Interdisciplinary Toxicology Program, Department of Crop and Soil Sciences , University of Georgia , Griffin , Georgia 30223 , United States.
School of Environmental and Chemical Engineering , Jiangsu University of Science and Technology , Zhenjiang , Jiangsu 212003 , China.
Environ Sci Technol. 2018 Sep 18;52(18):10617-10626. doi: 10.1021/acs.est.8b00839. Epub 2018 Aug 27.
Perfluorooctanesulfonate (PFOS) is a compound that has wide applications with extreme persistence in the environment and the potential to bioaccumulate, and could induce adverse effects to ecosystems. We investigated the degradation of PFOS by laccase-induced enzyme catalyzed oxidative humification reactions (ECOHRs) using 1-hydroxybenzotriazole (HBT) as a mediator. Approximately 59% of PFOS was transformed over 162 days of incubation, and the reaction appeared to follow a pseudo-first-order model with reaction rate constant of 0.0066/ d ( r = 0.87) under one condition tested. Using differential absorption spectra and theoretical simulation, we elucidated the interaction between Cu/Mg and PFOS, and proposed that Cu and Mg could serve as a bridge to bring the negatively charged PFOS and laccase to proximity, thus increasing the chance of radicals that are released from laccase to reach and react with PFOS. In addition, density functional theory modeling showed that PFOS complexation to the metal ions could unlock its helical configuration and decrease the C-C bond energy of PFOS. These changes allow the attack of PFOS C-C backbone by radicals to become easier. On the basis of products identification, we proposed that direct attack of PFOS by the HBT radical initiated the free radical chain reaction processes and led to the formation of fluoride and partially fluorinated compounds. These results suggest that ECOHR is a potential pathway by which PFOS could be degraded in the environment, and it may make a viable approach to remediate PFOS contamination via amendment of appropriate enzymes and mediators.
全氟辛烷磺酸 (PFOS) 是一种化合物，具有广泛的应用，在环境中具有极强的持久性和潜在的生物累积性，并可能对生态系统产生不利影响。我们研究了漆酶诱导的酶催化氧化腐殖化反应 (ECOHR) 对全氟辛烷磺酸的降解作用，使用 1-羟基苯并三唑 (HBT) 作为介体。在 162 天的孵育过程中，大约有 59%的 PFOS 发生了转化，反应似乎遵循假一级动力学模型，在一种测试条件下，反应速率常数为 0.0066/ d ( r = 0.87)。通过差分吸收光谱和理论模拟，我们阐明了 Cu/Mg 与 PFOS 的相互作用，并提出 Cu 和 Mg 可以作为桥梁，将带负电荷的 PFOS 和漆酶拉近，从而增加从漆酶释放的自由基与 PFOS 接触和反应的机会。此外，密度泛函理论建模表明，PFOS 与金属离子的络合可以解锁其螺旋构象并降低 PFOS 的 C-C 键能。这些变化使得自由基更容易攻击 PFOS 的 C-C 骨架。基于产物鉴定，我们提出 HBT 自由基直接攻击 PFOS 引发了自由基链式反应过程，导致氟化物和部分氟化化合物的形成。这些结果表明，ECOHR 是 PFOS 在环境中降解的一种潜在途径，通过添加适当的酶和介体来修复 PFOS 污染可能是一种可行的方法。
