Biodegradation of benzo(a)pyrene by Pseudomonas strains, isolated from petroleum refinery effluent: Degradation, inhibition kinetics and metabolic pathway.

Benzo(a)pyrene, a five-ring polyaromatic hydrocarbon, originating from coal tar, crude oil, tobacco, grilled foods, car exhaust etc, is highly persistent in the environment. It has been classified as a Group I carcinogen, as on its ingestion in human body, diol epoxide metabolites are generated, which bind to DNA causing mutations and eventual cancer. Among various removal methods, bioremediation is most preferred as it is a sustainable approach resulting in complete mineralization of benzo(a)pyrene. Therefore, in this study, biodegradation of benzo(a)pyrene was performed by two strains of Pseudomonas, i. e WDE11 and WD23, isolated from refinery effluent. Maximum benzo(a)pyrene tolerance was 250 mg/L and 225 mg/L against Pseudomonas sp. WD23 and Pseudomonas sp. WDE11 correspondingly. Degradation rate constants varied between 0.0468 and 0.0513/day at 50 mg/L with half-life values between 13.5 and 14.3 days as per first order kinetics, while for 100 mg/L, the respective values varied between 0.006 and 0.007 L/mg. day and 15.28-16.67 days, as per second order kinetics. The maximum specific growth rate of strains WDE11 and WD23 was 0.3512/day and 0.38/day accordingly, while concentrations over 75 mg/L had an inhibitory effect on growth. Major degradation metabolites were identified as dihydroxy-pyrene, naphthalene-1,2-dicarboxylic acid, salicylic acid, and oxalic acid, indicating benzo(a)pyrene was degraded via pyrene intermediates by salicylate pathway through catechol meta-cleavage. The substantial activity of the catechol 2,3 dioxygenase enzyme was noted during the benzo(a)pyrene metabolism by both strains with minimal catechol 1,2 dioxygenase activity. This study demonstrates the exceptional potential of indigenous Pseudomonas strains in complete metabolism of benzo(a)pyrene.

Correlation of soil microbiome with crude oil contamination drives detection of hydrocarbon degrading genes which are independent to quantity and type of contaminants.

The impacts of crude oil contamination on soil microbial populations were explored in seven different polluted areas near oil and gas drilling sites and refineries of Assam, India. Using high-throughput sequencing techniques, the functional genes and metabolic pathways involved in the bioconversion of crude oil contaminants by the indigenous microbial community were explored. Total petroleum hydrocarbon (TPH) concentrations in soil samples ranged from 1109.47 to 75,725.33 mg/kg, while total polyaromatic hydrocarbon (PAH) concentrations ranged from 0.780 to 560.05 mg/kg. Pyrene, benzo[a]anthracene, naphthalene, phenanthrene, and anthracene had greater quantities than the maximum permitted limits, suggesting a greater ecological risk, in comparison to other polyaromatic hydrocarbons. According to the metagenomic data analysis, the bacterial phyla Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroides were the most prevalent among all polluted areas. The most prominent hydrocarbon degraders in the contaminated sites included Burkholderia, Mycobacterium, Polaromonas, and Pseudomonas. However, the kinds of pollutants and their concentrations did not correlate with the abundances of respective degrading genes for all polluted locations, as some of the sites with little to low PAH contamination had significant abundances of corresponding functional genes for degradation. Thus, the findings of this study imply that the microbiome of hydrocarbon-contaminated areas, which are biologically involved in the degradation process, has various genes, operons and catabolic pathways that are independent of the presence of a specific kind of contaminant.

Mn oxides enhanced pyrene removal with both rhizosphere and non-rhizosphere microorganisms in subsurface flow constructed wetlands.

