Optimization of medium using response surface methodology to enhance the growth of Effrenium voratum (Symbiodiniaceae, Dinophyceae).

Survival of coral reef-associated Symbiodiniaceae is vital to maintain the healthy coral community in coral reefs. However, knowledge about cultivation of free-living or symbiotic Symbiodiniaceae has been limited. In this study, the response surface methodology was applied to optimize the medium for Effrenium voratum. The results showed that the impacts of nutrient components on algal growth were: FeCl3 > NaH2 PO4 >MnSO4 > MgSO4 /CoSO4 > KCl>ZnSO4 > CaCl2 /NaNO3 , among which NaH2 PO4 and FeCl3 significantly affected algal growth. The optimal medium was: natural seawater supplemented with NaH2 PO4 ·2H2 O 0.25 mM,FeCl3 ·6H2 O 14.24 µM, NaNO3 0.94 mM, MgSO4 ·7H2 O 40.63 mM, KCl 5.37 mM, CaCl2 ·2H2 O 4.08 mM, ZnSO4 ·7H2 O 0.35 µM, MnSO4 9.93 µM, and CoSO4 0.36 µM. The use of the optimized medium resulted in an increase of biomass yield (0.76 g dry weight · L-1 ) by 46% over that using the initial medium, which agreed with the predicted value (0.71 g · L-1 ). Additionally, fatty acids, mainly consisting of palmitic acid (C16:0) and ethyl carbonate (C20:0), accounted for approximately 50% of the total fatty acids in E. voratum. Interestingly, docosahexaenoic acid (DHA) accounted for 6% of total fatty acids, a high proportion that makes E. voratum a potential candidate feedstock in aquaculture for DHA production.