Investigation of the Effects of Saline Stress and Light Intensity on the Growth Rate of Dunaliella salina and Its Beta-carotene Content and Physiochemical Characteristics

Dunaliella salina is a unicellular, mobile green alga, which lacks a rigid cell wall. One of the unique characteristics of Dunaliella salina is the ability to produce and accumulate high contents of beta-carotene. The aim of the present study was to assess and enhance carotenoid, protein and antioxidant compound production in Dunaliella salina cells.

In this study, Dunaliella salina microalga was cultured in modified Johnson culture media under three levels of saline stress (0.5, 1.5 and 2.5 mol) and three levels of light intensity (0,250 and 500 µmol/m2 s) and then effects of the these parameters were investigated.

Results showed that increasing the level of saline stress up to 1.5 mol enhanced the cell growth; however, further increases led to decreases in the cell growth rate. The maximum growth rate of Dunaliella salina was achieved at 1.5 mol salinity and 500 µmol/m2 s light intensity, which was equal to 36.1 cell/ml and the highest content of carotenoids was 24.9 mg/ml. Furthermore, the highest contents of chlorophyll, antioxidants and proteins were 11.5 mg/g, 25.3% and 62.9%, respectively.

Light intensity included more effects on the growth rate and active ingredient content of Dunaliella salina than that it included on salinity. Cultivation under high light intensity (500 µmol/m2 s) increased beta-carotene, chlorophyll, protein and antioxidant contents as well as the high cell growth rate. Salinity of 1.5 mol was suggested as the optimum culture media salinity.