Initial oxidative and subsequent conjugative metabolites produced during the metabolism of phenanthrene by fungi

Tracking gene expression, metabolic profiles, and biochemical analysis in the halotolerant basidiomycetous yeast Rhodotorula mucilaginosa EXF-1630 during benzo[a]pyrene and phenanthrene biodegradation under hypersaline conditions

Polyaromatic phenanthrene (Phe) and benzo[a]pyrene (BaP) are highly toxic, mutagenic, and carcinogenic contaminants widely dispersed in nature, including saline environments. Polyextremotolerant Rhodotorula mucilaginosa EXF-1630, isolated from Arctic sea ice, was grown on a huge concentration range -10 to 500 ppm- of Phe and BaP as sole carbon sources at hypersaline conditions (1 M NaCl). Selected polycyclic aromatic hydrocarbons (PAHs) supported growth as well as glucose, even at high PAH concentrations. Initially, up to 40% of Phe and BaP were adsorbed, followed by biodegradation, resulting in 80% removal in 10 days. While extracellular laccase, peroxidase, and un-specific peroxygenase activities were not detected, NADPH-cytochrome c reductase activity peaked at 4 days. The successful removal of PAHs and the absence of toxic metabolites were confirmed by toxicological tests on moss Physcomitrium patens, bacterium Aliivibrio fischeri, human erythrocytes, and pulmonary epithelial cells (A549). Metabolic profiles were determined at the midpoint of the biodegradation exponential phase, with added Phe and BaP (100 ppm) and 1 M NaCl. Different hydroxylated products were found in the culture medium, while the conjugative metabolite 1-phenanthryl-β-D-glucopyranose was detected in the medium and in the cells. Transcriptome analysis resulted in 870 upregulated and 2,288 downregulated transcripts on PAHs, in comparison to glucose. Genomic mining of 61 available yeast genomes showed a widespread distribution of 31 xenobiotic degradation pathways in different yeast lineages. Two distributions with similar metabolic capacities included black yeasts and mainly members of the Sporidiobolaceae family (including EXF-1630), respectively. This is the first work describing a metabolic profile and transcriptomic analysis of PAH degradation by yeast.

Degradation of mecoprop in polluted landfill leachate and waste water in a moving bed biofilm reactor

Mecoprop is a common pollutant in effluent-, storm- and groundwater as well as in leachates from derelict dumpsites. Thus, bioremediation approaches may be considered. We conducted batch experiments with moving bed biofilm (MBBR)-carriers to understand the degradation of mecoprop. As a model, the carriers were incubated in effluent from a conventional wastewater treatment plant which was spiked to 10, 50 and 100 μg L^-1 mecoprop. Co-metabolic processes as well as mineralization were studied. Initial mecoprop concentration and mecoprop degradation impacted the microbial communities. The removal of (S)-mecoprop prevailed over the (R)-mecoprop. This was associated with microbial compositions, in which several operational taxonomic units (OTUs) co-varied positively with (S)-mecoprop removal. The removal-rate constant of (S)-mecoprop was 0.5 d^-1 in the 10 μg L^-1 set-up but it decreased in the 50 and 100 μg L^-1 set-ups. The addition of methanol prolonged the removal of (R)-mecoprop. During mecoprop degradation, 4-chloro-2-methylphenol was formed and degraded. A new metabolite (4-chloro-2-methylphenol sulfate) was identified and quantified.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) by fungal enzymes: A review

Polycyclic aromatic hydrocarbons (PAHs) are a large group of chemicals. They represent an important concern due to their widespread distribution in the environment, their resistance to biodegradation, their potential to bioaccumulate and their harmful effects. Several pilot treatments have been implemented to prevent economic consequences and deterioration of soil and water quality. As a promising option, fungal enzymes are regarded as a powerful choice for degradation of PAHs. Phanerochaete chrysosporium, Pleurotus ostreatus and Bjerkandera adusta are most commonly used for the degradation of such compounds due to their production of ligninolytic enzymes such as lignin peroxidase, manganese peroxidase and laccase. The rate of biodegradation depends on many culture conditions, such as temperature, oxygen, accessibility of nutrients and agitated or shallow culture. Moreover, the addition of biosurfactants can strongly modify the enzyme activity. The removal of PAHs is dependent on the ionization potential. The study of the kinetics is not completely comprehended, and it becomes more challenging when fungi are applied for bioremediation. Degradation studies in soil are much more complicated than liquid cultures because of the heterogeneity of soil, thus, many factors should be considered when studying soil bioremediation, such as desorption and bioavailability of PAHs. Different degradation pathways can be suggested. The peroxidases are heme-containing enzymes having common catalytic cycles. One molecule of hydrogen peroxide oxidizes the resting enzyme withdrawing two electrons. Subsequently, the peroxidase is reduced back in two steps of one electron oxidation. Laccases are copper-containing oxidases. They reduce molecular oxygen to water and oxidize phenolic compounds.

