Biodegradation of polycyclic aromatic hydrocarbons by an acidophilic Stenotrophomonas maltophilia strain AJH1 isolated from a mineral mining site in Saudi Arabia

The present study aims at analyzing the degradation of polycyclic aromatic hydrocarbons (PAHs) at acidic conditions (pH = 2) by acidophilic Stenotrophomonas maltophilia strain AJH1 (KU664513). The strain AJH1 was obtained from an enrichment culture obtained from soil samples of mining area in the presence of PAH as sole sources of carbon and energy. Strain AJH1was able to degrade low (anthracene, phenanthrene, naphthalene, fluorene) and high (pyrene, benzo(e)pyrene and benzo(k)fluoranthene) molecular weight PAHs in acidophilic mineral salt medium at pH 2, with removal rates of up to 95% (LMW PAH) and 80% (HMW PAH), respectively. In addition, strain AJH1 treated petroleum wastewater with 89 ± 1.1% COD removal under acidic condition (pH 2) in a continuously stirred reactor. Acidophilic S. maltophilia strain AJH1, hence holds the promise as an effective degrader for biological treatment of PAHs contaminated wastewater at acidic pH.

     

Conversion of polycyclic aromatic hydrocarbons by <Emphasis Type="Italic">Sphingomonas</Emphasis> sp. VKM B-2434

A versatile bacterial strain able to convert polycyclic aromatic hydrocarbons (PAHs) was isolated, and a conversion by the isolate of both individual substances and PAH mixtures was investigated. The strain belonged to the Sphingomonas genus as determined on the basis of 16S rRNA analysis and was designated as VKM B-2434. The strain used naphthalene, acenaphthene, phenanthrene, anthracene and fluoranthene as a sole source of carbon and energy, and cometabolically oxidized fluorene, pyrene, benz[a]anthracene, chrysene and benzo[a]pyrene. Acenaphthene and fluoranthene were degraded by the strain via naphthalene-1,8-dicarboxylic acid and 3-hydroxyphthalic acid. Conversion of most other PAHs was confined to the cleavage of only one aromatic ring. The major oxidation products of naphthalene, phenanthrene, anthracene, chrysene, and benzo[a]pyrene were identified as salicylic acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, o-hydroxyphenanthroic acid and o-hydroxypyrenoic acid, respectively. Fluorene and pyrene were oxidized mainly to hydroxyfluorenone and dihydroxydihydropyrene, respectively. Oxidation of phenanthrene and anthracene to the corresponding hydroxynaphthoic acids occurred quantitatively. The strain converted phenanthrene, anthracene, fluoranthene and carbazole of coal-tar-pitch extract.     

Predicting the Efficacy of Polycyclic Aromatic Hydrocarbon Bioremediation in Creosote-Contaminated Soil Using Bioavailability Assays

Nonexhaustive extraction (propanol, butanol, hydroxypropyl-β-cyclodextrin [HPCD]), persulfate oxidation and biodegradability assays were employed to determine the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in creosote-contaminated soil. After 16 weeks incubation, greater than 89% of three-ring compounds (acenaphthene, anthracene, fluorene, and phenanthrene) and 21% to 79% of four-ring compounds (benz[a]anthracene, chrysene, fluoranthene, and pyrene) were degraded by the indigenous microorganisms under biopile conditions. No significant decrease in five- (benzo[a]pyrene, benzo[b+k]fluoranthene) and six-ring compounds (benz[g,h,i]perylene, indeno[1,2,3-c,d]pyrene) was observed. Desorption of PAHs using propanol or butanol could not predict PAH biodegradability: low-molecular-weight PAH biodegradability was underestimated whereas high-molecular-weight PAH biodegradability was overestimated. Persulfate oxidation and HPCD extraction of creosote-contaminated soil was able to predict three- and four-ring PAH biodegradability; however, the biodegradability of five-ring PAHs was overestimated. These results demonstrate that persulfate oxidation and HPCD extraction are good predictors of PAH biodegradability for compounds with octanol-water partitioning coefficients of < 6.     

