Compound degraded:2,3,7,8-Tetrachlorodibenzo-P-dioxin

General Description (About POP compound)

The most toxic and most extensively studied representative of the chlorinated dioxins (PCDDs) is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

Biodegradation pathway

Publications

Abstract Title Authors Article Link
This study aims to find a high-efficiency degradation strain which can biodegrade the 2,3,7,8-Tetrachlorodibenzo-P-dioxin (2,3,7,8-TCDD). In this paper, a new fungus strain was isolated from activated sludge of Dagu Drainage River in Tianjin which was able to degrade 2,3,7,8-TCDD in the medium. Based on its morphology and phylogenetic analysis of its 18S rDNA sequence, the strain was identified as Penicillium sp. QI-1. Response surface methodology using central composite rotatable design of cultural conditions was successfully employed for optimization resulting in 87.9?% degradation of 2,3,7,8-TCDD (1 µg/mL) within 6 days. The optimum condition for degrading 2,3,7,8-TCDD was at 31? and pH 7.4. The biodegradation process was fitted to a first-order kinetic model. The kinetic equation was Ct=0.939e??0.133t and its half-life was 5.21d. The fungus strain degraded 2,3,7,8-TCDD to form intermediates, they were 4,5-Dichloro-1,2-benzoquinone, 4,5-Dichlorocatechol, 2-Hydrooxy-1,4-benzoquinone, 1,2,4-Trihydroxybenzene and ?-ketoadipic acid. A novel degradation pathway for 2,3,7,8-TCDD was proposed based on analysis of these metabolites. The results suggest that Penicillium sp. QI-1 may be an ideal microorganism for biodegradation of the 2,3,7,8-TCDD-contaminated environments. Isolation and identification of a 2,3,7,8-Tetrachlorodibenzo-P-dioxin degrading strain and its biochemical degradation pathway Qiu et al., 2021 Link
Aerobic biotransformation of the diaryl ethers 2,7-dichlorodibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzo-p-dioxin by the dibenzo-p-dioxin-utilizing strain Sphingomonas wittichii RW1, producing corresponding metabolites, was demonstrated for the first time. Our strain transformed 2,7-dichlorodibenzo-p-dioxin, yielding 4-chlorocatechol, and 1,2,3,4-tetrachlorodibenzo-p-dioxin, producing 3,4,5,6-tetrachlorocatechol and 2-methoxy-3,4,5,6-tetrachlorophenol; all of these compounds were unequivocally identified by mass spectrometry both before and after N,O-bis(trimethylsilyl)-trifluoroacetamide derivatization by comparison with authentic standards. Additional experiments showed that strain RW1 formed a second metabolite, 2-methoxy-3,4,5,6-tetrachlorophenol, from the original degradation product, 3,4,5,6-tetrachlorocatechol, by methylation of one of the two hydroxy substituents. Biotransformation of 2,7-Dichloro- and 1,2,3,4-Tetrachlorodibenzo-p-Dioxin by Sphingomonas wittichii RW1 Hong et al., 2002 Link
Sphingomonas wittichii RW1 is able to catabolize 1,2,3,4-tetrachlorodibenzo-p-dioxin (H. B. Hong, Y. S. Chang, I. H. Nam, P. Fortnagel, and S. Schmidt, Appl. Environ. Microbiol. 68:2584-2588, 2002). Here we demonstrate the aerobic bacterial catabolism of the ubiquitous toxic diaryl ether pollutant 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin by this strain. The products of this biotransformation were identified as tetrachlorocatechol and 2-methoxy-3,4,5,6-tetrachlorophenol by comparing mass spectra recorded before and after n-butylboronate and N,O-bis(trimethylsilyl)-trifluoroacetamide derivatization with those of authentic compounds. Additional experiments showed that the less-chlorinated 1,2,3,7,8-pentachlorodibenzo-p-dioxin was not transformed by the strain RW1. The importance of substitution patterns for the degradability of individual congeners was illustrated by the fact that the 1,2,3-trichlorodibenzo-p-dioxin was catabolized to yield 3,4,5-trichlorocatechol, whereas the 2,3,7-trichlorodibenzo-p-dioxin was not attacked. Biotransformation of 1,2,3-Tri- and 1,2,3,4,7,8-Hexachlorodibenzo-p- Dioxin by Sphingomonas wittichii Strain RW1 Nam et al., 2006 Link