Polar metabolites of polycyclic aromatic compounds from fungi are potential soil and groundwater contaminants

This study investigated the sorption to soil of water-soluble metabolites from polycyclic aromatic compounds (PACs). The soil fungus Cunninghamella elegans was used to produce PAC metabolites from two un-substituted PACs (phenanthrene, pyrene), three alkyl-substituted PACs (2-methylnaphthalene, 1-methylphenanthrene, 1-methylpyrene), and one sulfur-containing heterocyclic PAC (dibenzothiophene). Fifty-eight metabolites were tentatively identified; metabolites from the un-substituted PACs were hydroxylated and sulfate conjugated, whereas metabolites from alkyl-substituted PACs were sulfate conjugated and either hydroxylated or oxidized to carboxylic acids at the methyl group. The metabolism of the sulfur-containing heterocyclic PAC resulted in sulfate conjugates. The sorption of the PAC metabolites to three soils was determined using a batch equilibrium method, and partition coefficients (Kd's) were calculated for fourteen representative metabolites. Sulfate conjugated metabolites displayed Kd's below 70 whereas the metabolites with both a sulfate and a carboxylic acid group had Kd's below 2.8. The low Kd's of water-soluble PAC metabolites indicate high mobility in soil and a potential for leaching to surface- and groundwaters.

Biotransformation of 4-sec-butylphenol by Gram-positive bacteria of the genera Mycobacterium and Nocardia including modifications on the alkyl chain and the hydroxyl group

The environmental pollutant 4-sec-butylphenol (4-sec-BP) which possesses estrogenic properties was transformed by the aerobic Gram-positive bacteria Mycobacterium neoaurum and Nocardia cyriacigeorgica into three main products (P1-P3) which were isolated and structurally characterized in detail. Two of them were products of a process resembling anaerobic metabolism of alkylphenols based on modifications of the alkyl side chain of 4-sec-BP. The first product (P1) was identified as 4-(2-hydroxy-1-methylpropyl)-phenol. The second product P2 was isolated as a mixture of at least four structures which could be identified as I 4-sec-butylidenecyclohexa-2,5-dienone; II 4-(1-methylenepropyl)-phenol; III 4-(1-methylpropenyl)-phenol; and IV 4-(1-methylallyl)-phenol. In contrast to P1 and P2, the third product (P3) resulted from a modification of the hydroxyl group of 4-sec-BP. This product was only formed by M. neoaurum and was identified as the glucoside conjugate 4-sec-butylphenol-α-D-glucopyranoside. Since in general, fungi synthesize sugar conjugates to detoxify hazardous pollutants, the formation of this conjugate is a peculiarity of M. neoaurum. Thus, altogether, six products were formed from 4-sec-BP and different transformation pathways are introduced. The hydroxylating and glucosylating capacity of the characterized bacteria open up applications in environmental protection.

Heterologous expression of manganese peroxidase in Aspergillus niger and its effect on phenanthrene removal from soil

A strain of Aspergillus niger, previously isolated from sugarcane bagasse because of its capacity to degrade phenanthrene in soil by solid culture, was used to express a manganese peroxidase gene (mnp1) from Phanerochaete chrysosporium, aiming at increasing its polycyclic aromatic hydrocarbons degradation capacity. Transformants were selected based on their resistance to hygromycin B and the discoloration induced on Poly R-478 dye by the peroxidase activity. The recombinant A. niger SBC2-T3 strain developed MnP activity and was able to remove 95% of the initial phenanthrene (400 ppm) from a microcosm soil system after 17 days, whereas the wild strain removed 72% under the same conditions. Transformation success was confirmed by PCR amplification using gene-specific primers, and a single fragment (1,348 bp long, as expected) of the recombinant mnp1 was amplified in the DNA from transformants, which was absent from the parental strain.

