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Introduction: The composition and structure of natural soil are very complex, leading to the difficult contact between hydrophobic organic compounds and degrading-bacteria in contaminated soil, making pollutants hard to be removed from the soil. Several researches have reported the bacterial migration in unsaturated soil mediated by fungal hyphae, but bacterial movement in soil of different particle sizes or in heterogeneous soil was unclear. The remediation of contaminated soil enhanced by hyphae still needs further research. Methods: In this case, the migration and biodegradation of Diaphorobacter sp. LW2 in soil was investigated in presence of Pythium ultimum. Results: Hyphae could promote the growth and migration of LW2 in culture medium. It was also confirmed that LW2 was able to migrate in the growth direction and against the growth direction along hyphae. Mediated by hyphae, motile strain LW2 translocated over 3 cm in soil with different particle size (CS1, 1.0-2.0 mm; CS2, 0.5-1.0mm; MS, 0.25-0.5 mm and FS, <0.25 mm), and it need shorter time in bigger particle soils. In inhomogeneous soil, hyphae participated in the distribution of introduced bacteria, and the total number of bacteria increased. Pythium ultimum enhanced the migration and survival of LW2 in soil, improving the bioremediation of polluted soil. Discussion: The results of this study indicate that the mobilization of degrading bacteria mediated by Pythium ultimum in soil has great potential for application in bioremediation of contaminated soil. [ABSTRACT FROM AUTHOR]

Highlights • Enrichment of mixed bacterial cultures for phenanthrene & fluoranthene degradation. • Bioaugmentation & biostimulation have enhanced the degradation efficiency of ASPF. • Phenanthrene & fluoranthene degradation in presence of petroleum hydrocarbons. Abstract Polycyclic aromatic hydrocarbons (PAHs) are highly recalcitrant compounds and difficult to degrade. Therefore in this work, using a bioremediation approach, mixed bacterial cultures (ASPF) was developed and enriched from polluted marine sediments capable of degrading 400 mg/L of phenanthrene and fluoranthene in Bushnell Hass medium. ASPF consists of 22 bacterial genera dominated by Azoarcus and Chelativorans. The biostimulation effect of three water soluble fertilizers (NPK, urea, and ammonium sulfate) showed that NPK and ammonium sulfate have enhanced the degradation, whereas urea has decreased their degradation. ASPF was also able to degrade phenanthrene and fluoranthene in the presence of petroleum hydrocarbons. But degradation was found to decrease in the presence of pathway intermediates (phthalic acid and catechol) due to enzymatic feedback inhibition. Optimum degradation of both PAHs was observed under room temperature, suggesting the practical applicability of ASPF. [ABSTRACT FROM AUTHOR]

Highlights • A bioelectrochemical process was used in an AD system for phenanthrene removal. • SCOD can increase the bio-availability of phenanthrene. • Carbon-based cathodes mainly enhance direct electron transfer (DIET) in the system. • Carbon-based cathodes exhibit high adsorption to microbes. • Metallic cathodes mainly enhance H 2 transfer in the system. Abstract The purpose of this study was to investigate the enhanced biogas production and biodegradation of phenanthrene in sludge treated anaerobic digestion (AD) reactors fitted with a bioelectrode system (AD-MEC reactors). Different cathodes were considered for installation in the AD-MEC reactor. The result showed that the maximum methane yield (113.45 L/kg TS) and the highest phenanthrene degradation rate (52.3%) were obtained in a reactor with a carbon paper (CP) cathode; this performance was 30.5% and 83.5% greater, respectively, than that in the AD control reactor. Clostridia spp., bacteria that degrade pollutants, were specifically adsorbed onto the electrodes, and Methanosaeta spp. and Geobacter spp. were enriched on the anode. These results implied that a potential direct electron transfer occurred between Methanosaeta and Geobacter. Two hydrogenotrophic methanogens (Methanospirillum spp. and Methanobacterium spp.) were enriched on the surface of the cathode, which enhanced interspecies H 2 transfer in the AD-MEC reactors. [ABSTRACT FROM AUTHOR]

The influence of different initial moisture content on the degradation of phenanthrene was studied during sewage sludge composting under the same aerobic fermentation conditions. Wood chips were used as amendment and the moisture content of mixture was adjusted to 56.21% (treatment 1) or 60.89% (treatment 2). The results showed that initial moisture content has a significant effect on sewage sludge composting, the composting of two treatments all lasted 12 days. In addition, variations in moisture content led to different temperature tendencies, with the temperature of treatment 1 increasing faster than that of treatment 2, while the thermophilic stage of treatment 2 lasted for longer than that of treatment 1. The overall oxygen content, moisture content, volatile solids, pH, and total nitrogen content of the two treatments were basically the same. Microbial degradation of phenanthrene during sewage sludge composting primarily occurred in the rapid heating stage and thermophilic temperature stage, and a portion of the 4-5 ring polycyclic aromatic hydrocarbons would concentrate relatively. The phenanthrene degradation rate of treatment 1 and treatment 2 were 52.37% and 45.64%, respectively. Based on the phenanthrene degradation efficiency, an initial moisture water content of 56.21% should be used during the sewage sludge composting. [ABSTRACT FROM AUTHOR]

Despite many reports of the use of biodegradation to remove contaminants, the biodegradation of polycyclic aromatic hydrocarbons (PAHs) is challenging because of the hydrophobicities and low aqueous solubilities of most PAHs. In this study, phenanthrene (PHE) was used as a sole carbon and energy source to screen and identify Achromobacter sp. LH-1 for the production of biodemulsifiers that enhance the bioavailability and solubilization of PAHs. LH-1 achieved a 94% degradation rate and a 40% mineralization rate with 100 mg/L PHE. Additionally, LH-1 degraded various PAHs, and the factors that influenced the growth and PAHs degradation activity of LH-1 were not only the toxicities and structures of the substances but also the acclimation of LH-1 to these substances. Three kinetic models were used to describe the fermentation processes of cell growth, product formation and substrate degradation over time. Finally, multiple PHE degradation pathways were proposed to be utilized by strain LH-1. [ABSTRACT FROM AUTHOR]

Bacteria play an important role in the removal of polycyclic aromatic hydrocarbons (PAHs) from polluted environments. In marine environments, Cycloclasticus is one of the most prevalent PAH-degrading bacterial genera. However, little is known regarding the degradation mechanisms for multiple PAHs by Cycloclasticus. Cycloclasticus sp. strain P1 was isolated from deep-sea sediments and is known to degrade naphthalene, phenanthrene, pyrene, and other aromatic hydrocarbons. Here, six ring-hydroxylating dioxygenases (RHDs) were identified in the complete genome of Cycloclasticus sp. P1 and were confirmed to be involved in PAH degradation by enzymatic assays. Further, five gene clusters in its genome were identified to be responsible for PAH degradation. Degradation pathways for naphthalene, phenanthrene, and pyrene were elucidated in Cycloclasticus sp. P1 based on genomic and transcriptomic analysis and characterization of an interconnected metabolic network. The metabolic pathway overlaps in many steps in the degradation of pyrene, phenanthrene, and naphthalene, which were validated by the detection of metabolic intermediates in cultures. This study describes a pyrene degradation pathway for Cycloclasticus. Moreover, the study represents the integration of a PAH metabolic network that comprises pyrene, phenanthrene, and naphthalene degradation pathways. Taken together, these results provide a comprehensive investigation of PAH metabolism in Cycloclasticus. [ABSTRACT FROM AUTHOR]

