The main objective of this study was to optimize the environmental conditions for maximum growth of Dunaliella salina algae. In this study, effective environmental parameters in algae growth, such as temperature in two levels of 18± °C and 28±2 °C, pH in three levels of 7.0, 7.5, and 8.0 and salinity seven levels of 0.5, 1.0, 1.5, 2.0, 2.5, 3, and 4 molar NaCl in a 30-day culture period were investigated. The dark: light cycle and the constant light intensity were considered 24:0 and 130 130 molPAR. m^-2.s^-1, respectively. Results depicted that an increase in temperature affecting specific growth rate and a decrease in cell’s population doubling time. The highest specific growth rate and the shortest cell’s doubling time were observed under the condition of pH = 7. Furthermore, the highest specific growth rate was obtained in the salinity of 1.5 molar (0.59 per day) while the lowest specific growth rate in the salinity of 4molar (0.04 per day). The shortest (approximately 1.5 day) and longest (from 10 to 19 days) cell’s doubling time were recorded in salinities of 1.5 and 4molar, respectively, such that by increasing salinity from 0.5 to 1.5 molar, doubling time decreased while by increasing salinity from 1.5 to 4 molar, the doubling time showed a decrease trend. The algae cell concentration increased by an increase in temperature. There were significant differences among cell concentrations in various pH levels. pHs higher and lower than 7.5 led to a decrease in cell concentration. Therefore, in most samples, the maximum cell concentration was observed at pH of 7.5. An increase in temperature when pH was 7.5 let cell concentration to reach its maximum amount faster. By increasing salinity from 0.5 to 1.5 molar, cell concentration increased. In comparison, an adverse effect was observed when salinity increased from 2 to 4 molar. Cell concentration in 1.5 molar salinity condition ranged from  to  and in 4 molar salinity, cell concentration varied from  to . Based on the results of this study, the optimum environmental condition for growth of Dunaliella salina recorded under the salinity = 1.5 molar, temperature = 28±2 °C, and pH = 7.5. Condition of 1and 2 molar salinities with the aforementioned temperature and pH, is suggested as the further option for production of this algae.
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