Huang Chenchen, Zeng Yanhong, Jiang Yiye, Zhang Yanting, Lu Qihong, Liu Yin-E, Guo Jian, Wang Shanquan, Luo Xiaojun, Mai Bixian
China University of Mining & Technology, School of Environmental Science & Spatial Informatics, Xuzhou 221116, Jiangsu, China; State Key Laboratory of Organic Geochemistry and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Key Laboratory of Pollution Exposure and Health Intervention of Zhejiang Province, Hangzhou, 310015, China.
State Key Laboratory of Organic Geochemistry and Guangdong Provincial Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong-Hong Kong-MaCao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
Environ Pollut. 2024 Apr 1;346:123650. doi: 10.1016/j.envpol.2024.123650. Epub 2024 Feb 23.
Anaerobic microbial transformation is a key pathway in the natural attenuation of polychlorinated biphenyls (PCBs). Much less is known about the transformation behaviors induced by pure organohalide-respiring bacteria, especially kinetic isotope effects. Therefore, the kinetics, pathways, enantioselectivity, and carbon and chlorine isotope fractionation of PCBs transformation by Dehalococcoides mccartyi CG1 were comprehensively explored. The results indicated that the PCBs were mainly dechlorinated via removing their double-flanked meta-chlorine, with their first-order kinetic constants following the order of PCB132 > PCB174 > PCB85 > PCB183 > PCB138. However, PCBs occurred great loss of stoichiometric mass balance during microbial transformation, suggesting the generation of other non-dehalogenation products and/or stable intermediates. The preferential transformation of (-)-atropisomers and generation of (+)-atropisomers were observed during PCB132 and PCB174 biotransformation with the enantiomeric enrichment factors of -0.8609 ± 0.1077 and -0.4503 ± 0.1334 (first half incubation times)/-0.1888 ± 0.1354 (second half incubation times), respectively, whereas no enantioselectivity occurred during PCB183 biotransformation. More importantly, although there was no carbon and chlorine isotope fractionation occurring for studied substrates, the δC values of dechlorination products, including PCB47 (-28.15 ± 0.35‰ ∼ -27.77 ± 0.20‰), PCB91 (-36.36 ± 0.09‰ ∼ -34.71 ± 0.49‰), and PCB149 (-28.08 ± 0.26‰ ∼ -26.83 ± 0.10‰), were all significantly different from those of their corresponding substrates (PCB85: -30.81 ± 0.02‰ ∼ -30.22 ± 0.21‰, PCB132: -33.57 ± 0.15‰ ∼ -33.13 ± 0.14‰, and PCB174: -26.30 ± 0.09‰ ∼ -26.01 ± 0.07‰), which further supported the generation of other non-dehalogenation products and/or stable intermediates with enrichment or depletion of C. These findings provide deeper insights into the anaerobic microbial transformation behaviors of PCBs.
厌氧微生物转化是多氯联苯（PCBs）自然衰减的关键途径。对于纯有机卤化物呼吸细菌诱导的转化行为，尤其是动力学同位素效应，人们了解得较少。因此，全面探究了脱卤球菌CG1对PCBs转化的动力学、途径、对映选择性以及碳和氯同位素分馏情况。结果表明，PCBs主要通过去除其间位两侧的氯进行脱氯，其一级动力学常数顺序为PCB132 > PCB174 > PCB85 > PCB183 > PCB138。然而，PCBs在微生物转化过程中出现了化学计量质量平衡的巨大损失，这表明生成了其他非脱卤产物和/或稳定中间体。在PCB132和PCB174生物转化过程中观察到（-）-阻转异构体的优先转化和（+）-阻转异构体的生成，对映体富集因子分别为-0.8609±0.1077和-0.4503±0.1334（前半孵育时间）/-0.1888±0.1354（后半孵育时间），而在PCB183生物转化过程中未出现对映选择性。更重要的是，尽管所研究的底物没有发生碳和氯同位素分馏，但脱氯产物的δC值，包括PCB47（-28.15±0.35‰～-27.77±0.20‰）、PCB91（-36.36±0.09‰～-34.71±0.49‰）和PCB149（-28.08±0.26‰～-26.83±0.10‰），均与其相应底物（PCB85：-30.81±0.02‰～-
