Removal of cefradine by Chlorella sp. L166 and Scenedesmus quadricauda: Toxicity investigation, degradation mechanism and metabolic pathways

Cefradine is a broad-spectrum antibiotic employed in humans to resist bacterial infection. A large amount of cefradine was not fully utilized, which caused harm to aquatic life and aquatic environment. Herein, the toxicity, degradation and metabolic pathway of cefradine to the two microalgal species (Chlorella sp. L166 and Scenedesmus quadricauda) were investigated. The results showed that both microalgae showed excellent degradation performance for cefradine. Chlorella sp. L166 and Scenedesmus quadricauda exposed to 5 mg/L reached the highest removal rates, which were 97.27% and 98.50%, respectively. Although high concentration of cefradine inhibited the growth of both microalgal species, both microalgae showed the capacity to restore growth in high concentration of cefradine. In addition, hydrolysis and biodegradation were regarded as the main mechanisms of cefradine degradation on algae. Seven by-products of cefradine metabolism were identified by HPLC-MS and three metabolic pathways of cefradine in medium were revealed, including decarboxylation, demethylation, hydrolysis, side chain breaking and oxidation processes. These results provide a better understanding of the environmental risks of cefradine in wastewater and the efficient removal of cefradine in wastewater by microalgae.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study investigated the toxicity, degradation, and metabolic pathway of cefradine in two microalgal species. The results showed that both microalgae exhibited excellent degradation performance for cefradine and had the capacity to restore growth in high concentrations. Hydrolysis and biodegradation were identified as the main mechanisms of cefradine degradation on algae. The study provides valuable insights into the environmental risks of cefradine in wastewater and the efficient removal of cefradine by microalgae.