Spirulina platensis is a unicellular microalgae that has high nutritional value such as proteins, carbohydrates, lipids and carotenoids like β-carotene. The microalgae rapidly grows in Bold Bassal Medium modification and high intensity of light. The aims of this research were to optimize the culture growth and determine antioxidant activity of S. platensis. Culture was optimized by adding urea and NaHCO3 I nto the medium and applying dark : light period (12:12 h/h) under solar or fluorescent light (3000 lux). The optimum growth of Spirulina platensis was in 0,3 g/L urea, pH 9 at fluoresense light (3000 lux). Antioxidant acivity of various spirulina extract was studied by 1,1- diphenyl-2-picryl-hydrazyl (DPPH) free radicals scavenging method. The Spirulina radicals scavenging activity of acetone : methanol (1:1) extract was 46,39 %. The acetone:methanol (1:1) extract showed better antioxidant activity than acetone extract. The β-carotene was determined using HPLC in a silica gel column with dichloromethane, acetonitrile, methanol (20:70:10, v/v/v) as a mobile phase. The acetone extract displayed the highest sample area and produced 1.32% of β-carotene out of total biomass.
