Changes in antioxidant systems and biomass in response to selenate in blue-green microalgae Spirulina platensis, Cyanophyta

==The effects of selenium (Se) on the growth and antioxidant activity in Spirulina platensis were investigated. S. platensis was grown in zarrouk medium containing three different concentrations of selenate (Na2SeO4) (0 as a control, 5 and 10 mg l-1) for 7 days. Selenate at the concentration of 5 mg l-1was found to improve S. platensis growth. However, selenate was toxic to S. platensis at the concentration of 10 mg l-1. Selenium increased the activity of enzymatic (peroxidase and catalase) and non-enzymatic (carotenoids) antioxidants when Se was applied to the microalgae at low concentration (5 mgl-1). Phenolic compounds were significantly increased in Se-treated samples. The contents of chlorophyll a and carotenoids in Se-treated S. platensis did not significantly change as compared to control. The FTIR analysis clearly indicated that the spectra of cells grown on different Se concentrations did not significantly change as compared to control. In addition, the variety of different compounds such as aromatic, phosphine, alcohols and carboxylic acids were synthesized in all examined treatments. The present results suggest that Se at low concentration has suitable effects on the physiology of S. platensis.