Functional robustness of a polycyclic aromatic hydrocarbon metabolic network examined in a nidA aromatic ring-hydroxylating oxygenase mutant of Mycobacterium vanbaalenii PYR-1

In this study, we obtained over 4,000 transposon mutants of Mycobacterium vanbaalenii PYR-1 and analyzed one of the mutants, 8F7, which appeared to lose its ability to degrade pyrene while still being able to degrade fluoranthene. This mutant was identified to be defective in nidA, encoding an aromatic ring-hydroxylating oxygenase (RHO), known to be involved in the initial oxidation step of pyrene degradation. When cultured with pyrene as a sole source of polycyclic aromatic hydrocarbon (PAH), high-pressure liquid chromatography analysis revealed that the nidA mutant showed a significant decrease in the rate of pyrene degradation compared to the wild-type PYR-1, although pyrene was still being degraded. However, when incubated with PAH mixtures including pyrene, phenanthrene, and fluoranthene, the pyrene degradation rate of the mutant was higher than that of the mutant previously incubated with pyrene as a sole source of PAH. There was no significant difference between wild-type PYR-1 and the mutant in the rates of phenanthrene and fluoranthene degradation. From the whole-cell proteome analysis of mutant 8F7 induced by pyrene, we identified expression of a number of RHO enzymes which are suspected to be responsible for pyrene degradation in the nidA mutant, which had no expression of NidA. Taken together, results in this study provide direct evidence for the in vivo functional role of nidA in pyrene degradation at the level of the ring-cleavage-process (RCP) functional module but also for the robustness of the PAH metabolic network (MN) to such a genetic perturbation.     

Phenanthrene stimulates the degradation of pyrene and fluoranthene by <Emphasis Type="Italic">Burkholderia</Emphasis> sp. VUN10013

Pyrene and fluoranthene, when supplied as the sole carbon source, were not degraded by Burkholderia sp. VUN10013. However, when added in a mixture with phenanthrene, both pyrene and fluoranthene were degraded in liquid broth and soil. The amounts of pyrene and fluoranthene in liquid media (initial concentrations of 50 mg l⁻¹ each) decreased to 42.1% and 41.1%, respectively, after 21 days. The amounts of pyrene and fluoranthene in soil (initial concentrations of 75 mg kg⁻¹ dry soil each) decreased to 25.8% and 12.1%, respectively, after 60 days. None of the high molecular weight (HMW) polycylic aromatic hydrocarbons (PAHs) tested adversely affected phenanthrene degradation by this bacterial strain and the amount of phenanthrene decreased rapidly within 3 and 15 days of incubation in liquid broth and soil, respectively. Anthracene also stimulated the degradation of pyrene or fluoranthene by Burkholderia sp. VUN10013, but to a lesser extent than phenanthrene. The extent of anthracene degradation decreased in the presence of these HMW PAHs.     

Characterization of fluoranthene- and pyrene-degrading bacteria isolated from PAH-contaminated soils and sediments

Sixteen environmental samples, from the United States, Germany and Norway, with histories of previous exposure to either creosote, diesel fuel or coal tar materials, were screened for bacteria which could degrade high molecular weight (HMW) polycyclic aromatic hydrocarbons (PAHs). A modified version of the spray plate technique was used for the isolations. Using fluoranthene (FLA) and pyrene (PYR) as model HMW PAHs, we isolated 28 strains on FLA and 21 strains on PYR. FLA degraders were defined as able to grow on FLA but not PYR. PYR degraders grew on both PAHs. All PYR degraders were found to be Gram-positive and all FLA degraders were Gram-negative. GC-FAME analysis showed that many of the PYR degraders were Mycobacterium spp and many of the FLA degraders were Sphingomonas spp. Comparison of the metabolic characteristics of the strains using the spray plate technique and direct growth studies revealed that more than half of the FLA degraders (59%) were able to cometabolize PYR (ie, they produced clearing zones or colored metabolites on spray plates but did not grow on the PAH) and the ability of many of these strains to cometabolize fluorene, anthracene, benzo[b]fluorene, benzo[a]anthracene and benzo[a]pyrene was significantly affected by pre-exposure to phenanthrene. Studies on the metabolic products produced from PYR cometabolism by strain EPA 505 suggested the possibility of attack at two different sites on the PYR molecule. However, the inability to derive degradable carbon from initial opening of one of the PYR rings probably accounted for the lack of growth on this PAH by the FLA-degrading strains. The PYR degraders on the other hand, were less able to cometabolize HMW PAHs, even following pre-exposure to PHE. Characterization of the FLA degradation pathway for several of the Sphingomonas isolates indicated oxidation and ring opening through to acenaphthenone as the principle metabolite. Strain CO6, however, also oxidized FLA through fluorenone, suggesting a dual attack on the FLA molecule, similar to that observed by others in Mycobacterium spp. Journal of Industrial Microbiology & Biotechnology (2000) 24, 100–112. Received 01 May 1999/ Accepted in revised form 01 November 1999     

