Degradation of straight-chain aliphatic and high-molecular-weight polycyclic aromatic hydrocarbons by a strain of Mycobacterium austroafricanum

AIMS: Our goal was to characterize a newly isolated strain of Mycobacterium austroafricanum, obtained from manufactured gas plant (MGP) site soil and designated GTI-23, with respect to its ability to degrade polycyclic aromatic hydrocarbons (PAHs). METHODS AND RESULTS: GTI-23 is capable of growth on phenanthrene, fluoranthene, or pyrene as a sole source of carbon and energy; it also extensively mineralizes the latter two in liquid culture and is capable of extensive degradation of fluorene and benzo[a]pyrene, although this does not lead in either of these cases to mineralization. Supplementation of benzo[a]pyrene-containing cultures with phenanthrene had no significant effect on benzo[a]pyrene degradation; however, this process was substantially inhibited by the addition of pyrene. Extensive and rapid mineralization of pyrene by GTI-23 was also observed in pyrene-amended soil. CONCLUSIONS: Strain GTI-23 shows considerable ability to mineralize a range of polycyclic aromatic hydrocarbons, both in liquid and soil environments. In this regard, GTI-23 differs markedly from the type strain of Myco. austroafricanum (ATCC 33464); the latter isolate displayed no (or very limited) mineralization of any tested PAH (phenanthrene, fluoranthene or pyrene). When grown in liquid culture, GTI-23 was also found to be capable of growing on and mineralizing two aliphatic hydrocarbons (dodecane and hexadecane). SIGNIFICANCE AND IMPACT OF THE STUDY: These findings indicate that this isolate of Myco. austroafricanum may be useful for bioremediation of soils contaminated with complex mixtures of aromatic and aliphatic hydrocarbons.     

Pyrene and benzo(a)pyrene Metabolism by an Aspergillus Terreus Strain Isolated from a Polycylic Aromatic Hydrocarbons Polluted Soil

A strain of Aspergillus terreus was isolated from a polycyclic aromatic hydrocarbons (PAHs) polluted soil. The metabolism of pyrene and benzo(a)pyrene by this fungus was investigated in liquid submerged culture added of 50 and 25 ppm respectively of each compound. Depletion of pyrene and Benzo(a)pyrene was evident during the first stages of growth and was 60% and 27.5% respectively of the added amount after nine days of culture. Solvent extracts of the fermentation broth and mycelium were analysed for presence of metabolites by HPLC-MS technique. Under the present cultural conditions pyrene was mainly metabolised to pyrenylsulfate similarly to benzo(a)pyrene that led to benzo(a)pyrenylsulfate. The structure of 1-pyrenilsulfate was determined after purification of extracts and H-NMR analysis. The result show that the isolated A. terreus strain metabolises PAHs by reaction similar to those previously reported for non lignolinolytic fungi with a mechanism that suggests the hydroxylation by a cytochrome P-450 monooxygenase followed by conjugation with sulfate ion.     

Microbial degradation and detoxification of high molecular weight polycyclic aromatic hydrocarbons by Stenotrophomonas maltophilia strain VUN 10,003

The ability of Stenotrophomonas maltophilia strain VUN 10,003 to degrade and detoxify high molecular weight polycyclic aromatic hydrocarbons (PAHs) was evaluated in a basal liquid medium. Using high cell density inocula of strain VUN 10,003, the concentration of pyrene, fluoranthene, benz[a]anthracene, benzo[a]pyrene, dibenz[a, h]anthracene and coronene decreased by 98, 45, 26, 22, 22 and 55% over periods ranging from 5 to 42 d. When a PAH mixture containing three- to seven-ring compounds was used, degradation of both low and high molecular weight compounds occurred concurrently. Mutagenicity assays (Ames Test) demonstrated a decrease in the mutagenic potential of dichloromethane culture extracts from all cultures containing single PAH over the incubation period, corresponding to the decrease in the concentration of the PAH. These observations indicate that strain VUN 10,003 could be used for the detoxification of PAH-contaminated wastes.     

