Evaluation of Dunaliella salina Growth in Different Salinities for Potential Application in Saline Water Treatment and Biomass Production

This study investigated the adaptability of Dunaliella salina to different salinity levels, with an emphasis on growth, pigment concentration, and desalination potential. It was found that among the 21 salinity levels, Salinity 75 produced consistently favorable results in cell count (13.08 × 103 ± 1.41 × 103 cells/mL), dry biomass (2.46 ± 0.06 g/L), pigment content (chlorophyll a = 97,500,000 ± 100,000 pg/L, chlorophyll b = 123,600,000 ± 300,000 pg/L), and desalination (9.32 ± 0.47 reduction). Therefore, Salinity 75 was selected for the final trial (scale-up), which revealed unanticipatedly high cell counts (58.96 × 103 ± 535.22 cells/mL), with the dry biomass weight being statistically different (higher) than expected (4.21 ± 0.02 g/L) (p < 0.0001), most likely due to the high cell count and energy reserve storage for high-salinity adaption in the form of bio-compounds. Pigment growth continued (chlorophyll a = 95,400,000 ± 2,200,000 pg/L, chlorophyll b = 128,100,000 ± 5,100,000 pg/L), indicating pigment production under salt stress. Notably, desalination did not occur in this stage, possibly due to the necessity for a bigger initial inoculate, prolonged exposure or bioaccumulation becoming the prevailing mechanism over desalination. Nevertheless, the trial highlights D. salina’s strong adaptation to various salinity levels. This suggests a promising future in halophyte research, particularly in understanding the mechanisms that prevent salt accumulation in cells and how to overcome this barrier. Additionally, these results suggest that microalgae could be a viable resource in saline-rich environments unsuitable for conventional agriculture, promoting industrial adaptation to adverse conditions.