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PubMed1990

Sensitivity to and Degradation of Pentachlorophenol by Phanerochaete spp.

This research measured mycelial extension rates of selected strains of Phanerochaete chrysorhiza, Phanerochaete laevis, Phanerochaete sanguinea, Phanerochaete filamentosa, Phanerochaete sordida, Inonotus circinatus, and Phanerochaete chrysosporium and the ability of these organisms to tolerate and degrade the wood preservative pentachlorophenol (PCP) in an aqueous medium and in soil. Most of the tested species had mycelial extension rates in the range of </=0.5 to 1.5 cm day, but there were large interspecific differences. A notable exception, P. sordida, grew very rapidly, with an average mycelial extension rate of 2.68 cm day at 28 degrees C. Rank of species by growth rate was as follows: P. chrysosporium > P. sordida > P. laevis > P. chrysorhiza = P. sanguinea > I. circinatus = P. filamentosa. There were also significant intraspecific differences in mycelial extension rates. For example, mycelial extension rates among strains of P. sordida ranged from 1.78 to 4.81 cm day. Phanerochaete spp. were very sensitive to PCP. Growth of several species was prevented by the presence of 5 ppm (5 mug/g) PCP. However, P. chrysosporium and P. sordida grew at 25 ppm PCP, albeit at greatly decreased mycelial extension rates. In an aqueous medium, mineralization of PCP by P. sordida 13 (ca. 12% after 30 days) was significantly greater than that by all other tested P. sordida strains and P. chrysosporium. After 64 days, the level of PCP had decreased by 96 and 82% in soil inoculated with P. chrysosporium and P. sordida, respectively. Depletion of PCP by these fungi occurred in a two-stage process. The first stage was characterized by a rapid depletion of PCP that coincided with an accumulation of pentachloroanisole (PCA). At the end of the first stage, ca. 64 and 71% of the PCP was converted to PCA in P. chrysosporium and P. sordida cultures, respectively. In the second stage, levels of PCP and PCA were reduced by 9.6 and 18%, respectively, in soil inoculated with P. chrysosporium and by 3 and 23%, respectively, in soil inoculated with P. sordida. PCA was mineralized by both P. chrysosporium and P. sordida in an aqueous medium.

Journal Article↗

PubMed1991

Effects of sulfuroxy anions on degradation of pentachlorophenol by a methanogenic enrichment culture.

We studied the degradation of pentachlorophenol (PCP) under methanogenic and sulfate-reducing conditions with an anaerobic mixed culture derived from sewage sludge. The consortium degraded PCP via 2,3,4,5-tetrachlorophenol, 3,4,5-trichlorophenol, and 3,5-dichlorophenol and eventually accumulated 3-chlorophenol. Dechlorination of PCP and metabolites was inhibited in the presence of sulfate, thiosulfate, and sulfite. A decrease in the rate of PCP transformation was noted when the endogenous dissolved H(2) was depleted below 0.11 muM in sulfate-reducing cultures. The effect on dechlorination observed with sulfate could be relieved by addition of molybdate, a competitive inhibitor of sulfate reduction. Addition of H(2) reduced the inhibition observed with sulfuroxy anions. The inhibitory effect of sulfuroxy anions may be due to a competition for H(2) between sulfate reduction and dechlorination. When cultured under methanogenic conditions, the consortium degraded several chlorinated and brominated phenols.

Journal Article↗

PubMed1992

Toxicity of pentachlorophenol to six species of white rot fungi as a function of chemical dose.

The growth of six species of white rot fungi was a function of pentachlorophenol (PCP) dose, expressed as mass of PCP per mass of mycelia, at PCP doses </=35 mug mg of mycelium, and not concentration. At higher doses, Inonotus dryophilus, Perenniporia medulla-panis, and Ganoderma oregonense removed less PCP than three other species of white rot fungi. Phanerochaete chrysosporium grown under nitrogen-deficient conditions was inactivated at PCP doses that under nitrogen-sufficient conditions resulted in only 2-day lag periods in growth. Trametes versicolor was the fastest-growing species that remained viable at higher PCP doses. Both Trametes versicolor and Phellinus badius were able to degrade PCP at higher PCP doses.

Journal Article↗

PubMed1992

Biodegradation of the herbicide bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) by purified pentachlorophenol hydroxylase and whole cells of Flavobacterium sp. strain ATCC 39723 is accompanied by cyanogenesis.

A pentachlorophenol (PCP)-degrading Flavobacterium sp. (strain ATCC 39723) degraded bromoxynil with the production of bromide and cyanide. No aromatic intermediates were detected in the spent culture fluid. The cyanide produced upon bromoxynil metabolism was inhibitory to the Flavobacterium sp. Whole cells degraded PCP more rapidly than they did bromoxynil. Bromoxynil metabolism and PCP metabolism were coinduced, either substrate serving as the inducer. Purified PCP hydroxylase degraded bromoxynil with stoichiometric accumulation of cyanide and without bromide production. A product accumulated which was more hydrophilic than bromoxynil upon high-pressure liquid chromatographic analysis and which, when analyzed by gas chromatography-mass spectrometry, had a mass spectrum consistent with that expected for dibromohydroquinone. PCP hydroxylase consumed NADPH, oxygen, and bromoxynil in a 2:1:1 molar ratio, producing 1 mol of cyanide per mol of bromoxynil degraded. We propose a pathway by which bromoxynil is metabolized by the same enzymes which degrade PCP. The initial step in the pathway is the conversion of bromoxynil to 2,6-dibromohydroquinone by PCP hydroxylase. In addition to its utility for decontaminating PCP-polluted sites, the Flavobacterium sp. may be useful for decontaminating bromoxynil spills. This is the first report of cyanide production accompanying the metabolism of a benzonitrile derivative.

