Nutrient manipulation for Spirulina cultivation and environmental impact

CO₂ is a major greenhouse gas leading to a rise in global temperature. Reducing emissions and utilizing CO₂ are key strategies to mitigate this impact. Cyanobacteria are photosynthetic organisms that effectively capture CO₂ and convert it into biomass and valuable compounds. This study aimed to enhance CO₂ fixation in a commercial cyanobacterium, Spirulina (Arthrospira), through nutrient manipulation, focusing on the amounts and sources of carbon and nitrogen, and their effects on growth and biochemical composition. Spirulina was cultivated in standard Zarrouk’s medium (control) and modified Zarrouk’s media with reduced amounts of carbon (4 g L^-1 NaHCO₃) and nitrogen (0.85 g L^-1 NaNO₃ or 0.3 g L^-1 urea) under conditions of either air or 1% CO₂ supply for 48 hours. The results revealed a significant improvement in biomass productivity in the urea-containing culture with CO₂ supply. In addition, 3.0-times increase in carbohydrate productivity, along with 0.6-times decrease in protein productivity compared to the control was observed. Furthermore, the combination of CO₂ and urea significantly increased CO₂ fixation rate (0.574 g L^-1 d^-1). Nutrient manipulation in Spirulina cultivation is an effective strategy to promote CO₂ fixation, reduce greenhouse gas emissions, and produce valuable products, thus contributing to sustainable CO₂ utilization.

Keywords: Spirulina, CO₂ fixation, nutrients