Polynuclear Aromatic Hydrocarbons (PAHs) in fish from the Red Sea Coast of Yemen

A detailed analytical study using combined normal phase high pressure liquid chromatography (HPLC), gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) of Polynuclear Aromatic Hydrocarbons (PAHs) in fish from the Red Sea was undertaken. This investigation involves a preliminary assessment of the sixteen parent compounds issued by the U.S. Environmental Protection Agency(EPA). The study revealed measurable levels of Σ PAHs (the sum of three to five or six ring parent compounds) (49.2 ng g⁻¹ dry weight) and total PAHs (all PAH detected) (422.1 ng g⁻¹ dry weight) in edible muscle of fishes collected from the Red Sea. These concentrations are within the range of values reported for other comparable regions of the world. Mean concentrations for individual parent PAH in fish muscles were; naphthalene 19.5, biphenyl 4.6, acenaphthylene 1.0, acenaphthene 1.2, fluorene 5.5, phenanthrene 14.0, anthracene 0.8, fluoranthene 1.5, pyrene 1.8, benz(a)anthracene 0.4, chrysene 1.9, benzo(b)fluoranthene 0.5, benzo(k)fluoranthene 0.5, benzo(e)pyrene 0.9, benzo(a)pyrene 0.5, perylene 0.2, and indeno(1,2,3-cd)pyrene 0.1 ng g⁻¹ dry weight respectively. The Red Sea fish extracts exhibit the low molecular weight aromatics as well as the discernible alkyl-substituted species of naphthalene, fluorene, phenanthrene and dibenzothiophene. Thus, it was suggested that the most probable source of PAHs is oil contamination originating from spillages and/or heavy ship traffic. It was concluded that the presence of PAHs in the fish muscles is not responsible for the reported fish kill phenomenon. However, the high concentrations of carcinogenic chrysene encountered in these fishes should be considered seriously as it is hazardous to human health. Based on fish consumption by Yemeni‘s population it was calculated that the daily intake of total carcinogens were 0.15 μg/person/day. This revised version was published online in August 2006 with corrections to the Cover Date.     

Enhanced Degradation of a Mixture of Polycyclic Aromatic Hydrocarbons by a Defined Microbial Consortium in a Two-Phase Partitioning Bioreactor

Biological treatment methods are effective at destroying polycyclic aromatic hydrocarbons (PAHs), and some of the highest rates of PAH degradation have been achieved using two-phase-partitioning bioreactors (TPPBs). TPPBs consist of a cell-containing aqueous phase and a biocompatible and immiscible organic phase that partitions toxic and/or recalcitrant substrates to the cells based on their metabolic demand and on maintaining the thermodynamic equilibrium of the system. In this study, the degradation of a 5-component mixture of high and low molecular weight PAHs by a defined microbial consortium of Sphingomonas aromaticivorans B0695 and Sphingomonas paucimobilis EPA505 in a TPPB was examined. The extremely low aqueous solubilities of the high molecular weight (HMW) PAHs significantly reduce their bioavailability to cells, not only in the environment, but in TPPBs as well. That is, in the two-phase system, the originally selected solvent, dodecane, was found to sequester the HMW PAHs from the cells in the aqueous phase due to the inherent high solubility of the hydrophobic compounds in this solvent. To circumvent this limitation, the initial PAH concentrations in dodecane were increased to sufficient levels in the aqueous phase to support degradation: LMW PAHs (naphthalene, phenanthrene) and fluoranthene were degraded completely in 8 h, while the HMW PAHs, pyrene and benzo[a]pyrene, were degraded by 64% and 11%, at rates of 42.9 mg l⁻¹ d⁻¹ and 7.5 mg l⁻¹ d⁻¹, respectively. Silicone oil has superior PAH partitioning abilities compared to dodecane for the HMW PAHs, and was used to improve the extent of degradation for the PAH mixture. Although silicone oil increased the bioavailability of the HMW PAHs and greater extents of biodegradation were observed, the rates of degradation were lower than that obtained in the TPPB employing dodecane.     

