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PubMedDate not supplied

Peroxidase-catalyzed oxidation of chlorophenols to polychlorinated dibenzo-p-dioxins and dibenzofurans.

Chlorophenols are transformed in vitro to polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) by peroxidase-catalyzed oxidations. This is demonstrated with bovine lactoperoxidase as well as horseradish peroxidase, and with 3,4,5- and 2,4,5-trichlorophenol (TrCP). The yield of total PCDD/Fs with lactoperoxidase was 11 micrograms per g 345-TrCP and 10 micrograms per g 245-TrCP, of which 2,3,7,8-substituted PCDD/Fs constituted 8.5 and 2.2 micrograms/g, respectively, corresponding to 0.85 and 1.2 micrograms/g of Nordic TCDD-equivalents.

Animals↗
PubMed1989

Bovine spermatozoa as an in vitro model for studies on the cytotoxicity of chemicals: effects of chlorophenols.

The suitability of ejaculated bovine spermatozoa as an in vitro model for the assessment of the cytotoxic potential of chemicals was evaluated using several endpoints: swimming activity, adenine nucleotide content, membrane integrity and oxygen consumption. A series of chlorophenols inhibited sperm motion (motility and velocity) in a concentration-dependent manner. This could be determined quantitatively and reproducibly by means of videomicrography and automatic computer image analysis. The sperm immobilizing potency increased with increasing chlorination and was positively correlated with lipophilicity. Concentrations which reduced the percentage of moving sperm to 50% of controls ranged from 43 microM for pentachlorophenol (PCP) to 1440 microM for 4-monochlorophenol (4-MCP). Determinations of adenine nucleotides and percentages of viable cells revealed qualitative differences between the action of PCP and the lower chlorinated phenols. While the latter decreased the total adenine nucleotide contents and the percentage of unstained cells in parallel to motion inhibition, no such changes occurred after exposure to immobilizing concentrations of PCP. Penta-, tetra- and trichlorinated phenols stimulated cellular respiration, indicating their uncoupling activity, at concentrations lower than those necessary for motion inhibition. The results indicate that bovine spermatozoa may become a useful in vitro model for the toxicological evaluation of chemicals providing quantitative as well as qualitative data.

Adenine Nucleotides↗
PubMed2003

Combined isobutoxycarbonylation and tert-butyldimethylsilylation for the GC/MS-SIM detection of alkylphenols, chlorophenols and bisphenol A in mackerel samples.

The alkylphenols, chlorophenols, and bisphenol A were determined by gas chromatography/mass spectrometry-selected ion monitoring (GC/MS-SIM) followed by two work-up methods for comparison: isobutoxycarbonyl (isoBOC) derivatization and tert-butyldimethylsilyl (TBDMS) derivatization. Eleven endocrine disrupting chemicals (EDCs) of phenols in biological samples were extracted with acetonitrile and then the acetonitrile layer underwent freezing filtration 60 degrees C for 2 hours. Solid-phase extraction (SPE) was used with XAD-4 and subsequent conversion to isoBOC or TBDMS derivatives for sensitivity analysis with the GC/MS-SIM mode. For isoBOC derivatization and TBDMS derivatization the recoveries were 92.3 approximately 150.6% and 93.8-108.3%, the method detection limits (MDLs) of bisphenol A for SIM were 0.062 microg/kg and 0.010 microg/kg, and the SIM responses were linear with the correlation coefficient varying by 0.9755-0.9981 and 0.9908-0.9996, respectively. When these methods were applied to mackerel samples, the concentrations of the 11 phenol EDCs were below the MDL.

Aldehydes↗
PubMed1999

Diversity of chlorophenol-degrading bacteria isolated from contaminated boreal groundwater.