Initial Oxidation Products in the Metabolism of Pyrene, Anthracene, Fluorene, and Dibenzothiophene by the White Rot Fungus Pleurotus ostreatus

The initial metabolites in the degradation of pyrene, anthracene, fluorene, and dibenzothiophene by Pleurotus ostreatus were isolated by high-pressure liquid chromatography and characterized by UV-visible, gas-chromatographic, mass-spectrometric, and (sup1)H nuclear magnetic resonance spectral techniques. The metabolites from pyrene, dibenzothiophene, anthracene, and fluorene amounted to 45, 84, 64, and 96% of the total organic-solvent-extractable metabolites, respectively. Pyrene was metabolized predominantly to pyrene trans-4,5-dihydrodiol. Anthracene was metabolized predominantly to anthracene trans-1,2-dihydrodiol and 9,10-anthraquinone. In contrast, fluorene and dibenzothiophene were oxidized at the aliphatic bridges instead of the aromatic rings. Fluorene was oxidized to 9-fluorenol and 9-fluorenone; dibenzothiophene was oxidized to the sulfoxide and sulfone. Circular dichroism spectroscopy revealed that the major enantiomer of anthracene trans-1,2-dihydrodiol was predominantly in the S,S configuration and the major enantiomer of the pyrene trans-4,5-dihydrodiol was predominantly R,R. These results indicate that the white rot fungus P. ostreatus initially metabolizes polycyclic aromatic hydrocarbons by reactions similar to those previously reported for nonligninolytic fungi. However, P. ostreatus, in contrast to nonligninolytic fungi, can mineralize these polycyclic aromatic hydrocarbons. The identity of the dihydrodiol metabolites implicates a cytochrome P-450 monooxygenase mechanism.

Novel evidence of cytochrome P450-catalyzed oxidation of phenanthrene in Phanerochaete chrysosporium under ligninolytic conditions

The presence of cytochrome P450 and P450-mediated phenanthrene oxidation in the white rot fungus Phanerochaete chrysosporium under ligninolytic condition was first demonstrated in this study. The carbon monoxide difference spectra indicated induction of P450 (130 pmol mg(-1) in the microsomal fraction) by phenanthrene. The microsomal P450 degraded phenanthrene with a NADPH-dependent activity of 0.44 ± 0.02 min(-1). One of major detectable metabolites of phenanthrene in the ligninolytic cultures and microsomal fractions was identified as phenanthrene trans-9,10-dihydrodiol. Piperonyl butoxide, a P450 inhibitor which had no effect on manganese peroxidase activity, significantly inhibited phenanthrene degradation and the trans-9,10-dihydrodiol formation in both intact cultures and microsomal fractions. Furthermore, phenanthrene was also efficiently degraded by the extracellular fraction with high manganese peroxidase activity. These results indicate important roles of both manganese peroxidase and cytochrome P450 in phenanthrene metabolism by ligninolytic P. chrysosporium.

Fungal PAH-metabolites resist mineralization by soil microorganisms

This study investigated the mineralization of water-soluble polycyclic aromatic hydrocarbon (PAH) metabolites produced by the soil fungus Cunninghamella elegans. Eleven soil fungi were screened for their ability to metabolize (14)C-phenanthrene, (14)C-fluoranthene, and (14)C-pyrene into water-soluble compounds. Eight fungi produced water-soluble metabolites from all or some of the PAHs. The composition of the water-soluble PAH-metabolites from the most effective solubilizer C. elegans was analyzed by an ultraperformance liquid chromatograph interfaced to a quadrupole time-of-flight mass spectrometer. Thirty-eight metabolites were detected. All of 34 identified metabolites were sulfate-conjugated. The mineralization of (14)C-metabolites, produced by C. elegans, was compared to mineralization of the parent (14)C-PAHs in soil slurries. It was hypothesized that the increased bioavailability and metabolic activation of the metabolites would increase mineralization in soil slurries compared to mineralization of the parent PAHs. Unexpectedly, the mineralization of the (14)C-metabolites was in all cases extremely slow compared to the mineralization of the parent (14)C-PAHs. Slow (14)C-metabolite mineralization was not caused by metabolite toxicity, neither was cometabolic mineralization of (14)C-metabolites stimulated by the presence of active PAH-degraders. High water solubility, low lipophilicity, and extremely slow mineralization of the metabolites indicate a potential problem of leaching of fungal PAH-metabolites to the groundwater.