Changes in phytotoxicity of polycyclic aromatic hydrocarbons in the course of microbial degradation

Phytotoxicity of six polycyclic aromatic hydrocarbons (PAHs) and their 16 oxidized derivatives that may be microbial metabolites arising in the course of PAH degradation was determined using an express test with the seedlings of sorghum (Sorghum bicolor L. Moench) and alfalfa (Medicago sativa L.). It was shown that germinating capacity is the least informative characteristic and the most useful parameter is development of seedlings during 3 days in the presence of compounds under investigation. Among unsubstituted compounds, toxicity in respect to seedlings decreased in the series fluorene > phenanthrene > anthracene. Chrysene, fluoranthene, and pyrene stimulated shoot development. It was found that some of the metabolites produced as a result of microbial degradation of phenanthrene (9,10-phenanthrenequinone, 1-hydroxy-2-naphthoic and benzoic acids) are more toxic for plants than starting PAH molecules. The obtained results are important for understanding rhizosphere processes associated with phytoremediation technique.     

Microbiological characterization of a coke oven contaminated site and evaluation of its potential for bioremediation

The soil microbial population of a coke oven site was investigated in order to evaluate its potential for bioremediation. The study was carried out in soil samples with distinct polynuclear aromatic hydrocarbon (PAH) contamination levels, comparing the population profiles constituted by total heterotrophic and PAH-utilizing strains. Isolation of degrading strains was performed with phenanthrene or pyrene as sole carbon sources. The ability to degrade other PAHs, such as anthracene, fluorene and fluoranthene was also investigated. The results showed a reduction of 30% in species diversity and microbial density drops one order of magnitude in contaminated samples. Furthermore, the number of PAH-utilizing colonies was higher in the contaminated area and about 20% of the isolates were able to degrade phenanthrene and pyrene, while this value decreased to 0.15% in uncontaminated samples. Three PAH-degrader strains were identified as: CDC gr. IV C-2, Aeromonas sp. and Pseudomonas vesicularis. The ability of these strains to degrade other PAHs was also investigated.     

Utilization of solubilized and crystalline mixtures of polycyclic aromatic hydrocarbons by a Mycobacterium sp.

A strain of Mycobacterium, that is able to degrade fluorene, phenanthrene, fluoranthene and pyrene was grown on various mixtures of these substrates. The polycyclic aromatic hydrocarbons (PAH) were provided either as crystals or solubilized by a surfactant. Mixed PAH were degraded simultaneously, but not in parallel, indicating that the degradation pathways were not incompatible. Certain interactions of the substrates were observed. For example, the degradation of solubilized pyrene was delayed in the presence of fluorene and enhanced in the presence of phenanthrene. Fluorene was degraded cometabolically with the other PAH serving as growth substrates, but not as the only source of carbon. The utilization of phenanthrene occurred at the fastest rate and was not affected by the presence of fluorene, pyrene or fluoranthene.     

Degradation of fluoranthene, pyrene, benz[a]anthracene and dibenz[a,h]anthracene by Burkholderia cepacia

Microbiological analysis of soils from a polycyclic aromatic hydrocarbon (PAH)-contaminated site resulted in the enrichment of five microbial communities capable of utilizing pyrene as a sole carbon and energy source. Communities 4 and 5 rapidly degraded a number of different PAH compounds. Three pure cultures were isolated from community 5 using a spray plate method with pyrene as the sole carbon source. The cultures were identified as strains of Burkholderia ( Pseudomonas ) cepacia on the basis of biochemical and growth tests. The pure cultures (VUN 10 001, VUN 10 002 and VUN 10 003) were capable of degrading fluorene, phenanthrene and pyrene (100 mg l⁻¹) to undetectable levels within 7–10 d in standard serum bottle cultures. Pyrene degradation was observed at concentrations up to 1000 mg l⁻¹. The three isolates were also able to degrade other PAHs including fluoranthene, benz[ a ]anthracene and dibenz[ a , h ]anthracene as sole carbon and energy sources. Stimulation of dibenz[ a , h ]anthracene and benzo[ a ]pyrene degradation was achieved by the addition of small quantities of phenanthrene to cultures containing these compounds. Substrate utilization tests revealed that these micro-organisms could also grow on n -alkanes, chlorinated- and nitro-aromatic compounds.     

