Transformation Of Phenanthrene Research Articles

Biotic/abiotic transformation mechanisms of phenanthrene in iron-rich constructed wetland under redox fluctuation

Iron-rich constructed wetlands (CWs) could promote phenanthrene bioremediation efficiently through biotic and abiotic pathways, which have gained increasing attention. However, the biotic/abiotic transformation mechanisms of trace organic contaminants in iron-rich CW are still ambiguous. Herein, three CWs (i.e., CW-A: Control; CW-B: Iron-rich CW, CW-C: Iron-rich CW + tidal flow) were constructed to investigate the transformation mechanisms of phenanthrene through Mössbauer spectroscopy and metagenomics. Results demonstrated CW-C achieved the highest phenanthrene removal (94.0 %) and bacterial toxicity reduction (92.1 %) due to the optimized degradation pathway, and subsequently achieved the safe transformation of phenanthrene. Surface-bound/low-crystalline iron regulated hydroxyl radical (·OH) production predominantly, and its utilization was promoted in CW-C, which also improved electron transfer capacity. The enhanced electron transfer capacity led to the enrichment of PAH-degrading microorganisms (e.g., Thauera) and keystone species (Sphingobacteriales bacterium 46–32) in CW-C. Additionally, the abundances of phenanthrene transformation (e.g., EC:1.14.12.-) and tricarboxylic-acid-cycle (e.g., EC:2.3.3.1) enzyme were up-regulated in CW-C. Further analysis indicated that the safe transformation of phenanthrene was mainly attributed to the combined effect of abiotic (·OH and surface-bound/low-crystalline iron) and biotic (microbial community and diversity) mechanisms in CW-C, which contributed similarly. Our study revealed the essential role of active iron in the safe transformation of phenanthrene, and was beneficial for enhanced performance of iron-rich CW.

Application of High-Performance Liquid Chromatography/High Resolution Mass Spectrometry to the Investigation of the Biodegradation and Transformation of Phenanthrene by a Plasmid Bearing Rhizosphere Bacteria Pseudomonas aureofaciens

Mass spectrometry was applied to identify metabolites and estimate the efficiency of phenanthrene biodegradation and transformation by rhizosphere bacteria Pseudomonas aureofaciens BS1393. Strains P. aureofaciens BS1393(pOV17) and P. aureofaciens BS1393(NPL-41) bearing various naphthalene biodegradation plasmids were used in the work. The strain BS1393(pOV17) contains the pOV17 wild type naphthalene biodegradation plasmid that determines the oxidation of naphthalene to Krebs cycle metabolites. The strain BS1393(NPL-41) contains the mutant plasmid NPL-41 governing the initial stages of naphthalene oxidation into salicylic acid. The limiting stages of phenanthrene biodegradation in bacteria with various plasmids have been identified according to the accumulation of intermediates. When bacteria were grown on phenanthrene, the main metabolites were as follows: (a) 2-hydroxy-2H-benzo[h]chromene-2-carboxylic acid/trans-4-(1-hydroxynaph-2-yl)-2-oxobut-3-enoic acid, (b) 1-hydroxy-2-naphthoic acid, and (c) salicylic acid. In the strain BS1393(pOV17), metabolite (а) was observed during 1–14 days of cultivation. Unlike it, in the strain BS1393(NPL-41), an insignificant amount of this metabolite was found after only 14 days. The availability of metabolite (b) in the growth of both strains was an evidence of the limited rate of its further decarboxylation. Metabolite (c) as a final product was found in the growth of the strain BS1393(NPL-41). Contrastingly, in the strain BS1393(pOV17), this metabolite was not found, which indicates the complete oxidation of phenanthrene.