Fungal hydroxylation of polychlorinated naphthalenes with chlorine migration by wood rotting fungi

Biodegradation of the polychlorinated naphthalenes (PCNs) 1,4-dichloronaphthalene (1,4-DCN), 2,7-dichloronaphthalene (2,7-DCN), and 1,2,3,4-tetrachloronaphthalene (1,2,3,4-TCN), by the white-rot fungus Phlebia lindtneri was investigated. 1,4-DCN was metabolized to form six metabolites by the fungus. It was estimated from GC-MS fragment patterns that the metabolites were four putative hydroxylated and two dihydrodihydroxylated compounds. One of the hydroxylated products was identified as 2,4-dichloro-1-naphthol by GC-MS analysis using an authentic standard. This intermediate indicated chlorine migration in a biological system of P. lindtneri. 2,7-DCN was metabolized to five hydroxylated metabolites and a dihydrodihydroxylated metabolite. Significant inhibition of the degradation of DCNs and formation of their metabolic products was observed in incubation with the cytochrome P-450 monooxygenase inhibitor piperonyl butoxide. The formation of the dihydrodiol-like metabolites, chlorine migration and the experiment with P-450 inhibitor suggested that P. lindtneri provides hydroxyl metabolites via benzene oxide intermediates of DCNs by a cytochrome P450 monooxygenase. In addition, P. lindtneri degraded 1,2,3,4-TCN; two hydroxylated compounds and a dihydrodihydroxylated compound were formed.

Metabolism of fluoroorganic compounds in microorganisms: impacts for the environment and the production of fine chemicals

Incorporation of fluorine into an organic compound can favourably alter its physicochemical properties with respect to biological activity, stability and lipophilicity. Accordingly, this element is found in many pharmaceutical and industrial chemicals. Organofluorine compounds are accepted as substrates by many enzymes, and the interactions of microorganisms with these compounds are of relevance to the environment and the fine chemicals industry. On the one hand, the microbial transformation of organofluorines can lead to the generation of toxic compounds that are of environmental concern, yet similar biotransformations can yield difficult-to-synthesise products and intermediates, in particular derivatives of biologically active secondary metabolites. In this paper, we review the historical and recent developments of organofluorine biotransformation in microorganisms and highlight the possibility of using microbes as models of fluorinated drug metabolism in mammals.

Microbial biodegradation of polyaromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are widespread in various ecosystems and are pollutants of great concern due to their potential toxicity, mutagenicity and carcinogenicity. Because of their hydrophobic nature, most PAHs bind to particulates in soil and sediments, rendering them less available for biological uptake. Microbial degradation represents the major mechanism responsible for the ecological recovery of PAH-contaminated sites. The goal of this review is to provide an outline of the current knowledge of microbial PAH catabolism. In the past decade, the genetic regulation of the pathway involved in naphthalene degradation by different gram-negative and gram-positive bacteria was studied in great detail. Based on both genomic and proteomic data, a deeper understanding of some high-molecular-weight PAH degradation pathways in bacteria was provided. The ability of nonligninolytic and ligninolytic fungi to transform or metabolize PAH pollutants has received considerable attention, and the biochemical principles underlying the degradation of PAHs were examined. In addition, this review summarizes the information known about the biochemical processes that determine the fate of the individual components of PAH mixtures in polluted ecosystems. A deeper understanding of the microorganism-mediated mechanisms of catalysis of PAHs will facilitate the development of new methods to enhance the bioremediation of PAH-contaminated sites.

Sequence-based screening for self-sufficient P450 monooxygenase from a metagenome library

AIMS

Cytochrome P450 monooxygenases (CYPs) are useful catalysts for oxidation reactions. Self-sufficient CYPs harbour a reductive domain covalently connected to a P450 domain and are known for their robust catalytic activity with great potential as biocatalysts. In an effort to expand genetic sources of self-sufficient CYPs, we devised a sequence-based screening system to identify them in a soil metagenome.

