| Summary: | ABSTRACT Background and Objective: Microalgae are a group of algae that produce biochemical products consisting of a wide range of carbohydrates, lipids and proteins that are commercially valuable. Interest in microalgal cultivation is currently blossoming globally. Species of Dunaliella are found in freshwater, euryhaline habitats of all continents, oceans including the Dead Sea and even the salt lakes of the Antarctic. This study investigates the effect of different salinity levels on β-carotene production by Dunaliella sp. Methods: Water samples from a hyper-saline lake (the Maharlu Lake in Shiraz) were cultured in modified Johnson media. The β-carotene content was measured after the samples were treated with different salinities (1, 2 and 3M NaCl). Results: The cell count and β-carotene content of Dunaliella sp. samples ranged between 0.46×106 to 2.12×106 cell.mL-1 and 0.15 to 9.98 pg.cell-1, respectively. At the end of the experiments, the mean maximum cell content (1.78×106 cell. mL-1) and the highest mean β-carotene content (7.41 pg. cell-1) were obtained at 2 and 3M NaCl concentrations, respectively. Conclusion: Salinity of the medium might affect the quantity and composition of carotenoids in Dunaliella sp. isolates. Alteration of the culture medium’s salinity to 3M NaCl significantly increases the accumulation of β-carotene and total carotenoids in Dunaliella sp. isolates. Keywords: Dunaliella, Microalgae, Maharlu Lake, β-carotene.
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