Chlorophenol-degrading bacteria from a long-term polluted groundwater aquifer were characterized. All isolates degraded 2,4,6-trichlorophenol and 2,3,4,6-tetrachlorophenol at concentrations detected in the contaminated groundwater (< 10 mg 1(-1)). Pentachlorophenol was degraded by three isolates when present alone. In two gram-positive isolates, 2,3,4,6-tetrachlorophenol was required as an inducer for the degradation of pentachlorophenol. The gram-positive isolates were sensitive to pentachlorophenol, with an IC50 value of 5 mg/l. Isolates belonging to the Cytophaga/Flexibacter/Bacteroides phylum had IC50 values of 25 and 63 mg/l. Isolates belonging to alpha-, beta- and gamma-Proteobacteria generally tolerated the highest pentachlorophenol concentrations (> 100 mg/l). Polychlorophenol-degrading capacity was found in strains of Nocardioides, Pseudomonas, Ralstonia, Flavobacterium, and Caulobacter previously not known to degrade polychlorophenols. In addition, six polychlorophenol-degrading sphingomonads were found.

Bacteria↗
PubMed2001

A Desulfitobacterium strain isolated from human feces that does not dechlorinate chloroethenes or chlorophenols.

An anaerobic bacterium, strain DP7, was isolated from human feces in mineral medium with formate and 0.02% yeast extract as energy and carbon source. This rod-shaped motile bacterium used pyruvate, lactate, formate, hydrogen, butyrate, and ethanol as electron donor for sulfite reduction. Other electron acceptors such as thiosulfate, nitrate and fumarate stimulated growth in the presence of 0.02% yeast extract and formate. Acetate was the only product during fermentative growth on pyruvate. Six mol of pyruvate were fermented to 7 mol of acetate. 13C-NMR labeling experiments showed homoacetogenic 13C-CO2 incorporation into acetate. The pH and temperature optimum of fermentative growth on pyruvate was 7.4 and 37 degrees C, respectively. The growth rate under these conditions was approximately 0.10 h(-1). Strain DP7 was identified as a new strain of Desulfitobacterium frappieri on the basis of 16S rRNA sequence analysis (99% similarity) and DNA-DNA hybridization (reassociation value of 83%) with Desulfitobacterium frappieri TCE1. In contrast to described Desulfitobacterium strains, the newly isolated strain has not been isolated from a polluted environment and did not use chloroethenes or chlorophenols as electron acceptor.

Bacteria, Anaerobic↗
PubMed2005

Lichen-based biosensor for the determination of benzene and 2-chlorophenol: microcalorimetric and amperometric investigations.

Preliminary microcalorimetric studies have been performed to analyse the response of a whole epiphytic lichen tissue (Evernia prunastri) to 2-chlorophenol (2Cl-phi), a pollutant of oil mill waste-water, in order to evaluate whether the tissue might be used to assess the toxic characteristics of polluted waters. The obtained results (lichen viability expressed in hours, enthalpy variations for the 2Cl-phi/lichen interactions) were used to create a lichen-based biosensor that uses an amperometric oxygen electrode (a Clark electrode) as a transducer. The lichen catalyses aromatic ring cleavage (via pyrocatechase enzymes present in the lichen), and transforms aromatic substances like 2Cl-phi into muconic acid (C6H6O4). Following a full electroanalytical characterisation, the performance of the proposed lichen biosensor was compared to that of a biosensor based on Pseudomonas putida cells, which was originally constructed to monitor benzene in different matrices (water, air, petrol and oil) and was tested in our laboratory previously.

Benzene↗
PubMed2005

Aquatic degradation of triclosan and formation of toxic chlorophenols in presence of low concentrations of free chlorine.

The degradation of 2-(2,4-dichlorophenoxy)-5-chlorophenol (triclosan) in chlorinated water samples was investigated. Sensitive determination of the parent compound and its transformation products was achieved by gas chromatography with mass spectrometry detection after sample concentration, using a solid-phase extraction sorbent and silylation of the target compounds. Experiments were accomplished using ultrapure water spiked with chlorine and triclosan concentrations in the low mg/l and ng/ml ranges respectively. Chlorination of the phenolic ring and cleavage of the ether bond were identified as the main triclosan degradation pathways. Both processes led to the production of two tetra- and a penta-chlorinated hydroxylated diphenyl ether, as well as 2,4-dichlorophenol. The formation of 2,3,4-trichlorophenol was not detected in any experiment; however, significant amounts of 2,4,6-trichlorophenol were noticed. All of these five compounds were also identified when triclosan was added to tap-water samples with free chlorine concentrations below 1 mg/l. Minor amounts of three di-hydroxylated phenols, containing from one to three atoms of chlorine in their structures, were also identified as unstable triclosan chlorination by-products. The analysis of several raw wastewater samples showed the co-existence of important concentrations of triclosan and its most stable by-products (2,4-dichlorophenol and 2,4,6-trichlorophenol), reinforcing the potential occurrence of the described transformations when products containing triclosan are mixed with chlorinated tap water.

