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PubMed2003

Characterization of chlorophenol 4-monooxygenase (TftD) and NADH:flavin adenine dinucleotide oxidoreductase (TftC) of Burkholderia cepacia AC1100.

Burkholderia cepacia AC1100 uses 2,4,5-trichlorophenoxyacetic acid, an environmental pollutant, as a sole carbon and energy source. Chlorophenol 4-monooxygenase is a key enzyme in the degradation of 2,4,5-trichlorophenoxyacetic acid, and it was originally characterized as a two-component enzyme (TftC and TftD). Sequence analysis suggests that they are separate enzymes. The two proteins were separately produced in Escherichia coli, purified, and characterized. TftC was an NADH:flavin adenine dinucleotide (FAD) oxidoreductase. A C-terminally His-tagged fusion TftC used NADH to reduce either FAD or flavin mononucleotide (FMN) but did not use NADPH or riboflavin as a substrate. Kinetic and binding property analysis showed that FAD was a better substrate than FMN. TftD was a reduced FAD (FADH(2))-utilizing monooxygenase, and FADH(2) was supplied by TftC. It converted 2,4,5-trichlorophenol to 2,5-dichloro-p-quinol and then to 5-chlorohydroxyquinol but converted 2,4,6-trichlorophenol only to 2,6-dichloro-p-quinol as the final product. TftD interacted with FADH(2) and retarded its rapid oxidation by O(2). A spectrum of possible TftD-bound FAD-peroxide was identified, indicating that the peroxide is likely the active oxygen species attacking the aromatic substrates. The reclassification of the two enzymes further supports the new discovery of FADH(2)-utilizing enzymes, which have homologues in the domains Bacteria and Archaea.

Bacterial Proteins↗
PubMed1986

Non-Hodgkin's lymphoma and exposure to phenoxyherbicides, chlorophenols, fencing work, and meat works employment: a case-control study.

A previous case-control study which used the occupational information available on the New Zealand Cancer Registry found that agricultural workers were at increased risk of developing non-Hodgkin's lymphoma. The findings are now presented for the second phase of the study which entailed interviewing 83 cases of non-Hodgkin's lymphoma registered under code 202 of the International Classification of Diseases together with 168 controls with other types of cancer and 228 general population controls. The findings for the two control groups were similar, and there were no significant differences between cases and controls regarding potential exposure to phenoxy-herbicides (odds ratio = 1.4, 90% confidence limits 0.7-2.5, p = 0.26) or chlorophenols (odds ratio = 1.3, 90% confidence limits 0.6-2.7, p = 0.39). The odds ratio for fencing work, necessitating exposure to several potential risk factors including arsenic and sodium pentachlorophenate was 2.0 (90% confidence limits 1.3-3.0, p = 0.01). The odds ratio for employment in a meat works, necessitating potential exposure to 2, 4, 6-trichlorophenol and zoonotic viruses, was 1.8 (90% confidence limits 1.1-3.1, p = 0.04). There was a significant statistical interaction between the risks associated with these two activities, the odds ratio for involvement in both activities compared with involvement in neither being 5.7 (90% confidence limits 2.3-14.3, p = 0.03).

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1998

Blood lipid concentrations of dioxins and furans in a sample of BASF employees included in the IARC registry of workers exposed to phenoxy acid herbicides and/or chlorophenols.

Depending on process conditions, polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) may be generated as low-level byproducts of chlorophenol and chlorophenoxy herbicides manufacture. A stratified random sample of 20 active employees from a cohort of phenoxy herbicide workers was selected in 1995 for determining PCDD and PCDF congeners in blood lipids to assess the extent of past PCDD and PCDF exposure in this cohort and whether that exposure might explain site-specific cancer findings in the total cohort. This cohort is included in the IARC International Registry of Persons Exposed to Phenoxyacid Herbicides and Their Contaminants. For the 19 persons who participated, median PCDD and PCDF concentrations were comparable to background concentrations in the general population. Median levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin, the sum of hexachlorodibenzo-p-dioxin, pentachlorodibenzofurans, and two dioxin toxicity equivalents values were statistically higher in 7 employees assigned to synthesis operations than for 12 employees assigned to other operations. However, the PCDD and PCDF concentrations were low relative to those seen in other dioxin-exposed cohorts. We conclude that PCDD and PCDF exposures of cohort members are unlikely to explain the elevated standardized mortality ratios observed in this cohort for several cancer sites.

