Bacterial scission of ether bonds (original) (raw)
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The use of diphenyl ether (DE) and its 4-monohalogenated derivatives (4-HDE) as flame retardants, solvents, and substrates in biocide production significantly increases the risk of ecosystem contamination. Their removal is important from the point of view of environmental protection. The aim of this study was to evaluate the degradation processes of DE and 4-HDE by enzymes of the environmental bacterial strains under one-substrate and co-metabolic conditions. The study is focused on the biodegradation of DE and 4-HDE, the enzymatic activity of microbial strains, and the cell surface properties after contact with compounds. The results show that the highest biodegradation (96%) was observed for 4-chlorodiphenyl ether in co-metabolic culture with P. fluorescens B01. Moreover, the activity of 1,2-dioxygenase during degradation of 4-monohalogenated diphenyl ethers was higher than that of 2,3-dioxygenase for each strain tested. The presence of a co-substrate provoked changes in dioxygena...
Materials, methods & technologies, 2019
The compounds as 1, 2-dibromoethane, 1, 2-dichloroethane and phenol are ones of the most dangerous pollutants in the environment. 1, 2-Dibromoethane (DBE) is a synthetic organic chemical that is mainly used as a gasoline additive. It is also one of the widely used pesticide fumigants. 1,2Dichloroethane is one of the most commonly used chlorinated industrial products and falls into the environment by using it as a chemical intermediate in the synthesis of a number of chlorinated hydrocarbons. Phenol is a waste product from the plastics, petroleum and pharmaceutical industries. There are different methods for treating wastewater containing the listed xenobiotics. Applied physicochemical methods are often economically ineffective and may cause other toxic products to occur. For this reason, microbiological treatment methods are preferred. We tested three different bacterial strains: Pseudomonas putida, Bradyrhizobium japonicum and Xanthobacter autotrophicus GJ10. In our studies for a p...
Mechanism of Anaerobic Ether Cleavage
Journal of Biological Chemistry, 2002
2-Phenoxyethanol is converted into phenol and acetate by a strictly anaerobic Gram-positive bacterium, Acetobacterium strain LuPhet1. Acetate results from oxidation of acetaldehyde that is the early product of the biodegradation process (Frings, J., and Schink, B. (1994) Arch. Microbiol. 162, 199-204). Feeding experiments with resting cell suspensions and 2-phenoxyethanol bearing two deuterium atoms at either carbon of the glycolic moiety as substrate demonstrated that the carbonyl group of the acetate derives from the alcoholic function and the methyl group derives from the adjacent carbon. A concomitant migration of a deuterium atom from C-1 to C-2 was observed. These findings were confirmed by NMR analysis of the acetate obtained by fermentation of 2-phenoxy-[2-13 C,1-2 H 2 ]ethanol, 2-phenoxy-[1-13 C,1-2 H 2 ]ethanol, and 2-phenoxy-[1,2-13 C 2 ,1-2 H 2 ]ethanol. During the course of the biotransformation process, the molecular integrity of the glycolic unit was completely retained, no loss of the migrating deuterium occurred by exchange with the medium, and the 1,2deuterium shift was intramolecular. A diol dehydrataselike mechanism could explain the enzymatic cleavage of the ether bond of 2-phenoxyethanol, provided that an intramolecular H/OC 6 H 5 exchange is assumed, giving rise to the hemiacetal precursor of acetaldehyde. However, an alternative mechanism is proposed that is supported by the well recognized propensity of ␣-hydroxyradical and of its conjugate base (ketyl anion) to eliminate a -positioned leaving group. Ether linkages are comparably stable, and their cleavage requires rather rigorous conditions. Such cleavage reactions represent challenges also to microbes and their enzymes, and this difficulty causes the relative stability of many ether compounds in nature (1). An important group of xenobiotic ether compounds, the linear polyether PEG 1 and its derivatives, is released into the * This work was supported in part by a grant from the Deutsche Forschungsgemeinschaft, Bonn in its priority program "Radicals in enzymatic catalysis." The costs of publication of this article were defrayed in part by the payment of page charges.
Biodegradation of Ether Pollutants by Pseudonocardia sp. Strain ENV478
Applied and Environmental Microbiology, 2006
A bacterium designated Pseudonocardia sp. strain ENV478 was isolated by enrichment culturing on tetrahydrofuran (THF) and was screened to determine its ability to degrade a range of ether pollutants. After growth on THF, strain ENV478 degraded THF (63 mg/h/g total suspended solids [TSS]), 1,4-dioxane (21 mg/h/g TSS), 1,3-dioxolane (19 mg/h/g TSS), bis-2-chloroethylether (BCEE) (12 mg/h/g TSS), and methyl tert-butyl ether (MTBE) (9.1 mg/h/g TSS). Although the highest rates of 1,4-dioxane degradation occurred after growth on THF, strain ENV478 also degraded 1,4-dioxane after growth on sucrose, lactate, yeast extract, 2-propanol, and propane, indicating that there was some level of constitutive degradative activity. The BCEE degradation rates were about threefold higher after growth on propane (32 mg/h/g TSS) than after growth on THF, and MTBE degradation resulted in accumulation of tert-butyl alcohol. Degradation of 1,4-dioxane resulted in accumulation of 2-hydroxyethoxyacetic acid (2...