Density functional theory (DFT) calculations were used to explore the relationship between the biotransformation of dibenzo-p-dioxin and selected chlorinated derivatives by resting cells of Sphingomonas wittichii RW1 and measuring the thermodynamic properties of the biotransformation substrates. Sphingomonas wittichii RW1 can aerobically catabolize dibenzo-p-dioxin as well as 2,7-dichloro-, 1,2,3-trichloro-, 1,2,3,4-tetrachloro-, and 1,2,3,4,7,8-hexachlorodibenzo-p-dioxin; however, neither the 2,3,7-trichloro- nor the 1,2,3,7,8-pentachlorodibenzo-p-dioxin was transformed to its corresponding metabolic intermediate. The experimental biotransformation rates established were apparently governed by the selected thermodynamic properties of the substrates tested. Is the biotransformation of chlorinated dibenzo-p-dioxins by Sphingomonas wittichii RW1 governed by thermodynamic factors? Nam et al., 2014 Link
We are developing a bioreactor system for treating dioxin-contaminated soil or water using the dioxin-degrading fungus, Pseudallescheria boydii (P. boydii). In order to design the bioreactor system, this study estimated the rate at which P. boydii degraded 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), which is the most toxic of the dioxins. The experimental results showed that P. boydii degraded 2,3,7,8-TCDD during its logarithmic growth phase, using glucose as a carbon source for growth, and that the growth of P. boydii was not affected by 2,3,7,8-TCDD concentrations usually found at contaminated sites. These results were then used to apply successfully an existing mathematical model to the degradation of 2,3,7,8-TCDD by P. boydii. This allowed an estimation of the rate of degradation of 2,3,7,8-TCDD by P. boydii that can be used in the design of the bioreactor system. Estimation of the biodegradation rate of 2,3,7,8-tetrachlorodibenzo-p-dioxin by using dioxin-degrading fungus, Pseudallescheria boydii Ishii et al., 2009 Link
Polychlorinated dibenzo-p-dioxins and -furans (PCDD/Fs) are among the most harmful environmental contaminants. Their widespread distribution due to unintentional or unknown release coincides with environmental persistence, acute and chronic toxicity to living organisms, and long-term effects due to the compounds’ tendency for bioaccumulation and biomagnification. While microbial aerobic degradation of PCDD/Fs is mainly reported for the turnover of low chlorinated congeners, this review focuses on anaerobic reductive dehalogenation, which may constitute a potential remediation strategy for polychlorinated compounds in soils and sediments. Microorganisms in sediments and in microcosms or enrichment cultures have been shown to be involved in the reductive dechlorination of dioxins. Bacteria related to the genus Dehalococcoides are capable of the reductive transformation of dioxins leading to lower chlorinated dioxins including di- and monochlorinated congeners. Thus, reductive dehalogenation might be one of the very few mechanisms able to mediate the turnover of polychlorinated dioxins by reducing their toxicity and paving the way for a subsequent breakdown of the carbon skeleton. Anaerobic reductive dehalogenation of polychlorinated dioxins Bunge and Lechner. 2009 Link
The potential for microbial dechlorination of the weathered polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was determined in sediments with historical contamination by the chlorophenol wood preservative Ky-5 and its associated dimeric impurities. Sediments were collected from four sites of the Kymijoki River in South-Eastern Finland located at 0, 20, 30, and 60 km downstream from the source of contamination, and at a reference site. We examined the congener profiles of historical PCDD/Fs, including non-2,3,7,8-substituted congeners, and determined the dechlorination potential in sediments at the different sites of the river. The measured mean total concentrations for 2,3,7,8-PCDD/Fs were extremely high, 1200 mg/kg dw, at the most contaminated site, Kuusankoski. The mean concentrations for the predominant 2,3,7,8-congeners were 1,2,3,4,6,7,8-HpCDF 780 mg/kg dw, and for OCDF 380 mg/kg dw at Kuusankoski. At all other study sites of the river the mean