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PubMed2000

Reactions of pentachlorophenol with laccase from Coriolus versicolor.

Laccase, purified from Coriolus versicolor, removed pentachlorophenol (PCP) from solution at pH 5, depending on initial PCP concentration and amount of laccase. With 100 units of laccase, 100% of 25 microg ml(-1) PCP and 60% of 200 microg ml(-1) PCP were removed respectively over 72 h. No free chloride was released in the reaction. In reaction with 100 microg PCP, products were primarily polymers (about 80,000 MW) with only 2-3 pg of o- and p-chloranils formed. Polymers were stable to acid hydrolysis and no release of PCP, or other low-molecular-weight products, was detected over several weeks. Laccase has a potential use in the biotreatment of aqueous effluents containing PCP, with polymerised products being removed from solution due to their high molecular weight.

Biodegradation, Environmental↗
PubMed1996

Influence of environmental parameters on pentachlorophenol biotransformation in soil by Lentinula edodes and Phanerochaete chrysosporium.

The influences of temperature, soil moisture potential and initial pH on the biotransformation of pentachlorophenol (PCP) by the lignicolous fungi Lentinula edodes and Phanerochaete chrysosporium were examined. At 10 degrees C, L. edodes was more effective in degrading PCP (P < 0.05) than P. chrysosporium. At 15 degrees C similar results were obtained for the two fungi. The highest levels of degradation occurred for both fungi at 25 degrees C. With P. chrysosporium, the extent of PCP elimination was directly related to soil moisture content and optimal at approximately 47%. With L. edodes, in contrast, the process was inversely related to moisture content and maximal at 26%. The initial soil pH also had a marked influence, and pH 4.0 was optimal for both fungi.

Agaricales↗
PubMed1997

Pentachlorophenol biodegradation kinetics of an oligotrophic fluidized-bed enrichment culture.

A fluidized-bed reactor (FBR) was used to enrich an aerobic chlorophenol-degrading microbial culture. Long-term continuous-flow operation with low effluent concentrations selected oligotrophic microorganisms producing good-quality effluent for pentachlorophenol(PCP)-contaminated water. PCP biodegradation kinetics was studied using this FBR enrichment culture. The results from FBR batch experiments were modeled using a modified Haldane equation, which resulted in the following kinetic constants: qmax = 0.41 mg PCP mg protein-1 day-1, Ks = 16 micrograms l-1, Ki = 5.3 mg l-1, and n = 3.5. These results show that the culture has a high affinity for PCP but is also inhibited by relatively low PCP concentrations (above 1.1 mg PCP l-1). This enrichment culture was maintained over 1 year of continuous-flow operation with PCP as the sole source of carbon and energy. During continuous-flow operation, effluent concentrations below 2 micrograms l-1 were achieved at 268 min hydraulic retention time (tHR) and 2.5 mg PCP l-1 feed concentration. An increase in loading rate by decreasing tHR did not significantly deteriorate the effluent quality until a tHR decrease from 30 min to 21 min resulted in process failure. Recovery from process failure was slow. Decreasing the feed PCP concentration and increasing tHR resulted in an improved process recovery.

Biodegradation, Environmental↗
PubMed1997

Comparative biotransformation of pentachlorophenol in soils by solid substrate cultures of Lentinula edodes.

Sterilised and non-sterilised soils contaminated with pentachlorophenol (PCP) were inoculated with solid substrate cultures of Lentinula edodes LE2 ("shiitake" mushroom) to simulate monoculture bioremediation treatments and treatments in which the fungus competes with natural microflora. With monocultures of L. edodes, rates of PCP depletion were rapid for the initial 4 weeks and, although thereafter the rate decreased, 99% biotransformation was obtained in 10 weeks. In mixed culture, PCP biotransformation by L. edodes was markedly slower and only 42% of the PCP was depleted after 10 weeks. Maximal rates of PCP transformation, biomass (ergosterol) accumulation and oxidative enzymes (phenol oxidase and manganese-peroxidase) production were observed after 2 weeks of incubation. In monocultures, phenol oxidase activity was 195.5 U g-1 and Mn-peroxidase 138.4 U g-1. In mixed cultures, fungal enzyme activities were markedly lower: 70.33 U g-1 for phenol oxidase and 85.0 g-1 for Mn-peroxidase. Analyses of soil metabolites after 10 weeks revealed that monocultures of L. edodes had eliminated both PCP and pentachloroanisole. Pentachloroanisole, however, was detected in soils with the mixed microflora. Both dechlorination and mineralisation of the xenobiotic compound were effected by L. edodes LE2.

