Algae cultivation can be carried out in open raceway ponds and photobioreactors depending on the type of algae chosen. In case of Dunaliella salina, after the inoculation stage, a two-stage open raceway pond cultivation is followed – green stage where Dunaliella salina keeps doubling to increase the cell density and red stage where carotenogenesis occurs under stressful conditions.
In the green stage cultivation pond, algae is subjected to mass cultivation process with adequate nutrients and CO2 added to it. Depending on the type of brine used, trace elements may also need to be added. Paddle wheels are used for continuous flow of water. Abundant sunlight is important for Dunaliella salina cultivation. The temperature of the culture medium is maintained at or above 40°C. The salinity of the water at this stage could be maintained at around 60-80‰.
The commonly used culture medium for Dunaliella salina is modified Johnsons medium. The cells are allowed to grow under these conditions and reach the required cell density.
Once the cell density reaches ~0.5 g/l, the algae is shifted to red stage pond.