Growth effects on mixed culture of Dunaliella salina and Phaeodactylum tricornutum under different inoculation densities and nitrogen concentrations

Dunaliella salina and Phaeodactylum tricornutum are two important marine microalgae rich in bioactive substances and other high-value constituents. In this study, growth effects on mixed culture of these two microalgae were studied under different inoculation proportions (10:0, 7:3, 5:5, 3:7, 0:10) and low, medium and high nitrogen concentrations of 1.4, 14 and 140 mg/l, respectively. By evaluating cell density, OD 680 , biomass, chlorophyll a and protein content in the culture, it was found that colony cell growth of D. salina and P. tricornutum was increased with the increasing of nitrogen concentrations. Additionally, mixed culture of D. salina and P. tricornutum under high and medium nitrogen concentrations increased the growth of cell colonies (especially when the inoculation proportion was 7:3) and chlorophyll a content by as much as 96.7 and 132.8%. Protein content was also increased by 1.3 and 2.8 folds when compared with that obtained with monoculture of D. salina and P. tricornutum . In contrast, when the mixed culture was done under low concentration of nitrogen, cell colonies growth was restricted due to limitation of nitrogen. Key words: Dunaliella salina, Phaeodactylum tricornutum, inoculation density, mixed-culture, nitrogen concentration.