Role of coke-bounded environmentally persistent free radicals in phenanthrene degradation by hydrogen peroxide

ABSTRACTEmission of polycyclic aromatic hydrocarbons (PAHs) is accompanied with the discharge of carbonaceous particles during the coke production. To degrade the adsorbed PAHs, hydrogen peroxide (H2O2) was applied as an oxidising agent, which might be activated by the inherent environmentally persistent free radicals (EPFRs) on coke particles. The transformation of phenanthrene (PHE), selected as model molecule, was achieved in H2O2/coke particle system without the addition of additional activating agent. This process consumed the particle-bounded EPFRs, inducing the decreasing of spin density from 1.92 × 1018 to 4.4 × 1017 spins g−1 in 30 min of reaction time. Electron paramagnetic resonance (EPR) technique coupled with spin-trapping agent 5, 5-dimethyl-1-pyrroline-N-oxide (DMPO) was used to probe the potential formation of reactive oxygen species. A higher capture [] concentration was observed with larger decreases in EPFRs concentration, indicating that EPFRs were the main contributor to the formation of . The obtained results suggested that the activation of H2O2 by EPFRs on coke particles resulted in the generation of hydroxyl radical (), which then back-reacted with adsorbed PHE. The finding of this study shed light on a new remediation technology for toxic carbonaceous byproducts discharged during the coke production.

Insights into the genome and proteome of Sphingomonas paucimobilis strain 20006FA involved in the regulation of polycyclic aromatic hydrocarbon degradation.

In order to study the mechanisms regulating the phenanthrene degradation pathway and the intermediate-metabolite accumulation in strain S. paucimobilis 20006FA, we sequenced the genome and compared the genome-based predictions to experimental proteomic analyses. Physiological studies indicated that the degradation involved the salicylate and protocatechuate pathways, reaching 56.3% after 15 days. Furthermore, the strain degraded other polycyclic aromatic hydrocarbons (PAH) such as anthracene (13.1%), dibenzothiophene (76.3%), and fluoranthene. The intermediate metabolite 1-hydroxy-2-naphthoic acid (HNA) accumulated during phenanthrene catabolism and inhibited both bacterial growth and phenanthrene degradation, but exogenous-HNA addition did not affect further degradation. Genomic analysis predicted 126 putative genes encoding enzymes for all the steps of phenanthrene degradation, which loci could also participate in the metabolism of other PAH. Proteomic analysis identified enzymes involved in 19 of the 23 steps needed for the transformation of phenanthrene to trichloroacetic-acid intermediates that were upregulated in phenanthrene cultures relative to the levels in glucose cultures. Moreover, the protein-induction pattern was temporal, varying between 24 and 96h during phenanthrene degradation, with most catabolic proteins being overexpressed at 96 h-e. g., the biphenyl dioxygenase and a multispecies (2Fe-2S)-binding protein. These results provided the first clues about regulation of expression of phenanthrene degradative enzymes in strain 20006FA and enabled an elucidation of the metabolic pathway utilized by the bacterium. To our knowledge the present work represents the first investigation of genomic, proteomic, and physiological studies of a PAH-degrading Sphingomonas strain.

Effect of red clover on the microbial transformation of phenanthrene and octadecane in the soil

The influence of red clover (Trifolium pratense L.) plants on the decomposition of phenanthrene and octadecane in the soil has been studied. Effect of plant root mass on the abundance of hydrocarbondegrading bacteria, the composition of their communities, and the degradation of hydrocarbons in the soil has been revealed. Changes in the taxonomic composition of hydrocarbon-degrading bacteria under the effect of red clover are characterized by an increase in the abundance of species from the genera Acinetobacter, Kaistia, Novosphingobium, Pseudomonas, and Xanthomonas. A positive effect of the studied microbial–plant association on the degradation of octadecane and especially phenanthrene in the soil has been revealed.