嗜麦芽寡养单胞菌PX1的降解芘特性及定殖效能

为丰富多环芳烃降解菌菌种库、降低农作物的污染风险,本研究对一株可高效降解多环芳烃(PAHs)的植物内生菌进行筛选鉴定,并初步探究其降解途径以及定殖效能。结果表明: 菌株PX1为嗜麦芽寡养单胞菌。该菌株对多环芳烃的降解具有广谱性,7 d几乎可彻底降解PAH无机盐培养基中的萘,在分别含有50.0 mg·L^-1菲、20.0 mg·L^-1芘、20.0 mg·L^-1荧蒽和10.0 mg·L^-1苯并[a]芘的培养体系中,对菲、芘、荧蒽、苯并[a]芘的降解率分别为72.6%、50.7%、31.9%和12.9%。选取芘作为PAHs模型研究菌株PX1的降解特性。酶活性试验表明,芘可诱导菌株PX1体内邻苯二甲酸双加氧酶、邻苯二酚-1,2-双加氧酶和邻苯二酚-2,3-双加氧酶的活性。在芘降解过程中检测到4,5-环氧化芘、4,5-二羟基芘、龙胆酸/原茶儿酸、水杨酸、顺-己二烯二酸/2-羟粘糠酸半醛、顺-2′-羧基苯丙酮酸、1-羟基-2-萘甲酸、水杨醛等中间产物。浸种定殖试验表明,菌株PX1可高效定殖到空心菜和小麦体内,显著促进空心菜和小麦生长,并能够将空心菜、小麦体内及其生长基质中的芘浓度分别降低29.8%～50.7%、52.4%～67.1%和8.0%～15.3%。表明菌株PX1主要通过“水杨酸途径”和“邻苯二甲酸途径”降解芘,且可以定殖到植物体内,促进植物生长。     

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.

     

Degradation and mineralization of high-molecular-weight polycyclic aromatic hydrocarbons by defined fungal-bacterial cocultures

This study investigated the biodegradation of high-molecular-weight polycyclic aromatic hydrocarbons (PAHs) in liquid media and soil by bacteria (Stenotrophomonas maltophilia VUN 10,010 and bacterial consortium VUN 10,009) and a fungus (Penicillium janthinellum VUO 10, 201) that were isolated from separate creosote- and manufactured-gas plant-contaminated soils. The bacteria could use pyrene as their sole carbon and energy source in a basal salts medium (BSM) and mineralized significant amounts of benzo[a]pyrene cometabolically when pyrene was also present in BSM. P. janthinellum VUO 10,201 could not utilize any high-molecular-weight PAH as sole carbon and energy source but could partially degrade these if cultured in a nutrient broth. Although small amounts of chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene were degraded by axenic cultures of these isolates in BSM containing a single PAH, such conditions did not support significant microbial growth or PAH mineralization. However, significant degradation of, and microbial growth on, pyrene, chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene, each as a single PAH in BSM, occurred when P. janthinellum VUO 10,201 and either bacterial consortium VUN 10,009 or S. maltophilia VUN 10,010 were combined in the one culture, i.e., fungal-bacterial cocultures: 25% of the benzo[a]pyrene was mineralized to CO(2) by these cocultures over 49 days, accompanied by transient accumulation and disappearance of intermediates detected by high-pressure liquid chromatography. Inoculation of fungal-bacterial cocultures into PAH-contaminated soil resulted in significantly improved degradation of high-molecular-weight PAHs, benzo[a]pyrene mineralization (53% of added [(14)C]benzo[a]pyrene was recovered as (14)CO(2) in 100 days), and reduction in the mutagenicity of organic soil extracts, compared with the indigenous microbes and soil amended with only axenic inocula.     

Physiological characterization of Mycobacterium sp. strain 1B isolated from a bacterial culture able to degrade high-molecular-weight polycyclic aromatic hydrocarbons

