Investigating the growth rate of Dunaliella tertiolecta in the optimum N:P ratio in mono and mixed cultures

Microalgae have various industrial applications; therefore optimizing their growth conditions is very important. Different ratios of nitrogen to phosphorus as well as the type of used culture medium affect the growth of different species which can determine the dominance of one species over other species. The purpose of this study is to determine the optimum ratio of nitrogen to phosphorus on the growth rate of Dunaliella tertiolecta and to investigate the growth rate and biomass production of these microalgae in mixed culture of several species of algae in this ratio. First, the effect of different weight ratios of nitrogen to phosphorus in different concentrations on the growth rate, biomass production, chemical compounds, and fatty acid profile of microalgae were investigated by using chemical, separation and spectrophotometry methods in 10 different treatments. Then the growth rates of microalga and biomass production were explored in the determined optimum ratio in the medium of mixed culture including D. tertiolecta , Nannochloropsis oculata, Chlorella and Tetraselmis . The results indicated that the weight ratio of nitrogen to phosphorus at 45:1 and threefold the standard culture medium concentration is the optimum ratio for the growth of D. tertiolecta . At this ratio, either biomass production was more than other ratios, or the growth rate of D. tertiolecta dominates the growth of other species. Graphical abstract