Biotransformation Of Naphthalene Research Articles

Anaerobic Naphthalene Biotransformation Coupled to Sulfate Reduction

Anaerobic Naphthalene Biotransformation Coupled to Sulfate Reduction

Silica ecosystem for synergistic biotransformation.

Synergistical bacterial species can perform more varied and complex transformations of chemical substances than either species alone, but this is rarely used commercially because of technical difficulties in maintaining mixed cultures. Typical problems with mixed cultures on scale are unrestrained growth of one bacterium, which leads to suboptimal population ratios, and lack of control over bacterial spatial distribution, which leads to inefficient substrate transport. To address these issues, we designed and produced a synthetic ecosystem by co-encapsulation in a silica gel matrix, which enabled precise control of the microbial populations and their microenvironment. As a case study, two greatly different microorganisms: Pseudomonas sp. NCIB 9816 and Synechococcus elongatus PCC 7942 were encapsulated. NCIB 9816 can aerobically biotransform over 100 aromatic hydrocarbons, a feat useful for synthesis of higher value commodity chemicals or environmental remediation. In our system, NCIB 9816 was used for biotransformation of naphthalene (a model substrate) into CO2 and the cyanobacterium PCC 7942 was used to provide the necessary oxygen for the biotransformation reactions via photosynthesis. A mathematical model was constructed to determine the critical cell density parameter to maximize oxygen production, and was then used to maximize the biotransformation rate of the system.

NMR- and MS-based metabolomics: various organ responses following naphthalene intervention.

Naphthalene, a polycyclic aromatic hydrocarbon, is a ubiquitous environmental pollutant capable of causing illness. In this study, we deconvoluted the metabolites related to naphthalene intervention in various organs by using nuclear magnetic resonance (NMR) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Male ICR mice were intraperitoneally dosed with olive oil (vehicle), and a low dose and a high dose (100 and 200 mg kg(-1) body wt, respectively) of naphthalene. After 48 h, the lungs, liver, and kidneys were collected for analysing the metabolic responses. The metabolites were extracted and non-targeted profiled using NMR. Low NMR resolution limited the identification of the hydrophobic metabolites. Therefore, LC-MS/MS-based focus lipidomics was applied to profile phosphorylcholine-containing lipids and sphingolipids. Chemometric analysis revealed that succinate and lactate were significantly increased in the lungs, suggesting that energy metabolisms and antioxidation were increased following naphthalene treatment. In the liver, anti-oxidative stress-related metabolites increased, enabling the oxidative stress during naphthalene biotransformation and detoxification to be overcome. The elevation of glutathione protected kidneys from reactive-naphthalene-metabolite-induced injury. Significant alteration of hydrophobic metabolites (membrane constituents) revealed lung and liver were the target organs of naphthalene treatment. MS data demonstrated that phosphatidylcholine (PC) and ceramide species were significantly altered in the lungs and liver, whereas only PC was observed in the kidneys. Elevated numbers of unsaturated bonds and fatty acyl chains in both ceramides and PCs were determined to reduce cellular membrane rigidity and facilitating the trafficking of recovery elements into the cell for rejuvenation. To conclude, the complementary results of NMR- and MS-based metabolomics enabled the characterization of naphthalene-induced changes in various organs.

Does a concomitant exposure to lead influence unfavorably the naphthalene subchronic toxicity and toxicokinetics?

Rats were given 20 times during 40 d either naphthalene per gavage or the same and lead acetate intraperitoneally in single doses corresponding to 5% of the respective 50% lethal doses. The concomitant exposure to lead not only added some typical indicators of lead toxicity to the moderate naphthalene intoxication picture but also exaggerated some less specific indices for intoxication. However, a number of such indices testified to attenuation of naphthalene's adverse effects under the impact of lead. Lead also lowered urinary excretion of both total and conjugated naphthalene, while the free- to total naphthalene ratio in urine sharply increased. These results corroborate implicitly the initial hypothesis that lead, being an inhibitor of cytochrome P450, hinders phase I of the naphthalene biotransformation and, thus, the formation of derivates which can be more toxic but are capable of entering into reactions of conjugation with resulting detoxication and elimination of naphthalene from the body.