Biodegradation, Environmental↗

PubMed1996

Accelerated Mineralization of Pentachlorophenol in Soil upon Inoculation with Mycobacterium chlorophenolicum PCP1 and Sphingomonas chlorophenolica RA2.

Mineralization of pentachlorophenol (PCP) was studied in nonsterile soil from a PCP-contaminated site upon inoculation with two PCP-degrading bacterial strains. At spiked [(sup14)C]PCP concentrations of 30 and 100 mg/kg, the effects of organism type, different inoculation techniques, including structural amendment with sawdust and cell attachment to polyurethane (PU), as well as the effect of different inoculum sizes of 10(sup4) to 10(sup8) cells per g (dry weight) of soil were compared with PCP mineralization by indigenous bacteria. Gas chromatographic analysis was used to monitor PCP disappearance and to check mass balances. The survival and activity of the released bacteria were examined by immunofluorescence microscopy and respiking experiments. Noninoculated soil completely mineralized 30 mg of PCP per kg within 7 months but showed no or only low degradation activity at 100 mg/kg in the same period. Structural amendment with PU or sawdust initiated slow mineralization after half a year. Soil inoculation with Sphingomonas chlorophenolica RA2 shortened the mineralization time drastically to 1 month at 30 mg of PCP per kg using 10(sup8) cells per g, with approximately 80% of the added radioactivity being converted to CO(inf2). The inoculated cells disappeared rapidly, with a count of 2 x 10(sup6) cells per g after 2.3 months and nondetectability after 7 months. At 100 mg/kg, mineralization was slower because of PCP toxicity but approached completion within 7.5 months. The inhibition could be overcome by addition of sawdust (1 g/kg of soil), resulting in a mineralization rate of 3 to 4 mg/kg(middot)d. PU had the opposite effect. Lower inoculum densities resulted in prolonged lag phases and lower rates, although mineralization was still enhanced over the background level. At 30 mg of PCP per kg, inoculation with Mycobacterium chlorophenolicum PCP1 increased mineralization slightly over the indigenous bacterial activity, regardless of inoculum size, but only when the organisms were attached to PU. At 100 mg of PCP per kg, only 27% were mineralized within 7.5 months. After 7 months, the original strain PCP1 inoculum of 10(sup8) cells per g was recovered at 5 x 10(sup6) to 3 x 10(sup7) cells per g, depending on the PCP concentration, but independent of PU amendment. Amendment with sawdust had no effect on the performance of this organism. Possible reasons for the poor performance of this strain include its sensitivity to PCP and its preference for slightly acidic soil conditions.

Journal Article↗

PubMed1991

Purification and properties of pentachlorophenol hydroxylase, a flavoprotein from Flavobacterium sp. strain ATCC 39723.

A pentachlorophenol (PCP) hydroxylase which catalyzed the conversion of PCP to 2,3,5,6-tetrachlorohydroquinone and released iodide from triiodophenol in the presence of NADPH and oxygen was identified. The enzyme was purified by protamine sulfate precipitation, ammonium sulfate precipitation, hydrophobic chromatography, anion-exchange chromatography, gel filtration chromatography, and crystallization. The enzyme was a monomer with a molecular weight of 63,000. Under certain conditions, dimer and multimer conformations were also observed. The pI of the enzyme was pH 4.3. The optimal conditions for activity were a pH of 7.5 to 8.5 and a temperature of 40 degrees C. Each enzyme molecule contained one flavin adenine dinucleotide molecule. The Km for PCP was 30 microM and the Vmax was 16 mumol/min/mg of protein. The enzymatic reaction required 2 mol of NADPH per mol of halogenated substrate. On the basis of the data we present, it is likely that PCP hydroxylase is a flavoprotein monooxygenase. The addition of flavins to the reaction mixture did not stimulate the enzymatic reaction; however, we identified the photodegradation of triiodophenol and tribromophenol, but not PCP, by flavin mononucleotide or riboflavin and light.

Chromatography, Affinity↗

PubMed1992

Diverse substrate range of a Flavobacterium pentachlorophenol hydroxylase and reaction stoichiometries.

An understanding of the enzymatic reactions catalyzing the degradation of substituted phenols, a major group of environmental pollutants, is required for the development of biological methods for the decontamination of halophenol-polluted sites. We found that a flavomonooxygenase, pentachlorophenol hydroxylase, isolated from a Flavobacterium sp., catalyzed a primary attack on a broad range of substituted phenols, hydroxylating the para position and removing halogen, nitro, amino, and cyano groups to produce halide, nitrite, hydroxylamine, and cyanide, respectively. Elimination of 1 mol of a halogen, nitro, or cyano group required 2 mol of NADPH, while only 1 mol of NADPH was required to remove 1 mol of an amino group or hydrogen.

Aminophenols↗

PubMed1991