Biodegradation of Bis(2-Chloroethyl) Ether by Xanthobacter sp. Strain ENV481
Applied and Environmental Microbiology, 2007
Degradation of bis(2-chloroethyl) ether (BCEE) was observed to occur in two bacterial strains. Strain ENV481, a Xanthobacter sp. strain, was isolated by enrichment culturing of samples from a Superfund site located in the northeastern United States. The strain was able to grow on BCEE or 2-chloroethylethyl ether as the sole source of carbon and energy. BCEE degradation in strain ENV481 was facilitated by sequential dehalogenation reactions resulting in the formation of 2-(2-chloroethoxy)ethanol and diethylene glycol (DEG), respectively. 2-Hydroxyethoxyacetic acid was detected as a product of DEG catabolism by the strain. Degradation of BCEE by strain ENV481 was independent of oxygen, and the strain was not able to grow on a mixture of benzene, ethylbenzene, toluene, and xylenes, other prevalent contaminants at the site. Another bacterial isolate, Pseudonocardia sp. strain ENV478 (S. Vainberg et al., Appl. Environ. Microbiol. 72:5218-5224, 2006), degraded BCEE after growth on tetrahydrofuran or propane but was not able to grow on BCEE as a sole carbon source. BCEE degradation by strain ENV478 appeared to be facilitated by a monooxygenase-mediated Odealkylation mechanism, and it resulted in the accumulation of 2-chloroacetic acid that was not readily degraded by the strain.
Biodegradation of Xenobiotics in Environment and Technosphere
The Handbook of Environmental Chemistry
Microorganisms play an important role in the removal of synthetic organic compounds from the environment. This chapter gives an overview of the evolution of biodegradation pathways and describes the strategies that microorganisms have evolved to transform important molecular structures. The actual effectiveness of biodegradation in the environment is determined by the bioavailability of the compounds. As a general rule, one could state that the release rates of synthetic compounds should not exceed the environment's ability to degrade them.
Microbial diversity: Application of micro- organisms for the biodegradation of xenobiotics
2005
Environmental pollution caused by the release of a wide range of compounds as a consequence of industrial progress has now assumed serious proportions. Thousands of hazardous waste sites have been generated worldwide resulting from the accumulation of xenobiotics in soil and water over the years. Nitroaromatic compounds (NACs), polycyclic aromatics and other hydrocarbons (PAHs) that are constituents of crude oil, and halogenated organic compounds together constitute a large and diverse group of chemicals that are responsible for causing widespread environmental pollution. The physico-chemical remedial strategies to clean up sites contaminated by these compounds are not cost effective or adequate enough. Therefore, research is increasingly being focused on biological methods for the degradation and elimination of these pollutants. Sites contaminated by these compounds need urgent remedial solutions, the search for which has revealed a diverse range of bacteria that can utilize these xenobiotics as substrates, often mineralizing them or converting them into harmless products, and in the process helping to clean up the environment. New genes, enzymes and metabolic routes involved in bacterial degradation of PAHs, NACs and halogenated organic compounds (HOCs) have been discovered, and new methods have been developed which allow the discovery and broad flexibility of microorganisms in environmental clean up. Studies to understand the interaction between xenobiotics and microorganisms in the environment have to intersect with biochemical and genetic engineering areas. Such a strategy will provide the ground for successful interventions into environmental processes and ultimately lead to optimized strategies for tapping of microbial diversity for efficient and effective bioremediation of xenobiotics.
Anaerobic microbial and photochemical degradation of 4,4′-dibromodiphenyl ether
Water Research, 2003
The anaerobic microbial and photochemical degradation pathways of 4,4 0 -dibromodiphenyl ether (BDE15) were examined. BDE15 was reductively debrominated within a fixed-film plug-flow biological reactor at hydraulic retention times of 3.4 and 6.8 h, leading to exclusive production of 4-bromodiphenyl ether (BDE3) and diphenyl ether (DE). A suite of potential BDE15 metabolites arising from reductive debromination, hydroxylation, and methoxylation of the aromatic C-Br and C-H bonds were not observed. Following initial debromination of BDE15, degradation of BDE3 to DE readily occurs, suggesting the rate-limiting step for anaerobic BDE15 degradation is conversion of BDE15 to BDE3. The photochemical degradation of BDE15 was also examined in organic (CH 3 CN and CH 3 OH) and aqueous (H 2 O:CH 3 CN; 1:1 v/v) solvent systems at 300 nm. Only photochemically induced reductive debromination was found to occur via homolytic C-Br bond cleavage, with no evidence of C-O bond cleavage or products arising from heterolytic bond cleavage. r
Environmental Toxicology and Chemistry, 2008
Nine bacterial strains isolated from two hydrocarbon-contaminated soils were selected because of their capacity for growth in culture media amended with 200 mg/L of one of the following gasoline oxygenates: Methyl-tert-butyl ether (MTBE), ethyl-tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). These strains were identified by amplification of their 16S rRNA gene, using fD1 and rD1 primers, and were tested for their capacity to grow and biotransform these oxygenates in both mineral and cometabolic media. The isolates were classified as Bacillus simplex, Bacillus drentensis, Arthrobacter sp., Acinetobacter calcoaceticus, Acinetobacter sp., Gordonia amicalis (two strains), Nocardioides sp., and Rhodococcus ruber. Arthrobacter sp. (strain MG) and A. calcoaceticus (strain M10) consumed 100 (cometabolic medium) and 82 mg/L (mineral medium) of oxygenate TAME in 21 d, respectively, under aerobic conditions. Rhodococcus ruber (strain E10) was observed to use MTBE and ETBE as the sole carbon and energy source, whereas G. amicalis (strain T3) used TAME as the sole carbon and energy source for growth. All the bacterial strains transformed oxygenates better in the presence of an alternative carbon source (ethanol) with the exception of A. calcoaceticus (strain M10). The capacity of the selected strains to remove MTBE, ETBE, and TAME looks promising for application in bioremediation technologies.