Reductive dechlorination of perchloroethene (PCE) and bacterial community changes in a continuous-flow, two-stage anaerobic column

Wei

Water Science and Technology

et al. 2022

Complete dechlorination of trichloroethene (TCE) by Dehalococcoides mccartyi is catalyzed by reductive dehalogenases (RDases), which possess cobalamin as the crucial cofactor. However, virtually all D. mccartyi isolated thus far are corrinoid auxotrophs. The exogenous addition of commercially available cobalamin for TCE-contaminated site decontamination is costly. In this study, TCE reduction by a D. mccartyi-containing microbial consortium utilizing biosynthetic cobalamin generated by interior corrinoid-producing organisms within this microbial consortium was studied. The results confirmed that subcultures without exogenous cobalamin in the medium were apparently unaffected and were able to successively metabolize TCE to nonchlorinated ethene. The 2-bromoethanesulfonate and ampicillin resistance tests results suggested that ampicillin-sensitive bacteria rather than methanogenic archaea within this microbial consortium were responsible for biosynthesizing cobalamin. Moreover, relatively stable carbon isotopic enrichment factor (ɛ-carbon) values of TCE were obtained regardless of whether exogenous cobalamin or selective inhibitors existed in the medium, indicating that the cobalamin biosynthesized by these organisms was absorbed and utilized by D. mccartyi for RDase synthesis and eventually participated in TCE reduction. Finally, the Illumina MiSeq sequencing analysis indicated that Desulfitobacterium and Acetobacterium in this microbial consortium were responsible for the de novo cobalamin biosynthesis to fulfill the requirements of D. mccartyi for TCE metabolism.

Section: Microbial Consortium Descriptionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Interspecies transfer of biosynthetic cobalamin for complete dechlorination of trichloroethene by Dehalococcoides mccartyi

Wei

Water Science and Technology

et al. 2022

“…The concentration of TCE was about 0.0 to 0.7μM, however, there was accumulation of cDCE and VC, the by-products of the degradation of PCE and TCE.The anaerobic simulated aquifer also saw a large amount of methane production (3.6 to 11.4 μM). Since the fermenters, methanogens, and dechlorination bacteria all competed for hydrogen at the same time (Patil et al, 2014;Ziv-El et al, 2012;Wen et al, 2015), the dechlorination ability of the dechlorination bacteria was reduced, so PCE could only be dechlorinated to cDCE and VC.Many studies have also shown that the anaerobic biodegradation of PCE usually results in the accumulation of cDCE and VC and is accompanied by the formation of a large amount of methane (Anam et al,2019;Major et al, 2002).Some studies have found that TCE, cDCE and VC can be cometabolically degraded by using methane as a substrate under aerobic conditions (Fogel et al, 1986;Němeček et al, 2020;Wymore et al, 2007). Therefore, this test inoculated acclimated methanotrophs in the following aerobic simulated aquifer, using methane generated in the anaerobic simulated aquifer as the carbon source and energy source of the methanotrophs, to produce methane monooxygenases.…”

Section: Resultsmentioning

confidence: 99%

Cometabolic biodegradation of chlorinated ethenes with methanotrophs in anaerobic/aerobic simulated aquifer

Chen¹,

Chin²,

Yang³

et al. 2021

JEB

Aim: This study explores anaerobic/aerobic biodegradation efficiencies of aerobic cometabolism with methanotrophs when contaminants trichloroethylene (TCE) and cis-1,2-dichloroethylene (cDCE) are present individually or in tandem. Methodology: Batch tests and an anaerobic/aerobic column system were used to simulate saturated, contaminated aquifers. A brown glass bottle with an effective volume of 44 m l-1 was prepared for the batch test. An integrated one-dimensional sequential anaerobic/aerobic column system was used to simulate the accumulative intermediates such as TCE, cDCE and VC caused by incomplete degradation of PCE during the upgradient anaerobic stage in the saturated aquifer. In the downgradient aquifer, aerobic cometabolism was employed to degrade the intermediates. Methanotrophs in the aerobic aquifer were inoculated to degrade the by-products of incomplete degradation of PCE by aerobic cometabolism. Results: In the batch test, biodegradation of TCE was significantly inhibited by cDCE. However, biodegradation of cDCE was not significantly inhibited by TCE. In the simulated aquifer test, aerobic cometabolism completely degraded intermediates (TCE, cDCE, and VC) produced by incomplete anaerobic degradation of tetrachloroethylene (PCE). The results showed that methane, a by-product of anaerobic reductive dechorination of PCE, was used as a primary substrate for aerobic degradation, at a utilization rate of almost 100%. Interpretation: Biodegradation of TCE was significantly inhibited by cDCE. Bioremediation should have sufficient oxygen and methane at aerobic stage to ensure that chlorinated ethenes fully mineralize.

“…In many cases, pure chemicals are used. The most typical in research studies is lactate, which is a by-product of the fermentation process and can also serve as an effective electron donor and organic carbon source [7,14,[44][45][46]. However, many other sources were successfully tested, e.g., emulsified vegetable oils [47,48], glucose [47,49], acetate [50], formate, and fumarate [51].…”

Section: Chemical Analysesmentioning

confidence: 99%

Thermally Enhanced Biodegradation of TCE in Groundwater

Najmanová

Steinová

Czinnerová

et al. 2022

Water

In situ remediation is usually restricted by temperature, lack of substrate for reductive dechlorination (anaerobic respiration), the presence of dehalogenating microorganisms, and specific bedrock conditions. In this work, trichloroethene (TCE) degradation was studied by a number of methods, from physical–chemical analyses to molecular biological tools. The abundance changes in dechlorinating bacteria were monitored using real-time PCR. The functional genes vcrA and bvcA as well as the 16S rRNA specific for representatives of genera Dehalococcoides, Dehalobacter, and Desulfitobacterium were monitored. Furthermore, the sulfate-reducing bacteria and denitrifying bacteria were observed by amplifying the functional genes apsA and nirK. The elevated temperature and the substrate (whey) addition significantly affected TCE dechlorination. The chlorine index decreased after nine weeks from 2.5 to 0.1 at 22 °C, to 1.1 at 17 °C and 1.7 at 12 °C and complete dechlorination was achieved at 22 °C with whey addition. The achieved results of this work show the feasibility and effectiveness of biological dechlorination of TCE enhanced with elevated temperature and whey addition.