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 (NO3) 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 NO3: 0.5 g (T0.5); 1.0 g (T1.0); 1.5 g (T1.5); BG-11 under NO3 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 NO3 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 NO3 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.