Phytotoxicity of single and combined polycyclic aromatic hydrocarbons toward economic crops

Toxicity of anthracene, fluoranthene, fluorene, phenanthrene, and the mixtures of these polycyclic aromatic hydrocarbons (PAHs) to three economic crops in Thailand was compared. Seeds of sweet corn, waxy corn, and rice were planted in soils contaminated with each PAH alone, binary mixtures, and total four PAH mixture. Rice seedlings were most sensitive to PAHs. Germination of sweet corn, waxy corn, and rice seeds was delayed by single PAH and their mixtures, especially at their high concentrations. More than 20 mg/kg of anthracene and 2 mg/kg of phenanthrene significantly retarded the seed germination rate in waxy corn. Root and shoot elongation were more sensitive to toxic PAHs than other growth indices. Fluorene was more toxic to all the tested plants than other PAHs. (Anthracene + fluoranthene) was most toxic to plants when compared with other PAH mixtures. There was synergistic combine effect of PAHs on corn root length, but there were antagonistic combine effects on fresh weights of both plants and rice root length. PAH mixtures did not affect dry weights of all plants.     

Mycoremediation of PAH-contaminated soil

Out of a number of white-rot fungal cultures, strains ofIrpex lacteus andPleurotus ostreatus were selected for degradation of 7 three- and four-ring unsubstituted aromatic hydrocarbons (PAH) in two contaminated industrial soils. Respective data for removal of PAH in the two industrial soils byI. lacteus were: fluorene (41 and 67%), phenanthrene (20 and 56%), anthracene (29 and 49%), fluoranthene (29 and 57%), pyrene (24 and 42%), chrysene (16 and 32%) and benzo[a]anthracene (13 and 20%). In the same two industrial soilsP. ostreatus degraded the PAH with respective removal figures of fluorene (26 and 35%), phenanthrene (0 and 20%), anthracene (19 and 53%), fluoranthene (29 and 31%), pyrene (22 and 42%), chrysene (0 and 42%) and benzo[a]anthracene (0 and 13%). The degradation of PAH was determined against concentration of PAH in non-treated contaminated soils after 14 weeks of incubation. The fungal degradation of PAH in soil was studied simultaneously with ecotoxicity evaluation of fungal treated and non-treated contaminated soils. Compared to non-treated contaminated soil, fungus-treated soil samples indicated decrease in inhibition of bioluminescence in luminescent bacteria (Vibrio fischerii) and increase in germinated mustard (Brassica alba) seeds. An erratum to this article is available at .     

Enhanced Solubilisation of Six PAHs by Three Synthetic Cyclodextrins for Remediation Applications: Molecular Modelling of the Inclusion Complexes

Solubilisation of six polycyclic aromatic hydrocarbons (PAHs) (acenaphthene, anthracene, fluoranthene, fluorene, phenanthrene and pyrene) by three synthetic cyclodextrins (CDs) (2-hydroxypropyl-β-CD, hydroxypropyl-γ-CD and ramdomly methylated-β-CD) was investigated in order to select the CD which presents the greatest increase in solubility and better complexation parameters for its use in contaminated scenarios. The presence of the three cyclodextrins greatly enhanced the apparent water solubility of all the PAHs through the formation of inclusion complexes of 1∶1 stoichiometry. Anthracene, fluoranthene, fluorene and phenanthrene clearly presented a higher solubility when β-CD derivatives were used, and especially the complexes with the ramdomly methylated-β-CD were favoured. On the contrary, pyrene presented its best solubility results when using 2-hydroxypropyl-γ-CD, but for acenaphthene the use of any of the three CDs gave the same results. Complementary to experimental phase-solubility studies, a more in-depth estimation of the inclusion process for the different complexes was carried out using molecular modelling in order to find a correlation between the degree of solubilisation and the fit of PAH molecules within the cavity of the different CDs and to know the predominant driving forces of the complexation.     

