| Summary: | Nitrogen represents a critical macronutrient that regulates the metabolism and consequently, the growth and biochemical composition of microalgae. In this study, the effect of different nitrogen concentrations (0, 36, 72, 144 and 288 mg/L) on the growth rate and biochemical composition of Isochrysis galbana was investigated. Cell growth, pigments and protein content of I. galbana biomass decreased with diminishing nitrogen concentration; while carbohydrates showed the highest value, 47%, in case of total nitrogen deprivation. Poly unsaturated fatty acids (PUFAs) increased five-fold under sufficient nitrogen concentrations (72 mg/L), compared to nitrogen deprivation. In contrast, concentration of saturated fatty acids (SFAs), 75.79% under nitrogen deprivation, was higher than in case of nitrogen sufficiency, 36.63%. The highest carbohydrate, protein and lipid productivities observed were 156.7, 326.2 and 264.6 mg/L under nitrogen concentrations of 72, 0 and 72 mg/L, respectively. The results of this study indicate that nitrogen concentration significantly affects the growth and biochemical compositions of I. galbana.
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