The polycyclic aromatic hydrocarbons (PAHs) are substantial wastewater pollutants emitted mostly by petroleum refineries and petrochemical industries, and their environmental fate has been of increasing concern among the public. Consequently, subsurface flow constructed wetlands (SFCWs) filled with Mn oxides (W-CW) or without Mn oxides (K-CW) were established to investigate the performance and mechanisms of pyrene (PYR) removal. The average removal rates of PYR in W-CW and K-CW were 96.00% and 92.33%, respectively. The PYR removal via other pathways (microbial degradation, photolysis, volatilisation, etc.) occupied a sizeable proportion, while the total PYR content in K-CW plant roots was significantly higher than that of W-CW. The microorganisms on the root surface and rhizosphere played an important role in PYR degradation in W-CW and K-CW and were higher in W-CW than that in K-CW in all matrix zones. The microorganisms between the 10-16 cm zone from the bottom of W-CW filled with Mn oxides (W-16) were positively correlated with PYR-degrading microorganisms, aerobic bacteria and facultative anaerobes, whereas K-16 without birnessite-coated sand was negatively correlated with these microorganisms.

Biodegradation of high molecular weight hydrocarbons under saline condition by halotolerant Bacillus subtilis and its mixed cultures with Pseudomonas species.

Biodegradation of high-molecular-weight petroleum hydrocarbons in saline conditions appears to be complicated and requires further investigation. This study used heavy crude oil to enrich petroleum-degrading bacteria from oil-contaminated saline soils. Strain HG 01, with 100% sequence similarity to Bacillus subtilis, grew at a wide range of salinities and degraded 55.5 and 77.2% of 500 mg/l pyrene and 500 mg/l tetracosane, respectively, at 5% w/v NaCl. Additionally, a mixed-culture of HG 01 with Pseudomonas putida and Pseudomonas aeruginosa, named TMC, increased the yield of pyrene, and tetracosane degradation by about 20%. Replacing minimal medium with treated seawater (C/N/P adjusted to 100/10/1) enabled TMC to degrade more than 99% of pyrene and tetracosane, but TMC had lesser degradation in untreated seawater than in minimal medium. Also, the degradation kinetics of pyrene and tetracosane were fitted to a first-order model. Compared to B. subtilis, TMC increased pyrene and tetracosane's removal rate constant (K1) from 0.063 and 0.110 per day to 0.123 and 0.246 per day. TMC also increased the maximum specific growth rate of B. subtilis, P. putida, and P. aeruginosa, respectively, 45% higher in pyrene, 24.5% in tetracosane, and 123.4% and 95.4% higher in pyrene and tetracosane.

The metabolism of pyrene by a novel Altererythrobacter sp. with in-situ co-substrates: A mechanistic analysis based on pathway, genomics, and enzyme activity.

Using co-substrates to enhance the metabolic activity of microbes is an effective way for high-molecular-weight polycyclic aromatic hydrocarbons removal in petroleum-contaminated environments. However, the long degradation period and exhausting substrates limit the enhancement of metabolic activity. In this study, Altererythrobacter sp. N1 was screened from petroleum-contaminated soil in Shengli Oilfield, China, which could utilize pyrene as the sole carbon source and energy source. Saturated aromatic fractions and crude oils were used as in-situ co-substrates to enhance pyrene degradation. Enzyme activity was influenced by the different co-substrates. The highest degradation rate (75.98%) was achieved when crude oil was used as the substrate because strain N1 could utilize saturated and aromatic hydrocarbons from crude oil simultaneously to enhance the degrading enzyme activity. Moreover, the phthalate pathway was dominant, while the salicylate pathway was secondary. Furthermore, the Rieske-type aromatic cyclo-dioxygenase gene was annotated in the Altererythrobacter sp. N1 genome for the first time. Therefore, the co-metabolism of pyrene was sustained to achieve a long degradation period without the addition of exogenous substrates. This study is valuable as a potential method for the biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons.

Biodegradation of aliphatic and polycyclic aromatic hydrocarbons by the thermophilic bioemulsifier-producing Aeribacillus pallidus strain SL-1.

The utilization of thermophilic hydrocarbon-degrading microorganisms is a suitable strategy for improving biodegradation of petroleum hydrocarbons and PAHs, as well as enhancing oil recovery from high-temperature reservoirs. In this study, the thermophilic strain Aeribacillus pallidus SL-1 was evaluated for the biodegradation of crude oil and PAHs at 60 °C. Strain SL-1 was found to preferentially degrade short-chain n-alkanes (

Effects of the Razor Clam Tagelus plebeius on the Fate of Petroleum Hydrocarbons: A Mesocosm Experiment.

