Modulation of lipid productivity under nitrogen, salinity and temperature stress in microalgae Dunaliella sp.

Aim : Effect of physiological stress, namely, nitrogen depletion, salinity and temperature on the biomass productivity and lipid productivity in Dunaliella sp. was investigated. Methodology : Culture conditions of Dunaliella sp. was optimized to maximise biomass productivity. Under this condition, it was subjected to two specific pattern of physiological stress, namely nitrogen depletion with increased salinity and increased salinity with temperature shock. The biomass and lipid productivities under these stress conditions were monitored. The extracted lipids were further characterized using gas chromatography - mass spectroscopy method. Results : Laboratory culture conditions for Dunaliella sp. were optimized to yield maximized biomass productivity. It exhibited doubling of lipid content under nitrogen limitation with high salinity, though overall biomass yield under this stress pattern had significantly decreased. Characterization of the accumulated lipids showed a significant increase in the unsaturated fatty acid production. However, a noticeable decrease in saturated fatty acid was observed under the stress pattern of high salinity followed by temperature shock. Interpretation : Algae biomass yield for Dunaliella sp. was maximum under laboratory conditions to which physiological stress was applied. It results in modulation of biomass and lipid productivity with a decrease in biomass and increase in lipid accumulation per unit dry biomass. Interestingly, it was found that such physiological perturbation in Dunaliella sp. result in modulation of lipid profile leading to increased accumulation of Omega 3 fatty acid. [GRAPHICS] .