Effect of nitrate on Ankistrodesmus fusiformis culture: evaluation of growth, biomolecules and extracellular polymeric substances (EPS)

The aim was to test the effect of nitrate (NO 3 ) supplementation and restriction on biomass production, synthesis of biomolecules and extracellular polymeric substances (EPS) in the microalga Ankistrodesmus fusiformis . The treatments contained BG-11 medium + different concentrations of NO 3 : 0.5 g (T0.5); 1.0 g (T1.0); 1.5 g (T1.5); BG-11 under NO 3 limitation (TN) and control containing only BG-11 (TC). TN showed higher production of biomass (0.68 g L −1 ), µ (0.50 day −1 ) and proteins (11.16 µg mL −1 ). Carbohydrate content decreased with increasing NO 3 concentration in the treatments. T1.5 had the highest lipid content (49.30 mg). The major fatty acids were C16:0; C18:3n3; C18:1n9c and C18:2n6c. Higher saturation was observed in treatments with lower concentrations of NO 3 and TN, inverse behavior to the monounsaturated. The TN treatment showed high EPS production (30.90 mg L −1 ). Therefore, globally TN was the best treatment, due to its high biomass production, high EPS synthesis and relevant production of lipids and proteins, together with reduced use of nitrate.