The relationship between organisms and contaminants may be a two-way interaction: contaminants affecting the biota and the biota affecting the environmental fate and distribution of the contaminants. This may be especially so for sediment-dwelling organisms, because their burrowing and feeding can drastically influence sediment characteristics. The present study looked at the influence of the suspension-feeding stout razor clam Tagelus plebeius on the distribution of crude oil and pyrene in greenhouse mesocosm experiments. Water column turbidity and sediment redox also were monitored during the 15- to 30-day exposures to provide information on the influence of hydrocarbons and the razor clams on environmental conditions. For the experiment with crude oil, sediment was taken from the mesocosms at the end of the experiment, and the hydrocarbon-degradation potential was assessed in incubations with 14C-naphthalene. The experiments used four treatments: hydrocarbons present/absent and razor clams present/absent. Hydrocarbon dosing levels were relatively low (1 mL of oil or 30 mg of pyrene per mesocosm with 22 L of natural sediment and 11 L of seawater). The presence of the razor clams resulted in hydrocarbon concentrations at the sediment surface being 25% lower than in mesocosms without clams. No consistent effects were noted for polycyclic aromatic hydrocarbon (PAH) concentrations in the water column or in subsurface sediment. The naphthalene-degradation potential was elevated for sediment from mesocosms dosed with oil, but the presence of the clams did not affect this potential. The presence of the razor clams resulted in a lowering of water column turbidity, but no effect on sediment redox. The hydrocarbon addition had no effect on turbidity, but sediment redox was lowered. While results show that the presence of the razor clams resulted in a loss of hydrocarbons from the surface sediment, the other results do not provide a clear picture of the underlying mechanisms and the fate of the PAHs lost from the sediment surface. We hypothesize that the loss of surface sediment PAHs was due to burial of surface sediment and possibly bioaccumulation by the clams. While additional research is needed for further insights into underlying mechanisms, the present work demonstrates that the presence of sediment-burrowing suspension feeders decreases hydrocarbon levels in surface sediment. This means that assessments of the impact of an oil spill should pay attention to effects on these organisms and to their influence on the fate and distribution of the spilled oil.

Effect of tea saponin on phytoremediation of Cd and pyrene in contaminated soils by Lolium multiflorum.

Tea saponin (TS), a kind of green biosurfactant produced by plants, was added into the Cd-pyrene co-contaminated soils to evaluate its influence on phytoremediation of Cd and pyrene by Lolium multiflorum. The results showed that the accumulation of pyrene in L. multiflorum was significantly promoted by the TS. Compared with no TS treatments (PL and ML), the aboveground concentrations of pyrene in TS treatments (PLT and MLT) increased by 135 and 30%, respectively, and the underground concentrations of pyrene in TS treatments (PLT and MLT) increased by 40 and 25%. The concentrations of Cd in the aboveground and underground parts in single contaminated treatments were all significantly more than those in co-contaminated treatments, while the situation of pyrene was quite the reverse. Besides, the addition of TS enhanced activities of dehydrogenase and polyphenol oxidase in soils and increased the biomass of L. multiflorum. The micromorphology of L. multiflorum was not affected by TS. The study suggests that the use of L. multiflorum with TS is an alternative technology for remediation of Cd-pyrene co-contaminated soils.

Pyrene biodegradation enhancement potential of lipopeptide biosurfactant produced by Paenibacillus dendritiformis CN5 strain.

