Isochrysis galbana is a brown microalgae widely used as a feed for marine organism in aquaculture. The aim of present study is to investigate the growth, biochemical composition, fatty acid profile, photosynthetic parameters and antioxidant activity (radical scavenging activity) of Isochrysis galbana cells cultivated under different levels (sub-optimum; 50 ± 1.5,optimum; 125 ± 2.5 and supra-optimum; 325 ± 3.5 µmol photons m-2 s -1) of photosynthetic active radiation (PAR), and subsequently

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... ed with different concentration of nitrate deprivation (8mM, 2mM and 0.5mM). The experiment was carried out under controlled conditions utilizing a factorial design 3x3 (light intensity and nitrate concentration). The result depicts that PAR positively influences the growth of Isochrysis galbana which is maximum under supra-optimum PAR. Nitrate deprivation (2mM & 0.5mM) induced decline in growth in terms of dry weight is observed as 60.1% & 61.9% in suboptimum and 26.5% and 34.9% in supra- HIGHLIGHTS • Influence of abiotic stress on the biochemical composition of microalgae has considerable physiological and biotechnological importance. • High light conditions and nitrogen limitations enhanced lipid and carbohydrate productivity in Isochrysis galbana. • Limitation of nitrogen significantly decreased all photosynthetic pigments, TPC and antioxidant activity. • These stresses induce significant increase of palmitic, and oleic, acids and decrease polyunsaturated fatty acid except docosahexaenoic acid. Mishra, N.; et al.