Abstract
Triclosan (TCS) is one of the most widespread emerging contaminants and has adverse impact on aquatic ecosystem, yet little is known about its complete biodegradation mechanism in bacteria. Sphingomonas sp, strain YL-JM2C, isolated from activated sludge of a wastewater treatment plant, was very effective on degrading TCS. Response surface methodology (RSM) was applied to optimize the conditions like temperature and pH. From RSM, the optimal TCS degradation conditions were found to be 30 °C and pH 7.0. Under optimal conditions, strain YL-JM2C completely mineralized TCS (5 mg L−1) within 72 h. Gas chromatography-mass spectrometry analysis revealed that 2,4-dichlorophenol, 2-chlorohydroquinone and hydroquinone are three main by-products of TCS. Furthermore, stable isotope experimental results revealed that the 13C12-TCS was completely mineralized into CO2 and part of heavier carbon (13C) of labeled TCS was utilized by strain YL-JM2C to synthesize fatty acids (PLFAs). Cell surface hydrophobicity (CSH) and degradation test results suggested that the strain could enhance degradation capacity of TCS through increasing CSH. In addition, the bacterium also completely degraded spiked TCS (5 mg L−1) in wastewater collected from the wastewater treatment plant. Hence, these results suggest that the strain has potential to remediate TCS in the environment.
Highlights
Triclosan [5-chloro-2-(2,4-dichlorophenoxy)-phenol, TCS], known as Ingrasan, is a biocide that inhibits the enoyl-acyl-carrier protein-reductase, which is an essential enzyme for the synthesis of fatty acids to develop bacterial cells[1]
A TCS-degrading bacterial strain YL-JM2C was isolated from a wastewater treatment plant (WWTP), Xiamen, China
Sphingomonas sp. strain YL-JM2C isolated in the present study appeared to be efficient in degrading TCS
Summary
Triclosan [5-chloro-2-(2,4-dichlorophenoxy)-phenol, TCS], known as Ingrasan, is a biocide that inhibits the enoyl-acyl-carrier protein-reductase, which is an essential enzyme for the synthesis of fatty acids to develop bacterial cells[1]. Since TCS is considered as an emerging contaminant, researchers have employed various chemical treatment methods for its degradation[10,11,12]. Incomplete degradation of TCS in the chemical treatment could result in the production of toxic by- products like chlorophenoxy-phenols, chlorophenols, trihalomethanes, and dioxins, which are known to be carcinogenic[13,14,15,16,17,18]. Understanding the TCS degradation mechanism and pathway in different wastewater bacteria are critical for enhancing effective biodegradation of TCS in wastewater. The changes of the bacterial CSH during biodegradation of TCS were studied to provide a theoretical basis for the bacterial interaction of emerging contaminants like TCS in the ecosystem.
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