Identification of naphthalene metabolism by white rot fungus Pleurotus eryngii

The use of biomaterials or microorganisms in PAHs degradation had presented an eye-catching performance. Pleurotus eryngii is a white rot fungus, which is easily isolated from the decayed woods in the tropical rain forest, used to determine the capability to utilize naphthalene, a two-ring polycyclic aromatic hydrocarbon as source of carbon and energy. In the meantime, biotransformation of naphthalene to intermediates and other by-products during degradation was investigated in this study. Pleurotus eryngii had been incubated in liquid medium formulated with naphthalene for 14days. The presence of metabolites of naphthalene suggests that Pleurotus eryngii begin the ring cleavage by dioxygenation on C1 and C4 position to give 1,4-naphthaquinone. 1,4-Naphthaquinone was further degraded to benzoic acid, where the proposed terepthalic acid is absent in the cultured extract. Further degradation of benzoic acid by Pleurotus eryngii shows the existence of catechol as a result of the combination of decarboxylation and hydroxylation process. Unfortunately, phthalic acid was not detected in this study. Several enzymes, including manganese peroxidase, lignin peroxidase, laccase, 1,2-dioxygenase and 2,3-dioxygenase are enzymes responsible for naphthalene degradation. Reduction of naphthalene and the presence of metabolites in liquid medium showed the ability of Pleurotus eryngii to utilize naphthalene as carbon source instead of a limited glucose amount.

Degradation of naphthalene by thermophilic bacteria via a pathway, through protocatechuic acid

Abstract A number of thermophilic bacteria capable of utilizing naphthalene as a sole source of carbon were isolated from a high-temperature oilfield in Lithuania. These isolates were able to utilize several other aromatic compounds, such as anthracene, benzene, phenol, benzene-1, 3-diol, protocatechuic acid as well. Thermophilic isolate G27 ascribed to Geobacillus genus was found to have a high aromatic compound degrading capacity. Spectrophotometric determination of enzyme activities in cell-free extracts revealed that the last aromatic ring fission enzyme in naphthalene biotransformation by Geobacillus sp. G27 was inducible via protocatechuate 3, 4-dioxygenase; no protocatechuate 4, 5-dioxygenase, protocatechuate 2, 3-dioxygenase activities were detected. Intermediates such as o-phthalic and protocatechuic acids detected in culture supernatant confirmed that the metabolism of naphthalene by Geobacillus sp. G27 can proceed through protocatechuic acid via ortho-cleavage pathway and thus differs from the pathways known for mesophilic bacteria.

Aromatic oxidations by Streptomyces griseus: Biotransformations of naphthalene to 4-hydroxy-1-tetralone

Streptomyces griseus NRRL 8090 catalyzed the biotransformation of naphthalene ( 1) to 4-hydroxy-1-tetralone ( 4) in good yield. The bioconversion pathway from 1 to 1-naphthol ( 2) and 1-tetralone ( 3) was surmised by feeding 2 and 3 as substrates and measuring 4 formation by gas chromatography. Tetralin and 1, 4-naphthoquinone were not biotransformed by S. griseus. 2-Methyl-1,4-naphthoquinone (5) was converted to 2-methyl-4-hydroxytetralone ( 6) while 2-methylnaphthalene was not a substrate for S. griseus. All products were isolated by solvent extraction, chromatographically purified and characterized by gas chromatography/mass spectrometry (GC/MS) and 1H- and 13C-NMR spectroscopy. Unlike previous work in fungi, 4 is the major naphthalene metabolite, and the pathway for S. griseus conversion of naphthalene is different.

