Microalgae offer a sustainable and versatile source of bioactive compounds. Their rapid growth, efficient CO₂ utilization, and adaptability make them a promising alternative to traditional production methods. Key compounds, such as proteins, polyunsaturated fatty acids (PUFAs), polyphenols, phytosterols, pigments, and mycosporine-like amino acids (MAAs), hold significant commercial value and are widely utilized in food, nutraceuticals, cosmetics, and pharmaceuticals, driving innovation across multiple industries. Their antiviral and enzyme-producing capabilities further enhance industrial and medical applications. Additionally, microalgae-based biostimulants and plant elicitor peptides (PEPs) contribute to sustainable agriculture by enhancing plant growth and resilience to environmental stressors. The GRAS status of several species facilitates market integration, but challenges in scaling and cost reduction remain. Advances in biotechnology and metabolic engineering will optimize production, driving growth in the global microalgae industry. With increasing consumer demand for natural, eco-friendly products, microalgae will play a vital role in health, food security, and environmental sustainability.

Selenium (Se) is essential for human and animal nutrition, playing a key role in antioxidant and immune functions. Organic Se is better for supplementation because it is more efficiently assimilated and less toxic than its inorganic form. Due to the scarcity of Se in European soils, supplementation in feed and food is necessary. Currently, inorganic Se (sodium selenite and selenate) and organic Se in Se-enriched yeast are approved by the European Food Safety Authority (EFSA) to address Se deficiency. However, Se-enriched microalgae present a promising alternative. By supplementing their growth media with Se, microalgae convert it into organic forms like Se-cysteine and Se-methionine, creating Se-enriched biomass. This biomass can serve as a valuable Se source with the additional benefits of microalgae. This review evaluates the viability of microalgae as a Se supplementation vehicle in food and feed and explores its commercial applications in the European Union (EU), along with emerging projects and innovations in the field.

The marine environment is a rich source of bioactive compounds with a wide range of applications. In this study, 65 extracts from sponges, ascidians, and a gorgonian collected from the Yucatán Peninsula, Mexico, were evaluated for their modulatory effects on the growth of four microalgal species. Some extracts were found to exhibit pronounced algicidal activity, while others promoted growth. Bioassay-guided fractionation of the extract from Haliclona (Rhizoniera) curacaoensis led to the identification of arenosclerins A and C as potent algicidal agents, active across all tested microalgae. In contrast, the extract from Halichondria melanadocia enhanced microalgal growth, and chemical analysis revealed the presence of medelamine A and B as putative growth-promoting compounds. This study provides a new report on microalgae-modulating activities of marine sponge metabolites. The dual activity observed, both inhibitory and stimulatory, not only contributes to our understanding of marine compound diversity but also underscores the potential of these marine-derived compounds for sustainable environmental management practices.