Growth potential, biochemical properties and nutrient removal efficiency of some freshwater microalgae and their consortia from wastewater

Impact of varying nitrate (NO₃-N) and phosphate (PO₄-P) concentrations and sewage water (SW) on the growth, nutrient removal, lipid accumulation, enzymatic antioxidant activity and phytochemical contents of the microalgae <i>Scenedesmus dimorphus, Coelastrella tenuitheca, Chroococcus turgidus</i> and <i>Parachlorella kessleri</i> under monoculture and their consortia have been investigated. High growth rates were observed for all the four algae in both mono and mixed culture conditions at enhanced concentrations of N (1500 mg/L NO₃-N) and P (40 mg/L PO₄-P). The species <i>Scenedesmus dimorphus</i> outperformed other microalgae growing in SW in efficiently removing nitrogen. The algal consortia of mixed species was found to be more effective in phosphorus removal. The carbohydrate and protein contents were highest in <i>Parachlorella kessleri,</i> about 37% and 44%, respectively, in SW cultivation. The algal consortia demonstrated highest starch content (4%) in nitrogen deprived growth medium. Highest lipid production (43%) was observed in the SW culture. The species <i>Coelastrella tenuitheca, Chroococcus turgidus</i> and <i>Scenedesmus dimorphus</i> irrespective of the growth media indicated significant accumulation of phenol, flavonoid and tannin. The DPPH, catalase and ascorbic peroxidase assay showed pronounced antioxidant activity. Nutrient (N and P) enrichment exhibited enhanced antioxidant enzymatic activity and accumulation of cell storage products.