Effects of nanoplastics and microplastics on toxicity, bioaccumulation, and environmental fate of phenanthrene in fresh water

Contamination of fine plastic particles (FPs), including micrometer to millimeter plastics (MPs) and nanometer plastics (NPs), in the environment has caught great concerns. FPs are strong adsorbents for hydrophobic toxic pollutants and may affect their fate and toxicity in the environment; however, such information is still rare. We studied joint toxicity of FPs with phenanthrene to Daphnia magna and effects of FPs on the environmental fate and bioaccumulation of 14C-phenanthrene in fresh water. Within the five sizes particles we tested (from 50 nm to 10 μm), 50-nm NPs showed significant toxicity and physical damage to D. magna. The joint toxicity of 50-nm NPs and phenanthrene to D. magna showed an additive effect. During a 14-days incubation, the presence of NPs significantly enhanced bioaccumulation of phenanthrene-derived residues in daphnid body and inhibited the dissipation and transformation of phenanthrene in the medium, while 10-μm MPs did not show significant effects on the bioaccumulation, dissipation, and transformation of phenanthrene. The differences may be attributed to higher adsorption of phenanthrene on 50-nm NPs than 10-μm MPs. Our findings underlined the high potential ecological risks of FPs, and suggested that NPs should be given more concerns, in terms of their interaction with hydrophobic pollutants in the environment.

The coupling of the plant and microbial catabolisms of phenanthrene in the rhizosphere of Medicago sativa

We studied the catabolism of the polycyclic aromatic hydrocarbon phenanthrene by four rhizobacterial strains and the possibility of enzymatic oxidation of this compound and its microbial metabolites by the root exudates of alfalfa (Medicago sativa L.) in order to detect the possible coupling of the plant and microbial metabolisms under the rhizospheric degradation of the organic pollutant. A comparative study of phenanthrene degradation pathways in the PAH-degrading rhizobacteria Ensifer meliloti, Pseudomonas kunmingensis, Rhizobium petrolearium, and Stenotrophomonas sp. allowed us to identify the key metabolites from the microbial transformation of phenanthrene, including 9,10-phenanthrenequinone, 2-carboxybenzaldehyde, and 1-hydroxy-2-naphthoic, salicylic, and o-phthalic acids. Sterile alfalfa plants were grown in the presence and absence of phenanthrene (0.03gkg−1) in quartz sand under controlled environmental conditions to obtain plant root exudates. The root exudates were collected, concentrated by ultrafiltration, and the activity of oxidoreductases was detected spectrophotometrically by the oxidation rate for various substrates. The most marked activity was that of peroxidase, whereas the presence of oxidase and tyrosinase was detected on the verge of the assay sensitivity. Using alfalfa root exudates as a crude enzyme preparation, we found that in the presence of the synthetic mediator, the plant peroxidase could oxidize phenanthrene and its microbial metabolites. The results indicate the possibility of active participation of plants in the rhizospheric degradation of polycyclic aromatic hydrocarbons and their microbial metabolites, which makes it possible to speak about the coupling of the plant and microbial catabolisms of these contaminants in the rhizosphere.

Application of Markov Chain Model on Environmental Fate of Phenanthrene in Soil and Groundwater

Based on the indoor physical models and the theories of Markov Chain Model the thesis scientifically depicts the migration and transformation of phenanthrene in soil and groundwater system. Phenanthrene is devided into two states in Markov Chain Model: absorption state (photolytic degradation, biological degradation, volatilization and migration output of groundwater) and transfer state (in soil and groundwater).The use of Matlab6.5 to simulate Markov Chain Model is revealed in the temporal migration and transformation of phenanthrene of the indoor physical model. The values of photolytic degradation, biological degradation, volatilization and migration of phenanthrene in surface soil layer are respectively 4.39630mol, 5.16179mol, 0.49147mol, and 71.58263mol. The values of biological degradation and migration of phenanthrene in vadose zone are respectively 51.18468mol and 44.78492mol. The values of biological degradation and migration of phenanthrene in acquifer are 0.08960mol and 0.09102mol.The results show that (1) various environmental fate states influencing the migration and transformation in different zone systems function differently; (2) that phenanthrene withholding capacity in unsaturated zone is about 4-5 times that in saturated zone; (3) that phenanthrene contents occurred in the liquid phase is much greater than that in the solid phse in terms of the steady phenanthrene distribution contents of various layers; (4)that it takes about 140 days for phenanthrene in surface soil layer to reach the steady state, 55 days and 20 day in sub-vadose zone and acquifer respectively.