total concentrations for 2,3,7,8-PCDD/Fs varied between 9 and 96 mg/kg dw, (6–80 mg/kg dw for 1,2,3,4,6,7,8-HpCDF, 3–13 mg/kg dw for OCDF). The sediment PCDD/F composition was similar to that of Ky-5, indicating that no or only minimal biodegradation of PCDD/F congeners has occurred in the river sediments over the last few decades since the contamination events. Microbes capable of PCDD/F dechlorination were present at all study sites based on Dehalococcoides-like Chloroflexi community determination and dechlorination of spiked 1,2,3,4-tetrachlorodibenzofuran. However, no substantial changes in the relative abundances of PCDD/Fs were observed over 2.5 years in laboratory microcosm studies, indicating that anaerobic dechlorination of weathered PCDD/Fs was limited over the course of the experiment. Therefore, concentrations of weathered PCDD/Fs in the sediments of the Kymijoki River are expected to remain at the same level for decades or centuries with further migration towards the Baltic Sea. Dechlorinating bacteria are abundant but anaerobic dechlorination of weathered polychlorinated dibenzo-p-dioxins and dibenzofurans in contaminated sediments is limited? Mäntynen et al., 2017 Link
Anaerobic enrichment cultures derived from contaminated Kymijoki River sediments dechlorinated 1,2,3,4-tetrachlorodibenzofuran (1,2,3,4-tetra-CDF), octachlorodibenzofuran (octa-CDF) and 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-tetra-CDD). 1,2,3,4-tetra-CDF was dechlorinated via 1,2,3-, 2,3,4-, and 1,3,4/1,2,4-tri-CDFs to 1,3-, 2,3-, and 2,4-di-CDFs and finally to 4-mono-CDF. The dechlorination rate of 1,2,3,4-tetra-CDF was generally slower than that of 1,2,3,4-tetra-CDD. The rate and extent of 1,2,3,4-tetra-CDD dechlorination was enhanced by addition of pentachloronitrobenzene (PCNB) as a co-substrate. Dechlorination of spiked octa-CDF was observed with the production of hepta-, hexa-, penta- and tetra-CDFs over 6 months. Two major phylotypes of the Chloroflexi community showed an increase, one of which was identical to the Dehalococcoides mccartyi Pinellas subgroup. A set of twelve putative reductive dehalogenase (rdh) genes increased in abundance with addition of 1,2,3,4-tetra-CDF, 1,2,3,4-tetra-CDD and/or PCNB. This information will aid in understanding how indigenous microbial communities impact the fate of PCDFs and in developing strategies for bioremediation of PCDD/F contaminated sediments. Enriching for microbial reductive dechlorination of polychlorinated dibenzo-p-dioxins and dibenzofurans Liu et al., 2014 Link
Pentachlorophenol (PCP) is a toxic and persistent wood and cellulose preservative extensively used in the past decades. The production process of PCP generates polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) as micropollutants. PCDD/Fs are also known to be very persistent and dangerous for human health and ecosystem functioning. Several physico-chemical and biological technologies have been used to remove PCP and PCDD/Fs from the environment. Bacterial degradation appears to be a cost-effective way of removing these contaminants from soil while causing little impact on the environment. Several bacteria that cometabolize or use these pollutants as their sole source of carbon have been isolated and characterized. This review summarizes current knowledge on the metabolic pathways of bacterial degradation of PCP and PCDD/Fs. PCP can be successfully degraded aerobically or anaerobically by bacteria. Highly chlorinated PCDD/Fs are more likely to be reductively dechlorinated, while less chlorinated PCDD/Fs are more prone to aerobic degradation. The biochemical and genetic basis of these pollutants’ degradation is also described. There are several documented studies of effective applications of bioremediation techniques for the removal of PCP and PCDD/Fs from soil and sediments. These findings suggest that biodegradation can occur and be applied to treat these contaminants. Bacterial Biotransformation of Pentachlorophenol and Micropollutants Formed during Its Production Process Lopez-Echartea et al., 2016 Link