Chlorine↗
PubMed2001

A stable glucose biosensor prepared by co-immobilizing glucose oxidase into poly(p-chlorophenol) at a platinum electrode.

An amperometric glucose biosensor was successfully developed by electrochemical polymerization of p-chlorophenol (4-CP) at a Pt electrode in the presence of glucose oxidase. The amperometric response of this biosensor to hydrogen peroxide, formed as the product of enzymatic reaction, was measured at a potential of 0.6 V (vs. SCE) in phosphate buffer solution. The performances of sensors, prepared at different monomer concentrations and polymerization potentials, were investigated in detail. The biosensor prepared under optimal conditions had a linear response to glucose ranging from 2.5 x 10(-4) to 1.5 x 10(-2) mol L(-1) with a correlation coefficient of 0.997 and a response time of less than 2 s. Substrate selectivity of the polymer-based enzyme electrode was tested for coexisting interferents such as uric acid and ascorbic acid, and no discernible response was observed. After 90 days, the response of the biosensor remained almost unchanged, indicating very good stability.

Biosensing Techniques↗
PubMed2002

Developing and sustaining 3-chlorophenol-degrading populations in up-flow anaerobic column reactors under circum-denitrifying conditions.

Microbial consortia capable of degrading 3-chlorophenol (3-CP) were enriched in continuous up-flow column reactors under circum-denitrifying conditions. 3-CP degradation capability was developed and sustained when 3-CP was supplied at 16-21 microM, although suppression of the 3-CP degradation capability was observed when 3-CP was supplied at 42 microM. When 3-CP was stably degraded, the ratio of nitrate consumption to 3-CP degradation approached the theoretical stoichiometric value, which was calculated by assuming a 3-CP degradation-dependent nitrate reduction. Batch-incubation experiments demonstrated that the microbial consortium that was enriched in the column reactors required either nitrate or oxygen for degrading 3-CP, while 3-CP was not degraded under sulfate-degrading conditions. Although many attempts were made to sustain the microbial 3-CP degradation capability under denitrifying conditions, mostly in batch cultures, none of them have been successful so far. Therefore, the results obtained in this study may be the first to demonstrate sustainable 3-CP degradation capability under circum-denitrifying conditions.

Anaerobiosis↗
PubMed2002

Degradation of chlorophenols by Phanerochaete chrysosporium: effect of 3,4-dichlorophenol on extracellular peroxidase activities.

Extracellular peroxidases play an important role in the degradation of chlorophenols by Phanerochaete chrysosporium. Depending on the moment of 3,4-dichlorophenol addition, the production of lignin peroxidase and manganese peroxidase in C-limited agitated cultures was affected in opposite ways. In cultures that received 3,4-dichlorophenol at the time of inoculation, fungal growth was reduced and peroxidases were not produced, whereas peroxidase activities were stabilized after 3,4-dichlorophenol addition to pregrown cultures. Further investigation revealed that mRNA encoding lignin peroxidase was not produced in cultures started with 3,4-dichlorophenol, suggesting that the onset of secondary metabolism was affected. In addition, the stabilization of lignin peroxidase activity was not the result of an activation of lignin peroxidase gene transcription, as shown by Northern blot experiments, but likely due to the inhibition of peroxidase degradation by extracellular proteases.

Biodegradation, Environmental↗
PubMed2002

Adaptation of the white-rot basidiomycete Panus tigrinus for transformation of high concentrations of chlorophenols.