Effect of biosurfactant on biodegradation of pyrene was studied using a microbial consortium predominantly composed of Pseudomonas viridiflava (49.5%) and Pseudomonas nitroreducens (32.5%) in a batch experiment containing lipopeptidic biosurfactant, produced by Paenibacillus dendritiformis CN5 strain, and mineral salt medium. The results showed that the lipopeptide at 600 and 300mgL-1 enhanced pyrene degradation to 83.5% and 67% respectively in 24days compared to 16% degradation in its absence. However degradation of pyrene was reduced to 57% as the lipopeptide supplementation was raised to 900mgL-1. This demonstrates that the biodegradation of pyrene was found to increase with an increase in the lipopeptide concentration up to a threshold level. The experimental data were fitted to the logistic kinetic model which provided best fit with a coefficient of determination (R2) values≥0.97. Maximum specific growth rate, µmax of 0.97 and 0.69d-1 were achieved in the 600 and 300mgL-1 lipopeptide amendments in comparison to 0.54d-1 in the unamended one. The carrying capacity, Xmax increased 4.4-fold in 600mgL-1 lipopeptide supplemented samples in comparison to its absence. Generally the lipopeptide showed potential application in improving bioremediation of polycyclic aromatic hydrocarbons contaminated environmental media.

Synergistic Effect of Sarocladium sp. and Cryptococcus sp. Co-Culture on Crude Oil Biodegradation and Biosurfactant Production.

This study was conducted to evaluate the co-culture ability of two yeast (Sarocladium sp. and Cryptococcus sp.) isolates as compared to their individual cultures in surfactant production and oil degradation. The results showed that individual culture of each strain was capable of producing surfactant, degrading oil, and pyrene; also, a synergistic effect was observed when a co-culture was applied. Oil removal and biomass production were 28 and 35% higher in the co-culture than in individual cultures, respectively. To investigate the synergistic effects of mix culture on oil degradation, the surface tension, emulsification activity (EA), and cell surface hydrophobicity of individual and co-culture were studied. A comparison between the produced biosurfactant and chemical surfactants showed that individual culture of each yeast strain could reduce the surface tension like SDS and about 10% better than Tween 80. The results showed that the microbial consortium could reduce the surface tension more, by 10 and 20%, than SDS and Tween 80, respectively. Both individual cultures of Sarocladium sp. and Cryptococcus sp. showed good emulsification activity (0.329 and 0.412, respectively) when compared with a non-inoculated medium. Emulsification activity measurement for the two yeast mix cultures showed an excellent 33 and 67% increase as compared to the individual culture of Sarocladium sp. and Cryptococcus sp., respectively. The cell surface hydrophobicity of Sarocladium sp. and Cryptococcus sp. increased (38 and 85%) when the cells were treated with pyrene as a hydrophobic substrate for four generations. Finally, a 40% increase for pyrene degradation was measured in a co-culture of the two yeast mix culture. According to the results of the present study, the co-culture system exhibited better performance and this study will enhance the understanding of the synergistic effects of yeast co-culture on oil degradation.

Biodegradation of pyrene by pseudomonas sp. JPN2 and its initial degrading mechanism study by combining the catabolic nahAc gene and structure-based analyses.

In this study, a pyrene-degrading bacterial strain Pseudomonas sp. JPN2 was isolated from crude oil in Dagang Oilfield, China. The degrading percent of the strain JPN2 to pyrene was increased with the extension of culture time and achieved a maximum of 82.88% after 25 d culture. Meanwhile, four metabolites 4,5-dihydroxy-4,5-dihydropyrene, 4-phenanthrol, 1-hydroxy-2-naphthoic acid and phthalate were detected in the culture solution by GC-MS analysis. In addition, DNA fragments of nahAc gene, encoding α subunit of naphthalene dioxygenase, were amplified by PCR program and sequenced. As a result, it was presumed that the initial cleavage of the aromatic rings on pyrene was occurred at C4 and C5 positions and formed the intermediate 4,5-dihydroxy-4,5-dihydropyrene. This issue had been verified by the interaction analysis between pyrene and the active site of naphthalene dioxygenase in the strain JPN2 by molecular docking. Meanwhile, the differences of the amino acid residues in the active sites of template and target enzymes may be a factor leading to the different biological activity between the strain JPN2 and the other bacteria from the genus Pseudomonas. Additionally, the microcalorimetry analysis displayed that the strain JPN2 had high tolerance for pyrene, and the effect could be negligible under the experimental concentration (100 mg L-1). Consequently, the strain JPN2 was considered as an excellent candidate for the further bioremediation study of pyrene and the other aromatic contaminants.

