The stress response and removal mechanism of Chlorella vulgaris to sulfamethoxazole

This study aimed to assess the removal efficiency and mechanism by which microalgae remove sulfamethoxazole (SMX). As a sustainable and environmentally friendly method, microalgae-based biotechnology to remove antibiotics has received increasing attention. However, the mechanism of sulfamethoxazole removal by microalgae is still unclear. This study investigated the ecological toxicity of sulfamethoxazole and its removal by Chlorella vulgaris. The results showed that the removal efficiency was from 6.4 % to 49.9 % at different initial antibiotic concentrations. Biodegradation contributed 5.04 %–44.6 % to SMX removal, while abiotic degradation contributed 1.35 %–5.25 %. Low concentrations (1 and 10 mg/L) of SMX promoted the growth and total protein content of microalgae, while high concentrations (20, 40, 70, and 100 mg/L) had inhibitory effects. High concentrations of antibiotics also significantly inhibited the photosynthetic pigments of microalgae. After 96 h of exposure, the content of exopolysaccharides and lipids in microalgae increased compared to the control group. As the initial concentration of SMX increased, the superoxide dismutase, catalase, and malondialdehyde content increased, which indicated that SMX caused oxidative stress in microalgae. Throughout the entire exposure period, 14 TPs (transformation products) were identified. The risk assessment of TPs indicated that SMX treatment using microalgae tends to produce less toxic TPs.