Summary: Anaerobic degradation processes are very important to attenuate polycyclic aromatic hydrocarbons (PAHs) in saturated, anoxic sediments. However, PAHs are poorly degradable, leading to very slow microbial growth and thus resulting in only a few cultures that have been enriched and studied so far. Here, we report on a new phenanthrene‐degrading, sulfate‐reducing enrichment culture, TRIP1. Genome‐resolved metagenomics and strain specific cell counting with FISH and flow cytometry indicated that the culture is dominated by a microorganism belonging to the Desulfobacteraceae family (60% of the community) and sharing 93% 16S rRNA sequence similarity to the naphthalene‐degrading, sulfate‐reducing strain NaphS2. The anaerobic degradation pathway was studied by metabolite analyses and revealed phenanthroic acid as the major intermediate consistent with carboxylation as the initial activation reaction. Further reduced metabolites were indicative of a stepwise reduction of the ring system. We were able to measure the presumed second enzyme reaction in the pathway, phenanthroate‐CoA ligase, in crude cell extracts. The reaction was specific for 2‐phenanthroic acid and did not transform other isomers. The present study provides first insights into the anaerobic degradation pathways of three‐ringed PAHs. The biochemical strategy follows principles known from anaerobic naphthalene degradation, including carboxylation and reduction of the aromatic ring system. [ABSTRACT FROM AUTHOR]

Adsorption-synergic biodegradation of a model PAH (phenanthrene, Phe) on MWCNT buckypaper surface with a potential PAH biodegrading bacterial strain Bacillus thuringiensis AT.ISM.11 has been studied in aqueous medium. Adsorption of Phe on buckypaper follows Dubinin-Ashtakhov model (R 2 = 0.9895). MWCNT generally exerts toxicity to microbes but adsorbed layer of Phe prevents the direct contact between MWCNT and bacterial cell wall. FESEM study suggests that formation of biofilms occurred on buckypaper. Lower layer cells are disrupted and flattened as they are in direct contact with MWCNT but the upper layer cells of the developed biofilm are fully intact and functional. Force-distance curves of Bacillus thuringiensis AT.ISM.11 with buckypaper indicates adhesion forces varied from −10.3 to −15.6 nN with increasing contact time, which supports the phenomenon of biofilm formation. AFM surface statistical data of buckypaper suggests increase in bacterial cell count increases the Rms roughness (95.7242–632.565) while adhering to the buckypaper surface to form biofilm. We observed an enhanced Phe biodegradation of 93.81% from that of the 65.71% in 15 days’ study period, using buckypaper as a bio-carrier or a matrix for the microbial growth. GC-MS study identified phthalic acid ester as metabolite, which is the evidence of protocatechuate pathway degradation of Phe. Current study enlightens the interaction between hydrocarbons and microbes in presence of MWCNT buckypaper matrix in aqueous system for the first time. An enhancement in biodegradation of Phe by 28.10% has also been reported which can be a basis for CNT aided enhanced biodegradation studies in future. [ABSTRACT FROM AUTHOR]

Hydrocarbon contamination is a serious problem that degrades the quality of mangrove ecosystems, and bioremediation using autochthonous bacteria is a promising technology to recover an impacted environment. This research investigates the biodegradation rates of diesel, hexadecane and phenanthrene, by conducting a microcosm study and survey of the autochthonous microbial community in contaminated mangrove sediment, using an Illumina MiSeq platform. The biodegradation rates of diesel, hexadecane and phenanthrene were 82, 86 and 8 mg kg −1  sediment day −1 , respectively. The removal efficiencies of hexadecane and phenanthrene were >99%, whereas the removal efficiency of diesel was 88%. A 16S rRNA gene amplicon sequence analysis revealed that the major bacterial assemblages detected were Gammaproteobacteria , Deltaproteobacteria , Alphaproteobacteria . The bacterial compositions were relatively constant, while reductions of the supplemented hydrocarbons were observed. The results imply that the autochthonous microorganisms in the mangrove sediment were responsible for the degradation of the respective hydrocarbons. Diesel-, hexadecane- and phenanthrene-degrading bacteria, namely Bacillus sp., Pseudomonas sp., Acinetobacter sp. and Staphylococcus sp., were also isolated from the mangrove sediment. The mangrove sediment provides a potential resource of effective hydrocarbon-degrading bacteria that can be used as an inoculum or further developed as a ready-to-use microbial consortium for the purpose of bioremediation. [ABSTRACT FROM AUTHOR]

Phenanthrene, as a widespread polycyclic aromatic hydrocarbons (PAHs) contaminant in vitro and in vivo of plant, has the characteristics of carcinogenicity, teratogenicity and mutagenicity. This work aimed to explore the phenanthrene metabolic mechanism by Phomopsis liquidambari in vitro, as well as the bioremediation ability through P. liquidambari -rice combination. This strain was able to use phenanthrene as source of carbon and energy to grow, more than 77% of added 50 mg L −1 phenanthrene was removed after 10 d in MSM. We identified the metabolic products via HPLC-MS and proposed two possible degradation pathways. Phenanthrene was firstly combined with oxygen to become phenanthrene 9,10-oxide, and then degraded to 9-phenanthrol, followed by oxidization to 9,10-dihydroxyphenanthrene. In addition, that epoxide (phenanthrene 9,10-oxide) was also hydrolyzed to phenanthrene trans -9,10-dihydrodiol, and then dehydrogenized to 9,10-dihydroxyphenanthrene, which was further degraded to 9,10-phenanthrenequinone; during this metabolic pathway, the changes of P450 monooxygenase, epoxide hydrolase, dehydrogenase and catechol 2,3-dioxygenase activities and their corresponding gene transcription levels were closely related. What's more, P. liquidambari could combine with rice to eliminate phenanthrene accumulated in vivo of rice seedlings, and the removal rate in inoculation treatment represented a significant difference (increased 25.68%) compared with uninoculation treatment after cultivation 30 d. Therefore, we concluded that P. liquidambari could not only respond to phenanthrene pollution stress in vitro but also exert a mitigation effect on plants accumulated phenanthrene. This work provides a foundation for applying endophytic fungi to PAHs bioremediation in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Natural and cost-effective materials such as minerals can serve as supportive matrices to enhance biodegradation of polycyclic aromatic hydrocarbons (PAHs). In this study we evaluated and compared the regulatory role of two common soil minerals, i.e. kaolinite and quartz in phenanthrene (a model PAH) degradation by a PAH degrader Sphingomonas sp. GY2B and investigated the underlying mechanism. Overall kaolinite was more effective than quartz in promoting phenanthrene degradation and bacterial growth. And it was revealed that a more intimate association was established between GY2B and kaolinite. Si and O atoms on mineral surface were demonstrated to be involved in GY2B-mineral interaction. There was an higher polysaccharide/lipid content in the EPS (extracellular polymeric substances) secreted by GY2B on kaolinite than on quartz. Altogether, these results showed that differential bacterial growth, enzymatic activity, EPS composition as well as the interface interaction may explain the effects minerals have on PAH biodegradation. It was implicated that different interface interaction between different minerals and bacteria can affect microbial behavior, which ultimately results in different biodegradation efficiency. [ABSTRACT FROM AUTHOR]

The degradation of two isomeric three-ringed polycyclic aromatic hydrocarbons by the white rot fungus Pleurotus ostreatus D1 and the litter-decomposing fungus Agaricus bisporus F-8 was studied. Despite some differences, the degradation of phenanthrene and anthracene followed the same scheme, forming quinone metabolites at the first stage. The further fate of these metabolites was determined by the composition of the ligninolytic enzyme complexes of the fungi. The quinone metabolites of phenanthrene and anthracene produced in the presence of only laccase were observed to accumulate, whereas those formed in presence of laccase and versatile peroxidase were metabolized further to form products that were further included in basal metabolism (e.g. phthalic acid). Laccase can catalyze the initial attack on the PAH molecule, which leads to the formation of quinones, and that peroxidase ensures their further oxidation, which eventually leads to PAH mineralization. A . bisporus , which produced only laccase, metabolized phenanthrene and anthracene to give the corresponding quinones as the dominant metabolites. No products of further utilization of these compounds were detected. Thus, the fungi's affiliation with different ecophysiological groups and their cultivation conditions affect the composition and dynamics of production of the ligninolytic enzyme complex and the completeness of PAH utilization. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) pollution in urban river sediments is a serious problem to ecological systems and human health. We examined novel remediation approaches, using a biochar amendment combined with bioaugmentation or/and nitrate stimulation, to degrade phenanthrene in sediment. Biochar amendment combined with nitrate stimulation enhanced phenanthrene degradation by 2.3 times that of the control and 1.9 times that of biochar alone. Nitrate stimulation altered the microbial succession and encouraged the growth of potential nitrate-reducing PAH-degraders Thiobacillus and Stenotrophomonas . Biochar was an excellent sorbent for phenanthrene and the shelter that it provided PAH-degraders increased contact between phenanthrene and PAH-degraders. Biochar also enhanced the aging effects of phenanthrene and reduced the ecological risk by 7.7% to 11%. These results suggest that biochar amendment combined with nitrate stimulation can achieve high-efficiency phenanthrene degradation in sediments. [ABSTRACT FROM AUTHOR]