Isolation and identification of Bacillus megaterium YB3 from an effluent contaminated site efficiently degrades pyrene.

Industrial effluents contaminated sites may serve as repositories of ecologically adapted efficient pyrene degrading bacteria. In the present study, six bacterial isolates from industrial effluents were purified using serial enrichment technique and their pyrene degrading potential on pyrene supplemented mineral salt medium was assessed. 16S rRNA sequence analysis showed that they belong to four bacterial genera, namely Acinetobacter, Bacillus, Microbacterium, and Ochrobactrum. Among these isolates, Bacillus megaterium YB3 showed considerably good growth and was further evaluated for its pyrene-degrading efficiency. B. megaterium YB3 could degrade 72.44% of 500 mg L(-1) pyrene within 7 days. GC-MS analysis of ethyl acetate extracted fractions detected two relatively less toxic metabolic intermediates of the pyrene degradation pathway. B. megaterium YB3 also tested positive for catechol 1, 2-dioxygenase and aromatic-ring-hydroxylating dioxygenase indole-indigo conversion assays. Considering the ability and efficiency of B. megaterium YB3 to degrade high pyrene content, the strain can be used as a tool to develop bioremediation technologies for the effective biodegradation of pyrene and possibly other PAHs in the environment.

Influence of tea saponin on enhancing accessibility of pyrene and cadmium phytoremediated with Lolium multiflorum in co-contaminated soils.

Tea saponin (TS), a kind of biodegradable surfactant, was chosen to improve the accessible solubilization of pyrene and cadmium (Cd) in co-contaminated soils cultivated Lolium multiflorum. TS obviously improved the accessibility of pyrene and Cd for L. multiflorum to accelerate the process of accumulation and elimination of the pollutants. The chemical forms of Cd was transformed from Fe-Mn oxides and associated to carbonates fractions into exchangeable fractions by adding TS in single Cd and pyrene-Cd contaminated soils. Moreover, the chemical forms of pyrene were transformed from associated fraction into bioaccessible fraction by adding TS in pyrene and pyrene-Cd contaminated soils. In pyrene-Cd contaminated soil, the exchangeable fraction of Cd was hindered in the existence of pyrene, and bioaccessible fraction of pyrene was promoted by the cadmium. Besides, in the process of the pyrene degradation and Cd accumulation, the effect could be improved by the elongation of roots with adding TS, and the microorganism activity was stimulated by TS to accelerate the removal of pollutions. Therefore, Planting L. multiflorum combined with adding TS would be an effective method on the phytoremediation of organics and heavy metals co-contaminated soils.

Degradation of ¹³C-labeled pyrene in soil-compost mixtures and fertilized soil.

Polycyclic aromatic hydrocarbons (PAH) are toxic pollutants widely distributed in the environment due to natural and anthropogenic processes. In order to mitigate tar oil contaminations with PAH, research on improving bioremediation approaches, which are sometimes inefficient, is needed. However, the knowledge on the fate of PAH-derived carbon and the microbial degraders in particular in compost-supplemented soils is still limited. Here we show the PAH carbon turnover mass balance in microcosms with soil-compost mixtures or in farmyard fertilized soil using [(13)C6]-pyrene as a model PAH. Complete pyrene degradation of 100 mg/kg of soil was observed in all supplemented microcosms within 3 to 5 months, and the residual (13)C was mainly found as carbon converted to microbial biomass. Long-term fertilization of soil with farmyard manure resulted in pyrene removal efficiency similar to compost addition, although with a much longer lag phase, higher mineralization, and lower carbon incorporation into the biomass. Organic amendments either as long-term manure fertilization or as compost amendment thus play a key role in increasing the PAH-degrading potential of the soil microbial community. Phospholipid fatty acid stable isotope probing (PLFA-SIP) was used to trace the carbon within the microbial population and the amount of biomass formed from pyrene degradation. The results demonstrate that complex microbial degrader consortia rather than the expected single key players are responsible for PAH degradation in organic-amended soil.