Adult↗
PubMed2002

4-chlorophenol degradation by chloroperoxidase from Caldariomyces fumago: formation of insoluble products.

This study investigated the degradation of 4-chlorophenol (4-CP) by Caldariomyces fumago chloroperoxidase (CPO). Enzymatic oxidations were studied in reaction mixtures at pH 3.0, 4.0, and 6.0 in the presence and absence of Cl- containing 3.5 IU of CPO and 4-CP and hydrogen peroxide concentrations within the range of 0.5-50 and 0.005-50 mM, respectively. Distinct patterns of products regarding color, concentration, and solubility were observed. Reaction mixtures at pH 6.0 containing 3.5 IU of CPO and 5.0 mM 4-CP and H2O2 (1:1 stoichiometry) showed the highest 4-CP removal of 95% and the highest formation of a dark precipitate.

Archaea↗
PubMedDate not supplied

Enzymatic oxidative transformation of chlorophenol mixtures.

Chlorinated phenols are major industrial and agricultural xenobiotics that pollute soil and ground water. It has been shown that laccases catalyze the oxidative coupling of phenolic compounds. Therefore, the transformation of one or a mixture of several chlorinated phenols by a laccase from the fungus Trametes villosa was studied. Generally, if more than one phenol was added, the transformation of chlorinated phenols decreased, and if the concentration of the laccase was increased, the transformation of the phenols was enhanced. There were exceptions to these observations: for instance, the transformation of 0.1 mM 4-chlorophenol incubated with 1 mM 2,4-dichlorophenol in buffered salt solutions was not enhanced if the concentration of the laccase was increased from 2 to 20 DMP units/mL. The reason for the reduced transformation of chlorinated phenols in the presence of additional phenols is still unknown. However, in spite of some limitations, the application of laccase to decontaminate wastewater polluted with chlorinated phenols appears feasible.

Biotransformation↗
PubMed2006

Biodegradation of high 4-chlorophenol concentrations in a discontinuous reactor fed with an optimally controlled influent flow rate.

This work presents the results of the application of an optimally controlled influent flow rate strategy to biodegrade, in a discontinuous reactor, high concentrations of 4-chlorophenol used as toxic compound model. The influent is fed into the reactor in such a way as to obtain the maximal degradation rate, thus avoiding the inhibition of the microorganisms. The optimal strategy was able to manage increments of toxic concentrations in the influent up to 7,000 mg 4CP/L without any problem. It was shown not only that higher concentrations of toxic could be treated, but also that a reduction in degradation time (around 52%) and in the supplied air volume was obtained.

Bacteria, Anaerobic↗
PubMed2006

Effect of starvation on activity and viability of Pseudomonas aeruginosa ATCC 10145 degrading 4-chlorophenol.

The evolution of degradsation capacity and in the viability of Pseudomonas aeruginosa ATCC 10145 acclimated to 25 mg4CP/L degradation and, later, exposed to starvation periods of 24, 48, 72, 96, 132 and 156 hours was studied. Degradation rate heterotrophic plate count and cell cytometry were used to evaluate the starvation influence. Results demonstrated that the exposition of P. aeruginosa to starvation produces a decrease in the viability and activity for the degradation of 4-chlorophenol.

Acclimatization↗
PubMed1993

Ten and ninety-day toxicity studies of 2-chlorophenol in Sprague-Dawley rats.