AIM: The aim of this study was to further characterize a bacterial culture (VUN 10,010) capable of benzo[a]pyrene cometabolism. METHODS AND RESULTS: The bacterial culture, previously characterized as a pure culture of Stenotrophomonas maltophilia (VUN 10,010), was found to also contain another bacterial species (Mycobacterium sp. strain 1B), capable of degrading a similar range of PAH substrates. Analysis of its 16S rRNA gene sequence and growth characteristics revealed the strain to be a fast-growing Mycobacterium sp., closely related to other previously isolated PAH and xenobiotic-degrading mycobacterial strains. Comparison of the PAH-degrading characteristics of Mycobacterium sp. strain 1B with those of S. maltophilia indicated some similarities (ability to degrade phenanthrene and pyrene), but some differences were also noted (S. maltophilia able to degrade fluorene, but not fluoranthene, whereas Mycobacterium sp. strain 1B can degrade fluoranthene, but not fluorene). Unlike the S. maltophilia culture, there was no evidence of benzo[a]pyrene degradation by Mycobacterium sp. strain 1B, even in the presence of other PAHs (ie pyrene) as co-metabolic substrates. Growth of Mycobacterium sp. strain 1B on other organic carbon sources was also limited compared with the S. maltophilia culture. CONCLUSIONS: This study isolated a Mycobacterium strain from a bacterial culture capable of benzo[a]pyrene cometabolism. The Mycobacterium strain displays different PAH-degrading characteristics to those described previously for the PAH-degrading bacterial culture. It is unclear what role the two bacterial strains play in benzo[a]pyrene cometabolism, as the Mycobacterium strain does not appear to have endogenous benzo[a]pyrene degrading ability. SIGNIFICANCE AND IMPACT OF THE STUDY: This study describes the isolation and characterization of a novel PAH-degrading Mycobacterium strain from a PAH-degrading culture. Further studies utilizing this strain alone, and in combination with other members of the consortium, will provide insight into the diverse roles different bacteria may play in PAH degradation in mixed cultures and in the environment.     

Degradation of high molecular weight polycyclic aromatic hydrocarbons by Pseudomonas cepacia

Summary When inoculated at high cell densities, three strains of Pseudomonas cepacia degraded the polycyclic aromatic hydrocarbons (PAHs) benzo[a]pyrene, dibenz[a,h]anthracene and coronene as sole carbon and energy sources. After 63 days incubation, there was a 20 to 30% decrease in the concentration of benzo[a]pyrene and dibenz[a,h]anthracene and a 65 to 70% decrease in coronene concentration. The three strains were also able to degrade all the PAHs simultaneously in a PAH substrate mixture containing three-, four-, five- and seven-benzene ring compounds. Furthermore, improved degradation of the five- and seven-ring PAHs was observed when low molecular weight PAHs were present.     

Screening of ectomycorrhizal fungi for degradation of polycyclic aromatic hydrocarbons

Ectomycorrhizal fungi belonging to 16 species (27 strains) were tested for their ability to degrade polycyclic aromatic hydrocarbons (PAHs): phenanthrene, chrysene, pyrene and benzo[a]pyrene. Cultivated on a complex liquid medium, most of the fungi tested were able to metabolise these compounds. Approximately 50% of the benzo[a]pyrene was removed by strains of Amanita excelsa, Leccinum versipelle, Suillus grevillei, S. luteus, and S. variegatus during a 4-week incubation period. The same amount of phenanthrene was also metabolised by A. muscaria, Paxillus involutus, and S. grevillei. The degradation of the other two PAHs was, for the most part, less effective. Only S. grevillei was able to remove 50% of the pyrene, whereas Boletus edulis and A. muscaria removed 35% of the chrysene. Received: 12 April 1999 / Received revision: 27 May 1999 / Accepted: 28 May 1999     

Influence of cadmium and mercury on activities of ligninolytic enzymes and degradation of polycyclic aromatic hydrocarbons by Pleurotus ostreatus in soil

The white-rot fungus Pleurotus ostreatus was able to degrade the polycyclic aromatic hydrocarbons (PAHs) benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, and benzo[ghi]perylene in nonsterile soil both in the presence and in the absence of cadmium and mercury. During 15 weeks of incubation, recovery of individual compounds was 16 to 69% in soil without additional metal. While soil microflora contributed mostly to degradation of pyrene (82%) and benzo[a]anthracene (41%), the fungus enhanced the disappearance of less-soluble polycyclic aromatic compounds containing five or six aromatic rings. Although the heavy metals in the soil affected the activity of ligninolytic enzymes produced by the fungus (laccase and Mn-dependent peroxidase), no decrease in PAH degradation was found in soil containing Cd or Hg at 10 to 100 ppm. In the presence of cadmium at 500 ppm in soil, degradation of PAHs by soil microflora was not affected whereas the contribution of fungus was negligible, probably due to the absence of Mn-dependent peroxidase activity. In the presence of Hg at 50 to 100 ppm or Cd at 100 to 500 ppm, the extent of soil colonization by the fungus was limited.     