Detection of DNA damage in fish Oreochromis mossambicus induced by co-exposure to phenanthrene and nitrite by ESI-MS/MS

Mutagenic nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) have been known to arise in the environment through direct emissions from combustion sources and nitration of PAHs, primarily in the atmosphere. In the marine environment, PAHs are one of the classic anthropogenic organic pollutants, while nitrite (NO(2)(-)) is produced naturally via various biological processes like imbalance in nitrification/denitrification or eutrophication and subsequent oxygen depletion from an oversupply of nutrients. In this paper, we report the formation of PAH-DNA adducts in fish contaminated with PAHs and exposed to NO(2)(-) in the ambient water. Electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis of the bile of the euryhaline fish Oreochromis mossambicus exposed simultaneously to field relevant sublethal concentrations of phenanthrene and NO(2)(-) and collision-induced dissociation of selected ions revealed the presence of DNA-PAH adducts. The present study indicates that, although several high sensitivity techniques have been developed for the analysis of PAH derived DNA adducts, MS/MS has emerged as a powerful tool in the detection and structure elucidation of DNA adducts. Juvenile O. mossambicus from a local estuarine fish farm were used with increasing frequency for carcinogenicity testing and comparative cancer research. The fish were exposed to the alkylating agent phenanthrene in the presence of NO(2)(-). Composite untreated bile samples after dilution with methanol: water (1:1; v/v) were analyzed by ESI-MS. Several adducts could be evidenced in the bile by MS/MS. Deoxyadenosine/deoxyguanosine having a mass in the range of 450-650 amu is detected. In addition, a segment of modified dinucleotide with a mass that corresponds to a dimer consisting of a modified guanosine and a normal guanosine has also been identified in the bile. The formation of certain types of DNA adducts is a crucial step in the induction of cancer and a primary stage in mutagenesis. Phenanthrene injected by i.p. route led to the transformation of phenanthrene to N-formyl amino phenanthrene-N(6)-deoxyadenosine adduct, whereas the fish co-exposed to phenanthrene and ambient nitrite metabolizes PAH to mono-, di- as well as trinitro derivatives, which then react with DNA leading to the formation of mainly modified guanosine and adenosine adducts. In the present investigation, dinitrophenanthrene diol epoxide (DNPDE) adduct with guanosine (m/z 587) seems to be the dominant adduct in the mixture, and its presence is shown first as a comparatively less stable adduct, which decomposes to give a more stable N(2) adduct (m/z 567). MS/MS has proved to be useful in the rapid determination and discrimination of structurally different phenanthrene/derivatives DNA adducts in a complex mixture of fish bile co-exposed to phenanthrene and nitrite. However, the nature of metabolites formed is likely determined by the route of PAH administration, and there is a need to further define the early biochemical events of carcinogenesis in these species. DNA adduct analysis in fish bile offers a promising approach to study the risk of potentiation of anthropogenic chemicals into genotoxic compounds in the presence of nitrite in the marine environment. We believe this is the first report on the formation of DNA-phenanthrene adducts on co-exposure of the fish to PAH and nitrite.

The Microbial Transformation of Phenanthrene and Anthracene

The transformation of phenanthrene and anthracene by Rhodococcus rhodnii 135, Pseudomonas fluorescens 26K, and Arthrobacter sp. K3 is studied. Twenty-one intermediates of phenanthrene and anthracene transformation are identified by HPLC, mass spectrometry, and NMR spectroscopy. P. fluorescens 26K and Arthrobacter sp. K3 are found to produce a wide range of intermediates, whereas R. rhodnii 135 oxidizes phenanthrene, resulting in the formation of a sole product, 3-hydroxyphenanthrene. Putative transformation pathways of phenanthrene and anthracene are proposed for the three bacterial strains studied. These strains can be used to obtain valuable compounds (such as hydroxylated polycyclic aromatic hydrocarbons) that are difficult to produce by chemical synthesis.

