Study of the inhibitory effect of the media culture parameters and cell population to increase the biomass production of Dunaliella tertiolecta

Microalgal growth curve, after the exponential phase, shows a stationary phase where algal biomass production is inhibited and remains constant by some factors such as nutrient depletion and intrinsic behavior. The present study is concerned with evaluating effects of the culture medium condition and intrinsic behavior on biomass production by Dunaliella tertiolecta. To this end, effect of pH, nutrient concentration, CO2 (NaHCO3) concentration, possible secreted substances, and cell density on the biomass production by D. tertiolecta were investigated. The results showed that biomass yield can be significantly affected by pH (p<0.01) and nutrient (p<0.05). In a combination of pH and nutrient, the biomass was found to be more influenced by the pH, compared with the nutrients. The results showed a significant interaction between nutrient and NaHCO3 (p<0.05), suggesting that CO2 concentration may limit biomass production only when sufficient nutrients are available. Nutrients concentration and biomass production showed a direct correlation (p<0.05). The rate of reaching the maximum biomass was showed to be increased in higher nutrients concentration; however, the maximum point could not to be affected. The existence of secreted compounds with inhibitory effect on the growth was not observed. The inhibitory effect of the cell density on biomass production can not be confirmed.