The Effect of Certain Environmental Factors on Growth and β-Carotene Production by Dunaliella sp. Isolated from the Dead Sea

Microalga Dunaliella sp. was isolated and identified from ponds of the south-east shores of the Dead Sea. The most suitable media for the isolated Dunaliella sp. was found to be M1 (modified BG-11) which gave the highest growth and β-carotene production. The effects of different physical (temperature and light intensity) and chemical (different nitrogenous and sulfate compounds) factors were tested. The best salinity for Dunaliella growth was 2.5 % NaCl, while the maximum β-carotene to chlorophyll a (Chl. a) ratio was found in high salinities: Dead Sea water- M1 (DSw-M1) dilution (1:1), 10% NaCl and DSw-M1 (3:1). By using NaNO3 at 40 mg N l-1 concentration as a nitrogen source and MgSO4 at 25 mg l-1 concentration as a sulfate source, the maximum growth and β-carotene production was obtained. In response to different light intensities, the maximum growth was obtained at 61 μmol s-1 m-2, and the maximum β-carotene production was at 200 μmol s-1 m-2 , while the maximum β-carotene to chlorophyll a ratio was recorded in cells grown at 1000 μmol s-1 m-2 .