Nonionic Micelles Promote Whole Cell Bioconversion of Aromatic Substrates in an Aqueous Environment

This paper illustrates the use of a nonionic micellar system to enhance the efficiency of a bacterial whole cell oxidation of a polycyclic aromatic substrate. We have studied the biotransformation of naphthalene operated by an isolated strain of an engineered Escherichia coli to (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene in a direct micellar system and in microemulsion. The rationale of the use of an engineered bacterial strain is the high regiochemical and stereochemical specificity in yielding chiral precursors that can be subsequently used in a variety of syntheses of technological and pharmaceutical interest. These bacteria are able to degrade several polycyclic aromatic hydrocarbons (PAHs). Since these substrates are poorly water soluble, new reaction media have to be designed, where such microorganisms are still viable and fully efficient. In a narrow composition range of the L 1 phase region, the ternary system Triton X100/water/ethyloleate provides an ideal microcompartmented medium, where the engineered bacteria grow and where the PAH solubility and bioavailability increase the efficiency of bacterial conversion. A physicochemical characterization of the micellar phase and the conversion efficiency has been studied as a function of the oil content.

Biotransformation of naphthalene and diaryl ethers by green microalgae.

The role of green microalgae in the biotransformation of naphthalene (a polycyclic aromatic hydrocarbon) and diaryl ethers was investigated using axenic cultures of Chlorella vulgaris and two environmental isolates, Scenedesmus SI1 and Ankistrodesmus SI2. Biotransformation experiments with dense cell cultures showed that these three green algae transformed toxic xenobiotics to more polar metabolites. Chlorella vulgaris metabolized naphthalene to 1-naphthol (0.36-0.65%). Ankistrodesmus SI2 biotransformed dibenzofuran to six metabolites (total over 7%), three of which (possibly four) were identified as monohydroxylated dibenzofurans, the remaining two may be dihydroxylated derivatives. Scenedesmus SI1 biotransformed dibenzo-p-dioxin to three metabolites, one of which was tentatively identified as 2-hydroxydibenzo-p-dioxin (approximately 3.8%), the remainder may be dihydroxylated derivatives. This is the first time that the biotransformation of diaryl ethers by green microalgae has been investigated.

Tissue disposition and biotransformation of naphthalene in striped bass ( Morone saxatilis)

The striped bass population in the San Francisco Bay and Delta region is currently declining. Exposure to crude oil and petroleum products, in combination with increased water salinity encountered during seaward migration, could be contributing factors. Therefore, striped bass acclimated to either fresh- or seawater were individually exposed to a sublethal water concentration (30 μg/liter) of a model petroleum-based hydrocarbon, [ 14C]naphthalene. Exposure occurred in a closed, flow-through system for 24 h, after which some fish were allowed an additional 24-h clean water period to depurate accumulated residues. Residue disposition was determined by tissue dissection, digestion and liquid scintillation counting (LSC). Large concentrations were found in both the liver and brain of seawater acclimated fish, whereas in fish acclimated to freshwater, large concentrations were found in the viscera-gonad and liver. Depurated metabolites were identified by high-pressure liquid chromatography and quantified via fraction collection and LSC. Whereas very little (< 1%) naphthalene was metabolized by freshwater acclimated bass, a substantial amount (11.7%) was metabolized by seawater acclimated bass. In both cases, the main metabolites were 1,2-dihydro-1,2-dihydroxynaphthalene and 1- and/or 2-naphthylsulfate. Increased oxidation of accumulated naphthalene, as observed in seawater acclimated bass, could indicate an increase in activation of the aromatic hydrocarbon via epoxidation. This, together with the large residue concentrations found in neural tissues, may explain the increased sensitivity of seawater acclimated striped bass to petroleum hydrocarbons.

