Sun Kai, Kang Fuxing, Waigi Michael Gatheru, Gao Yanzheng, Huang Qingguo
Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China; Department of Crop and Soil Sciences, University of Georgia, Griffin, GA 30223, USA; School of Resources and Environment, Anhui Agricultural University, Hefei 230036, China.
Institute of Organic Contaminant Control and Soil Remediation, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Environ Pollut. 2017 Jan;220(Pt A):105-111. doi: 10.1016/j.envpol.2016.09.028. Epub 2016 Sep 15.
Triclosan (TCS) is a broad-spectrum antimicrobial agent that is found extensively in natural aquatic environments. Enzyme-catalyzed oxidative coupling reactions (ECOCRs) can be used to remove TCS in aqueous solution, but there is limited information available to indicate how metal cations (MCs) and natural organic matter (NOM) influence the environmental fate of TCS during laccase-mediated ECOCRs. In this study, we demonstrated that the naturally occurring laccase from Pleurotus ostreatus was effective in removing TCS during ECOCRs, and the oligomerization of TCS was identified as the dominant reaction pathway by high-resolution mass spectrometry (HRMS). The growth inhibition studies of green algae (Chlamydomonas reinhardtii and Scenedesmus obliquus) proved that laccase-mediated ECOCRs could effectively reduce the toxicity of TCS. The presence of dissolved MCs (Mn, Al, Ca, Cu, and Fe ions) influenced the removal and transformation of TCS via different mechanisms. Additionally, the transformation of TCS in systems with NOM derived from humic acid (HA) was hindered, and the apparent pseudo first-order kinetics rate constants (k) for TCS decreased as the HA concentration increased, which likely corresponded to the combined effect of both noncovalent (sorption) and covalent binding between TCS and humic molecules. Our results provide a novel insight into the fate and transformation of TCS by laccase-mediated ECOCRs in natural aquatic environments in the presence of MCs and NOM.
三氯生（TCS）是一种广谱抗菌剂，在天然水生环境中广泛存在。酶催化氧化偶联反应（ECOCRs）可用于去除水溶液中的TCS，但关于金属阳离子（MCs）和天然有机物（NOM）如何影响漆酶介导的ECOCRs过程中TCS的环境归宿的信息有限。在本研究中，我们证明了来自平菇的天然漆酶在ECOCRs过程中能有效去除TCS，并且通过高分辨率质谱（HRMS）确定TCS的低聚反应是主要反应途径。绿藻（莱茵衣藻和斜生栅藻）的生长抑制研究证明，漆酶介导的ECOCRs能有效降低TCS的毒性。溶解的MCs（Mn、Al、Ca、Cu和Fe离子）的存在通过不同机制影响TCS的去除和转化。此外，在含有腐殖酸（HA）衍生的NOM的体系中，TCS的转化受到阻碍，并且随着HA浓度的增加，TCS的表观伪一级动力学速率常数（k）降低，这可能对应于TCS与腐殖分子之间非共价（吸附）和共价结合的综合作用。我们的结果为在存在MCs和NOM的天然水生环境中漆酶介导的ECOCRs对TCS的归宿和转化提供了新的见解。
