Photoinhibition and β-carotene production from Dunaliella sp . isolated from salt pans of Goa

The microalgae Dunaliella is a commercially viable species and is well known for its extreme environmental tolerance and β-carotene production under stressful conditions. We examined the effect of salinity and light intensity on the growth and β-carotene production, respectively, in two different species of Dunaliella: Dunaliella sp. and D . salina , isolated from the salt pans of Goa. Both the species were cultured in growth media with different salinity levels to establish the optimum salinity favouring maximum cell growth. Thereafter, the cells were cultured under optimum NaCl concentration, exposed to a range of light intensity and monitored for β-carotene production. The two species, identified based on their molecular characteristics, displayed a significant difference in growth and β-carotene production. Both D . salina and Dunaliella sp. achieved a maximum of 11.82 × 10 6 cells mL −1 (0.613 µd −1 ) and 18.76 × 10 6 cells mL −1 (0.731 µd −1 ) at 0.75 M and 0.5 M salinity, respectively. D . salina accumulated a large amount of total carotenoid (36.95 pg. cell −1 ) when cultured at 0.75 M salinity and exposed to high light intensity (1000 µmol m −2 S −1 ). In contrast, the carotenoid content per cell was low in Dunaliella sp. (3.07 pg. cell −1 ) when cultured under optimal salinity (0.5 M) and high light intensity, indicating photoinhibition. We found that different Dunaliella species exhibit different photo-physiological properties that need further evaluation to identify the right candidate for industrial applications.