Impact of Thermal Extremes and Nutrient Availability on the Biochemical Profile and Antioxidant Capacity of the Halophilic Microalga Dunaliella Salina

Microalgae are increasingly recognized as a promising biomass feedstock for the production of biofuels, pharmaceuticals, and cosmeceuticals. Among these, Dunaliella salina, a halophilic species capable of harnessing solar energy via photosynthesis stands out for its proficiency in synthesizing high-value organic compounds, including carotenoids, lipids, and phenolics. Consequently, this study investigated the microalgal strain D. salina CCAP 19/18 to evaluate the accumulation of these metabolites and their associated antioxidant capacity under cold stress and nutrient deprivation. The findings indicate that the most significant accumulation occurred on day 12 post-induction under a combined regime of cold stress (10°C for 6 hours/day) and complete NPK depletion. Conversely, exposure to a thermal stress of 45°C in conjunction with nutrient deficiency proved catastrophic; optical microscopy revealed that cells underwent lysis and clumping, with no signs of viability recorded after three days of stress. These findings provide a scientific foundation for optimizing cultivation strategies of the microalga D. salina, aimed at harvesting biomass with elevated contents of bioactive compounds for applications in pharmaceuticals and functional foods.