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...     

Biodegradation of benzo(a)pyrene by a newly isolated Fusarium sp

Benzo(a)pyrene (BaP) is a five-ring polycyclic aromatic hydrocarbon produced by the incomplete combustion of organic materials. It is one of the priority pollutants listed by the US Environmental Protection Agency. This study describes a fungal isolate that is able to biodegrade benzo(a)pyrene. The filamentous fungus, isolated from leaves of Pterocarpus macrocarpus Kurz., was identified as a Fusarium sp. (strain E033). Fusarium sp. E033 was able to survive in the presence of benzo(a)pyrene concentrations up to 1.2 mM (300 mg L(-1)). Biodegradation experiments using 0.4 mM (100 mg L(-1)) benzo(a)pyrene demonstrated that Fusarium sp. E033 was able to degrade 65-70% of the initial benzo(a)pyrene provided, and two transformation products, a dihydroxy dihydro-benzo(a)pyrene and a benzo(a)pyrene-quinone, were detected within 30 days of incubation at 32 degrees C. The factors affecting biodegradation efficiency were also investigated. While increasing aeration promoted better fungal growth and benzo(a)pyrene biodegradation, increasing the glucose concentration from 5 to 50 mM had an adverse effect on biodegradation. Ethanol and methanol, provided at 5 mM to increase benzo(a)pyrene water solubility, increased the fungal biomass yield but did not promote degradation. The Fusarium sp. E033 isolated in this study can tolerate and degrade relatively high concentrations of benzo(a)pyrene, suggesting its potential application in benzo(a)pyrene bioremediation.     

Biodegradation studies of polyaromatic hydrocarbons in aqueous media

Sixteen bacterial strains isolated from an activated sludge and Mycobacterium ssp. PYR-1 were tested for their ability to degrade polyaromatic hydrocarbons (PAHs). The bacterial strains Pasteurella ssp. (B-2) and Mycobacterium ssp. PYR-1 (AM) showed a high biodegradation potential of three- and four-ring PAHs. Bacterial strain AM was able to degrade up to 80% of three and four-ring PAHs (phenanthrene, fluoranthene and pyrene) within the first month of incubation, while the bacterial strain B-2 achieved the same biodegradation in 2 months. The metabolic pathway of PAH degradation was studied using fluoranthene and the bacterial strain AM. Ninety per cent of fluoranthene was biodegraded within the first 9 d of incubation when applied as a single substrate. Retention factor values from thin-layer chromatography studies, gas chromatography with mass selective detection and tandem mass spectrometry identified 9-fluorenone-1-carboxylic acid as one of the stable metabolic products and from this a fluoranthene biodegradation pathway is proposed.     