Recently, the potential of magnetite facilitating anaerobic methanogenic degradation of organic matters in natural or engineered microbial ecosystems has been reported. Here, we evaluated the effects of magnetite powder (<5 μm) and nanoFe 3 O 4 powder (50–100 nm) on phenanthrene methanogenic degradation by a mixed consortium enriched from petroleum contaminated soil. The results showed that complete phenanthrene degradation in our enrichment cultures required a syntrophic cooperation between degrading bacteria and methanogens. The addition of magnetite and nanoFe 3 O 4 did not increase the relative abundance of methanogens, but improved phenanthrene degradation rates by 25.92% and 25.99%, and enhanced methane production rates by 21.5% and 20.1%, respectively. Further studies showed that the addition of magnetite and nanoFe 3 O 4 improved electron transporting system (ETS) activities in the enrichment cultures, possibly through serving as electron conduits to facilitate DIET between syntrophic bacteria and methanogens. [ABSTRACT FROM AUTHOR]

The toxicity of five polyaromatic hydrocarbons (PAHs) to metabolism of Escherichia coli ( E. coli ) was evaluated with key parameters, including growth constant (k) and inhibitory ratio ( I) from microcalorimetry analysis. The results showed that the toxicity followed pyrene > 9-phenanthrol > phenanthrene > 3-phenanthrenecarboxylic acid > naphthalene for the chemicals tested. Basing on physical and chemical parameters of these five PAHs, the quantitative structure–activity relationships (QASRs) equation was established by multiple linear regression analysis, indicating that narcosis, a non-specific and non-reactive toxic action, plays the predominant role in toxicity of these five PAHs to bacterial cells. This study illustrates that the toxicity of PAHs are determined by the number of the aromatic ring and the substituent groups, higher toxicity associated with the higher number of the aromatic rings. [ABSTRACT FROM AUTHOR]

A persulfate/percarbonate (PS/SPC) system activated with citric acid (CA) chelated-Fe(II), which combined the benefits of sole PS and SPC systems, was conducted for phenanthrene (PHE) degradation in aqueous solution. The effects of oxidant concentration, Fe(II)-CA dosage, PS/SPC molar ratio and initial solution pH were investigated in the laboratory. The results indicated that the addition of CA could remarkably enhance PHE removal, and PHE could be degraded completely at 0.5 mM PS, 0.5 mM SPC and 0.5 mM Fe(II) with 0.1 mM CA in 60 min. PHE oxidation process was more efficient in acidic condition, which presented a two-stage degradation pattern and PHE removal followed a pseudo-first-order kinetic model in the second stage. The results of free radical probe tests, scavenging tests and EPR analysis demonstrated that OH was the predominant radical for PHE oxidation. The major degradation intermediates of PHE were identified by LC–MS, and the possible reaction mechanism and PHE degradation pathways were proposed. [ABSTRACT FROM AUTHOR]

Previous study of the effects of surfactants on the biodegradation of phenanthrene focused on investigating alterations of the cell characteristics of Sphingomonas sp. GY2B. However, genes regulation associated with biodegradation and biological processes in response to the presence of surfactants, remains unclear. In this study, comparative transcriptome analysis was conducted to observe the gene expression of GY2B during phenanthrene biodegradation in the presence and absence of Tween80. A diverse set of genes was regulated by Tween80, leading to increased biodegradation of phenanthrene by GY2B: (i) Tween80 increased expression of genes related to H + transport in the plasma membrane to provide a driving force (i.e., ATP) for accelerating transmembrane transport of phenanthrene with increasing Tween80 concentrations, thereby enhancing the uptake and degradation of phenanthrene by GY2B; (ii) Tween80 (1 and 8 CMC) promoted intracellular biodegradation of phenanthrene by stimulating expression of genes encoding dioxygenases and monooxygenase, increasing expression of genes involved in intracellular metabolic processes (e.g., TCA cycle); and (iii) Tween80 likely increased GY2B vitality and growth by inducing expression of genes associated with ABC transporters and protein transport, regulating genes involved in other biological processes (e.g., transcription, translation). [ABSTRACT FROM AUTHOR]

The indigenous microorganisms responsible for degrading phenanthrene (PHE) in activated biosludge were identified using DNA-based stable isotope probing. Besides the well-known PHE degraders Burkholderia, Ralstonia, Sinobacteraceae and Arthrobacter, we for the first time linked the taxa Paraburkholderia and Kaistobacter with in situ PHE biodegradation. Analysis of PAH-RHD gene detected in the heavy DNA fraction of C-PHE treatment suggested the mechanisms of horizontal gene transfer or inter-species hybridisation in PAH-RHD gene spread within the microbial community. Additionally, three cultivable PHE degraders, Microbacterium sp. PHE-1, Rhodanobacter sp. PHE-2 and Rhodococcus sp. PHE-3, were isolated from the same activated biosludge. Among them, Rhodanobacter sp. PHE-2 is the first identified strain in its genus with PHE-degrading ability. However, the involvement of these strains in PHE degradation in situ was questionable, due to their limited enrichment in the heavy DNA fraction of C-PHE treatment and lack of PAH-RHD gene found in these isolates. Collectively, our findings provide a deeper understanding of the diversity and functions of indigenous microbes in PHE degradation. [ABSTRACT FROM AUTHOR]

Pollutant-degrading bacteria migrated by fungi may enhance the contacts between microorganisms and pollutants and improve the bioremediation efficiency of persistent organic pollutants in soil. Here, the migration of phenanthrene (PHE)-degrading bacteria Massilia sp. WF1 and Mycobacterium sp. WY10 by the hydrophobic fungi Phanerochaete chrysosporium ( P. chrysosporium ) and its effects on the PHE biodegradation in soil were investigated. Migration of the hydrophilic bacterium WF1 was better than that of the hydrophobic bacterium WY10 by P. chrysosporium mycelia since strain WF1 possesses flagellum and the type III secretion system. The interaction energy change of P. chrysosporium -WF1 was lower, but the interaction forces (van der Waals attractions, capillary forces, and cross-linking effects) were stronger than those of P. chrysosporium -WY10. Thus, the adhesive attraction between strain WF1 and P. chrysosporium was stronger, and consequently, strain WF1 was migrated by P. chrysosporium to a greater extent than WY10. The corresponding migration mechanism was inferred to be a bacterial ‘passive’ method: bacteria adhered to mycelia before they migrated with the growing mycelia. Moreover, migrated strain WF1 via P. chrysosporium showed effective PHE biodegradation in soil. Fungus-mediated migration of pollutant-degrading bacteria may play an important role in the bioremediation of pollutants in soil. [ABSTRACT FROM AUTHOR]

Phenanthrene, is one of the important polycyclic aromatic hydrocarbons (PAHs), which can be used as indicator for measuring PAHs and as a model molecule for studying PAHs biodegradation. During phenanthrene bioremediation bacterial species plays an important. In present work, a previously isolated PAHs-degrading bacterium, Pseudomonas stutzeri JP1, was used to investigate the phenanthrene degradation mechanism under low oxygen condition. RNA-sequencing was conducted for gene detections. The results indicated that methylcrotonoyl-CoA carboxylase gene and quinoprotein alcohol dehydrogenase genes of bacterium were up-regulated during the PAHs exposure. The results of RT-qPCR revealed that the genes encoding the quinoprotein alcohol dehydrogenase were 3.16-fold up-regulated. Further, two-dimensional electrophoresis (2-DE) and MALDI-TOF-TOF were used to study the proteins related to phenanthrene degradation. The results showed that expression of six proteins obviously increased upon phenanthrene induction. Quinoprotein alcohol dehydrogenase gene was involved in phenanthrene catabolism. The results correspond nicely to the RNA-Seq data. This work provided in-depth knowledge as well as technical support for bioremediation of polycyclic aromatic hydrocarbons contamination via microbes in low oxygen environment. [ABSTRACT FROM AUTHOR]