Photomutagenicity of 16 polycyclic aromatic hydrocarbons from the US EPA priority pollutant list

The photomutagenicity of 16 polycyclic aromatic hydrocarbons (PAHs), all on the United States Environmental Protection Agency (US EPA) priority pollutant list, was studied. Concomitant exposing the Salmonella typhimurium bacteria strain TA102 to one of the PAHs and light (1.1 J/cm2 UVA+2.1 J/cm2 visible) without the activation enzyme S9, strong photomutagenic response is observed for anthracene, benz[a]anthracene, benzo[ghi]perylene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, and pyrene. Under the same conditions, acenaphthene, acenaphthylene, benzo[k]fluoranthene, chrysene, and fluorene are weakly photomutagenic. Benzo[b]fluoranthene, fluoranthene, naphthalene, phenanthrene, and dibenz[a,h]anthracene are not photomutagenic. These results indicate that PAHs can be activated by light and become mutagenic in Salmonella TA102 bacteria. At the same time, the mutagenicity for all the 16 PAHs was examined with the standard mutagenicity test with 10% S9 as the activation system. Benzo[b]fluoranthene, benzo[k]fluoranthene, chrysene, acenaphthylene, and fluorene are weakly mutagenic, while the rest of the PAHs are not. In general, the photomutagenicity of PAHs in TA102 does not correlate with their S9-activated mutagenicity in either TA102 or TA98/TA100 since they involve different activation mechanisms.     

Biodegradation of a PAH Mixture by Native Subsurface Microbiota

Laboratory microcosm studies were conducted to estimate biodegradation rates for a mixture of five polycyclic aromatic hydrocarbon compounds (PAHs). Static microcosms were assembled using soil samples from two locations collected at a No. 2 fuel oil-contaminated site in the Atlantic Coastal Plain of Virginia. In microcosms from one location, five PAHs (acenaphthene, fluorene, phenanthrene, pyrene, and benzo(b)fluoranthene) biodegraded at net first-order rates of 1.08, 1.45, 1.13, 1.11, and 1.12 yr^?1, respectively. No observable lag period was noted and degradation in live microcosms ceased with the depletion of oxygen and sulfate after 125 days. In microcosms from a second location, net first-order biodegradation rates after an approximately 2-month lag period were 2.41, 3.28, and 2.98 yr^?1 for fluorene, phenanthrene, and pyrene, respectively. Acenaphthene and benzo(b)fluoranthene mass loss rates in the live microcosms were not statistically different from mass loss rates in control microcosms. Stoichiometric mass balance calculations indicate that the dominant PAH mass loss mechanism was aerobic biodegradation, while abiotic losses (attributed to micropore diffusion and oxidative coupling) ranged from 15 to 33% and biotic losses from sulfate-reduction accounted for 7 to 10% of PAH mass loss. Stoichiometric equations that include biomass yield are presented for PAH oxidation under aerobic and sulfate-reducing conditions.     

Initial characterization of new bacteria degrading high-molecular weight polycyclic aromatic hydrocarbons isolated from a 2-year enrichment in a two-liquid-phase culture system