An integrated approach of bioassay and molecular docking to study the dihydroxylation mechanism of pyrene by naphthalene dioxygenase in Rhodococcus sp. ustb-1.

Naphthalene dioxygenase (NDO) is the initial enzyme catalyzing the biodegradation of aromatic compounds, and it plays a key role in microbial remediation of polluting sites. In this study, Rhodococcus sp. ustb-1 derived from crude oil was selected to investigate the biodegradation characters and dihydroxylation mechanism of pyrene by an integrated approach of bioassay and molecular docking. The biodegradation experiment proved that the strain ustb-1 shows high effective biodegradability to pyrene with a 70.8% degradation on the 28th day and the metabolite pyrene cis-4,5-dihydrodiol was found. The results of molecular docking indicated that the regions surrounding pyrene are defined by hydrophobic amino acids which are favorable for the binding of dioxygen molecule at C4 and C5 positions of pyrene in a side-on mode. The binding positions of dioxygen are in agreement with the mass spectral analysis of the metabolite pyrene cis-4,5-dihydrodiol. In summary, this study provides a promising explanation for the possible binding behavior between pyrene and active site of NDO.

Combined effects of Iranian heavy crude oil and bacterial challenge (Streptococcus iniae) on biotransformation and innate immune responses in rockfish (Sebastes schlegeli).

To clarify the effects of spilled crude oil on fish bacterial disease resistance, rockfish (Sebastes schlegeli) were exposed to Iranian Heavy crude oil (IHCO) and Streptomyces iniae in combination. Hepatic biotransformation enzymes (ethoxyresorufin O-de-ethylase, glutathione-S-transferase) and plasma biochemical parameters (glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and glucose) in fish exposed to IHCO were not significantly different from those in unexposed fish. The level of biliary 1-OH-pyrene and cytochrome P4501A mRNA expression increased in a dose-dependent manner with IHCO exposure. The interferon stimulated gene 15, interleukin-1beta and cathepsin L were increased significantly in the liver in IHCO-exposed fish, but not dose-dependently, but the granulocyte colony stimulating factor was not related to IHCO exposure. The percentage mortality in fish following a single exposure to S. iniae was positively correlated with IHCO exposure concentration. We concluded that IHCO exposure exacerbates fish mortality following environmental bacterial infection.

Study on bioadsorption and biodegradation of petroleum hydrocarbons by a microbial consortium.

A microbial consortium isolated from Shengli oilfield polluted sludge was capable of degrading naphthalene (NAP), phenanthrene (PHE), pyrene (PYR) and crude oil. It performed high biodegradation activity and emulsifiability for petroleum hydrocarbons, and was tolerant to 6.2mM Cu(2+), 2.7 mM Zn(2+) and 9.5mM Pb(2+). Biodegradation rates of NAP, PHE, PYR and crude oil were 53%, 21%, 32% and 44% in the presence of heavy metal (Cu(2+), 1.7 mM and Zn(2+), 2mM), respectively. Exploration on the adsorption and uptake of petroleum hydrocarbons by microbe suggested the stability of surface adsorption and cell uptake by live microbial consortium followed a decreasing order of NAP > PHE ≈ PYR > crude oil. The adsorption by heat-killed microbial consortium was constant for PAHs, while decreased for crude oil. Experiments on enzymatic degradation indicated that the metabolic efficiency of periplasmic, cytoplasmic and extracellular enzymes secreted by the microbial consortium for diverse substrates was different.

Alteromonas as a key agent of polycyclic aromatic hydrocarbon biodegradation in crude oil-contaminated coastal sediment.