During feed-batch cultivation of the white-rot fungus Panus tigrinus in a 5-l bioreactor on N-limited medium, 100, 200, 500, 1,000 and 2,000 mg 2,4,6-trichlorophenol (2,4,6-TCP) l(-1) were added sequentially after 90% removal of the previous portion of the toxicant. The addition of 500 mg 2,4,6-TCP l(-1) without preliminary adaptation killed the culture. The addition of 300 mg 2,4,6-TCP l(-1) without prior adaptation resulted in its slower removal than removal of 2,000 mg 2,4,6-TCP l(-1) by this adapted culture. After adaptation of P. tigrinus to 2,4,6-TCP in a 72-l bioreactor, the mixture of 2,4-dichlorophenol, 2,4,6-TCP, and pentachlorophenol, each at 500 mg x l(-1), was totally removed over 3 weeks. No lignin peroxidase activity was found in the course of cultivation of the fungus. Laccase activity was suppressed by addition of 2,4,6-TCP. Mn-peroxidase was found to be responsible for transformation of the chlorophenols. As final products of the process, several newly formed aromatic polymers, both chlorinated and non-chlorinated, were found in the culture liquid.

Adaptation, Physiological↗
PubMed1999

4-Chlorophenol degradation by a bacterial consortium: development of a granular activated carbon biofilm reactor.

A bacterial consortium that can degrade chloro- and nitrophenols has been isolated from the rhizosphere of Phragmitis communis. Degradation of 4-chlorophenol (4-CP) by a consortium attached to granular activated carbon (GAC) in a biofilm reactor was evaluated during both open and closed modes of operation. During the operation of the biofilm reactor, 4-CP was not detected in the column effluent, being either adsorbed to the GAC or biodegraded by the consortium. When 4-CP at 100 mg l-1 was fed to the column in open mode operation (20 mg g-1 GAC total supply), up to 27% was immediately available for biodegradation, the rest being adsorbed to the GAC. Biodegradation continued after the system was returned to closed mode operation, indicating that GAC bound 4-CP became available to the consortium. Biofilm batch cultures supplied with 10-216 mg 4-CP g-1 GAC suggested that a residual fraction of GAC-bound 4-CP was biologically unavailable. The consortium was able to metabolise 4-CP after perturbations by the addition of chromium (Cr VI) at 1-5 mg l-1 and nitrate at concentrations up to 400 mg l-1. The development of the biofilm structure was analysed by scanning electron microscopy and confocal laser scanning microscopy (CLSM) techniques. CLSM revealed a heterogeneous structure with a network of channels throughout the biofilm, partially occupied by microbial exopolymer structures.

Anaerobiosis↗
PubMed2001

A GAC biofilm reactor for the continuous degradation of 4-chlorophenol: treatment efficiency and microbial analysis.

Using a continuous enrichment technique, a bacterial consortium capable of degrading 4-chlorophenol (4-CP) was obtained from the rhizosphere of Phragmites australis. A granular activated carbon (GAC) biofilm reactor was established using this consortium, and the degradation of 4-CP was investigated under continuous flow operation using a feed of 20-50 mg l(-1) with a hydraulic residence time of 17 min over a 6-month period. Chloride liberation occurred throughout the operation, and the reactor had 4-CP removal efficiencies of 69-100%. Periods of lower performance were attributed to clogging of the column with biomass and the formation of channels. Subsequently, the immobilized biofilm was subjected to a starvation period of 5 months, after which its degradative capacity was still maintained. The microbial consortium was characterized during the continuous flow experiment and dynamic population changes were observed throughout. One isolate recovered from the biofilm was shown to be capable of degrading 4-CP as a sole carbon and energy source.

Biofilms↗
PubMed1989

In vivo and in vitro studies of the hepatotoxic effects of 4-chlorophenol in mice.