Male and female Sprague-Dawley rats received 2-chlorophenol in corn oil daily by gavage for 10 or 90 consecutive days. The 10-day study doses were 13, 64, 129 and 257 mg/kg while the 90-day subchronic study doses were 17, 50 and 150 mg/kg. In the 10-day study, hematologic and clinical chemistry, food and water consumption, absolute and relative organ weights, and histopathological findings revealed no compound or sex-related effects. In the 90-day study there were no significant gross or histopathological findings that were treatment-related in either sex. There were statistically significant differences between control and treated groups associated with hematology, clinical chemistry and organ weights; however, none of the differences were considered to be biologically meaningful.

Animals↗
PubMed1989

Pharmacologic effects of 4-chlorophenol in rats: comparison to clofibrate.

4-Chlorophenol (4-CP) is an identified trace contaminant in commercial clofibrate preparations and the pharmacologic effects of 4-CP have not yet been widely established. We have examined the dose-dependent effects of oral 4-CP and clofibrate administration on selected hepatic parameters and on serum glucose, cholesterol, and triglyceride concentrations in male rats. 4-CP treatment (0.00125-0.08 mmol/kg, twice a day) of rats for 2 weeks increased hepatic microsomal protein (20-30%) and cytochrome P-450 (20-190%) contents without changing liver/body weight ratios. Both 4-CP (0.0025 mmol/kg body wt, twice a day) and CPIB (0.4 mmol/kg body wt, twice a day) treatment to rats for 2 weeks caused significant elevations in microsomal cytochrome P-450 content and in the maximal activities of ethylmorphine, aminopyrine, and benzphetamine N-demethylase, but not in the activity of zoxazolamine 6-hydroxylase. With the same dose of 4-CP, time-dependent increases in hepatic microsomal protein, cytochrome P-450, and the activity of benzphetamine N-demethylase were observed for a 4-week period, and the induction of hepatic microsomal benzphetamine N-demethylase activity by 4-CP was associated with an increased enzyme synthesis. 4-CP treatment produced a marked morphologic change in liver cell ultrastructure, including a proliferation of mitochondria and endoplasmic reticulum at lower 4-CP doses. A clustering of intracellular organelles (mitochondria and endoplasmic reticulum) and a foamy cytoplasm were seen at doses greater than 0.01 mmol/kg, twice a day for 2 weeks, and at 0.0025 mmol/kg, twice a day for greater than 4 weeks. The effects of 4-CP and clofibrate on fasting blood glucose and fasting serum lipid levels were also monitored throughout an 8-week period. Both 4-CP (0.005 mmol/kg body wt, twice a day) and clofibrate (0.2 mmol/kg body wt, twice a day) produced significant elevations in fasting serum glucose levels, but this dosage of 4-CP did not alter serum lipid and lipoprotein parameters, whereas clofibrate significantly reduced serum total cholesterol and high density lipoprotein cholesterol levels. These results lead us to conclude that 4-CP does not contribute to the antilipidemic effects of clofibrate.

Animals↗
PubMed1994

Retrospective assessment of exposure through modeling in a study on cancer risks among workers exposed to phenoxy herbicides, chlorophenols and dioxins.

OBJECTIVES: The study aimed at developing a model for the retrospective assessment of exposures in epidemiologic studies when little or no data on past exposures are available. METHODS: A deterministic model was developed for the level of exposure by industrial hygienists involved in an international study on cancer risks among phenoxy herbicide or chlorophenol manufacturing workers and pesticide sprayers. The general source-receptor model was used as the conceptual framework for the model. RESULTS: The model included variables related to job, the emission of chemicals, contact with chemicals, personal protection, and other relevant determinants of exposure. Cumulative dose indices were calculated from the duration of exposure (from the work histories) and the level of exposure (from the model). CONCLUSIONS: Deterministic modeling in complex exposure situations may provide more valid and reliable results than its conventional alternative, subjective assessment by an expert.

Chlorophenols↗
PubMed1998

Immobilization of manganese peroxidase from Lentinula edodes and its biocatalytic generation of MnIII-chelate as a chemical oxidant of chlorophenols.

