Comparison of growth and biochemical parameters of two strains of Rhodomonas salina (Cryptophyceae) cultivated under different combinations of irradiance, temperature, and nutrients

Growth and biochemical parameters of two strains of Rhodomonas salina (Cryptophyceae), cultivated under different combinations of irradiance, temperature, and nutrients, were compared. The microalgae were grown in batch mode for 10 days, in f/2 medium at 33‰ salinity. The experimental design was a 25 factorial design with the following variables: nitrate [0.441 mM (N1) and 3.529 mM (N2)], phosphate [0.018 mM (P1) and 0.144 mM (P2)], temperature [19 and 29 °C], continued irradiance [100 μmol photons m−2 s−1 (low light, LL), and 200 μmol photons m−2 s−1 (high light, HL)] and microalgae strains (CS-174 and CS-24). Growth parameters, protein and lipid content, and fatty acids profiles were analyzed. Principal component analysis showed that combined high nitrate, high phosphate availability, and high light, regardless of temperature, achieved the best growth in both strains; while combined high nitrate and high phosphate, regardless of irradiance or temperature, resulted in the highest protein accumulation in both strains. On the other hand, the content of total lipid, arachidonic (ARA), eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, as well as EPA/DHA ratio, were strongly influenced by temperature in both strains. Strain CS-174 grew better and achieved significantly higher (p < 0.05) total lipid content (maximum 25.4 ± 1.5 %), ARA, EPA and DHA content (maximum 3.5, 13.2 and 6.5 %, respectively), and EPA / DHA ratio (maximum 2.03), than strain CS-24, being thus more suitable for use in aquaculture nutrition.