4-Chlorophenol (4-CP) was studied for its toxicological effect on liver by using both in vivo and in vitro approaches. Male mice were administered 4-CP, 1.5 mmol/kg body weight, i.p., and were killed at 10, 20, 30 and 50 min after drug injection. Either i.p. or oral 4-CP administration significantly lowered total liver thiol levels by 20-30% after 30 min and 3 hr respectively. This time-dependent effect of 4-CP after i.p. treatment was enhanced when mice were pretreated with hepatic microsomal enzyme inducers (phenobarbital, 40 mg/kg body weight, b.i.d., 7 days; and beta-naphthoflavone, 80 mg/kg body weight once daily, 4 days). Further, the microsomal cytochrome P-450 inhibitor, SKF 525-A, 75 mg/kg body weight injected i.p. to mice 30 min prior to 4-CP administration, blocked the reduction of liver thiol content produced by 4-CP. The results suggest that a chemically reactive intermediate of 4-CP may be formed in liver which is responsible for the observed decrease in liver thiol content. Other investigations were done to characterize the in vitro irreversible binding of [14C]4-CP. [14C]4-CP was bound irreversibly to mouse liver microsomal proteins in a concentration-dependent manner. Binding was NADPH dependent and gave a maximal binding of 12.0 nmol/mg protein/20 min and an apparent binding constant of 0.222 mM. [14C]-Binding of 4-CP was increased by 155 and 127% in liver microsomes of phenobarbital- and beta-naphthoflavone. SKF 525-A, and CO:O2 (4:1, v/v)] and selected nucleophilic compounds (glutathione, L-cysteine or L-lysine) significantly reduced [14C]4-CP binding to mouse liver microsomes. An epoxide hydrolase inhibitor, cyclohexene oxide, did not alter the extent of irreversible binding, whereas scavengers of superoxide anions or agents that are reported to reduce accumulation of active semiquinone and quinone species (L-ascorbic acid, superoxide dismutase or epinephrine) decreased the binding of [14C]4-CP to mouse liver microsomal proteins by 56, 31 and 92% respectively. The data suggest that semiquinone and quinone species of 4-CP may be the chemically reactive intermediates leading to the in vivo reduction of liver thiol levels. Since 4-CP is a minor contaminant and possible metabolite of clofibrate and chemically related hypolipidemic agents, 4-CP and its metabolites may be partly responsible for some of the hepatotoxic effects seen after long-term administration of this therapeutic class of drugs.

Administration, Oral↗
PubMed1984

Toxicity and QSAR of chlorophenols on Lebistes reticulatus.

The 24-h toxicity of 20 substituted chlorophenols upon Lebistes reticulatus has been determined. The biological results have been tentatively connected with several of the following six parameters: logarithm of the octanol-water partition coefficient (log P); index of molecular connectivity (1 chi v); molecular refraction (RM); perimeter of the efficient section of the molecule (sigma D); constants of HAMMET (sigma); and melting point (F). A correlation is achieved using sigma D and sigma D2 with a correlation coefficient of 0.943.

Animals↗
PubMed1984

Fate and effects of 4-chlorophenol and 2,4-dichlorophenol in marine plankton communities in experimental enclosures.

The fate and effects of 4-chlorophenol (4CP) and 2,4-dichlorophenol (DCP) added to North Sea coastal plankton communities enclosed by large plastic bags were studied in three experiments of 4 to 6 weeks duration. The biodegradation of the compounds was studied in laboratory experiments using water from the enclosed ecosystems. 4CP and DCP, added at initial concentrations of 0.1-1.0 mg X liter-1, disappeared from the water in the enclosures in 5 to 23 days, 4CP generally being the less persistent. Degradation rates were generally comparable to those found in laboratory tests with the same water. 4CP was removed by biodegradation, and DCP was probably removed by a combination of biodegradation, photodegradation, and/or chemical degradation. Results indicated that biodegradation rates could be limited by lack of inorganic nutrients, leading to much lower degradation rates than would be expected from routine laboratory tests. Faster degradation after repeated addition of 4CP showed adaption of the bacterial community. Addition of 0.3 mg liter-1 4CP or DCP inhibited the phytoplankton growth rate slightly. The 1 mg liter-1 4CP or DCP inhibited the phytoplankton, changed the species composition, and also influenced the zooplankton. In two of the three experiments 1 mg liter-1 DCP resulted in a temporary lowering of bacterial numbers following the addition. In one experiment inhibitory effects were found after 4CP and DCP had disappeared from the water, pointing to the formation of a more toxic intermediate during the degradation of these compounds. The laboratory tests also indicated the formation of relatively stable intermediates. The concentrations causing the effects in the different bag experiments were quite similar. This indicates that, although the development of the plankton communities during the different experiments was different, the concentrations resulting in ecological effects are quite reproducible.

