Bioremediation Of Polycyclic Aromatic Hydrocarbons Research Articles

Mild acid and alkali treated clay minerals enhance bioremediation of polycyclic aromatic hydrocarbons in long-term contaminated soil: A 14C-tracer study

Bioremediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soils requires a higher microbial viability and an increased PAH bioavailability. The clay/modified clay-modulated bacterial degradation could deliver a more efficient removal of PAHs in soils depending on the bioavailability of the compounds. In this study, we modified clay minerals (smectite and palygorskite) with mild acid (HCl) and alkali (NaOH) treatments (0.5–3 M), which increased the surface area and pore volume of the products, and removed the impurities without collapsing the crystalline structure of clay minerals. In soil incubation studies, supplements with the clay products increased bacterial growth in the order: 0.5 M HCl ≥ unmodified ≥ 0.5 M NaOH ≥ 3 M NaOH ≥ 3 M HCl for smectite, and 0.5 M HCl ≥ 3 M NaOH ≥ 0.5 M NaOH ≥ 3 M HCl ≥ unmodified for palygorskite. A14C-tracing study showed that the mild acid/alkali-treated clay products increased the PAH biodegradation (5–8%) in the order of 0.5 M HCl ≥ unmodified > 3 M NaOH ≥ 0.5 M NaOH for smectite, and 0.5 M HCl > 0.5 M NaOH ≥ unmodified ≥ 3 M NaOH for palygorskite. The biodegradation was correlated (r = 0.81) with the bioavailable fraction of PAHs and microbial growth as affected particularly by the 0.5 M HCl and 0.5 M NaOH-treated clay minerals. These results could be pivotal in developing a clay-modulated bioremediation technology for cleaning up PAH-contaminated soils and sediments in the field.

Bioremediation of Polycyclic Aromatic Hydrocarbons by Bacillus Licheniformis ATHE9 and Bacillus Mojavensis ATHE13 as Newly Strains Isolated from Oil-Contaminated Soil

Bioremediation of Polycyclic Aromatic Hydrocarbons by Bacillus Licheniformis ATHE9 and Bacillus Mojavensis ATHE13 as Newly Strains Isolated from Oil-Contaminated Soil

Construction of PAH-degrading mixed microbial consortia by induced selection in soil

Bioremediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated soils through the biostimulation and bioaugmentation processes can be a strategy for the clean-up of oil spills and environmental accidents. In this work, an induced microbial selection method using PAH-polluted soils was successfully used to construct two microbial consortia exhibiting high degradation levels of low and high molecular weight PAHs. Six fungal and seven bacterial native strains were used to construct mixed consortia with the ability to tolerate high amounts of phenanthrene (Phe), pyrene (Pyr) and benzo(a)pyrene (BaP) and utilize these compounds as a sole carbon source. In addition, we used two engineered PAH-degrading fungal strains producing heterologous ligninolytic enzymes. After a previous selection using microbial antagonism tests, the selection was performed in microcosm systems and monitored using PCR-DGGE, CO2 evolution and PAH quantitation. The resulting consortia (i.e., C1 and C2) were able to degrade up to 92% of Phe, 64% of Pyr and 65% of BaP out of 1000 mg kg−1 of a mixture of Phe, Pyr and BaP (1:1:1) after a two-week incubation. The results indicate that constructed microbial consortia have high potential for soil bioremediation by bioaugmentation and biostimulation and may be effective for the treatment of sites polluted with PAHs due to their elevated tolerance to aromatic compounds, their capacity to utilize them as energy source.

