Large-scale production of microalgae and their bioactive compounds has steadily increased in response to global demand for natural compounds. Spirulina, in particular, has been used due to its high nutritional value, especially its high protein content. Promising biological functions have been associated with Spirulina extracts, mainly related to its high value added blue pigment, phycocyanin. Phycocyanin is used in several industries such as food, cosmetics, and pharmaceuticals, which increases its market value. Due to the worldwide interest and the need to replace synthetic compounds with natural ones, efforts have been made to optimize large-scale production processes and maintain phycocyanin stability, which is a highly unstable protein. The aim of this review is to update the scientific knowledge on phycocyanin applications and to describe the reported production, extraction, and purification methods, including the main physical and chemical parameters that may affect the purity, recovery, and stability of phycocyanin. By implementing different techniques such as complete cell disruption, extraction at temperatures below 45 °C and a pH of 5.5–6.0, purification through ammonium sulfate, and filtration and chromatography, both the purity and stability of phycocyanin have been significantly improved. Moreover, the use of saccharides, crosslinkers, or natural polymers as preservatives has contributed to the increased market value of phycocyanin.

Collagen, the most abundant structural protein in animals, is fundamental for tissue integrity and regeneration. Conventional mammalian sources face limitations related to sustainability, safety, and ethical concerns, underscoring the need for alternative biomaterials. Marine organisms, particularly jellyfish, offer a promising eco-friendly collagen source. In this study, collagen and collagen-derived peptides were extracted from the cnidarian Physalia physalis and biochemically characterized. Circular dichroism demonstrated partial loss of triple-helix structure, while SDS-PAGE revealed type I collagen related α-chains together with low-molecular-weight fragments. The hydrolyzed collagen fractions exhibited keratinocyte and fibroblast cytocompatibility and increased keratinocyte migration. Moreover, P. physalis-derived peptides modulated inflammatory cytokine release in lipopolysaccharide-stimulated macrophages reducing tumor necrosis factor (TNF)-α by 38% and increasing interleukin (IL)-10 by 29%. Based on these results, a stable bioactive serum formulation incorporating P. physalis collagen peptides was developed. Overall, this work demonstrates that bioactive peptides from P. physalis possess immunomodulatory and regenerative potential and represent a promising new marine resource for cosmetic applications.

Physalia physalis, commonly known as the Portuguese Man o’ War, is one of the most venomous members of the Cnidaria yet is poorly understood. This article investigates the toxicity of P. physalis venom by assessing its behavioral and toxicological effects on Drosophila melanogaster. The venom administered orally revealed dose- and time-dependent mortality, with an LD50 of 67.4 μg per fly. At sublethal doses, the treated flies displayed uncoordinated movement and fell when attempting to climb. Real-time analysis of flies exposed to the venom revealed hyperexcitability followed by paralysis, with phenotypes similar to those observed in vertebrate models. The venom was shown to be non-thermolabile, as no significant differences in behavior and locomotion were observed between flies exposed to untreated or thermally treated venom. The circadian rhythm alterations, the enhanced light attraction, and the reduction in heat avoidance suggest altered neuronal function. This abnormal behavior indicates that the venom contains bioactive molecules, opening avenues for discovering new compounds with potential for pharmacological applications.