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Biodegradation and metabolic fate of levofloxacin via a freshwater green alga, Scenedesmus obliquus in synthetic saline wastewater

Xiong, Jiu-Qiang, Kurade, Mayur B., Patil, Dilip V., Jang, Min, Paeng, Ki-Jung, Jeon, Byong-Hun
Algal research 2017 v.25 pp. 54-61
Scenedesmus obliquus, bioaccumulation, biochemical pathways, biodegradation, decarboxylation, ecotoxicology, freshwater, gas chromatography-mass spectrometry, half life, levofloxacin, metabolites, microalgae, microorganisms, salinity, sodium chloride, wastewater, water resources
Levofloxacin (LEV), a fluoroquinolone antibiotic has been frequently observed in water resources imposing ecotoxicological effects on aquatic microbiota. The biodegradation and metabolic fate of LEV via a microalga, Scenedesmus obliquus in synthetic saline wastewater were investigated in this study. LEV removal (1mgL−1) by S. obliquus was relatively low in the synthetic wastewater without the addition of sodium chloride (NaCl); however, its removal increased significantly from 4.5 to 93.4% with increasing of its salinity from 0 to 171mM NaCl. Kinetic studies showed that the removal rate constant (k) increased from 0.005 to 0.289d−1 and degradation half-life decreased from 272 to 5d in the presence of NaCl (0–856mM). The removal mechanism analysis showed that the major mechanism of NaCl mediated enhancement of LEV removal was the bioaccumulation and subsequent intracellular biodegradation of LEV in microalgal cells. Six metabolites were identified via gas chromatography–mass spectrometry analysis after biodegradation of LEV. A metabolic pathway was postulated with regard to various cellular biocatalytic reactions in S. obliquus, including decarboxylation, demethylation, dehydroxylation, side chain breakdown, and ring cleavage.