Co-metabolism of sulfamethoxazole by a freshwater microalga Chlorella pyrenoidosa. (15th May 2020)

• Record Type: Journal Article
• Authors: Xiong, Qian; Liu, You-Sheng; Hu, Li-Xin; Shi, Zhou-Qi; Cai, Wen-Wen; He, Liang-Ying; Ying, Guang-Guo
• Is Part Of: Water research. Volume 175(2020)
• Publication Date: 2020-05-15
• Subjects: Microalgae -- Antibiotic -- Sulfamethoxazole -- Co-metabolism -- Transformation products -- Biodegradation; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2020.115656
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Microalgae-mediated biodegradation of antibiotics has recently gained increased attention from international scientific community. However, limited information is available regarding microalgae-mediated biodegradation of SMX in a co-metabolic system. Here we investigated the biodegradation of sulfamethoxazole (SMX) by five algal species ( Pseudokirchneriella subcapitata, Scenedesmus quadricauda, Scenedesmus obliquus, Scenedesmus acuminatus and Chlorella pyrenoidosa ), and its transformation pathways by C . pyrenoidosa in a sodium acetate (3 mM) co-metabolic system. The results showed that the highest SMX dissipation (14.9%) was detected by C . pyrenoidosa after 11 days of cultivation among the five tested algal species in the absence of other carbon sources. The addition of sodium acetate (0–8 mM) significantly enhanced the dissipation efficiency of SMX (0.4 μM) from 6.05% to 99.3% by C . pyrenoidosa after 5 days of cultivation, and the dissipation of SMX followed the first-order kinetic model with apparent rate constants (k) ranging from 0.0107 to 0.9811 d −1 . Based on the results of mass balance analysis, biodegradation by C . pyrenoidosa was the main mechanism for the dissipation of SMX in the culture medium. Fifteen phase I and phase II metabolites were identified, and subsequently the transformation pathway was proposed, including oxidation, hydroxylation, formylation and side chain breakdown, as well as pterin-related conjugation. The majority of metabolites of SMX were only observed in the culture medium and varied with cultivation time. The findings of the present study showed effective co-metabolism of a sulfonamide by microalgae, and it may be applied in the aquatic environment remediation and wastewater treatment in the future. Graphical abstract: Image 1 Highlights: Five algal species were screened for biodegradation of sulfamethoxazole (SMX). C. pyrenoidosa showed the highest dissipation capacity of SMX. The dissipation efficiency of SMX was enhanced with the addition of sodium acetate. Fifteen TPs from phase I and phase II reactions were identified by UPLC-QTOF-MS. The co-metabolic pathway of SMX by C. pyrenoidosa was firstly proposed.