Manganese peroxidase (MnP) purified from commercial cultures of Lentinula edodes was covalently immobilized through its carboxyl groups using an azlactone-functional copolymer derivatized with ethylenediamine and 2-ethoxy-1-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) as a coupling reagent. The tethered enzyme was employed in a two-stage immobilized MnP bioreactor for catalytic generation of chelated MnIII and subsequent oxidation of chlorophenols. Manganese peroxidase immobilized in the enzyme reactor (reactor 1) produced MnIII-chelate, which was pumped into another chemical reaction vessel (reactor 2) containing the organopollutant. Reactor 1-generated MnIII-chelates oxidized 2,4-dichlorophenol and 2,4, 6-trichlorophenol in reactor 2, demonstrating a two-stage enzyme and chemical system. H2O2 and oxalate chelator concentrations were varied to optimize the immobilized MnP's oxidation of MnII to MnIII. Oxidation of 1.0 mM MnII to MnIII was initially measured at 78% efficiency under optimized conditions. After 24 h of continuous operation under optimized reaction conditions, the reactor still oxidized 1.0 mM MnII to MnIII with approximately 69% efficiency, corresponding to 88% of the initial MnP activity.

Bioreactors↗
PubMed2001

Heterogeneous catalytic ozonation of 2-chlorophenol aqueous solution with alumina as a catalyst.

Heterogenous catalytic ozonation of 2-chlorophenol (2-CP) in the presence of gamma-alumina as a solid catalyst has been investigated in this research. It showed that the rate for degradation of TOC could increase from 21% to 43%. The pseudo-first reaction constants of 2-CP could increase from 0.8688 min-1 to 0.1270, increasing by approximately 40%. At the same time, the consumption of ozone was only half that of ozone alone. This research also explored the effects of the catalyst dosage, pH values and removal kinetics of 2-CP. In addition, three consecutive running with the same catalyst revealed insignificant reduction of the activity. Furthermore, the elimination of toxicity was evaluated by Microtox analysis. The detoxification was more stable and with good results.

Aluminum Oxide↗
PubMedDate not supplied

Electrochemical oxidation of para-chlorophenol on Ti/SnO2-PbO2 electrodes: introduction of a parameter for the estimation of their efficiency.

To oxidate otherwise non-biodegradable organic pollutants as chlorophenol has recently been proposed the promising electro-combustion technique. We considered two different types of electrodic material: boron doped diamond (BDD) and lead dioxide electro-deposited on a Ti/SnO2 substrate and we investigated differences between them in terms of organics oxidation efficiency. In the batch system we utilised for the combustion, the experimental parameters we investigated, initial concentration of the organic compound, temperature and current density furnished to the system--showed us that a parameter like the Instantaneous Current Efficiency (ICE) is affected by mass-transfer limitation at the end of the tests. In this paper we therefore introduce a new parameter not influenced by these problems that can be very effective for the description of electrode efficiency during the conduction of experiences.

Chlorophenols↗
PubMed2001

[Adsorption of p-chlorophenol by biofilm and its components].

The p-chlorophenol (4-cp) adsorption to biofilm components was investigated by the experiment. Biofilm components included modeling water particulate (kaolin) with biofilm coating, bacterial cell, exopolysaccharide, kaolin and kaolin with exopolysaccharide. The adsorption of 4-cp in these systems could be described by Langmuir and Freundlich isotherm equations except the system of kaolin with exopolysaccharide. Under the condition of 25 degrees C and pH of 6.1 in these reaction systems, bacterial cell and EPS adsorbed more 4-cp than kaolin. The biofilm coating of kaolin affected its adsorption to 4-cp. Kaolin with biofilm coating adsorbed more 4-cp than that without biofilm coating.

Adsorption↗
PubMed2001

Factors affecting biodegradation of 2-chlorophenol by Alcaligenes sp. in aerobic reactors.