Following the 2007 oil spill in South Korean tidal flats, we sought to identify microbial players influencing the environmental fate of released polycyclic aromatic hydrocarbons (PAHs). Two years of monitoring showed that PAH concentrations in sediments declined substantially. Enrichment cultures were established using seawater and modified minimal media containing naphthalene as sole carbon source. The enriched microbial community was characterized by 16S rRNA-based DGGE profiling; sequencing selected bands indicated Alteromonas (among others) were active. Alteromonas sp. SN2 was isolated and was able to degrade naphthalene, phenanthrene, anthracene, and pyrene in laboratory-incubated microcosm assays. PCR-based analysis of DNA extracted from the sediments revealed naphthalene dioxygenase (NDO) genes of only two bacterial groups: Alteromonas and Cycloclasticus, having gentisate and catechol metabolic pathways, respectively. However, reverse transcriptase PCR-based analysis of field-fixed mRNA revealed in situ expression of only the Alteromonas-associated NDO genes; in laboratory microcosms these NDO genes were markedly induced by naphthalene addition. Analysis by GC/MS showed that naphthalene in tidal-flat samples was metabolized predominantly via the gentisate pathway; this signature metabolite was detected (0.04 µM) in contaminated field sediment. A quantitative PCR-based two-year data set monitoring Alteromonas-specific 16S rRNA genes and NDO transcripts in sea-tidal flat field samples showed that the abundance of bacteria related to strain SN2 during the winter season was 20-fold higher than in the summer season. Based on the above data, we conclude that strain SN2 and its relatives are site natives--key players in PAH degradation and adapted to winter conditions in these contaminated sea-tidal-flat sediments.

Characterization of pyrene biodegradation by white-rot fungus Polyporus sp. S133.

A white-rot fungus of Polyporus sp. S133 was isolated from an oil-polluted soil. The metabolism of pyrene by this fungus was investigated in liquid medium with 5 mg of the compound. Depletion of pyrene was evident during the 30-day growth period and was 21% and 90%, respectively, in cometabolism and metabolism of pyrene alone. Pyrene was absorbed to fungal cells or biodegraded to form simpler structural compounds. Seventy-one percent of eliminated pyrene was transformed by Polyporus sp. S133 into other compounds, whereas only 18% was absorbed in the fungal cell. The effects of pH and temperature on biomass production of Polyporus sp. S133 for pyrene were examined; the properties of laccase and 1,2-dioxygenase produced by Polyporus sp. S133 during pyrene degradation were investigated. The optimal values of pH were 3, 5, and 4 for laccase, 1,2-dioxygenase, and biomass production, respectively, whereas the optimal values of temperature were 25 °C for laccase and 50 °C for 1,2-dioxygenase and biomass production. Under optimal conditions, pyrene was mainly metabolized to 1-hydroxypyrene and gentisic acid. The structure of 1-hydroxypyrene and gentisic acid was determined by gas chromatography-mass spectrometry after identification using thin-layer chromatography.

Phytoremediation and removal mechanisms in Bouteloua curtipendula growing in sterile hydrocarbon spiked cultures.

Tolerance index and phytoremediation factors of side oats grama (Bouteloua curtipendula) with recalcitrant polycyclic aromatic hydrocarbons (PAH) phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP) and the resulting impact on phenotypic response, were evaluated in sterile conditions with whole plant growing in test-tube cultures with MS medium with PAH and compared with Tall fescue (Festuca arundinacea), control for this study. PAH mixture of PHE, PYR and BaP (1:1:1 w/w/w) blended with Maya crude oil (1:1 w/w), final concentration of 1500 mg kg(-1) was used. After 40 days, BaP removal, in the presence of Maya crude was superior compared with PHE and PYR removal Although the presence of PAH negatively affects the phenotypic response of the plants; sterile conditions experiments were helpful to evaluate phytoremediation factors to elucidate some important questions regarding phytoremediation mechanisms; in this study, B. curtipendula was able to phytostabilizate BaP associated to a significant hydrocarbon removal (57.4%) with high root accumulation but attenuated transport to stems, here reported as translocation factor. To our knowledge, this is the first time that quantifiable phytoremediation factors were used to evaluate the tolerance and removal capacity of a native semi-arid climate plant which is probably able to phytoremediate hydrocarbon contaminated soils.