METHODS AND RESULTS

We constructed a soil metagenome library and performed sequence-based screening for self-sufficient CYP genes. A new CYP gene, syk181, was identified from the metagenome library. Phylogenetic analysis revealed that SYK181 formed a distinct phylogenic line with 46% amino-acid-sequence identity to CYP102A1 which has been extensively studied as a fatty acid hydroxylase. The heterologously expressed SYK181 showed significant hydroxylase activity towards naphthalene and phenanthrene as well as towards fatty acids.

CONCLUSIONS

Sequence-based screening of metagenome libraries is expected to be a useful approach for searching self-sufficient CYP genes. The translated product of syk181 shows self-sufficient hydroxylase activity towards fatty acids and aromatic compounds.

SIGNIFICANCE AND IMPACT OF THE STUDY

SYK181 is the first self-sufficient CYP obtained directly from a metagenome library. The genetic and biochemical information on SYK181 are expected to be helpful for engineering self-sufficient CYPs with broader catalytic activities towards various substrates, which would be useful for bioconversion of natural products and biodegradation of organic chemicals.

The effect of the corticosteroid hormone cortexolone on the metabolites produced during phenanthrene biotransformation in Cunninghamella elegans

The metabolism of phenanthrene and the mammalian corticosteroid hormone cortexolone by the fungus Cunninghamella elegans was studied. The amounts of the cortexolone transformation products, cortisol and epicortisol, were affected by the presence of phenanthrene. Approximately 40% more cortisol was produced by C. elegans in cultures with phenanthrene. In contrast, epicortisol formation decreased. C. elegans transformed phenanthrene to phenanthrene trans-1,2-,3,4-, and 9,10-dihydrodiols, phenols, diphenols (diols) and glucoside conjugates of 1-, 2-, 3-, 4-, and 9-phenanthrols. Almost all of the phenanthrene initially added was metabolized to ethyl acetate extractable metabolites. In the mycelia and culture medium extracts, phenanthrol glucosides represented 80% and 94% of the total metabolites, respectively. The major metabolite was the glucoside conjugate of 1-phenanthrol. The presence of cortexolone affected the biodegradation of phenanthrene by decreasing the amounts of phenanthrene metabolites compared to control cultures.

The expression of cytochrome P-450 and cytochrome P-450 reductase genes in the simultaneous transformation of corticosteroids and phenanthrene byCunninghamella elegans

The expression of cytochrome P-450 and cytochrome P-450 reductase (CPR) genes in the conterminous biotransformation of corticosteroids and PAHs was studied in Cunninghamella elegans 1785/21Gp. We had previously used this strain as a microbial eucaryotic model for studying the relationship between mammalian steroid hydroxylation and the metabolization of PAHs. We reported that cytochrome P-450 reductase is involved in the biotransformaton of cortexolone and phenanthrene. RT-PCR and Northern blotting analyses indicated that the cytochrome P-450 and CPR genes appear to be inducible by both steroids and PAHs. The expression of the cytochrome P-450 gene was increased ninefold and the expression of the CPR gene increased 6.4-fold in cultures with cortexolone and/or phenanthrene in comparison with controls. We conclude that the increase in cytochrome P-450 gene expression was accompanied by an increase in cytochrome P-450 enzymatic activity levels.

Metabolism of aromatic hydrocarbons by the filamentous fungus Cyclothyrium sp

The metabolism of biphenyl, naphthalene, anthracene, phenanthrene, pyrene and benzo[a]pyrene by Cyclothyrium sp. CBS 109850, a coelomycete isolated for the first time in Brazil from industrially polluted estuarine sediment, was studied. The metabolites were extracted and separated by high performance liquid chromatography (HPLC) and characterized by UV spectral analyses and mass, and proton nuclear magnetic resonance ((1)H NMR) spectrometry. Cyclothyrium sp. transformed biphenyl to 4-hydroxybiphenyl and anthracene to anthracene trans-1,2-dihydrodiol. This isolate metabolized 90% of [9-(14)C]phenanthrene, producing phenanthrene trans-9,10-dihydrodiol as a major metabolite, phenanthrene trans-3,4-dihydrodiol, 1-hydroxyphenanthrene, 3-hydroxyphenanthrene, 4-hydroxyphenanthrene, and a novel metabolite, 2-hydroxy-7-methoxyphenanthrene. Circular dichroism spectra analyses indicated that the major enantiomers of phenanthrene trans-9, 10-dihydrodiol, phenanthrene trans-3,4-dihydrodiol and pyrene trans-4,5-dihydrodiol, a pyrene metabolite produced previously by Cyclothyrium sp. CBS 109850, were predominantly in the (R,R) configuration, revealing a high stereoselectivity for initial monooxygenation and enzymatic hydration of phenanthrene and pyrene by Cyclothyrium sp. CBS109850. The results also show a high regioselectivity since the K-regions of phenanthrene and pyrene were the major sites of metabolism.