AIMS: To characterize some polycyclic aromatic hydrocarbons (PAH)-degrading microorganisms isolated from an enriched consortium degrading high molecular weight (HMW) PAHs in a two-liquid-phase (TLP) soil slurry bioreactor, and to determine the effect of low molecular weight (LMW) PAH on their growth and HMW PAH-degrading activity. METHODS AND RESULTS: Several microorganisms were isolated from a HMW-PAH (pyrene, chrysene, benzo[a]pyrene and perylene) degrading consortium enriched in TLP cultures using silicone oil as the organic phase. From 16S rRNA analysis, four isolates were identified as Mycobacterium gilvum B1 (99% identity),Bacillus pumilus B44 (99% identity), Microbacterium esteraromaticum B21 (98% identity), and to the genus Porphyrobacter B51 (96% identity). The two latter isolates have not previously been associated with PAH degradation. Isolate B51 grew strongly in the interfacial fraction in the presence of naphthalene vapours and phenanthrene compared with cultures without LMW PAHs. Benzo[a]pyrene was degraded in cultures containing a HMW PAH mixture but pyrene had no effect on its degradation. The growth of isolates B1 and B21 was improved in the aqueous phase than in the interfacial fraction for cultures with naphthalene vapours. Pyrene was required for benzo[a]pyrene degradation by isolate B1. For isolate B21, pyrene and chrysene were degraded only in cultures without naphthalene vapours. CONCLUSION: Consortium enriched in a TLP culture is composed of microorganisms with different abilities to grow at the interface or in the aqueous phase according to the culture conditions and the PAH that are present. Naphthalene vapours increased the growth of the microorganisms in TLP cultures but did not stimulate the HMW PAH degradation. SIGNIFICANCE AND IMPACT OF THE STUDY: New HMW PAH-degrading microorganisms and a better understanding of the mechanisms involved in HMW PAH degradation in TLP cultures.     

糙皮侧耳和鞘脂菌NS7对多环芳烃污染土壤的生物强化与协同作用

【背景】真菌和细菌被认为在多环芳烃污染土壤生物修复过程中发挥协同作用,目前在真实土壤体系中开展真菌-细菌协同降解研究较少。【目的】研究真菌和细菌对不同种类多环芳烃降解的差异及对蒽和苯并[a]蒽的生物强化与协同作用。【方法】选用多环芳烃降解真菌和细菌各一株,在液体纯培养体系下分析它们对不同种类多环芳烃降解的差异,在土壤体系中采用放射性同位素示踪技术研究2种微生物对蒽和苯并[a]蒽的生物强化与协同作用。【结果】供试细菌鞘脂菌NS7能够很好地降解低环种类多环芳烃,以蒽作为唯一碳源时可以将其完全降解,在复合污染条件下对菲、蒽、荧蒽、芘等降解效果突出(>90%),对苯并[a]芘降解效果较差(9.76%)。相比而言,供试真菌糙皮侧耳菌对苯并[a]芘具有更好的降解效果(21.18%),对低环多环芳烃降解效果明显不如降解菌NS7。在自然土壤中,蒽和苯并[a]蒽具有明显不同的矿化效率,分别为18.61%和4.28%,在蒽污染土壤中加入鞘脂菌NS7并未显著提高蒽的矿化率(P>0.05),相比而言,苯并[a]蒽污染土壤中加入糙皮侧耳显著提高了污染物矿化效率(2.24倍),表明真菌和细菌在土壤环境...     

Degradation of High Molecular Weight PAHs in Contaminated Soil by a Bacterial Consortium: Effects on Microtox and Mutagenicity Bioassays

Bioaugmentation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil was investigated using a mixed bacterial culture (community five) isolated from an abandoned industrial site. Community five was inoculated into contaminated soil containing a total PAH (two- to five-ring compounds) concentration of approximately 820 mg/kg soil. PAH degradation by the indigenous microbial population was restricted to the lower molecular weight compounds (naphthalene, acenaphthene, fluorene and phenanthrene) even with yeast extract addition: these compounds decreased by 14 to 37%, in soil hydrated to 50% water capacity, following 91 days of incubation at 24°C. Inoculation of community five into this PAH-contaminated soil resulted in significant decreases in the concentration of all PAHs over the incubation period: greater than 86% of naphthalene, acenaphthene, fluorene, and phenanthrene were degraded after 91 days, while anthracene, fluoranthene, and pyrene were degraded to lesser extents (51.7 to 57.6%). A lag period of 48 to 63 days was observed before the onset of benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene removal. However, significant decreases in the concentration of these compounds (32.6, 25.2, and 18.5%, respectively) were observed after 91 days. No significant decrease in the mutagenic potential of organic soil extracts (as measured by the Ames Test) was observed after incubation of the soil with the indigenous microflora; however, the Microtox toxicity of aqueous soil extracts was reduced sevenfold. In contrast, extracts from contaminated soil inoculated with community five underwent a 43% decrease in mutagenic potential and the toxicity was reduced 170-fold after 91 days incubation. These observations suggest that community five could be utilised for the detoxification of PAH-contaminated soil.