Medium improvement for higher growth and longer stationary phase of Dunaliella

Beta-carotene is a valuable carotenoid in high demand as a natural food coloring agent, provitamin A, additive to cosmetics, and health food. It can be accumulated up to more than 10% of cellular dry weight of Dunaliella salina under carotenogenic conditions such as high irradiance, high temperature, high salt concentration and nutrient deficiency. High beta-carotene productivity in Dunaliella is best achieved in a two-phase culture system through biomass optimization and beta-carotene induction. A low-cost enriched natural seawater medium (MD4) was previously investigated for biomass optimization (Tran et al., 2014); However, the culture declined rapidly after reaching the stationary phase. Thus the present study is to further improve the effectiveness of this enriched natural seawater medium (MD4) for higher growth and longer stationary phase in order to avoid quick crash phase. Algal culture in MD4 medium used as control medium was subjected to 13 different feeding treatments (TM1 TM13) using a matrix of concentrations of various compounds (NPK, KNO3, KH2PO4). Dunaliella growth was determined based on chlorophyll concentration, cell density. Results revealed the best feeding treatment was TM4 (NPK 0.15g/l) with cell density doubling one week compared with cell density in the control medium, and is recommended for use in the first phase biomass optimization of Dunaliella.