidant pigments (polyhydroxynaphthoquinones—PHNQs) and fibrillar collagen can
be extracted to produce innovative biomaterials for biomedical applications. Can waste from other
edible sea urchin species (e.g., Sphaerechinus granularis) be similarly valorised? A comparative
study on PHNQs and collagen extraction was conducted. PHNQ extraction yields were compared,
pigments were quantified and identified, and antioxidant activities were assessed (by ABTS assay)
and correlated to specific PHNQ presence (i.e., spinochrome E). Similarly, collagen extraction yields
were evaluated, and the resulting collagen-based biomaterials were compared in terms of their
ultrastructure, degradation kinetics, and resistance to compression. Results showed a partially similar
PHNQ profile in both species, with significantly higher yield in P. lividus, while S. granularis exhibited
better antioxidant activity. P. lividus samples showed higher collagen extraction yield, but S. granularis
scaffolds showed higher stability. In conclusion, waste from different species can be successfully
valorised through PHNQ and collagen extraction, offering diverse applications in the biomedical
field, according to specific technical requirements.