INFLUENCE OF SALINITY ON THE GROWTH, PIGMENTATION AND ASCORBATE PEROXIDASE ACTIVITY OF DUNALIELLA SALINA ISOLATED FROM MAHARLU SALT LAKE IN SHIRAZ

Dunaliella salina was isolated from Maharlu salt lake in Shiraz, Iran, and was analyzed for the effects of salinity stress on its growth, pigment content and ascorbate peroxidase activity. Growth, expressed as number of cells ml-1, which was most rapid at 2 M NaCl, was reduced at salinity extremes. During the exponential phase of growth, increasing salinity from 0.5 to 4 M NaCl increased Chl a from 0.3 to 0.9 pg cell-1, while β-carotene was decreased from 3.6 to 2.4 pg cell-1 and Chl b remained unchanged. At stationary phase, increasing salinity increased the pigment content of cells. β-carotene content per cell reached its highest value of 10.1 pg at 4 M NaCl. Maximum β-carotene to total Chl ratio of 7.4 was obtained at 2 M NaCl. The TLC chromatogram of pigments extracted from cells at the exponential phase of growth resembled that of spinach leaves while the chromatogram of pigments extracted from cells at the stationary phase resembled that of carrot and commercial β-carotene. A significant increase in ascorbate peroxidase activity was observed with increasing salinity from 1 to 4 M NaCl. It is suggested that increased capacity to scavenge ROS may help to optimize algal biomass and β-carotene production.