Assessing the Physiology and Biochemistry of Freshwater Microalgae for Biotechnological Applications

Microalgae have gained prominence in the food, feed, and bioenergy sectors due to their capacity to produce valuable molecules and mitigate CO₂, but poor knowledge on species composition limits their applications. This study addresses the physiology of 12 freshwater microalgae belonging to Chlorophyta (Chlorella emersonii, Desmodesmus brasiliensis, Dimorphococcus sp., Pediastrum sp., Raphidocelis sp., Radiococcus sp., Tetranephris brasiliensis, Westella botryoides), Charophyta (Staurastrum leptocladum, Staurastrum pantanale), Cryptista (Cryptomonas obovata), and Heterokontophyta (Ophiocytium sp.). Physiological parameters as light saturation index (E_k), growth rate, dry biomass (DW) yield and the biochemical composition of the cells were determined. The results showed that E_k varied within 154 (T. brasiliensis) and 312 (C. emersonii) µmol photons.m^- 2.s^- 1. Pediastrum sp. and C. emersonii presented the highest growth rate (~ 1.0 d^- 1), while S. leptocladum the best antioxidant activity (43% DPPH inhibition). The Chlorophyta had the highest protein content (60% DW), while highest carbohydrate (40% DW) were present in the Charophyta. Dimorphococcus sp. and S. pantanale stood out for total lipids (25-30% DW). W. botryoides had 80% of its fatty acids as polyunsaturated molecules, dominated by alpha-linolenic acid and linoleic acid, followed by C. obovata, Pediastrum sp., S. leptocladum, and S. pantanale with 60%. Highest saturated and monounsaturated fatty acids (~ 28%) were present in Dimorphococcus sp. We highlight Pediastrum sp. for food applications because of its total proteins and polyunsaturated fatty acids content, and Dimorphococcus sp. for biofuels applications due to the saturated lipids. This work expands the knowledge on underexplored microalgae for biotechnological applications.