Anisoles↗
PubMed1997

Bioremediation of pentachlorophenol-contaminated soil by bioaugmentation using activated soil.

The use of an indigenous microbial consortium, pollutant-acclimated and attached to soil particles (activated soil), was studied as a bioaugmentation method for the aerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil. A 125-l completely mixed soil slurry (10% soil) bioreactor was used to produce the activated soil biomass. Results showed that the bioreactor was very effective in producing a PCP-acclimated biomass. Within 30 days, PCP-degrading bacteria increased from 10(5) cfu/g to 10(8) cfu/g soil. Mineralization of the PCP added to the reactor was demonstrated by chloride accumulation in solution. The soil-attached consortium produced in the reactor was inhibited by PCP concentrations exceeding 250 mg/l. This high level of tolerance was attributed to the beneficial effect of the soil particles. Once produced, the activated soil biomass remained active for 5 weeks at 20 degrees C and for up to 3 months when kept at 4 degrees C. The activated attached soil biomass produced in the completely mixed soil slurry bioreactor, as well as a PCP-acclimated flocculent biomass obtained from an air-lift immobilized-soil bioreactor, were used to stimulate the bioremediation of a PCP-impacted sandy soil, which had no indigenous PCP-degrading microorganisms. Bioaugmentation of this soil by the acclimated biomass resulted in a 99% reduction (from 400 mg/kg to 5 mg/kg in 130 days) in PCP concentration. The PCP degradation rates obtained with the activated soil biomass, produced either as a biomass attached to soil particles or as a flocculent biomass, were similar.

Biodegradation, Environmental↗
PubMed1998

Anaerobic biodegradation of pentachlorophenol in a contaminated soil inoculated with a methanogenic consortium or with Desulfitobacterium frappieri strain PCP-1.

Anaerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil from a wood-treating industrial site was studied in soil slurry microcosms inoculated with a PCP-degrading methanogenic consortium. When the microcosms containing 10%-40% (w/v) soil were inoculated with the consortium, more than 90% of the PCP was removed in less than 30 days at 29 degrees C. Less-chlorinated phenols, mainly 3-chlorophenol were slowly degraded and accumulated in the cultures. Addition of glucose and sodium formate to the microcosms was not necessary, suggesting that the organic compounds in the soil can sustain the dechlorinating activity. Inoculation of Desulfitobacterium frappieri strain PCP-1 along with a 3-chlorophenol-degrading consortium in the microcosms also resulted in the rapid dechlorination of PCP and the slow degradation of 3-chlorophenol. Competitive polymerase chain reaction experiments showed that PCP-1 was present at the same level throughout the 21-day biotreatment. D. frappieri, strain PCP-1, inoculated into the soil microcosms, was able to remove PCP from soil containing up to 200 mg PCP/kg soil. However, reinoculation of the strain was necessary to achieve more than 95% PCP removal with a concentration of 300 mg and 500 mg PCP/kg soil. These results demonstrate that D. frappieri strain PCP-1 can be used effectively to dechlorinate PCP to 3-chlorophenol in contaminated soils.

Bacteria, Anaerobic↗
PubMed2003

Enzymatic dehalogenation of pentachlorophenol by Pseudomonas fluorescens of the microbial community from tannery effluent.

Four different bacterial isolates obtained from a stable bacterial consortium were capable of utilizing pentachlorophenol (PCP) as sole carbon and energy source. The consortium was developed by continuous enrichment in the chemostat. The degradation of PCP by bacterial strain was preceded through an oxidative route as indicated by accumulation of tetrachloro-rho-hydroquinone and dichlorohydroquinone as determined by high performance liquid chromatography (HPLC). Among the four isolates, Pseudomonas fluorescens exhibited maximum degradation capability and enzyme production. PCP-monooxygenase enzyme was extracted from culture extract and fractionated by DEAE-cellulose ion exchange chromatography. The molecular weight of the enzyme, purified from Pseudomonas fluorescens, determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography was found to be 24000 Da.

Biodegradation, Environmental↗
PubMed2005

Degradation of chlorophenols using pentachlorophenol-degrading bacteria Sphingomonas chlorophenolica in a batch reactor.