Oxidation and ring cleavage of dibenzofuran by the filamentous fungus Paecilomyces lilacinus

The ability of the imperfect soil fungus Paecilomyces lilacinus to transform the environmental pollutant dibenzofuran was investigated. Transformation of dibenzofuran and related derivatives lead to 14 products, which were identified by UV spectroscopy, mass spectrometry, and proton nuclear magnetic resonance spectroscopy. Biotransformation was initiated by two separate hydroxylation steps, leading to the accumulation of 4-monohydroxylated and 4-dihydroxylateddibenzofurans. Hydroxylation at both aromatic rings produced 2,7-dihydroxydibenzofuran, 3,7-dihydroxydibenzofuran, and 2,8-dihydroxydibenzofuran. Further oxidation yields ring cleavage of dibenzofuran, which has not been described before for filamentous fungi. The ring fission products were identified as benzo[ b]furo[3,2-d]-2-pyrone-6-carboxylic acid and [2-(1-carboxy-methylidene)-benzofuran-3-ylidene]-hydroxy-acetic acid and its derivatives hydroxylated at carbon 7 and 8 at the non-cleaved ring. Other metabolites were riboside-conjugates of 2-hydroxydibenzofuran and 3-hydroxydibenzofuran. The results showed that P. lilacinus transforms the hydrophobic compound dibenzofuran by phase I/phase II reactions to produce hydroxylated products and excretable sugar conjugates.

Biodegradation of chloronaphthalenes and polycyclic aromatic hydrocarbons by the white-rot fungus Phlebia lindtneri

The biodegradation of chloronaphthalene (CN) and polycyclic aromatic hydrocarbons by the white-rot fungus Phlebia lindtneri, which can degrade dichlorinated dioxins and non-chlorinated dioxin-like compounds, was investigated. Naphthalene, phenanthrene, 1-chloronaphthalene (1-CN) and 2-chloronaphthalene (2-CN) were metabolized by the fungus to form several oxidized products. Naphthalene and phenanthrene were metabolized to the corresponding hydroxylated and dihydrodihydroxylated metabolites. 2-CN was metabolized to 3-chloro-2-naphtol, 6-chloro-1-naphtol and two other chloronaphtols, CN-dihydrodiols and CN-diols. Significant inhibition of the degradation of these substrates was observed when they were incubated with the cytochrome P-450 monooxygenase inhibitors 1-aminobenzotriazole and piperonyl butoxide. These results suggest that P. lindtneri initially oxidizes these substrates by a cytochrome P-450 monooxygenase.

Oxidation of chlorinated dibenzo-p-dioxin and dibenzofuran by white-rot fungus, Phlebia lindtneri

The actions of a white-rot fungus on two chlorinated aromatic compounds, known to be persistent environmental contaminants, were studied. Two models, both-ring chlorinated dioxin, 2,7-dichlorodibenzo-p-dioxin (2,7-diCDD) and 2,8-dichlorodibenzofuran (2,8-diCDF), were metabolized by the white-rot fungus Phlebia lindtneri. 2,7-DiCDD disappeared linearly in the culture of P. lindtneri; over a 20-day incubation period, with only 45% remaining in the culture. One of the metabolites produced by P. lindtneri from a 5-day incubated culture with 2,7-diCDD or 2,8-diCDF was identified by gas chromatography-mass spectrometry. P. lindtneri was shown to metabolize 2,7-diCDD and 2,8-diCDF to hydroxy-diCDD and hydroxy-diCDF, respectively.

