Harnessing Extremophilic Trait and Metabolic Flexibility of Microalgal Strains for the Treatment of Highly Alkaline Winery Wastewater

Microalgae possess traits that make them thrive under extreme environmental conditions, and this fascinating adaptability recognizes them as novel candidates for wastewater treatment and bioresource management. In this study, we assessed two extremophilic (acid-tolerant) microalgal strains, Desmodesmus sp. MAS1 and Heterochlorella sp. MAS3, for their ability to thrive in high-alkaline environments as existing in winery wastewater. These strains showed a rapid growth rate (1.10-1.30 d(-1)), a substantial increase in chlorophyll, and efficient removal of carbon (70-80%) as well as nitrogen and phosphate (80-90%) during mixotrophic cultivation in highly alkaline winery wastewater. Metabolic analysis unveiled the interplay among CO2 fixation, nitrogen assimilation, amino acid metabolism, and other key pathways, highlighting the ability of the microalgal strains to change their metabolic processes in response to extreme-pH conditions. Especially noteworthy is the elevated expression of organic acids in strain MAS1, suggesting their vital role in nutrient uptake in the alkaline environment. Harnessing these extremophilic traits negates the need for wastewater pretreatment and reduces both energy and chemical footprints, aligning with several UN Sustainable Development Goals. Our study thus presents new insights into the extremophilic nature of microalgal strains for remediation, biomass production, and broader biotechnological applications, paving the way for sustainable industrial innovations.