Concurrent corticosteroid and phenanthrene transformation by filamentous fungus Cunninghamella elegans

A filamentous fungus Cunninghamella elegans IM 1785/21 Gp which displays ability of 17α,21-dihydroxy-4-pregnene-3,20-dione (cortexolone) 11-hydroxylation (yielding epihydrocortisone (eF) and hydrocortisone (F)) and polycyclic aromatic hydrocarbons (PAHs) degradation, was used as a microbial eucaryotic model to study the relationships between mammalian steroid hydroxylation and PAHs metabolization. The obtained results showed faster transformation of phenanthrene in Sabouraud medium supplemented with steroid substrate (cortexolone). Simultaneously phenanthrene stimulated epihydrocortisone production from cortexolone. In phenanthrene presence the ratio between cortexolone hydroxylation products (hydrocortisone and epihydrocortisone) was changed from 1:5.1–6.2 to 1:7.6–8.4 in the culture without phenanthrene. Cytochrome P-450 content significantly increased after the culture supplementation by the second substrate, phenanthrene or cortexolone, adequately. To confirm the involvement of cytochrome P-450 in phenanthrene metabolism, the inhibition studies were performed. The cytochrome P-450 inhibitors SKF 525-A (1.5 mM) and 2-methyl-1,2-di-3-pyridyl-1-propanone (metyrapone) (2 mM) inhibited phenanthrene transformation by 80 and 62%, respectively. 1-Aminobenzotriazole (1 mM) completely blocked phenanthrene metabolism. The obtained results suggest a presence of connections between steroid hydroxylases and enzymes involved in PAH degradation in C. elegans.

Characterization of genes for enzymes involved in the phenanthrene degradation in Nocardioides sp. KP7

The nucleotide sequence of the gene cluster, phdEFABGHCD, encoding enzymes responsible for the transformation of phenanthrene to 1-hydroxy-2-naphthoate in Nocardioides sp. strain KP7 was determined. This gene cluster, which may constitute a single operon, resided at 6.1-kb downstream of the phdIJK gene cluster encoding the enzymes for the transformation of 1-hydroxy-2-naphthoate to o-phthalate. In general, the phd products exhibited moderate degrees of homology with isofunctional enzymes found in pathways for the degradation of other aromatic compounds. Remarkably, the phdC gene product had features of the [3Fe4S] type ferredoxin, which has not been found so far as a component of the ring-hydroxylating dioxygenase. Escherichia coli carrying the genes for phenanthrene dioxygenase, phdABCD, was capable to oxidize phenanthrene.

Relative Role of Eukaryotic and Prokaryotic Microorganisms in Phenanthrene Transformation in Coastal Sediments

