Amitriptyline toxicity mechanisms in Chlorella vulgaris and potential for bioremediation of contaminated wastewater

Traditional wastewater treatment processes have a relatively low removal rate of the tricyclic antidepressant amitriptyline. This study employed Chlorella vulgaris as the test organism to investigate the effects of exposure to different concentrations of amitriptyline on various biological functions of the microalga. The results showed that the physiological activities of C. vulgaris were inhibited by amitriptyline primarily through the disruption of photosynthesis, the imbalance of the antioxidant system, and the suppression of photosynthesis-related gene expression. The content of chlorophyll a was significantly reduced by 72.0 %, while the activities of superoxide dismutase and catalase were increased to 217.5 % and 67.2 %, respectively. The transcriptional levels of PsaB and PsbC genes were significantly suppressed by 75.5 % and 57.2 %, respectively. After 8 days of exposure to 5 mg/L amitriptyline, the maximum removal rate of amitriptyline by C. vulgaris was determined to be 62.62 %, with biodegradation identified as the predominant removal pathway. The removal of amitriptyline followed pseudo-first-order kinetics, with a degradation half-life of 5.93 days. The study provides theoretical foundations for optimizing microalgal based treatment processes of amitriptyline contaminated wastewater and delivers critical data support for environmental risk assessment of amitriptyline.