Impact of Temperature on the Biochemical Potential of Five Newly Isolated Strains of Microalgae Cultured in a Stirred Tank Reactor

The microalgal strains Picochlorum costavermella VAS2.5, Picochlorum oklahomense SAG4.4, Picochlorum oklahomense PAT3.2B, Microchloropsis gaditana VON5.3, and Nephroselmis pyriformis PAT2.7 were cultured in a Stirred Tank Reactor at 25 °C or 20 °C in modified artificial seawater and their biotechnological potential was assessed. VAS2.5, VON5.3, and PAT2.7 were high in biomass production at both temperatures (i.e., 438.8–671.3 mg/L and 418.4–546.7 mg/L at 25 °C and 20 °C, respectively), though P. oklahomense strains grew only at 25 °C. The highest lipid percentage was recorded for the cultures of VAS2.5 (19.3 ± 0.7%) and VON5.3 (16.4 ± 1.5%) at 25 °C, notably rich in ^{Δ5,8,11,14,17}C20:5, while PAT2.7 proved a major producer of ^Δ9C16:1. The predominant lipid fraction was glycolipids and sphingolipids (41.3–57.4%) for VAS2.5, PAT2.7 at 25 °C and VON5.3 at 20 °C and neutral lipids (55.6–63.5%) in the other cultures, indicating the different effect of temperature on lipid synthesis of the various microalgae. Additionally, almost all strains stood out for their high protein content, exceeding 50% in the culture of PAT3.2B, but polysaccharide and pigment content were not high. The biochemical profiles of the isolates showcased their suitability for use primarily as feed additives in the aquaculture sector.