Transformation of triclosan by Trametes versicolor and Pycnoporus cinnabarinus

We investigated the ability of Trametes versicolor and Pycnoporous cinnabarinus to metabolize triclosan. T. versicolor produced three metabolites, 2-O-(2,4,4'-trichlorodiphenyl ether)-beta-D-xylopyranoside, 2-O-(2,4,4'-trichlorodiphenyl ether)-beta-D-glucopyranoside, and 2,4-dichlorophenol. P. cinnabarinus converted triclosan to 2,4, 4'-trichloro-2'-methoxydiphenyl ether and the glucoside conjugate known from T. versicolor. The conjugates showed a distinctly lower cytotoxic and microbicidal activity than triclosan did.

Comparison of phenanthrene and pyrene degradation by different wood-decaying fungi

The degradation of phenanthrene and pyrene was investigated by using five different wood-decaying fungi. After 63 days of incubation in liquid culture, 13.8 and 4.3% of the [ring U-14C]phenantherene and 2.4 and 1.4% of the [4,5,9,10-14C]pyrene were mineralized by Trametes versicolor and Kuehneromyces mutabilis, respectively. No 14CO2 evolution was detected in either [14C]phenanthrene or [14C]pyrene liquid cultures of Flammulina velutipes, Laetiporus sulphureus, and Agrocybe aegerita. Cultivation in straw cultures demonstrated that, in addition to T. versicolor (15.5%) and K. mutabilis (5.0%), L. sulphureus (10.7%) and A. aegerita (3.7%) were also capable of mineralizing phenanthrene in a period of 63 days. Additionally, K. mutabilis (6.7%), L. sulphureus (4.3%), and A. aegerita (3.3%) mineralized [14C]pyrene in straw cultures. The highest mineralization of [14C] pyrene was detected in straw cultures of T. versicolor (34.1%), which suggested that mineralization of both compounds by fungi may be independent of the number of aromatic rings. Phenanthrene and pyrene metabolites were purified by high-performance liquid chromatography and identified by UV absorption, mass, and 1H nuclear magnetic resonance spectrometry. Fungi capable of mineralizing phenanthrene and pyrene in liquid culture produced enriched metabolites substituted in the K region (C-9,10 position of phenanthrene and C-4,5 position of pyrene), whereas all other fungi investigated produced metabolites substituted in the C-1,2, C-3,4, and C-9,10 positions of phenanthrene and the C-1 position of pyrene.

Novel metabolites in phenanthrene and pyrene transformation by Aspergillus niger

Aspergillus niger, isolated from hydrocarbon-contaminated soil, was examined for its potential to degrade phenanthrene and pyrene. Two novel metabolites, 1-methoxyphenanthrene and 1-methoxypyrene, were identified by conventional chemical techniques. Minor metabolites identified were 1- and 2-phenanthrol and 1-pyrenol. No 14CO2 evolution was observed in either [14C]phenanthrene or [14C]pyrene cultures.

Enzymatic Mechanisms Involved in Phenanthrene Degradation by the White Rot Fungus Pleurotus ostreatus

The enzymatic mechanisms involved in the degradation of phenanthrene by the white rot fungus Pleurotus ostreatus were examined. Phase I metabolism (cytochrome P-450 monooxygenase and epoxide hydrolase) and phase II conjugation (glutathione S-transferase, aryl sulfotransferase, UDP-glucuronosyltransferase, and UDP-glucosyltransferase) enzyme activities were determined for mycelial extracts of P. ostreatus. Cytochrome P-450 was detected in both cytosolic and microsomal fractions at 0.16 and 0.38 nmol min(sup-1) mg of protein(sup1), respectively. Both fractions oxidized [9,10-(sup14)C]phenanthrene to phenanthrene trans-9,10-dihydrodiol. The cytochrome P-450 inhibitors 1-aminobenzotriazole (0.1 mM), SKF-525A (proadifen, 0.1 mM), and carbon monoxide inhibited the cytosolic and microsomal P-450s differently. Cytosolic and microsomal epoxide hydrolase activities, with phenanthrene 9,10-oxide as the substrate, were similar, with specific activities of 0.50 and 0.41 nmol min(sup-1) mg of protein(sup-1), respectively. The epoxide hydrolase inhibitor cyclohexene oxide (5 mM) significantly inhibited the formation of phenanthrene trans-9,10-dihydrodiol in both fractions. The phase II enzyme 1-chloro-2,4-dinitrobenzene glutathione S-transferase was detected in the cytosolic fraction (4.16 nmol min(sup-1) mg of protein(sup-1)), whereas aryl adenosine-3(prm1)-phosphate-5(prm1)-phosphosulfate sulfotransferase (aryl PAPS sulfotransferase) UDP-glucuronosyltransferase, and UDP-glucosyltransferase had microsomal activities of 2.14, 4.25, and 4.21 nmol min(sup-1) mg of protein(sup-1), respectively, with low activity in the cytosolic fraction. However, when P. ostreatus culture broth incubated with phenanthrene was screened for phase II metabolites, no sulfate, glutathione, glucoside, or glucuronide conjugates of phenanthrene metabolites were detected. These experiments indicate the involvement of cytochrome P-450 monooxygenase and epoxide hydrolase in the initial phase I oxidation of phenanthrene to form phenanthrene trans-9,10-dihydrodiol. Laccase and manganese-independent peroxidase were not involved in the initial oxidation of phenanthrene. Although P. ostreatus had phase II xenobiotic metabolizing enzymes, conjugation reactions were not important for the elimination of hydroxylated phenanthrene.