Mass transfer and biodegradation of PAH compounds from coal tar

This study examines the role of physico-chemical mass transfer processes on the rate of biotransformation of polycyclic aromatic hydrocarbon (PAH) compounds released from non-aqueous phase liquid (NAPL) coal tar present at residual saturation within a microporous medium. A simplified coupled dissolution-degradation model is developed that describes the concurrent mass transfer and biokinetic processes occurring in the system. Model results indicate that a dimensionless Damkohler number can be utilized to distinguish between systems that are mass transfer limited, and those that are limited by biological phenomena. The Damkohler number is estimated from independent laboratory experiments that measure the rates of aqueous phase dissolution and biodegradation of naphthalene from coal tar. Experimental data for Stroudsburg coal tar imbibed within 236μm diameter silica particles yield Damkohler numbers smaller than unity, indicating, for the particular system under study, that the overall rate of biotransformation of naphthalene is not limited by the mass transfer of naphthalene from coal tar to the bulk aqueous phase. There is a need for investigation of mass transfer for larger particles and/or other PAH compounds, and study of microbial rate-limiting phenomena including toxicity, inhibition and competitive substrate utilization.

Dynamic response of naphthalene biodegradation in a continuous flow soil slurry reactor.

Periodic perturbations were used to evaluate the system stability and robustness of naphthalene biodegradation in a continuous flow stirred tank reactor (CSTR) containing a soil slurry. The experimental design involved perturbing the test system using a sinusoidal input either of naphthalene or non-naphthalene organic carbon at different frequencies during steady state operation of the reactors. The response of the test system was determined by using time series off-gas analysis for naphthalene liquid phase concentration and degradation, total viable cell counts, and gene probe analysis of naphthalene degradative genotype, and by batch mineralization assays. Naphthalene biodegradation rates were very high throughout the experimental run (95 to greater than 99% removed) resulting in very low or undetectable levels of naphthalene in the off-gas and reactor effluent. Attempts to reduce the rate of naphthalene biotransformation by either reducing the reactor temperature from 20 degrees C to 10 degrees C or the dissolved oxygen level (greater than 1 mg/L) were unsuccessful. Significant naphthalene biodegradation was observed at 4 degrees C. While variable, the microbial community as measured by population densities was not significantly affected by temperature changes. In terms of naphthalene biotransformation, the system was able to adapt readily to all perturbations in the reactor.

Seasonal Biotransformation of Naphthalene, Phenanthrene, and Benzo[ a ]pyrene in Surficial Estuarine Sediments

Transformation rates of naphthalene, phenanthrene, and benzo[a]pyrene in oxidized surficial sediments of a polluted urban estuary, Boston Harbor, Mass., were determined over a period of 15 months. Three sites characterized by muddy sediments were selected to represent a >300-fold range of ambient polycyclic aromatic hydrocarbon (PAH) concentration. Transformation rates were determined by a trace-level radiolabel PAH assay which accounted for PAH mineralization, the formation of polar metabolites, residue, and recovered parental PAHs in sediment slurries. Transformation rates of the model PAHs increased with increasing ambient PAH concentrations. However, turnover times for a given PAH were similar at all sites. The turnover times were as follows: naphthalene, 13.2 to 20.1 days; phenanthrene, 7.9 to 19.8 days, and benzo[a]pyrene, 53.7 to 82.3 days. At specific sites, rates were significantly affected by salinity, occasionally affected by temperature, but not affected by pH over the course of the study. Seasonal patterns of mineralization were observed for each of the PAHs at all sites. The timing of seasonal maxima of PAH mineralization varied from site to site. Seasonal potential heterotrophic activities as measured by acetate and glutamate mineralization rates did not always coincide with PAH mineralization maxima and minima, suggesting that the two processes are uncoupled in estuarine sediments.

Improved Understanding and Application of Hazardous Waste Biological Treatment Processes Using Microbial Systems Analysis Techniques

ABSTRACT A systems analysis technique known as the frequency response method was used to characterize the system structure, and the stability and robustness of naphthalene biotransformation in an a...