The aim of this study was to isolate and characterize a newly isolated bacterium, designated strain W10, a polycyclic aromatic hydrocarbon (PAHs) degrader and biosurfactant producer, belonged to Pseudomonas genus and closely related to Pseudomonas aeruginosa , with the 16 rRNA gene sequence similarity of 99.1%. Based on GC-MS analyses, it degraded around 80% of phenanthrene, used as the sole carbon and energy source, at an initial concentration of 200 mg l −1 , after 30 days of incubation at 37 °C and 180 rpm, reducing the surface tension (ST) from 56.1 to 42 mN m −1 after 4 days of incubation. Furthermore, strain W10 utilized about 10%, 20%, 90%, and 99% of hexadecane (C16), pyrene, fluoranthene, and crude oil, respectively, after 30 days of incubation at 37 °C and 180 rpm. During the growth of strain W10 on phenanthrene and fluoranthene, some metabolites were identified, supporting the biodegradation pathways of the two PAHs. Interestingly, strain W10 showed also a significant potential to produce surface-active agents reducing the surface tension to 32 mN m −1 and reaching a production around 2 g l −1 after 48 h of incubation, in the presence of olive oil (1%,v/v) as substrate, at 37 °C and 180 rpm. Its biosurfactant, namely BSW10, showed an interesting emulsification activity and a high stability over a wide range of salinity (0–150 g l −1 ), temperature (0–100 °C), pH (2–12) and thus a promising abilities in used motor oil and crude oil removal from contaminated soils. Overall, these results provide evidence that strain W10 and its biosurfactant (BSW10) could be potential candidates for further bioremediation applications. [ABSTRACT FROM AUTHOR]

This study focused on the role of bioaccessibility in the phenanthrene (PHE) biodegradation in diffusely contaminated soil, by combining chemical and microbiological approaches. First, we determined PHE dissipation rates and PHE sorption/desorption isotherms for two soils (PPY and Pv) presenting similar chronic PAH contamination, but different physico-chemical properties. Our results revealed that the PHE dissipation rate was significantly higher in the Pv soil compared to the PPY soil, while PHE sorption/desorption isotherms were similar. Interestingly, increases of PHE desorption and potentially of PHE bioaccessibility were observed for both soils when adding rhamnolipids (biosurfactants produced by Pseudomonas aeruginosa ). Second, using 13 C-PHE incubated in the same soils, we analyzed the PHE degrading bacterial communities. The combination of stable isotope probing (DNA-SIP) and 16S rRNA gene pyrosequencing revealed that Betaproteobacteria were the main PHE degraders in the Pv soil, while a higher bacterial diversity ( Alpha- , Beta- , Gammaproteobacteria and Actinobacteria ) was involved in PHE degradation in the PPY soil. The amendment of biosurfactants commonly used in biostimulation methods ( i.e. rhamnolipids) to the two soils clearly modified the PHE sorption/desorption isotherms, but had no significant impact on PHE degradation rates and PHE-degraders identity. These results demonstrated that increasing the bioaccessibility of PHE has a low impact on its degradation and on the functional populations involved in this degradation. [ABSTRACT FROM AUTHOR]

The fate of organic pollutants in the environment, especially the formation and stability of non-extractable (i.e., bound) residues (NERs) determines their environmental risk. Using 14C-tracers, we studied the fate of the carcinogen phenanthrene in active or sterilized oxic loamy soil in the absence and presence of the geophagous earthworm Metaphire guillelmi and characterized the NERs derived from phenanthrene. After incubation of 14C-phenanthrene in active soil for 28 days, 40 ± 3.1% of the initial amount was mineralized and 70.1 ± 1.9% was converted to NERs. Most of the NERs (>92%) were bound to soil humin. Silylation of the humin-bound residues released 45.3 ± 5.3% of these residues, which indicated that they were physically entrapped, whereas the remainder of the residues were chemically bound or biogenic. By contrast, in sterilized soil, only 43.4 ± 12.6% of the phenanthrene was converted to NERs and all of these residues were completely released upon silylation, which underlines the essential role of microbial activity in NER formation. The presence of M. guillelmi in active soil significantly inhibited phenanthrene mineralization (24.4 ± 2.6% mineralized), but NER formation was not significantly affected. Only a small amount of phenanthrene-derived residues (1.9-5.3% of the initial amount) accumulated in the earthworm body. When humin-bound residues were mixed with fresh soil, 33.9% (humin recovered from active soils) and 12.4% (humin recovered from sterilized soils) of the residues were mineralized after 75 days of incubation, respectively, which indicated a high bioavailability of NERs, albeit lower than the initial addition of phenanthrene. Our results indicated that many phenanthrene-derived NERs, especially those physically entrapped, are still bioavailable and may pose a toxic threat to soil organisms. [ABSTRACT FROM AUTHOR]

The phenanthrene (PHE) degradation by a halotolerant bacterial consortium enriched from production water of Sercina oilfield in Tunisia was investigated. The consortium PHMM utilized PHE (200 mg/L), as a sole carbon source, in the presence of a wide range of NaCl concentrations, from 1 to 5% (w/v). The maximum growth rate was obtained at 500 mg/L of PHE. A PHE metabolism was assayed by using FTIR, UV and GC–MS analyses. Results revealed that the consortium PHMM metabolized PHE via protochatechuate pathway since intermediates such as naphthalenol and phthalic acid were detected. Phylogenetic analysis showed that the adapted consortium PHMM was composed by two dominant bacterial strains, identified as Pseudomonas sp. (strain PH1) and Staphylococcus sp. (strain PH2). All the results indicated that the microorganisms from the Tunisian oilfield have a promising application in bioremediation of petrochemical contaminated environments and could be potentially useful for the study of PAHs biodegradation. [ABSTRACT FROM AUTHOR]

The indigenous microorganisms responsible for degrading phenanthrene (PHE) in polycyclic aromatic hydrocarbons (PAHs)-contaminated wastewater were identified by DNA-based stable isotope probing (DNA-SIP). In addition to the well-known PHE degraders Acinetobacter and Sphingobium, Kouleothrix and Sandaracinobacter were found, for the first time, to be directly responsible for indigenous PHE biodegradation. Additionally, a novel PHE degrader, Acinetobacter tandoii sp. LJ-5, was identified by DNA-SIP and direct cultivation. This is the first report and reference to A. tandoii involved in the bioremediation of PAHs-contaminated water. A PAH-RHDα gene involved in PHE metabolism was detected in the heavy fraction of 13C treatment, but the amplification of PAH-RHDα gene failed in A. tandoii LJ-5. Instead, the strain contained catechol 1,2-dioxygenase and the alpha/beta subunits of protocatechuate 3,4-dioxygenase, indicating use of the β-ketoadipate pathway to degrade PHE and related aromatic compounds. These findings add to our current knowledge on microorganisms degrading PHE by combining cultivation-dependent and cultivation-independent approaches and provide deeper insight into the diversity of indigenous PHE-degrading communities. [ABSTRACT FROM AUTHOR]