Metabolism of phenanthrene by the white rot fungus Pleurotus ostreatus

The white rot fungus Pleurotus ostreatus, grown for 11 days in basidiomycetes rich medium containing [14C] phenanthrene, metabolized 94% of the phenanthrene added. Of the total radioactivity, 3% was oxidized to CO2. Approximately 52% of phenanthrene was metabolized to trans-9,10-dihydroxy-9,10-dihydrophenanthrene (phenanthrene trans-9,10-dihydrodiol) (28%), 2,2'-diphenic acid (17%), and unidentified metabolites (7%). Nonextractable metabolites accounted for 35% of the total radioactivity. The metabolites were extracted with ethyl acetate, separated by reversed-phase high-performance liquid chromatography, and characterized by 1H nuclear magnetic resonance, mass spectrometry, and UV spectroscopy analyses. 18O2-labeling experiments indicated that one atom of oxygen was incorporated into the phenanthrene trans-9,10-dihydrodiol. Circular dichroism spectra of the phenanthrene trans-9,10-dihydrodiol indicated that the absolute configuration of the predominant enantiomer was 9R,10R, which is different from that of the principal enantiomer produced by Phanerochaete chrysosporium. Significantly less phenanthrene trans-9,10-dihydrodiol was observed in incubations with the cytochrome P-450 inhibitor SKF 525-A (77% decrease), 1-aminobenzotriazole (83% decrease), or fluoxetine (63% decrease). These experiments with cytochrome P-450 inhibitors and 18O2 labeling and the formation of phenanthrene trans-9R,10R-dihydrodiol as the predominant metabolite suggest that P. ostreatus initially oxidizes phenanthrene stereoselectively by a cytochrome P-450 monoxygenase and that this is followed by epoxide hydrolase-catalyzed hydration reactions.

Phase I and phase II enzymes produced by Cunninghamella elegans for the metabolism of xenobiotics

The filamentous fungus Cunninghamella elegans has the ability to metabolize xenobiotics, including polycyclic aromatic hydrocarbons and pharmaceutical drugs, by both phase I and II biotransformations. Cytosolic and microsomal fractions were assayed for activities of cytochrome P450 monooxygenase, aryl sulfotransferase, glutathione S-transferase, UDP-glucurono-syltransferase, UDP-glucosyltransferase, and N-acetyltransferase. The cytosolic preparations contained activities of an aryl sulfotransferase (15.0 nmol min-1 mg-1), UDP-glucosyltransferase (0.27 nmol min-1 mg-1) and glutathione S-transferase (20.8 nmol min-1 mg-1). In contrast, the microsomal preparations contained cytochrome P450 monooxygenase activities for aromatic hydroxylation (0.15 nmol min-1 mg-1) and N-demethylation (0.17 nmol min-1 mg-1) of cyclobenzaprine. UDP-glucuronosyltransferase activity was detected in both the cytosol (0.09 nmol min-1 mg-1) and the microsomes (0.13 nmol min-1 mg-1). N-Acetyltransferase was not detected. The results from these experiments provide enzymatic mechanism data to support earlier studies and further indicate that C. elegans has a broad physiological versatility in the metabolism of xenobiotics.