Kinetic parameters of Scenedesmus obliquus (Chlorophyceae) growth and yield under different cultivation conditions in...

The aim of the present study is to assess the kinetic growth and yield of microalgae belonging to the species Scenedesmus obliquus (Kützing, 1833) grown under different macronutrient concentrations (N:P:K), pH and temperature. A three-level three-variable Box-Behnken factorial design was developed to test the influence of environmental factors on the growth parameters applied to a microalgal crop, namely: maximum cell density (N_max), specific growth rate (µ, d^-1), doubling time (T₂) and maximum yield (P_max). A classical logistic growth model was applied to estimate the kinetic behavior of a S. obliquus culture in comparison to other studies in the literature. Maximum cell density (N_max) significantly changed between 32.3 ± 0.84 and 101.5 ± 12.5 × 105 cells mL^-1 (p = 0.004). Specific growth rates (µ) and P_max showed significant mean variations between 0.28 ± 0.10 day^-1 and 6.21 ± 4.57 cells mL^-1 d^-1, respectively. All growth curves were adjusted to the proposed logistic model and range variation was (0.65 ≤ r² ≤ 0.99, p = 0.01). Maximum microalgae cell density per crop was found at temperature of 24 °C (N_max = 49.0 × 105 cells mL^-1) (p = 0.01), in 20 mL Nitrogen, Phosphorus, and Potassium (NPK) dilution (N_max = 46.5 × 105 cells mL^-1) (p = 0.02). Despite the significant variation in pH values (5.0 ≤ pH ≤ 9.0, p = 0.05), it did not have strong influence on plant growth responses. In conclusion, the kinetic study applied to S. obliquus growth and yield parameters emerged as reference for this species' kinetic behavior and bioprospecting under controlled and experimentally standardized conditions, and as support for pilot projects on bioreactors.