Chlorophenols are common environmental contaminants that have been used as the major component in wide-spectrum biocides in industry and agriculture. Many chlorophenols tend to persist in the environment and may become public health hazards. This research studied the ability of the pentachlorophenol (PCP)-degrading bacterium Sphingomonas chlorophenolica to degrade and dechlorinate other chlorophenols. In addition, the characteristics of S. chlorophenolica were also investigated. When S. chlorophenolica cells were preincubated with PCP, the lag phase PCP degradation periods became shorter and the PCP concentrations that could be removed became higher. S. chlorophenolica was able to completely degrade 2,3,6-trichlorophenol (2,3,6-TCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and PCP within 38.1, 15.1, 11.8, and 11.8 h, and to release concentrations of 50.1, 60.9, 63.7, and 58.5 mg/L chloride at the same period of time. In the presence of supplementary carbon sources, the PCP removal efficiency increased with the presence of glucose or pyruvate. However, the removal efficiency of 75 mg/L 2,4-dichlorophenol did not increase with supplemental carbon sources.

Biodegradation, Environmental↗
PubMed2006

The recent evolution of pentachlorophenol (PCP)-4-monooxygenase (PcpB) and associated pathways for bacterial degradation of PCP.

Man-made polychlorinated phenols such as pentachlorophenol (PCP) have been used extensively since the 1920s as preservatives to prevent fungal attack on wood. During this time, they have become serious environmental contaminants. Despite the recent introduction of PCP in the environment on an evolutionary time scale, PCP-degrading bacteria are present in soils worldwide. The initial enzyme in the PCP catabolic pathway of numerous sphingomonads, PCP-4-monooxygenase (PcpB), catalyzes the para-hydroxylation of PCP to tetrachlorohydroquinone and is encoded by the pcpB gene. This review examines the literature concerning pcpB and supports the suggestion that pcpB/PcpB should be considered a model system for the study of recent evolution of catabolic pathways among bacteria that degrade xenobiotic molecules introduced into the environment during the recent past.

Bacterial Proteins↗
PubMed2006

Biosorption and biodegradation of pentachlorophenol (PCP) in an upflow anaerobic sludge blanket (UASB) reactor.

In order to understand the fate of PCP in upflow anaerobic sludge blanket reactor (UASB) more completely, the sorption and biodegradation of pentachlorophenol (PCP) by anaerobic sludge granules were investigated. The anaerobic granular sludge degrading PCP was formed in UASB reactor, which was seeded with anaerobic sludge acclimated by chlorophenols. At the hydraulic retention time (HRT) of 20-22 h, and PCP loading rate of 200-220 mg l(-1) d(-1), UASB reactor exhibited good performance in treating wastewater which containing 170-180 mg l(-1) PCP and the PCP removal rate of 99.5% was achieved. Sequential appearance of tetra-, tri-, di-, and mono-chlorophenol was observed in the reactor effluent after 20 mg l(-1) PCP introduction. Sorption and desorption of PCP on the anaerobic sludge granules were all fitted to the Freundlich isotherm equation. Sorption of PCP was partly irreversible. The Freundlich equation could describe the behavior of PCP amount sorbed by granular sludge in anaerobic reactor reasonably well. The results demonstrated that the main mechanism leading to removal of PCP on anaerobic granular sludge was biodegradation, not sorption or volatization.

Adsorption↗
PubMed2004

Seasonal variation in plankton community responses of mesocosms dosed with pentachlorophenol.

Seasonal variations in plankton community response to pentachlorophenol (PCP) were studied in four mesocosm experiments using enclosures in a small lake. The mesocosms (860 l) were dosed with single applications of technical grade PCP (0, 4, 10, 24, 36, 54, 81 and 121 microg/l PCP) and monitored for 20 days. Multivariate statistical analyses showed that plankton community taxonomic composition varied with season. In winter and spring, communities were most stable in time; species diversity and abundance were lowest in winter. Seasonally, the communities varied little with respect to the dominant species, which were the copepod Calamoecia lucasi, the alga Peridinium sp. and the rotifer Ascomorpha ovalis. The direct effects of the PCP additions varied little between seasons, but indirect effects were evident at lower treatment levels in autumn. Indirect effects were not evident in winter. Minor variations in plankton community responses to PCP with season were apparent in the following order of decreasing sensitivity; autumn > or = winter/spring > or = summer. At the species level, C. lucasi showed the largest response. The responses observed were greatest in autumn, with decreased abundance at PCP concentrations > or = 24 microg/l. In the other seasons, effects were observed at levels of 54 or 81 microg/l and higher. Ascomorpha ovalis was the most responding rotifer in winter and spring, whereas Anuraeopsis fissa responded more strongly in autumn and summer. The dinoflagellate alga Peridinium sp. had the largest negative response in all but winter, when Dinobryon cylindricum did. Cryptomonas sp. responded positively to PCP in all seasons, increasing in abundance in the highest treatments, possibly due to reduced grazing pressure, reduced competition, or increased decomposition. The plankton community no-observed effect-concentration (NOEC) was 24-36 microg/l PCP. Results reported here suggest that the Australian and New Zealand water quality guideline values for PCP are sufficient to protect plankton communities against adverse effects.