Degradation of benzo[a]pyrene by Mycobacterium vanbaalenii PYR-1

Metabolism of the environmental pollutant benzo[a]pyrene in the bacterium Mycobacterium vanbaalenii PYR-1 was examined. This organism initially oxidized benzo[a]pyrene with dioxygenases and monooxygenases at C-4,5, C-9,10, and C-11,12. The metabolites were separated by reversed-phase high-performance liquid chromatography (HPLC) and characterized by UV-visible, mass, nuclear magnetic resonance, and circular dichroism spectral analyses. The major intermediates of benzo[a]pyrene metabolism that had accumulated in the culture media after 96 h of incubation were cis-4,5-dihydro-4,5-dihydroxybenzo[a]pyrene (benzo[a]pyrene cis-4,5-dihydrodiol), cis-11,12-dihydro-11,12-dihydroxybenzo[a]pyrene (benzo[a]pyrene cis-11,12-dihydrodiol), trans-11,12-dihydro-11,12-dihydroxybenzo[a]pyrene (benzo[a]pyrene trans-11,12-dihydrodiol), 10-oxabenzo[def]chrysen-9-one, and hydroxymethoxy and dimethoxy derivatives of benzo[a]pyrene. The ortho-ring fission products 4-formylchrysene-5-carboxylic acid and 4,5-chrysene-dicarboxylic acid and a monocarboxylated chrysene product were formed when replacement culture experiments were conducted with benzo[a]pyrene cis-4,5-dihydrodiol. Chiral stationary-phase HPLC analysis of the dihydrodiols indicated that benzo[a]pyrene cis-4,5-dihydrodiol had 30% 4S,5R and 70% 4R,5S absolute stereochemistry. Benzo[a]pyrene cis-11,12-dihydrodiol adopted an 11S,12R conformation with 100% optical purity. The enantiomeric composition of benzo[a]pyrene trans-11,12-dihydrodiol was an equal mixture of 11S,12S and 11R,12R molecules. The results of this study, in conjunction with those of previously reported studies, extend the pathways proposed for the bacterial metabolism of benzo[a]pyrene. Our study also provides evidence of the stereo- and regioselectivity of the oxygenases that catalyze the metabolism of benzo[a]pyrene in M. vanbaalenii PYR-1.     

固定化引进菌降解土壤中芘和苯并(a)芘的效果比较

将引进菌用于有机污染土壤中芘和苯并(a)芘的生物修复,目的是使引进菌在环境工程中的利用成为可能.通过对引进的3株细菌进行固定化包埋,研究了它们对土壤中芘和苯并(a)芘的降解效果.结果表明,引进菌驯化固定后,无论是单株菌还是混合菌对污染物的降解都明显高于游离菌,与土著固定菌相比,部分引进菌具有一定的优势.通过不同时间采样点的对比分析可以看出,引进菌混合固定后对污染物的降解效果相对较好,在96 h时B61B67对芘和苯并(a)芘的降解率分别为43.49%和38.55%.     

Two-liquid-phase slurry bioreactors to enhance the degradation of high-molecular-weight polycyclic aromatic hydrocarbons in soil

High-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) are pollutants that persist in the environment due to their low solubility in water and their sequestration by soil and sediments. The addition of a water-immiscible, nonbiodegradable, and biocompatible liquid, silicone oil, to a soil slurry was studied to promote the desorption of PAHs from soil and to increase their bioavailability. First, the transfer into silicone oil of phenanthrene, pyrene, chrysene, and benzo[a]pyrene added to a sterilized soil (sandy soil with 0.65% total volatile solids) was measured for 4 days in three two-liquid-phase (TLP) slurry systems each containing 30% (w/v) soil but different volumes of silicone oil (2.5%, 7.5%, and 15% [v/v]). Except for chrysene, a high percentage of these PAHs was transferred from soil to silicone oil in the TLP slurry system containing 15% silicone oil. Rapid PAH transfer occurred during the first 8 h, probably resulting from the extraction of nonsolubilized and of poorly sorbed PAHs. This was followed by a period in which a slower but constant transfer occurred, suggesting extraction of more tightly bound PAHs. Second, a HMW PAH-degrading consortium was enriched in a TLP slurry system with a microbial population isolated from a creosote-contaminated soil. This consortium was then added to three other TLP slurry systems each containing 30% (w/v) sterilized soil that had been artificially contaminated with pyrene, chrysene, and benzo[a]pyrene, but different volumes of silicone oil (10%, 20%, and 30% [v/v]). The resulting TLP slurry bioreactors were much more efficient than the control slurry bioreactor containing the same contaminated soil but no oil phase. In the TLP slurry bioreactor containing 30% silicone oil, the rate of pyrene degradation was 19 mg L(-)(1) day(-)(1) and no pyrene was detected after 4 days. The degradation rates of chrysene and benzo[a]pyrene in the 30% TLP slurry bioreactor were, respectively, 3.5 and 0.94 mg L(-)(1) day(-)(1). Low degradation of pyrene and no significant degradation of chrysene and benzo[a]pyrene occurred in the slurry bioreactor. This is the first report in which a TLP system was combined with a slurry system to improve the biodegradation of PAHs in soil.     

