Biomass production of S. platensis has been evaluated under ultraviolet-B radiation (UV-B) stress to maximize the algal
growth. It was cultivated in Zarrouk's medium with applying some stress was treated under high dose rates of UV-B
radiation with altered time durations of (15, 30 and 40 mins). The highest content of its dry weigh, chlorophyll a, carotenoids,
protein and carbohydrates are recorded at UVB light (312 nm) for 15 mins. . As its phenolic content was maximized with
acetone extract at control while flavonoids were detected with ethanol extract at UV-B for 45mins. Antibacterial activity of S.
platensis was prepared in 70% (acetone, methanol and ethanol) at different (UV-B) radiation and tested against some
pathogenic bacterial. Its highest antibacterial activity was reported with 70% acetone extract. The impact of UV-B radiation
on S. platensis led to a drop in protective mechanisms with associated decline in growth and antimicrobial activity of S.
platensis.