Biotechnology Journal International

Cyanobacteria are photosynthetic prokaryotes that appeared on Earth more than 2.6 billion years ago. They are found in many environments, including land and water, and play an important role in primary production and nitrogen fixation. However, because they need sunlight for photosynthesis, cyanobacteria are often exposed to increasing levels of ultraviolet (UV) radiation at the Earth’s surface. Over time, cyanobacteria have developed different ways to protect themselves from UV radiation. One important mechanism is the production of mycosporine-like amino acids (MAAs), which act as natural UV protectants. MAAs are small, water-soluble, and colourless compounds that can absorb UV radiation. They contain amino acids linked to characteristic ring structures (cyclohexenone or cyclohexenimine), which create different types of MAAs. These structural differences affect how they absorb UV light. MAAs contribute to cellular protection by absorbing UV radiation and releasing the energy as heat. Because of these properties, some MAAs are already used in cosmetic products such as sunscreens. This review synthesises the literature on the chemical diversity and photochemical properties of cyanobacterial MAAs, their biosynthetic pathways and regulation, their distribution among cyanobacterial taxa, and their potential biotechnological and biomedical applications. Current evidence links MAA biosynthesis to the 4-deoxygadusol precursor and the mys gene cluster. Studies also indicate that light quality and intensity, UV-B exposure, salinity, desiccation, and nutrient availability influence MAA accumulation and composition. Reported photoprotective and antioxidant activities support interest in MAAs as potential ingredients for sunscreens and personal-care products. However, the strength of the evidence varies among compounds and experimental systems, and commercial development remains constrained by limited methodological standardization, production economics, and insufficient safety and regulatory data. Ongoing research efforts focus on identifying new MAAs and cyanobacterial producers to support the development of more effective photoprotective formulations. Overall, this review provides an overview of MAA-producing cyanobacteria and highlights their potential for future research and biotechnological applications.