Impact of PFAS compounds on microalgal growth, biochemical composition, and metabolism in Chlorella minutissima

This study systematically evaluated the effects of seven PFAS on Chlorella minutissima, revealing compound-specific physiological and biochemical responses. PFHxS maintained relatively higher growth rates and Fv/Fm values, with a slight increase in chlorophyll-a (11.64 ± 0.234) and photosynthetic efficiency (0.685 ± 0.005) compared to the control. PFDA induced the highest lipid accumulation (38 ± 1.9%) along with the lowest protein content (22 ± 1.1%). Compared to controls, PFHpA and PFDA treated microalgae showed increases in both saturated and unsaturated fatty acids, indicating minimal lipid disruption. In contrast, PFOS strongly reduced unsaturated fatty acids (notably C18:1 and C16:3), leading to a dominance of saturated fatty acids. Meanwhile, PFOA emerged as one of the most disruptive compounds, impairing growth and PSII efficiency, decreasing lipid (24 ± 1.2%), protein (26 ± 1.3%) levels, total phenolic compounds (TPC), total flavonoid compounds (TFC), reactive oxygen species (ROS) scavenging activity (71.73 ± 1.64%), and elevating carbohydrate content to 33.1 ± 1.65%. The heat map and principal component analysis (PCA) of microalgae metabolites exposed to seven different PFAS compounds revealed distinct biochemical responses in terms of carbohydrate, protein, lipid, and phenolic compound levels. Overall, the findings indicate that PFAS with different chain lengths and functional groups induce differential, structure-dependent toxicological responses and that even environmentally relevant concentrations can disrupt algal metabolism, highlighting potential risks to aquatic ecosystems.