The stability of black carbon (BC) as a slow cycling pool in the global C cycle is an important property and is likely governed by environmental conditions. Although the importance of role of the water regime in BC degradation was confirmed, direct impacts of water level fluctuations (WLF) on BC degradation were absent. This study investigated the changes in the physicochemical properties of BC and the behaviors of adsorption-desorption due to long-term WLF. The results showed that BC in the zone of WLF in soil contained higher amounts of carbon and lower amounts of oxygen, leading to contain few carboxylic functional groups and indicating that the WLF imposed on the reservoirs have altered BC decomposition, causing a decrease in mineralization. Furthermore, BC exhibited higher adsorption capacities and an apparent sorption–desorption hysteresis. Our results suggested that WLF has an advantageous role in preventing BC decomposition. Such protection has significance for the stability of BC in soils as well as for its effects on global C cycling and HOCs sorption. Understanding the decomposition mechanisms, dynamics and environmental influences should provide new insights into BC degradation and cycling. [ABSTRACT FROM AUTHOR]

The aim of this study was to characterize the ozone reaction with phenanthrene adsorbed in two types of soils (sand and agricultural). The effect of soil physicochemical properties (texture, bulk density, particle density, porosity, elemental composition, permeability, surface area and pore volume) on the phenanthrene decomposition was evaluated. Commercial sand has a uniform morphology (spherical) with a particle size range between 0.178 and 0.150 mm in diameter, regular elemental composition SiO 2 , specific density of 1701.38 kg/m 3 , a true density of 2492.50 kg/m 3 , with an effective porosity of 31%. On the other hand, the agricultural soil had heterogeneous morphology, particle size between 0.1779 and 0.05 mm in diameter, elemental composition was montmorrillonite silicon oxide, apparent density of 999.52 kg/m 3 , a true density of 2673.55 kg/m 3 , surface area of 34.92 m 2 /g and porosity of 57%. The percentage of phenanthrene decomposition in the sand was 79% after 2 h of treatment. On the other hand, the phenanthrene degradation in the agricultural soil was 95% during the same reaction time. The pore volume of soil limited the crystal size of phenanthrene and increased the contact surface with ozone confirming the direct impact of physicochemical properties of soils on the decomposition kinetics of phenanthrene. In the case of agricultural soil, the effect of organic matter on phenanthrene decomposition efficiency was also investigated. A faster decomposition of initial contaminant and byproducts formed in ozonation was obtained in natural agricultural soil compared to the sand. The partial identification of intermediates and final accumulated products produced by phenanthrene decomposition in ozonation was developed. Among others, phenanthroquinone, hydroquinone, phenanthrol, catechol as well as phthalic, diphenic, maleic and oxalic acids were identified. [ABSTRACT FROM AUTHOR]

Contaminated sediment samples were collected from the Eastern Province, Saudi Arabia for isolation of pyrene- and phenanthrene-degrading bacteria by enrichment method. Four isolates were morphologically characterized as Gram-negative rod strains and 16S rRNA sequence analysis revealed the isolates as closely related to Pseudomonas aeruginosa , P. citronellolis , Ochrobactrum intermedium and Cupriavidus taiwanensis . Degradation of the polycyclic aromatic hydrocarbons (PAHs) by the latter three strains was investigated in liquid cultures. Results of concentration reduction analyzed with gas chromatography show that P. citronellolis_ LB was efficient in removing phenanthrene, degrading 94% of 100 ppm in 15 days while O. intermedium _BC1 was more efficient in pyrene-removal, degrading 62% in 2 weeks. Furthermore, bacterial growth assessment using optical density and population counts revealed the latter as more suitable for microbial growth analysis in PAH-containing cultures. In conclusion, the isolated bacterial strains could be further developed for efficient use in biodegradation of PAH. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) constitute a large, diverse group of organic compounds that commonly have detrimental biological effects that pose a great environmental threat. Hence, development of isolation and culture techniques for PAH-degrading bacteria is necessary. In this study, a variety of phenanthrene-degrading bacteria were enriched and isolated using an in situ soil substrate membrane system (SSMS) and a traditional cultivation method with phenanthrene as the sole carbon source. In the traditional method, the major species of phenanthrene-degrading bacteria found was Pseudomonas ( Gammaproteobacteria ). By contrast, the major phenanthrene-degrading bacteria observed using SSMS were Sphingomonas ( Alphaproteobacteria ). Phenanthrene utilization by bacteria with SSMS was higher than traditional cultivation method. High throughput functional microarray, Geochip, and polymerase chain reaction-denaturing gradient gel electrophoresis were used to characterize the response of soil bacterial communities upon addition of phenanthrene. Results indicated that members of the class Alphaproteobacteria were the dominant bacteria in phenanthrene-contaminated soils, and their characteristic phenanthrene-degrading genes have important role in degradation of contaminants. Sphingomonas was isolated using SSMS and found to be capable of adapting to nutrient-poor environments by utilizing a variety of substrates. The SSMS method is more suitable for the growth of Sphingomonas in simulated environmental conditions. [ABSTRACT FROM AUTHOR]

The objective of this study was to stimulate microbial biodegradation of petroleum pollution in groundwater and to analyze changes in the abundance and distribution of organic compounds detectable in petroleum. Bioremediation was conducted in a closed bipolar system, by bioaugmentation with consortia of hydrocarbon degrading microorganisms (HD) and biostimulation with nutrients. Comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC-MS) was used to visualize all fractions simultaneously. During the study, the content of total petroleum hydrocarbon (TPH) in groundwater decreased by 92.7% of the initial level, and the average rate of biodegradation was 0.1 mg/L per day. Increased numbers of HD were observed and the dominant genera were Pseudomonas, Rhodococcus, Achromobacter, Bacillus, and Micromonospora. In the first 30 days of bioremediation, there was no significant biodegradation of n-alkanes and petroleum biomarkers - isoprenoids such as pristane and phytane, and polycyclic-saturated hydrocarbons such as terpanes and steranes. However, after 60 days of bioremediation, more than 95% of n-alkanes, terpanes and steranes were biodegraded. Phenanthrene and its methyl-, dimethyl-, and trimethyl-isomers were biodegraded and reduced by more than 99% of their initial levels. However, their decomposition had clearly commenced after just 30 days. This is a somewhat surprising result since it follows that the phenanthrenes were more susceptible to biodegradation than the n-alkanes and isoprenoids. Depending on the microbial community used for bioaugmentation, biodegradation of phenanthrene can precede biodegradation of saturated hydrocarbons. [ABSTRACT FROM AUTHOR]

A copper-tolerant phenanthrene (PHE)-degrading bacterium, strain Sphingobium sp. PHE-1, was newly isolated from the activated sludge in a wastewater treatment plant. Two key genes, ahdA1b-1 encoding polycyclic aromatic hydrocarbon ring-hydroxylating dioxygenase (PAH-RHDɑ) and xyLE encoding catechol-2,3-dioxygenase (C23O), involved in the PHE metabolism by strain PHE-1 were identified. The PAH-RHD gene cluster showed 96% identity with the same cluster of Sphingomonas sp. P2. Our results indicated the induced transcription of xylE and ahdA1b-1 genes by PHE, simultaneously promoted by Cu(II). For the first time, high concentration of Cu(II) is found to encourage the expression of PAH-RHDɑ and C23O genes during PHE degradation. Applying Sphingomonas PHE-1 in PHE-contaminated soils for bioaugmentation, the abundance of xylE gene was increased by the planting of ryegrass and the presence of Cu(II), which, in turn, benefited ryegrass growth. The best performance of PHE degradation and the highest abundance of xylE genes occurred in PHE-copper co-contaminated soils planted with ryegrass. [ABSTRACT FROM AUTHOR]

Aims We aimed to investigate the phenanthrene degradation characteristics and possible phenanthrene degradation pathways of Rhizobium petrolearium SL-1. Methods and Results Using high-performance liquid chromatography (HPLC), UV-visible and gas chromatography-mass spectrometry (GC-MS) analysis, the phenanthrene-degrading properties and metabolites of Rh. petrolearium SL-1 were analysed, and then combined with genome-based analysis to elucidate the possible biodegradation pathway of phenanthrene in Rh. petrolearium SL-1. The results of the analyses showed that phenanthrene (100 mg l−1) was completely degraded by strain SL-1 at 35°C, 0·02% salinity and pH 9·0 within 3 days. A wide range of polycyclic aromatic hydrocarbons, including naphthalene, fluorene, anthracene and pyrene, could also be degraded by this strain. Conclusions Based on the identified metabolites, the utilization of probable intermediates and the presence of putative phenanthrene catabolic genes, we concluded that phenanthrene was degraded via two different routes, namely the 'naphthalene' and the 'phthalic acid' routes. Significance and Impact of the Study For the first time, this study shows the degradation pathway of phenanthrene by a Rhizobium strain. Because of its excellent stress resistance, metabolic versatility, high degradation efficiency and potential application in phytoremediation, Rh. petrolearium SL-1 is a potential candidate for the bioremediation of polycyclic aromatic hydrocarbons-contaminated areas. [ABSTRACT FROM AUTHOR]