Oxidation of polycyclic aromatic hydrocarbons by the bacterial laccase CueO from E. coli

Laccases produced by white rot fungi are capable of rapidly oxidizing benzo[a]pyrene. We hypothesize that the polycyclic aromatic hydrocarbon (PAH)-degrading bacteria producing laccase can enhance the degree of benzo[a]pyrene mineralization. However, fungal laccases are glycoproteins which cannot be glycosylated in bacteria, and there is no evidence to show that bacterial laccases can oxidize benzo[a]pyrene. In this study, the in vitro oxidation of PAHs by crude preparations of the bacterial laccase, CueO, from Escherichia coli was investigated. The results revealed that the crude CueO catalyzed the oxidation of anthracene and benzo[a]pyrene in the same way as the fungal laccase from Trametes versicolor, but showed specific characteristics such as thermostability and copper dependence. In the presence of 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid), high amounts of anthracene and benzo[a]pyrene, 80% and 97%, respectively, were transformed under optimal conditions of 60°C, pH 5, and 5 mmol l(-1) CuCl(2) after a 24-h incubation period. Other PAHs including fluorene, acenaphthylene, phenanthrene, and benzo[a]anthracene were also oxidized by the crude CueO. These findings indicated the potential application of prokaryotic laccases in enhancing the mineralization of benzo[a]pyrene by PAH-degrading bacteria.     

Sphingobium sp. FB3 degrades a mixture of polycyclic aromatic hydrocarbons

A soil sample collected underneath a sewage pipe of the west side of Yangpu refining factory in Haikou city, Hainan Province, China was inoculated in minimum medium supplemented with fluoranthene. After 8 enrichment cycles, a bacterial consortium (Y12) was obtained through water-silicone oil dual system in the laboratory. The consortium Y12 could degrade a mixture of polycyclic aromatic hydrocarbons (PAHs) including phenanthrene, anthracene, fluoranthene, pyrene and benzo[a]pyrene. The consortium Y12 was repeatedly cultured for more than 40 circles, from which a bacterial strain FB3 was isolated. This strain was identified as a Sphingobium sp. through the 16S rDNA sequence alignment. Strain FB3 could degrade 99 ± 0.4%, 67 ± 2%, 97 ± 3%, 72 ± 8%, and 6 ± 2% (uncorrected degradation percentages) of phenanthrene, anthracene, fluoranthene and pyrene each at level of 100 mg L⁻¹ and benzo[a]pyrene at 10 mg L⁻¹, respectively, in 10 days, which the five PAHs were the sole carbon source as a mixture in minimum medium. The degradation percentages of phenanthrene, anthracene, fluoranthene, pyrene (each at level of 100 mg L⁻¹) and benzo[a]pyrene (10 mg L⁻¹) by consortium Y12 were 99 ± 0.1%, 65 ± 3%, 99 ± 0.3%, 79 ± 1% and 7 ± 6%, respectively, in 10 days. Strain FB3 could degrade those PAHs under a range of pH 5–9, being optimum at pH 7.     

Optimization of PAHs Oxidation from a Concentrate of Soil Attrition Using Potassium Permanganate

The treatment of soils contaminated with organic compounds, such as polycyclic aromatic hydrocarbons (PAHs), by attrition produced large amounts of highly concentrated attrition sludge (PAH – attrition concentrate – PAC). This paper studied the performance of an oxidation process using potassium permanganate (KMnO₄) to degrade PAHs that were initially present in attrition concentrates. The influence of operating conditions (temperature, concentration of KMnO₄ and reaction time) was studied, and these parameters were optimized using a response surface methodology (RSM). The results showed that the temperature and the reaction time had a significant and positive effect on the degradation of PAHs for the experimental domain studied (temperature between 20 and 60°C and reaction time between 1 and 7 h). The interaction between the temperature and the concentration of KMnO₄ significantly influenced the degradation of the PAHs. The temperature and the concentration of KMnO₄ were the main parameters that influenced the degradation of both phenanthrene (Phe) and benzo [a] pyrene (BaP). For benzo [a] anthracene (BaA), the temperature was the most influential factor. According to our results, the optimal conditions were defined as [KMnO₄] = 0.4 M for 5.5 h at 60°C. These optimal conditions led to degradations of 42.9%, 40.8%, 41.0% and 46.0% of the total PAHs, Phe, BaA and BaP, respectively.