The influence of variations in carbon source concentration, cell inocula, pH, presence of other substrates, and other organisms on the biodegradation of 2-chlorophenol (2-CP) was studied for Alcaligenes sp. isolated from natural sources. Assays of biodegradation were performed in batch and continuous-flow fluidized-bed aerobic reactors. Evaluation of biodegradation was performed by determining total phenols, chemical oxygen demand (COD), and 2-CP by ultraviolet (UV) spectrophotometry. Measurement of microbial growth was carried out by the plate count method. Bioassays of acute toxicity were performed to evaluate detoxification by using Daphnia magna. Results obtained show that under batch conditions with initial inocula of 10(6) cells/mL the strain grew exponentially with 100, 200, and 300 mg/L of 2-CP within 48 hr. A lag period was observed with low cell density inocula (10(5) cells/mL). The strain showed marked delay in the biodegradation of 2-CP at pH 5. Removal of target substrate from mixtures containing other carbon sources demonstrated the possibility of concurrent growth. Mineralization of 2-CP was assessed by gas chromatography carried out at the end of the batch assays and at the exit of the continuous-flow reactor. The presence of other organisms (bacteria, rotifers, ciliate, and algae) that developed in the fluidized-bed reactor did not affect the efficacy of the biodegradation of 2-CP. The removal of 2-CP in the two assayed systems was over 97% in all cases. Toxicity was not detected at the exit of the continuous reactor.

Alcaligenes↗
PubMed2002

[Degradation of 4-chlorophenol in aqueous solution by high-voltage pulsed discharge-ozone technology].

The combination of high voltage pulse discharge and ozonation as an advanced oxidation technology was used to investigate the degradation of 4-chlorophenol (4-CP) in water. The factors that affect the rate of degradation were discussed. The 1.95 x 10(-3) mol/L solutions of 4-CP were almost completely (96%) degraded after the discharge treatment of 30 min. The degradation of 4-CP was investigated as a function of the ozone concentration, radical scavenger and electrode distance. The rate of 4-CP degradation increases with an increase in ozone concentration and a decrease in the electrode distance from 20 mm to 10 mm. The presence of radical scavenger decreased the rate of 4-CP degradation.

Chlorophenols↗
PubMed2003

Automated sequencing batch bioreactor under extreme peaks of 4-chlorophenol.

The operation of a sequencing batch bioreactor is evaluated when high concentration peaks of a toxic compound (4-chlorophenol, 4CP) are introduced into the reactor. A control strategy based on the dissolved oxygen concentration, measured on line, is utilized. To detect the end of the reaction period, the automated system search for the moment when the dissolved oxygen has passed by a minimum, as a consequence of the metabolic activity of the microorganisms and right after to a maximum due to the saturation of the water (similar to the self-cycling fermentation, SCF, strategy). The dissolved oxygen signal was sent to a personal computer via data acquisition and control using MATLAB and the SIMULINK package. The system operating under the automated strategy presented a stable operation when the acclimated microorganisms (to an initial concentration of 350 mg 4CP/L), were exposed to a punctual concentration peaks of 600 mg 4CP/L. The 4CP concentrations peaks superior or equals to 1,050 mg/L only disturbed the system from a short to a medium term (one month). The 1,400 mg/L peak caused a shutdown in the metabolic activity of the microorganisms that led to the reactor failure. The biomass acclimated with the SCF strategy can partially support the variations of the toxic influent since, at the moment in which the influent become inhibitory, there is a failure of the system.

Automation↗
PubMed1992

In vitro activity of taurolidine, chlorophenol-camphor-menthol and chlorhexidine against oral pathogenic microorganisms.

The antimicrobial activity of taurolidine (Taurolin, CAS 19388-87-5), a synthetic broad-spectrum antimicrobial agent and anti-toxin, and two conventional antiseptics, chlorophenol-camphor-menthol (CCM) and chlorhexidine digluconate (CHX) were compared using the serial dilution test on 10 potential oral pathogenic bacterial species. The minimum inhibitory and minimum bactericidal concentrations were lowest for CHX (MIC 0.03-0.12 mg/ml), followed by taurolidine (MIC 0.12-0.5 mg/ml) and CCM (MIC 0.5-2.0 mg/ml). However, if both bacterial efficacy and cytotoxicity are considered, only taurolidine achieves extensive bactericidal activity with tissue tolerability.

Anti-Infective Agents, Local↗