The strain Pseudomonas sp. JPN2 had a high potential to degrade phenanthrene degrading 98.52 % of the initial amount of 100 mg L after 10 days incubation. The analysis of metabolites demonstrated that the cleavage of phenanthrene started at the C and C positions on the aromatic ring by the dioxygenation reaction, and then further degraded via a phthalate pathway. To understand the interaction between phenanthrene and the amino acid residues in the active site of the target enzyme, a molecular docking simulation was performed. The results showed that the distances of C-O and C-O atoms were 3.47 and 3.67 Å, respectively. The C and C positions of the phenanthrene ring are much closer to the dioxygen molecule in the active site relative to the other atoms. Therefore, the C and C positions are vulnerable to attack in the initial oxygenation process. [ABSTRACT FROM AUTHOR]

Bioremediation use to promote degradation and/or removal of contaminants into nonhazardous or less-hazardous substances from the environment using microbial metabolic ability. Pseudomonas spp. is one of saprotrophic soil bacterium and can be used for biodegradation of polycyclic aromatic hydrocarbons (PAHs) but this activity in most species is weak. Phenanthrene and pyrene could associate with a risk of human cancer development in exposed individuals. The aim of the present study was application of genetically engineered P. putida that produce dioxygenase for degradation of phenanthrene and pyrene in spiked soil using high-performance liquid chromatography (HPLC) method. The nahH gene that encoded catechol 2,3-dioxygenase (C23O) was cloned into pUC18 and pUC18-nahH recombinant vector was generated and transformed into wild P. putida, successfully. The genetically modified and wild types of P. putida were inoculated in soil and pilot plan was prepared. Finally, degradation of phenanthrene and pyrene by this bacterium in spiked soil were evaluated using HPLC measurement technique. The results were showed elimination of these PAH compounds in spiked soil by engineered P. putida comparing to dishes containing natural soil with normal microbial flora and inoculated autoclaved soil by wild type of P. putida were statistically significant (p<0.05). Although adding N and P chemical nutrients on degradation ability of phenanthrene and pyrene by engineered P. putida in soil were not statistically significant (p>0.05) but it was few impact on this process (more than 2%). Additional and verification tests including catalase, oxidase and PCR on isolated bacteria from spiked soil were indicated that engineered P. putida was alive and functional as well as it can affect on phenanthrene and pyrene degradation via nahH gene producing. These findings indicated that genetically engineered P. putida generated in this work via producing C23O enzyme can useful and practical for biodegradation of phenanthrene and pyrene as well as petroleum compounds in polluted environments. [ABSTRACT FROM AUTHOR]

The reuse feasibility of the bioremediated effluent of the combination of sequential soil washing followed by biological treatment for removal of phenanthrene (PHE) from contaminated soils was investigated for several soil washing. In the first stage a removal efficiency of 74.4% ± 3.5% was obtained under the optimum conditions of: surfactant (Tween 80) concentration of 5000 mg/L, liquid/soil ratio of 30 v/w, humic acid concentration of 2.31 mg/L (6.93%), and washing time of 2 h. In the second stage complete biodegradation of PHE from soil washing effluent was achieved by inoculating enriched bacterial consortium (OD 600nm = 1) within 7 days. Reuse possibility of biologically treated solution for the next cycles of soil washing process was conducted by adjusting the surfactant concentration. The findings displayed that reusability of the biologically recycled solution was maintained up to 7th cycle, reaching a removal efficiency of >99% and >97% in artificial and real contaminated soils respectively, indicating the effectiveness of reused surfactant solution. [ABSTRACT FROM AUTHOR]

A rice straw-derived sorbent for the removal of phenanthrene (PHE) was prepared by graft method using hexadecyltrimethyl ammonium bromide (HTAB) as a modifier. The surface morphology, electrostatic, and hydrophobic characteristics of the sorbent altered significantly after modification. The sorption performance of the modified rice straw, including sorption kinetics and isotherms, was evaluated by batch sorption experiments. The sorption process is strongly enhanced by grafted HTAB and could be appropriately described by pseudo-second-order model and linear sorption isotherms. As compared to adsorption, partition plays a more important role in the sorption of PHE to MRS. Correlations between sorbent properties and sorption capacity indicate that (O+N)/C, relative contact angle, and zeta potential are the key factors that govern the PHE sorption behavior. [ABSTRACT FROM PUBLISHER]

Surfactant-mediated bioremediation has been widely applied in decontaminating PAH-polluted sites. However, the impacts of surfactants on the biodegradation of PAHs have been controversial in the past years. To gain a clear insight into the influencing mechanisms, three nonionic surfactants (Tween80, TritonX-100 and Brij30) were selected to systematically investigate their effects on cell surface properties (membrane permeability, functional groups and elements), cell vitality as well as subsequent phenanthrene degradation ability of Sphingomonas sp. GY2B. Results showed that biodegradation of phenanthrene was stimulated by Tween80, slightly inhibited by TritonX-100 and severely inhibited by Brij30, respectively. Positive effect of Tween80 may arise from its role as the additional carbon source for GY2B to increase bacterial growth and activity, as demonstrated by the increasing viable cells in Tween80 amended degradation systems determined by flow cytometry. Although TritonX-100 could inhibit bacterial growth and disrupt cell membrane, its adverse impacts on microbial cells were weaker than Brij30, which may result in its weaker inhibitive extent. Results from this study can provide a rational basis on selecting surfactants for enhancing bioremediation of PAHs. [ABSTRACT FROM AUTHOR]

A novel phenanthrene (PHE)-degrading strain Massilia sp. WF1, isolated from PAH-contaminated soil, was capable of degrading PHE by using it as the sole carbon source and energy in a range of pH (5.0-8.0), temperatures (20-35 °C), and PHE concentrations (25-400 mg L). Massilia sp. WF1 exhibited highly effective PHE-degrading ability that completely degraded 100 mg L of PHE over 2 days at optimal conditions (pH 6.0, 28 °C). The kinetics of PHE biodegradation by Massilia sp. WF1 was well represented by the Gompertz model. Results indicated that PHE biodegradation was inhibited by the supplied lactic acid but was promoted by the supplied carbon sources of glucose, citric acid, and succinic acid. Salicylic acid (SALA) and phthalic acid (PHTA) were not utilized by Massilia sp. WF1 and had no obvious effect on PHE biodegradation. Only two metabolites, 1-hydroxy-2-naphthoic acid (1H2N) and PHTA, were identified in PHE biodegradation process. Quantitatively, nearly 27.7 % of PHE was converted to 1H2N and 30.3 % of 1H2N was further metabolized to PHTA. However, the PHTA pathway was broken and the SALA pathway was ruled out in PHE biodegradation process by Massilia sp. WF1. [ABSTRACT FROM AUTHOR]

Disappearance of phenanthrene and pyrene (on the basis of butanol-extractable fraction) from sediment with different submerged macrophytes, Hydrilla verticillata (H), Myriophyllum verticillatum (M), Vallisneria spiralis (V) and Potamogeton crispus L. (P), was investigated. A relationship between the remedial effect and the bacterial community structure was analyzed using PCR–DGGE. During a 54-day experimental period, removal efficiencies of the two contaminants were the highest in V treatment, followed by M treatment, H and P treatments, and then unplanted treatment. Moreover, only a small part of the removal increments was caused by plant accumulation, indicating that the enhanced removal was mainly due to microbial degradation. DGGE profile analysis indicated that bacterial community in sediments was relatively stable after planting. PAH-degrading bacteria were widely distributed in all of the sediment samples but species differences among the samples were obvious. Moreover, the DGGE band-based similarity between V. spiralis and the other three plants was the highest in M treatment, followed by H treatment, and then P treatment, which is similar to the trend of removal efficiencies of the two contaminants. Therefore, it can be concluded that the difference between the four submerged macrophytes in the removal of phenanthrene and pyrene from sediment might be largely due to the changes in the microbial community structure. [ABSTRACT FROM AUTHOR]

