Influence of Sulphate Nutrition on Growth Performance and Antioxidant Enzymes Activities of Spirulina platensis

The growth of Spirulina platensis is dependent on culture conditions. This study has established adequate conditions for the quality and quantity production of S. platensis. The effect of sulphate salts nutrition on growth performance and biochemical status of S. platensis was assessed in vitro. Prior to culture, the Paracas strain of S. platensis from SAGRIC pond was analysed in different magnesium sulphate (MgSO4; 0.08, 0.16, 0.32, 0.64 and 1.28 g/L), potassium sulphate (K2SO4; 0.08, 0.16, 0.32, 0.64 and 1.28 g/L) and MgSO4/K2SO4 (0.16/0.00, 0.08/0.08, 0.04/0.12, 0.02/0.14 and 0.01/0.15 g/L) concentrations. Culture media pH, total dissolved solids (TDS) and conductivity rate were monitored. Microscopic analysis revealed sulphate salt concentrations influenced the number of whorls and filaments of S. platensis. K2SO4 (1.28 g/L) produced the highest number of whorls and filaments. Moreover, pH level fluctuated by sulphate treatments. K2SO4 (1.28 g/L) had a pH level of 8.77±0.01 (day 5 of culture incubation). TDS and conductivity rate, protein and cysteine contents increased with culture age and K2SO4 concentration in a culture medium. Conversely, negative correlations between protein and cysteine contents were observed, and sugar content decreased. Sulphate salt type and concentrations affected polyphenol oxidase (PPO) and peroxidase (POD) activities. MgSO4/K2SO4 (0.02/0.14 g/L) displayed the best PPO and POD activities. Both enzymes appeared to be negatively correlated to the decreasing sugar content. These results indicate growth performances and biochemical status of S. platensis are significantly improved with the adequate supplementation of sulphate salts (MgSO4 and K2SO4) in culture media.