Growth, Productivity and Some Physico-chemical Factors of Spirulina platensis Cultivation as Influenced by Nutrients Change

Background and Objective: Microalga cells directly use nutrient elements, sunlight and CO 2 for their growth. Environmental factors such as temperature and pH affect metabolic process in microalga cells. The objective of this study was to evaluate the effect of nutrients change in the culture medium of Spirulina platensis (S. platensis) on its growth, productivity and some physico-chemical factors in order to define the optimal growth cultivation conditions. Materials and Methods: Spirulina platensis was grown in a 300 mL glass containers containing 100 mL nutrient medium at 30EC under 5000 lux illumination and 12:12 h light-dark cycle. Spirulina platensis cells were harvested after 42 days and analysed for dry weight (DW), specific growth rate (SGR) and productivity. Jourdans medium was taken as control. For experiments, Jourdans medium was enriched with iron sulphate (FeSO 4 .7H 2 O), sodium chloride (NaCl), magnesium sulphate (MgSO 4 .7H 2 O), urea (CO(NH 2 ) 2 ) and sodium bicarbonate (NaHCO 3 ) at different concentrations (0.01, 2.5, 0.1, 0.02 and 4 g LG 1 , respectively). The temperature, pH and electrical conductivity (EC) were monitored for 42 days on daily basis. Averages of data were statistically analyzed by using analysis of variance (one-way ANOVA). Statistical differences between treatment means were established using the fisher LSD test at p<0.05. Results: The DW, SGR and productivity were positively influenced by the addition of FeSO 4 .7H 2 O, NaCl, MgSO 4 .7H 2 O, CO(NH 2 ) 2 and NaHCO 3 to Jourdans medium at 0.01, 2.5, 0.1, 0.02 and 4 g LG 1 , respectively. No significant change in pH values of all culture media of S. platensis throughout the study period was observed. The temperature of the culture was positively influenced by the addition of FeSO 4 .7H 2 O and NaCl to Jourdans medium, while MgSO 4 .7H 2 O, CO(NH 2 ) 2 and NaHCO 3 lead to a decrease of the temperature from 31.66-25.90EC. Jourdans medium supplied with 15 g LG 1 NaCl showed significantly (p<0.05) higher EC compared to all other treatments. The values of secchi depth were ranged from 2.06-3.02 cm when the media were enriched with NaCl, MgSO 4 .7H 2 O, CO(NH 2 ) 2 and NaHCO 3 .