The halophilic bacteria could be useful for bioremediation of polycyclic aromatic hydrocarbons (PAHs) pollution in hypersaline environments, which has posed a significant environmental problem. The effect of salt contents on a halophilic bacterial consortium, which was enriched from an oil-contaminated saline soil, was investigated. At 20 per cent salt contents, the consortium maintained lower PAHs dioxygenase (PDO), catechol 2, 3-dioxygenase (C23O) and catechol 1, 2-dioxygenase (C12O) activity than at 10 per cent salt contents before complete degradation. Pyrosequencing results indicated that the predominant bacteria were closely related to genera Thalassospira , Rhodobium , Mariprofundus and Psychroflexus at 10 per cent salt contents, while at 20 per cent salt contents, the dominant bacteria were Chromohalobacter and Methylohalomonas , suggesting some bacteria could not survive at higher salt contents. Increased salt contents decreased the diversity of the bacterial consortium and favored the growth of bacteria in class Gammaproteobacteria . Three-dimensional excitation-emission matrix fluorescence spectra (3DEEMs) showed that elevated salt contents also made some intermediate products accumulated during degradation and then lowered the phenanthrene degradation rate. This study extended the knowledge on decontamination of PAHs in saline environments by an applicable halophilic bacterial consortium. [ABSTRACT FROM AUTHOR]

Co-contamination of soil and water with polycyclic aromatic hydrocarbon (PAH) and heavy metals makes biodegradation of the former extremely challenging. Modified clay-modulated microbial degradation provides a novel insight in addressing this issue. This study was conducted to evaluate the growth and phenanthrene degradation performance of Mycobacterium gilvum VF1 in the presence of a palmitic acid (PA)-grafted Arquad® 2HT-75-based organobentonite in cadmium (Cd)-phenanthrene co-contaminated water. The PA-grafted organobentonite (ABP) adsorbed a slightly greater quantity of Cd than bentonite at up to 30 mg L − 1 metal concentration, but its highly negative surface charge imparted by carboxylic groups indicated the potential of being a significantly superior adsorbent of Cd at higher metal concentrations. In systems co-contained with Cd (5 and 10 mg L − 1 ), the Arquad® 2HT-75-modified bentonite (AB) and PA-grafted organobentonite (ABP) resulted in a significantly higher (72–78%) degradation of phenanthrene than bentonite (62%) by the bacterium. The growth and proliferation of bacteria were supported by ABP which not only eliminated Cd toxicity through adsorption but also created a congenial microenvironment for bacterial survival. The macromolecules produced during ABP–bacteria interaction could form a stable clay-bacterial cluster by overcoming the electrostatic repulsion among individual components. Findings of this study provide new insights for designing clay modulated PAH bioremediation technologies in mixed-contaminated water and soil. [ABSTRACT FROM AUTHOR]

Over the last decades, understanding of the effects of plants on soil microbiomes has greatly advanced. However, knowledge on the assembly of rhizospheric communities in aged-contaminated industrial soils is still limited, especially with regard to transcriptionally active microbiomes and their link to the quality or quantity of carbon sources. We compared the short-term (2-10 days) dynamics of bacterial communities and potential PAH-degrading bacteria in bare or ryegrass-planted aged-contaminated soil spiked with phenanthrene, put in relation with dissolved organic carbon (DOC) sources and polycyclic aromatic hydrocarbon (PAH) pollution. Both resident and active bacterial communities (analyzed from DNA and RNA, respectively) showed higher species richness and smaller dispersion between replicates in planted soils. Root development strongly favored the activity of Pseudomonadales within the first 2 days, and of members of Actinobacteria, Caulobacterales, Rhizobiales, and Xanthomonadales within 6-10 days. Plants slowed down the dissipation of phenanthrene, while root exudation provided a cocktail of labile substrates that might preferentially fuel microbial growth. Although the abundance of PAH-degrading genes increased in planted soil, their transcription level stayed similar to bare soil. In addition, network analysis revealed that plants induced an early shift in the identity of potential phenanthrene degraders, which might influence PAH dissipation on the long-term. [ABSTRACT FROM AUTHOR]

Microbial degradation is a promising soil remediation strategy for polycyclic aromatic hydrocarbons (PAHs) frequently polluting some post-industrial environments. Thirteen PAH-degrading bacterial strains were isolated from bare or ryegrass-vegetated aged-contaminated soil, based on their potential for phenanthrene biodegradation. 16S rRNA gene phylogeny showed that all isolates were affiliated with three closely related taxonomic subgroups within the Pseudomonas genus. Two of these subgroups were exclusively retrieved from planted soil. Genes encoding PAH-ring hydroxylating dioxygenases were detected in all strains and matched known sequences in other Pseudomonas strains from polluted environments. Genes for protocatechuate-3,4-dioxygenases ( pca H) and catechol-2,3-dioxygenases were also detected in all strains, whereas the catechol-1,2-dioxygenase gene was absent. The presence of pca H genes, the utilization of protocatechuate, the strong inhibitory effect of salicylate and the detection of phthalate during phenanthrene biodegradation suggest that these isolates preferentially catabolize PAHs via the protocatechuate pathway. Metabolic profiling was further performed for three representative isolates on a large range of 61 organic substrates. Although closely related phylogenetically, they were able to use different sets of labile carbon compounds (e.g. sugars, amino acids), PAHs and their metabolites, and released different degradation products from phenanthrene. These contrasted metabolic capabilities might reflect differential adaptation to their respective environment. [ABSTRACT FROM AUTHOR]

The biological treatment of polycyclic aromatic hydrocarbons is an important issue. Most microbes have limited practical applications because of the poor bioavailability of polycyclic aromatic hydrocarbons. In this study, the extractive biodegradation of phenanthrene by Sphingomonas polyaromaticivorans was conducted by introducing the cloud point system. The cloud point system is composed of a mixture of (40 g/L) Brij 30 and Tergitol TMN-3, which are nonionic surfactants, in equal proportions. After phenanthrene degradation, a higher wet cell weight and lower phenanthrene residue were obtained in the cloud point system than that in the control system. According to the results of high-performance liquid chromatography, the residual phenanthrene preferred to partition from the dilute phase into the coacervate phase. The concentration of residual phenanthrene in the dilute phase (below 0.001 mg/L) is lower than its solubility in water (1.18 mg/L) after extractive biodegradation. Therefore, dilute phase detoxification was achieved, thus indicating that the dilute phase could be discharged without causing phenanthrene pollution. Bioavailability was assessed by introducing the apparent log P in the cloud point system. Apparent log P decreased significantly, thus indicating that the bioavailability of phenanthrene increased remarkably in the system. This study provides a potential application of biological treatment in water and soil contaminated by phenanthrene. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons are particularly important due to large distribution in the environment, high toxicity and their carcinogen and mutagen properties. The purpose of this study was isolation and identification of phenanthrene degrading bacteria from the soil around Oil Company of Andimeshk (Iran) and investigation of their growth kinetics. Sampling from three stations was done at two seasons, spring and summer. Phenanthrene degrading bacteria were isolated from soil using enrichment method. Bacterial identification was performed by biochemical tests and 16S rRNA gene sequencing. Minimum inhibitory concentrations (MIC) were determined at various concentrations of phenanthrene. Bacterial biodegradation rate was determined using HPLC analysis. Finally, the growth kinetics of resistant bacteria was determined with culturing at concentrations of 0.5–0.8 g/l of phenanthrene. According to biochemical and molecular testsPseudomonas aeruginosastrain SBL,Bacillus cereusstrain Z4B-11, Staphylococcus epidermidis, andMicrococcus luteuswere identified as phenanthrene degrading bacteria. The results showed thatP. aeruginosaSBL andB. cereusZ4B-11 with the greatest amount of MIC are the most phenanthrene resistant bacteria, respectively. These two strains degraded 70% and 50% of phenanthrene after one week of incubation, respectively. The most growth in different concentrations of phenanthrene belonged toP. aeruginosaSBL andB. cereusZ4B-11 while the least growth belonged toS. epidermidis and M. luteus, respectively. It could be concluded that two new strains SBL and Z4B-11 which were isolated in the soil around Oil Company of Andimeshk have relatively high potential to be used for bioremediation of phenanthrene. [ABSTRACT FROM PUBLISHER]

