Effects of macro/micronutrients on green and brown microalgal cell growth and fatty acids in photobioreactor and open-tank systems

This study described the optimization of growth parameters that affected locally-isolated green Nannochloropsis oculata and Tetraselmis suecica and brown Isochrysis galbana and Pavlova lutheri microalgae using Response Surface Methodology (RSM). Under deficiency conditions of 10�65 g L�1 KNO3, 3�7.5 g L�1 Na2HPO4 and 2.5 g L�1 FeCl3 the highest lipid accumulation of 37.3, 23.6, 28.3 and 37.2, with slightly reduced cell growth of 0.64, 0.49, 0.54 and 0.38 g L�1 were achieved for N. oculata, T. suecica, I. galbana and P. lutheri, respectively. The macronutrients significantly influenced the biomass and lipid content positively. However, the interaction of phosphate-phosphate for N. oculata, and nitrate-nitrate for I. galbana may affect cell growth negatively. The highest biomass of 0.62�0.96 g L�1 and lipid content of 31.6�42.2 in 5 L PBR and the highest biomass of 0.45�0.72 g L�1 and lipid content of 24.4�38.5 in 300 L open tank were achieved for all the four species. The total saturated fatty acids (44.3�63.8 and 30.4�55.03); monounsaturated fatty acids (6.1�37.0 and 4.2�13.1); and polyunsaturated fatty acids (8.3�22.3 and 1.02�15.2) were obtained, respectively, with pentadecanoic (C15:0), palmitic (C16:0), palmitoleic (C16:1), heptadecanoic (C17:0), oleic (C18:1), eicosanoic (C20:0), eicosapentaenoic (C20:5) and docosahexaenoic (C22:6) as predominant fatty acids. © 2018 Elsevier Ltd