THE RELATIVE ROLE OF EUKARYOTIC VERSUS PROKARYOTIC MICROORGANISMS IN PHENANTHRENE TRANSFORMATION WAS MEASURED IN SLURRIES OF COASTAL SEDIMENT BY TWO DIFFERENT APPROACHES: detection of marker metabolites and use of selective inhibitors on phenanthrene biotransformation. Phenanthrene biotransformation was measured by polar metabolite formation and CO(2) evolution from [9-C]phenanthrene. Radiolabeled metabolites were tentatively identified by high-performance liquid chromatography (HPLC) separation combined with UV/visible spectral analysis of HPLC peaks and comparison to authentic standards. Both yeasts and bacteria transformed phenanthrene in slurries of coastal sediment. Two products of phenanthrene oxidation by fungi, phenanthrene trans-3,4-dihydrodiol and 3-phenanthrol, were produced in yeast-inoculated sterile sediment. However, only products of phenanthrene oxidation typical of bacterial transformation, 1-hydroxy-2-naphthoic acid and phenanthrene cis-3,4-dihydrodiol, were isolated from slurries of coastal sediment with natural microbial populations. Phenanthrene trans-dihydrodiols or other products of fungal oxidation of phenanthrene were not detected in the slurry containing a natural microbial population. A predominant role for bacterial transformation of phenanthrene was also suggested from selective inhibitor experiments. Addition of streptomycin to slurries, at a concentration which suppressed bacterial viable counts and rates of [methyl-H]thymidine uptake, completely inhibited phenanthrene transformation. Treatment with colchicine, at a concentration which suppressed yeast viable counts, depressed phenanthrene transformation by 40%, and this was likely due to nontarget inhibition of bacterial activity. The relative contribution of eukaryotic microorganisms to phenanthrene transformation in inoculated sterile sediment was estimated to be less than 3% of the total activity. We conclude that the predominant degraders of phenanthrene in muddy coastal sediments are bacteria and not eukaryotic microorganisms.

Investigation of Solid State Reactions and Solid‐Solid Phase Transformations with Time‐ and Temperature‐resolved X‐ray Powder Diffractometry

AbstractAn X‐ray powder diffractometer has been equipped with a heatable sample holder which allows highly defined heating up to 250°C. A good temperature control permits isothermal as well as non‐isothermal runs. The applicability of time‐ and temperature‐resolved X‐ray powder diffractometry (TXRD) as a thermoanalytical method is demonstrated. Solid state reactions and solid‐solid phase transformations were investigated. As examples the phase transformation of phenanthrene and the dehydration of caffeine hydrate are presented. It is possible to extract the activation parameters for a solid state reaction from a single non‐isothermal run with a constant heating rate. The principles of the quantitative kinetic evaluation of time‐ and temperature‐resolved X‐ray powder diffraction data are outlined.

Regioselective metabolism of phenanthrene in Atlantic cod ( Gadus morhua): Studies on the effects of monooxygenase inducers and role of cytochromes P-450

The polycyclic aromatic hydrocarbon phenanthrene was converted mainly (>90%) to the 1,2-dihydrodiol when metabolized in vivo by the marine teleost cod. This is also found in other bony fishes, but contrary to what is known from cartilaginous fish, crustaceans and mammals, where the K-region 9,10-dihydrodiol is the main metabolite. When liver microsomal preparations from differently pretreated cod were incubated with phenanthrene in vitro, the metabolic profile was dramatically different from the in vivo pattern, as shown by gas chromatography—mass spectrometry. The microsomes from untreated, phenanthrene, phenobarbital and pregnenolone-16α-carbonitrile-treated cod converted phenanthrene mainly, but to a varying extent, to the 9,10-dihydrodiol. Treatment with β-naphthoflavone (BNF), however, resulted in a large increase in the oxidation at the 1,2-position, along with a four- to seven-fold increase in specific activity. The major cytochrome P-450 isozyme purified from BNF-treated cod liver ( P-450 c) showed highest activity with phenanthrene (a turnover of 0.18 nmol/min per nmol P-450), but with about equal selectivity for the 1,2- and 9,10-region of the substrate in a reconstituted system with phospholipid and NADPH-cytochrome P-450 reductase. The low regioselectivity was also observed as a lack of regioselective inhibition of microsomal phenanthrene metabolism with antiserum to cod P-450 c. Two of the minor isozymes, cod cytochromes P-450 b and d, showed a similar turnover to P-450 c, but with a stronger selectivity for the 1,2-position (55–60%). The results indicate that other control systems, in addition to the content of individual P-450-forms in the regulatory systems, in addition to the content of individual P-450-forms in the endoplasmic reticulum, are involved in the in vivo transformation of phenanthrene by cod to the 1,2-dihydrodiol metabolite.