Molecular microbial ecology of a naphthalene-degrading genotype in activated sludge

The concentration of cells in an activated sludge system containing a gene known to participate in degradation of naphthalene was experimentally related to the biotransformation and mineralization of naphthalene. The gene probe analysis for the naphthalene catabolic genotype was more sensitive in this system than other naphthalene degrader microbial analysis methods for naphthalene catabolic cells. Other live cells present were 1000-10,000-fold more numerous than the genotype. Naphthalene biotransformation and mineralization rates fell when the mean value of genotype replicates dropped below 10/sup 7/ genotypically positive cells/mL. The ability to enumerate a critical genotype and relate it to enzymatic activity in a mixed culture suggests an improved capability for system understanding at the ecological level and the potential for process control at the genotype level.

Metabolic activation of 1-naphthol and phenol by a simple superoxide-generating system and human leukocytes

Phenol and 1-naphthol, products of benzene and naphthalene biotransformation, are metabolized during O 2 − generation by xanthine oxidase/hypoxanthine and phorbol myristate acetate (PMA)-stimulated human neutrophils. The addition of 1-naphthol to xanthine oxidase/hypoxanthine incubations resulted in the formation of 1,4-naphthoquinone (1,4-NQ) whereas phenol addition yielded only small quantities of hydroquinone, catechol and a unidentified reducible product but not 1,4-benzoquinone. This formation of 1,4-NQ was dependent upon hypoxanthine, xanthine oxidase, and 1-naphthol and was inhibited by the addition of superoxide dismutase (SOD) demonstrating that the conversion was O 2 − mediated. During O 2 • generation by PMA-stimulated neutrophils, the addition of phenol interfered with luminol-dependent chemiluminescence and resulted in covalent binding of phenol to protein. Protein binding was 80% inhibited by the addition of azide or catalase to the incubations indicating that bioactivation was peroxidase-mediated. In contrast, the addition of 1-naphthol to PMA-stimulated neutrophils interfered with superoxide-dependent cytochrome c reduction as well as luminol-dependent chemiluminescence and also resulted in protein binding. Protein binding was only partially inhibited by azide or catalase. The addition of SOD in combination with catalase resulted in a significantly greater inhibition of binding when compared to that of catalase alone. The results of these experiments indicate that phenol and 1-naphthol are converted to reactive metabolites during superoxide generating conditions but by different mechanisms. The formation of reactive metabolites from phenol was almost exclusively peroxidase-mediated whereas the bioactivation of 1-naphthol could occur by two different mechanisms, a peroxidase-dependent and a direct superoxide-dependent mechanism.

Formation of reactive metabolites of 14C-naphthalene in isolated rat hepatocytes and the effect of decreased glucuronidation and sulfation.

Naphthalene is metabolized in the liver to its epoxide which either may be converted enzymatically to the glutathione conjugate or to the naphthalene dihydrodiol leading to quinones, or may rearrange non-enzymatically to the corresponding phenol (Jerina et al., 1970). Reactive metabolites are formed during biotransformation of naphthalene which bind irreversibly to proteins. Using microsomal fractions it has been shown that covalent binding of this aromatic hydrocarbon is mainly mediated via generation of naphthol and not by the primary epoxide (Hesse and Mezger, 1979). To examine whether secondary metabolism might also be important for the formation of reactive metabolites under conditions which more closely resemble those in vivo, we studied metabolism and binding of 14C-naphthalene in isolated rat hepatocytes. This system has been shown to be very suitable for toxicological studies as isolated hepatocytes exhibit neither the limitations of drug metabolism of subcellular fractions nor the complexity of the intact animal (Schwarz and Greim, 1981). Moreover, the system is easy to handle and allows selective modulation of drug metabolism. In the following, we describe the effect of decreased glucuronidation and sulfation on the steady state level of reactive metabolites of naphthalene.