A covalent immobilization method based on glutaraldehyde and amino-functionalized SBA-15 supports has been successfully applied to covalently and stably immobilize laccase from Trametes versicolor . The resultant biocatalysts displayed high incorporation yields of enzyme and led to excellent biodegradation rates of selected HPAs models, i.e. naphthalene, phenanthrene and anthracene, in water. The nature of the hydrocarbon chain accompanying the amino group has been shown as determinant for the immobilization as well as for the activity and reusability of the materials. Thus, alkyl moieties displayed higher enzyme loadings than phenyl moieties, being more adequate the larger n-butyl tethering residue likely due to its higher mobility. Using the aminobutyl-based laccase-SBA-15, 82%, 73%, and 55% conversion of naphthalene, phenanthrene and anthracene, respectively, were achieved after 48 h, very close to the values obtained with free laccase under the same reaction conditions. On the other hand, aminopropyl-based laccase-SBA-15 biocatalysts displayed the best reusability properties, retaining higher activity after four repeated uses than the corresponding aminobutyl-based materials. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs), a class of hazardous chemicals ubiquitous in many ecosystems, are of great concern due to their potential toxicity, carcinogenicity, teratogenicity, and mutagenicity. Phenanthrene, a low-molecular-weight hydrophobic PAH, binds to particulates in the soil and sediments, thus inhibiting biological uptake. In such PAH-contaminated environments, some well-adapted microorganisms, such as the sphingomonads (belonging to the Family Sphingomonadaceae in α-Proteobacteria) can degrade phenanthrene, whether in isolation or cometabolized with other PAHs. Some of the members of sphingomonads, consisting of the Sphingomonas , Sphingobium , Novosphingobium , and Sphingopyxis genera, have adjusted well to contaminated soil environments compared to most bacterial genera that degrade PAHs. This is manifested in phenanthrene, which has been found to induce strong up-regulation of extradiol cleavage pathway enzymes in sphingomonads with similar gene and enzyme homology to Sphingobium yanoikuyae B1, where enzymes like ring-hydroxylating dioxygenase, putative biphenyl-2,3-diol 1,2-dioxygenase, and catechol 2,3-dioxygenase are encoded by bphA2cA1c , bphA1 [a-e] A2 [a-e] (which both require bphA3bphA4 ) and bphC genes, respectively. With meta - and ortho -cleavage pathway routes, this has made sphingomonads a well-adapted group of microorganisms. This review will focus on taxonomic, autecological and genetic features of sphingomonads which impact on their ability to metabolize phenanthrene at different rates and under different conditions. [ABSTRACT FROM AUTHOR]

Environmental contamination by polycyclic aromatic hydrocarbons ( PAHs) typically occurs as mixtures of compounds. In this study, the response of indigenous soil bacterial and fungal communities to mixtures containing phenanthrene, fluoranthene and benzo( a)pyrene in various combinations was examined using molecular fingerprinting techniques and quantification of a key PAH degradative gene. Results were compared to a parallel study by Sawulski et al. (2014) which examined the effect of these PAHs on soil microbial communities when added as single contaminants. The rate of degradation of individual PAHs varied depending on whether the PAH was present as a single contaminant or in a mixture; phenanthrene was degraded most rapidly when present as a sole contaminant, fluoranthene was removed faster in the presence of the lower molecular weight phenanthrene and the rate of benzo( a)pyrene degradation was reduced in the presence of the 4-ring PAH, fluoranthene. Bacterial and fungal assemblages differed significantly between treatments regardless of which PAH was added to soil. Although less abundant than the Gram-negative PAH- RHDα gene, the gene associated with Gram-positive bacteria responded to a greater extent to the presence of PAHs, either as single compounds or as mixtures and this increase was significantly correlated with PAH degradation. Significance and Impact of the Study Contaminated sites generally contain complex mixtures of pollutants. Development of effective bioremediation strategies for contaminated soils requires knowledge of the response of soil microbial communities to such mixtures. This study provides information on the degradation of different mixtures of three priority pollutants in soil with a history of polycyclic aromatic hydrocarbon contamination and examines the response of soil bacterial and fungal communities to the presence of these pollutants as sole contaminants or as part of a mixture. This is one of few studies to-date to compare the effects of single compounds and pollutant mixtures on more than one soil microbial community. [ABSTRACT FROM AUTHOR]

Nitrogen- heterocyclic polycyclic aromatic hydrocarbons (N-PAHs) are ubiquitous constituents of contaminated sites in which their high water solubility and lower k values imply greater mobility and impacts. Biodegradation is a major route of loss for organic contaminants in soil. In this study, microbial degradation was investigated in soil artificially contaminated with N-PAHs and monitored for over 200 days. The results showed that all the aromatic chemicals exhibited loss with increasing incubation time; however, only 0.05 ± 0.04 mg kg day loss was observed for N-PAHs at 10 mg kg amendments over the first 30 days incubation, with the exception of 4,7-phenanthroline which recorded 0.19 ± 0.03 mg kg day. The study showed that soil microflora have the potential to degrade N-PAHs since all of the aromatics recorded chemical losses under aerobic condition. However, degradation rates varied between chemicals and this was attributed to N-atom position and/or number of N-substituents. Further, relatively little or no biodegradation was observed in B[h]Q amended soils with increasing concentration; indicating that B[h]Q is more resistance to biodegradation in soil. [ABSTRACT FROM AUTHOR]

Purpose: The fate of complex contaminants in soils has aroused increasing attention of environmental scientists. Although heavy metals and polycyclic aromatic hydrocarbons (PAHs) are often encountered together in contaminated sites, the interactions between the co-existing contaminants with clay minerals and humic substances require further investigation. Materials and methods: Phenanthrene, lead (Pb), and cadmium (Cd) were selected as the representatives to investigate their interactions on the surface of bentonite (primarily montmorillonite) and humic acid/fulvic acid-coated bentonite in batch sorption experiments. Their bonding strengths were assessed in terms of extractability by various chemical extraction methods. Results and discussion: The humic acid coating on bentonite enhanced the Pb and Cd sorption capacity, especially at the high Pb loading where the linear sorption coefficient was dramatically increased. The fulvic acid coating had less significant effects because of its higher solubility. The co-existing phenanthrene promoted the Pb sorption to a greater extent on humic acid-coated bentonite due to greater phenanthrene sorption, while the phenanthrene sorption was also promoted by the co-existing Pb. However, the enhancement was less obvious for Cd sorption, possibly due to greater hydration and weaker complexation with oxygen-containing groups despite higher electron polarizability of Cd. On the other hand, the presence of humic acid coating increased both (weakly bound) exchangeable fraction and (strongly bound) residual fraction of sorbed Pb. In contrast, co-existing phenanthrene and Pb resulted in redistribution of each other from weakly bound to strongly bound fractions. Such strengthened bonding of both Pb and phenanthrene indicated the significance of strong cation-π bonding on the bentonite. Yet, such enhancement might be alleviated by the humic acid coating. Conclusions: Understanding the intercorrelated interactions of humic substances, phenanthrene, and heavy metals on clay minerals would help us to maneuver an effective in situ remediation of complex soil contamination. [ABSTRACT FROM AUTHOR]