Animals↗
PubMed1993

AHA- heterodimer of a class-2 uncoupler: pentachlorophenol.

AHA- heterodimers formed by association of neutral molecules of weak acid (HA) with its conjugate anion (A-) have been proposed to be the charged membrane-permeable species of class-2 uncouplers. Past attempts to extract and identify AHA- heterodimers failed. We have measured optical spectra of HA+A- (1:1) solutions of pentachlorophenol (PCP) in various solvents and in the presence of PC liposomes. Optical studies were supplemented by nuclear magnetic resonance measurements of HA+A- (1:1) solutions of PCP in dichloroethane to gain insight into the formation of AHA- species in lipid membranes. From these experiments, we found evidence for AHA- formation in non-hydrogen-bonding solvents, then reported the AHA- formation constant Kf and the molar absorptivity epsilon AHA-(lambda). Kf decreases with increasing dielectric constant, kappa, from 1210 +/- 130 M-1 for dichloroethane (kappa 10.7), to 340 +/- 34 M-1 for acetonitrile (kappa 37.5); Kf also decreases with increasing concentration of water. In hydrogen-bonding solvents, octanol (kappa 10.3) and methanol (kappa 33.5) and in liposomes, AHA- heterodimers are not observed optically. We estimate Kf for PCP in lipid bilayers from a combination of data on membrane electrical conductivity and surface density of adsorbed PCP. Our estimate for lipid bilayer, 0.005 < Kf < 0.5 M-1, is consistent with our inability to detect the AHA- species optically in liposome suspensions. We propose that penetration of water into the membrane inhibits formation of AHA- in lipid bilayers.

Electric Conductivity↗
PubMed1987

Adsorption of ionized and neutral pentachlorophenol to phosphatidylcholine membranes.

We have studied adsorption of pentachlorophenol (PCP) to phosphatidylcholine (PC) membranes by measuring the electrophoretic mobility of multilayered lipid vesicles in PCP solutions. PC vesicles become negatively charged due to the adsorption of ionized PCP, and we have found that their zeta potential depends upon the ionic strength and pH of the aqueous suspension. We have shown that the experimental results can be adequately accounted for in terms of a two-component Langmuir-Stern-Grahame adsorption model assuming that the 'PCP adsorption sites' are occupied either by the neutral (HA) or the ionized (A-) species. The characteristics of adsorption isotherms of the PCP - PC membrane are as follows: the association constants are KA = 55,000 dm3/mol, KHA = 279,000 dm3/mol; 4.3 PC molecules make up each PCP adsorption site at saturation; the linear partition coefficients are beta HA = (15.5 +/- 0.7) x 10(-5) m and beta A = (3.0 +/- 0.3) x 10(-5) m. The properties of PCP adsorption isotherms for PC membranes predict an increased pKa value of membrane-bound PCP, which has been observed in related studies.

Adsorption↗
PubMed1987

Dielectric properties of adsorption/ionization site of pentachlorophenol in lipid membranes.

The results of three complementary studies focused on characterization of the local environment of the common pesticide pentachlorophenol (PCP) adsorbed to phosphatidylcholine (PC) and phosphatidylglycerol (PG) membranes are reported. The effect of cholesterol (Chol) was examined. These studies included: Measurements of solvatochromic shifts of the ultraviolet absorption spectra of PCP in membranes and in polar non-hydrogen-bonding (a red shift) and hydrogen-bonding (a blue shift) solvents. Pi-pi transition energies were analyzed in terms of the dielectric cavity models of Onsager, Block-Walker, which includes dielectric saturation, and a soft dipole model of Suppan, which accounts for PCP's polarizability. The estimates of dielectric constant of the PCP adsorption site yielded 8.1-8.7 for the PC and 16.8-20.1 for PG membranes. Solvatochromic effects indicate hydrogen bonding between the membrane-bound ionized PCP molecule and water, which is enhanced by the presence of cholesterol. Determinations of the pKa of PCP adsorbed to PC, PG, PC/Chol, PG/Chol membranes and dissolved in dioxane-water solutions of a known dielectric constant. The pKa value of PCP adsorbed to membranes was always greater than the standard pKa value and it increased with the membrane's negative charge. The pKa value sequence in 0.1 M KCl was 6.68 (PG), 6.32 (PG/Chol = 70:30 mole fractions), 5.97 (PC), and 5.75 (PC/Chol = 70:30). The intrinsic pKa values of PCP in membranes were 5.2-5.4 (PG) and 5.5-6.0 (PC). Estimates of the dielectric constant of PCP's ionization site in membranes yielded 10-22 (PC) and 27-37 (PG). Cholesterol facilitated the release of the hydrogen ion from membrane-bound PCP. Measurements of pH dependence of PCP-induced membrane electrical conductivity. pH values of conductivity maxima were always greater than the standard pKa of PCP, and their sequence corresponded to that of the pKa values of membrane-bound PCP. The anomalous properties of PCP as a Class 2 uncoupler are due to PCP's lipophilic character. In response to a low dielectric constant of the adsorption/ionization site, the physicochemical characteristics of PCP adsorbed to membranes are different from the standard values--a fact that needs to be taken into account in the development of models of PCP's toxicity.

