Effects of Culture Conditions on the Performance of Arthrospira platensis and Its Production of Exopolysaccharides

Exopolysaccharides (EPS) produced by Arthrospira platensis (A. platensis) has been widely applied in industry and commerce for its various activities but the accumulation of EPS in culture medium may influence the growth of A. platensis reversely. This work aims to explore the impacts of initial pH, nitrogen source and concentration, phosphate concentration and recycle times of the culture medium on the growth of A. platensis and the secretion of its EPS. The results showed that EPS accumulated with the increase in recycle times of culture medium. The optimal initial pH for the growth of A. platensis was 8.50, and high pH of 11.5 inhibited the growth of biomass while resulting in highest EPS content of 92.87 mg/g DW. Excessive and limited nitrogen (NaNO₃ of 25.00 g/L and NaNO₃ < 2.50 g/L) and phosphate (K₂HPO₄ of 5.00 g/L and K₂HPO₄ < 0.50 g/L) inhibited the biomass production of A. platensis by 1.28–30.77% and 14.29–45.05%, respectively. EPS yield of 97.57 mg/g DW and 40.90 mg/g DW were obtained under NaNO₃ of 25.00 g/L and K₂HPO₄ of 5.00 g/L due to salt stress. These findings are beneficial in providing a theoretical basis for high yield EPS from A. platensis without affecting biomass yield.