Combined toxicity of erythromycin and roxithromycin and their removal by Chlorella pyrenoidosa

Kai Liu; Jiping Li; Yuhao Zhou; Wei Li; Hu Cheng; Jiangang Han

doi:10.1016/j.ecoenv.2023.114929

Combined toxicity of erythromycin and roxithromycin and their removal by Chlorella pyrenoidosa

Ecotoxicol Environ Saf. 2023 Jun 1:257:114929. doi: 10.1016/j.ecoenv.2023.114929. Epub 2023 Apr 20.

Authors

Kai Liu¹, Jiping Li¹, Yuhao Zhou¹, Wei Li², Hu Cheng¹, Jiangang Han¹

Affiliations

¹ Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Longpan Road 159, Nanjing 210037, China; National Positioning Observation Station of Hung-tse Lake Wetland Ecosystem in Jiangsu Province, Hongze, Jiangsu 223100, China.
² Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Longpan Road 159, Nanjing 210037, China; National Positioning Observation Station of Hung-tse Lake Wetland Ecosystem in Jiangsu Province, Hongze, Jiangsu 223100, China. Electronic address: uwliwei@163.com.

PMID: 37084660
DOI: 10.1016/j.ecoenv.2023.114929

Abstract

The ecological effects of antibiotics in surface water have attracted increasing research attention. In this study, we investigated the combined ecotoxicity of erythromycin (ERY) and roxithromycin (ROX) on the microalgae, Chlorella pyrenoidosa, and the removal of ERY and ROX during the exposure. The calculated 96-h median effect concentration (EC₅₀) values of ERY, ROX, and their mixture (2:1 w/w) were 7.37, 3.54, and 7.91 mg∙L^-1, respectively. However, the predicted EC₅₀ values of ERY+ROX mixture were 5.42 and 1.51 mg∙L^-1, based on the concentration addition and independent action models, respectively. This demonstrated the combined toxicity of ERY+ ROX mixture showed an antagonistic effect on Chlorella pyrenoidosa. During the 14-d culture, low-concentration (EC₁₀) treatments with ERY, ROX, and their mixture caused the growth inhibition rate to decrease during the first 12 d and increase slightly at 14 d. In contrast, high-concentration (EC₅₀) treatments significantly inhibited microalgae growth (p < 0.05). Changes in the total chlorophyll contents, SOD and CAT activities, and MDA contents of microalgae suggested that individual treatments with ERY and ROX induced higher oxidative stress than combined treatments. After the 14-d culture time, residual Ery in low and high concentration Ery treatments were 17.75% and 74.43%, and the residual Rox were 76.54% and 87.99%, but the residuals were 8.03% and 73.53% in ERY+ ROX combined treatment. These indicated that antibiotic removal efficiency was higher in combined treatments than that in individual treatments, especially at low concentrations (EC₁₀). Correlation analysis suggested that there was a significant negative correlation between the antibiotic removal efficiency of C. pyrenoidosa and their SOD activity and MDA content, and the enhanced antibiotic removal ability of microalgae benefited from increased cell growth and chlorophyll content. Findings in this study contribute to predicting ecological risk of coexisting antibiotics in aquatic environment, and to improving biological treatment technology of antibiotics in wastewater.

Keywords: Antibiotic removal; Biodegradation; Macrolide antibiotics; Microalgae; Toxicity.

MeSH terms

Anti-Bacterial Agents / toxicity
Chlorella*
Chlorophyll / analysis
Erythromycin / toxicity
Microalgae*
Roxithromycin* / analysis
Roxithromycin* / toxicity
Superoxide Dismutase
Water Pollutants, Chemical* / analysis

Substances

Roxithromycin
Erythromycin
Anti-Bacterial Agents
Chlorophyll
Superoxide Dismutase
Water Pollutants, Chemical