Multistage defense response of microalgae exposed to pharmaceuticals in wastewater

Recently, the use of microalgae for bioremediation of pharmaceuticals (PhAs) has attracted increasing interest. However, most studies focused more on microalgae removal performance, its defensive response to the PhAs during wastewater treatment remains unexplored. Herein, microalgal three defensive systems have been investigated in synthetic wastewater, with six PhAs as the typical drug. Results show that PhAs could bind to EPS, and this action in turn could help to alleviate the direct toxicity of PhAs to microalgae. Subsequently, the physiological analyses revealed the increase of superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities, potentially reducing the oxidative stress induced by PhAs. Furthermore, the enzyme activities of cytochrome P450 (CYP450) and glutathione-S-transferase (GST) were significantly upregulated after exposure to SMX, CIP and BPA, followed by a significant decrease in biodegradation rates after the addition of CYP450 inhibitors, suggesting that the biotransformation and detoxification of PhAs occurred. Meanwhile, molecular docking further revealed that CYP450 could bind with PhAs via hydrogen bond and hydrophobic interaction, which proved their abilities to be metabolized and form transformation products in microalgae. These findings provide an advancing understanding of microalgae technologies to improve the treatment of wastewater contaminated with PhAs. (c) 2023 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

In recent years, the use of microalgae for the bioremediation of pharmaceuticals has gained attention. While most studies have focused on the removal performance of microalgae, their defensive response to pharmaceuticals during wastewater treatment has been overlooked. This study investigated the defensive systems of microalgae in synthetic wastewater and found that pharmaceuticals could bind to EPS, alleviating their direct toxicity to microalgae. Physiological analyses showed increased activity of antioxidant enzymes, suggesting a reduction in oxidative stress. Additionally, enzyme activities related to biotransformation and detoxification were upregulated, indicating the potential for the degradation and transformation of pharmaceuticals in microalgae.