Circular approach for the sustainable valorization of IMTA Codium sp. for multitarget skin care applications

This study developed an integrated approach for the sustainable exploitation of the green seaweed Codium sp., cultivated in an integrated multitrophic aquaculture (IMTA) system, as a source of ingredients for functional skin care products. Biomass was extracted following European Union cosmetic regulations using a polarity gradient system, yielding five fractions, and the antioxidant, cytotoxic, anti-inflammatory, photoprotective, and wound-healing activities of the extracts were evaluated in vitro using RAW 264.7 macrophages and HaCaT keratinocytes. Antimicrobial activity was also assessed against Staphylococcus epidermidis, Staphylococcus aureus , and Cutibacterium acnes , while the post-extracted biomass was valorized as biochar via conventional pyrolysis, hydrothermal carbonization, and acid-mediated carbonization. Fraction F1 showed the strongest photoprotective effect, reducing ROS production in UV-exposed HaCaT cells by 33%, whereas fractions F3 and F5 exhibited the highest wound-healing potential, increasing cell migration by 31% and 44%, respectively. Fractions F2 and F3 showed the greatest antimicrobial activity against C. acnes (IC50 = 67.74 and 51.23 µg/mL, respectively), with effects possibly linked to membrane potential disturbance. Biochars produced by the innovative routes had lower ash content than pyrochar, suggesting promise as precursors for activated carbons or as scaffolds for other applications. Overall, these findings highlight the potential of IMTA-produced Codium sp. as a sustainable source of bioactive ingredients for functional skin care applications and as feedstock for value-added biochars with potential use in activated carbon and biomaterial development.