Adsorption↗
PubMed1991

Biodegradation of triiodophenol by cell-free extracts of a pentachlorophenol-degrading Flavobacterium sp.

Pentachlorophenol (PCP) degrading Flavobacterium sp. ATCC 39723 was found to degrade other polyhalogenated phenolic compounds, including triiodophenol, tribromophenol, and trichlorophenol. Each compound was able to induce the degradation of the other compounds. A PCP Flavobacterium sp. mutant, F-2, was unable to degrade any of the halogenated compounds. The results suggest that all of the polyhalogenated phenols were degraded by the same enzyme system. This observation led us to exploit the sensitive leuco crystal violet assay, which measures the iodide released from triiodophenol. Cell free extracts from PCP-induced cells were able to release iodide from triiodophenol. The reaction required NADPH and oxygen.

Biodegradation, Environmental↗
PubMed1993

Highly cooperative inhibition of acetylcholinesterase by pentachlorophenol in human erythrocytes.

Pentachlorophenol (PCP) inhibited acetylcholinesterase (AchE) activity in human erythrocyte membranes with high cooperativity. The Hill coefficient for the inhibition was 4-5 in "untreated" membranes. Differences in the temperature (13, 25 and 37 degrees) or treatment with 1% Triton X-100 did not clearly affect the cooperativity which, however, increased after the erythrocyte membranes were treated with 2-mercaptoethanol and iodoacetatic acid, suggesting that higher cooperativity in the inhibition of AchE by PCP may reflect conformational changes of AchE. Thus, PCP may be useful for the study of AchE in human erythrocytes.

Acetylcholinesterase↗
PubMed1977

Subcellular distribution, a factor in risk evaluation of pentachlorophenol.

Pentachlorophenol (PCP) is a potent uncoupler of mitochondrial phosphorylation in vitro and also interferes with microsomal detoxication functions in vitro. This favours flavin mediated oxygenation compared with flavin cytochrome P-450 dependent reactions. Gas chromatographic analysis of subcellular fractions, obtained by zonal centrifugation showed markedly lower PCP concentration in mitochondria and a high accumulation in microsomes compared with cytosol. This increases the likelihood that PCP in vivo causes a malfunction in microsomal detoxication.

Acetylation↗
PubMed1979

Induction of the hepatic microsomal and nuclear cytochrome P-450 system by hexachlorobenzene, pentachlorophenol and trichlorophenol.

The application of hexachlorobenzene (HCB), pentachlorophenol (PCP) and 2,4,5-trichlorophenol (TCP) to female rats led to an induction of both the microsomal and the nuclear cytochrome P-450 system in the liver. The increase of th mixed-function hydroxylase activities examined (7-ethoxycoumarin deethylase, 7-ethoxyresorufin deethylase, NADPH-dependent cytochrome c reductase, aminopyrine demethylase, benzpyrene hydroxylase) did not correlate strictly with the cytochrome P-450 content. Depending on the inducers and the substrates used, the content and the activity of the cytochrome P-450 were essentially smaller in the nuclei than in the microsomes. It was striking that in the nuclei those activities (benzpyrene hydroxylase, 7-ethoxyresorufin deethylase, 7-ethoxycoumarin deethylase) were preferably induced which can be attributed to the methyl-cholanthrene-induced form of the cytochrome P-450 (cytochrome P-448). These results suggest, also in the light of findings of other authors, the induction of different species of cytochrome P-450 in the nuclei and microsomes.

7-Alkoxycoumarin O-Dealkylase↗