Animals↗
PubMed1995

Developmental toxicity and structure-activity relationships of chlorophenols using human embryonic palatal mesenchymal cells.

The chlorophenols (CPs) comprise a major class of widely distributed and frequently occurring environmental contaminants. Previous studies have demonstrated the adverse effects of CPs on embryonic and fetal development. HEPM (human embryonic palatal mesenchymal) and MOT (mouse ovarian tumor) cell lines have been utilized in complementary bioassays for the detection of teratogens, but not the CPs. In this study, our objectives were 2-fold: (1) to determine if the HEPM assay could be used to complement other bioassay systems of nonhuman origin, i.e., Hydra attenuata (HA) and rat whole embryo culture (WEC), in the evaluation of the developmental toxicity of CPs, and (2) to delineate the ability of the HEPM assay to evaluate structure-activity relationships of pentachlorophenol (C5P), 2,3,4,5-tetrachlorophenol (C4P), 2,3,5-trichlorophenol (C3P), 3,5-dichlorophenol (C2P), 4-monochlorophenol (CP), phenol, and CP derivatives (i.e., acetates, sodium phenates and anisoles). HEPM cells were seeded into each well of a 24-well plate and cultivated for 24 h. The medium was replaced with fresh medium containing various concentrations of test chemicals dissolved in dimethyl sulfoxide (DMSO, 0.1%). After culturing for 72 h, the medium was removed, cells were trypsinized, and cell number determined. The HEPM cell growth inhibition assay demonstrated a linear relationship between the IC50 values of the CPs and degree of chlorine substitution. The IC50 values of C5P, C4P, C3P, C2P, CP, and phenol were 18.8, 21.5, 27.5, 63.0, 150.0 and 470.0 microM, respectively. A clear structure-activity relationship was observed between toxicity of CPs and the degree of chlorine substitution. The rank order of CP toxicity from the HEPM assay (i.e., C5P > C4P > C3P > C2P > CP > phenol) is in excellent agreement with previous in vitro and in vivo studies. However, contrary to published reports, the HEPM assay predicted that all CPs were teratogenic (false positives). These findings suggest that the HEPM cell growth inhibition bioassay may be useful to discriminate between subtle differences in structure-activity and, in combination with other bioassays, might facilitate the rapid detection and prioritization of diverse cytotoxins, including various developmental toxicants. Importantly, conclusions about the teratogenicity of a test chemical (via HEPM testing) should be approached with caution and confirmed with other teratogen-sensitive systems.

Animals↗
PubMed2004

Influence of the origin of the inoculum and the acclimation strategy on the degradation of 4-chlorophenol.

The influence of the inoculum source and the acclimation strategy on the 4-chlorophenol (4CP) degradation in a sequencing batch reactor (SBR) was studied. Three different sources of inocula were obtained from the aeration tank of domestic, municipal and industrial wastewater treatment plants. The acclimation was performed using two strategies, the first one fixing the reaction time, independent of the removal efficiency (fixed time) and the second one fixing a removal efficiency of 90% as 4CP (variable time). The degradative activity was followed for each condition. Bacterial identification was carried out at the beginning and at the end of the experiments. Variable time strategy produced a microbial community with higher specific activity compared with those obtained for the fixed time strategy. The microbial activity was dependent of the origin of the inoculum. Each inoculum presented different specific activity to 4CP degradation. It was observed that the use of the fixed time strategy for the acclimation reduced the bacterial community diversity.

Acclimatization↗