Metabolic Responses of Newly Isolated Microalgal Strains Cultured in an Open Pond Simulating Reactor Under Balanced...

Microalgal strains-Picochlorum costavermella VAS2.5, Picochlorum oklahomense PAT3.2B and SAG4.4, Microchloropsis gaditana VON5.3, and Nephroselmis pyriformis PAT2.7-were evaluated in an Open Pond Simulating Reactor (OPSR) under varied conditions to assess their biomass yield and high-value metabolite production. Overall, the strains produced 269.1-523.0 mg/L of biomass under balanced growth conditions in modified Artificial Seawater, continuous illumination, and pH 8.5. Phosphorus limitation notably enhanced yields for SAG4.4 and PAT2.7 (529.0 ± 52.2 mg/L and 452.2 ± 21.0 mg/L, respectively). Conversely, nitrogen limitation reduced productivity. In most strains the glycolipid plus sphingolipid fraction was dominant. Significant quantities of 20:5(n-3) were traced in the cultures of VAS2.5 and VON5.3, while the PAT3.2B and SAG4.4 strains produced considerable amounts of 18:3(n-3). In contrast, the most interesting fatty acid synthesized by PAT2.7 was 16:1(n-7), which was also detected in significant quantities in VAS2.5 and VON5.3. Polysaccharide content remained stable across conditions (10-15%), and protein levels reached 45-50% under control and phosphorus-limited environments. Pigment synthesis peaked at control conditions. Overall, the biochemical profiles of these strains revealed their potential for use primarily as feed additives in the aquaculture sector.