Polycyclic aromatic hydrocarbons (PAHs) degradation potential, surfactant production, metal resistance and enzymatic activity of two novel cellulose-degrading bacteria isolated from koala faeces

Cellulose-degrading bacterial strains, KC3 and 5, capable also of degrading both low and high molecular weight PAHs were isolated from koala faeces for the first time. KC3 and 5 belong to the genera Bacillus and Pseudomonas, respectively. These strains completely degraded the model 3-(phenanthrene), 4-(pyrene) and 5-(benzo-a-pyrene) ring PAHs at 6, 7 and 40–50 days, correspondingly. They were shown to be able to produce a rhamnolipid type of biosurfactant during PAH degradation. The biosurfactants produced from both the strains showed good pH (2–12) as well as thermal (up to 80 °C) stability and were able to tolerate up to 20 g L−1 salinity. The strains also had resistance towards heavy metals, attributed to the amount of biosurfactant produced. The Bacillus strain in particular showed excellent metal resistance; the minimum inhibitory concentrations were 5 (Cd2+, Cu2+) and 7 (Pb2+, Zn2+) mg L−1 of relatively bioavailable metal ions, but >15 mg L−1 metal concentrations were lethal to the microbe. Additionally, both strains possessed activity of more than one extracellular enzyme (cellulase, lipase and protease). The limiting factors in PAH biodegradation are low PAH bioavailability and microbial intolerance towards HMW PAHs and co-contaminants (heavy metals). The novel strains identified thus had (a) potential to biodegrade both LMW and HMW PAHs, (b) pH, thermal and saline-tolerant biosurfactant production that aids PAH solubility enhancement, and importantly, (c) heavy metal resistance. Both Bacillus and Pseudomonas strains are appropriate candidates in field-scale PAH bioremediation at mixed contamination sites and for several industrial applications due to their enzymatic activities.

Bioremediation of polycyclic aromatic hydrocarbon (PAH) compounds: (acenaphthene and fluorene) in water using indigenous bacterial species isolated from the Diep and Plankenburg rivers, Western Cape, South Africa.

This study was conducted to investigate the occurrence of PAH degrading microorganisms in two river systems in the Western Cape, South Africa and their ability to degrade two PAH compounds: acenaphthene and fluorene. A total of 19 bacterial isolates were obtained from the Diep and Plankenburg rivers among which four were identified as acenaphthene and fluorene degrading isolates. In simulated batch scale experiments, the optimum temperature for efficient degradation of both compounds was determined in a shaking incubator after 14 days, testing at 25 °C, 30 °C, 35 °C, 37 °C, 38 °C, 40 °C and 45 °C followed by experiments in a Stirred Tank Bioreactor using optimum temperature profiles from the batch experiment results. All experiments were run without the addition of supplements, bulking agents, biosurfactants or any other form of biostimulants. Results showed that Raoultella ornithinolytica, Serratia marcescens, Bacillus megaterium and Aeromonas hydrophila efficiently degraded both compounds at 37 °C, 37 °C, 30 °C and 35 °C respectively. The degradation of fluorene was more efficient and rapid compared to that of acenaphthene and degradation at Stirred Tank Bioreactor scale was more efficient for all treatments. Raoultella ornithinolytica, Serratia marcescens, Bacillus megaterium and Aeromonas hydrophila degraded a mean total of 98.60%, 95.70%, 90.20% and 99.90% acenaphthene, respectively and 99.90%, 97.90%, 98.40% and 99.50% fluorene, respectively. The PAH degrading microorganisms isolated during this study significantly reduced the concentrations of acenaphthene and fluorene and may be used on a larger, commercial scale to bioremediate PAH contaminated river systems.

Bioremoval of priority polycyclic aromatic hydrocarbons by a microbial community with high sorption ability.

The treatment of large volumes of wastewater during oil refining is presently a challenge. Bioremediation has been considered an eco-friendly approach for the removal of polycyclic aromatic hydrocarbons (PAHs), which are one of the most hazardous groups of organic micropollutants. However, it is crucial to identify native PAH-removing microorganisms for the development of an effective bioremediation process. This study reports the high potential of an anaerobic microbial consortium enriched from a petrochemical refinery wastewater to remove two priority PAHs-acenaphthene and phenanthrene. Seventy-seven percent of acenaphthene was removed within 17h, whereas phenanthrene was no longer detected after 15h. Bioremoval rates were extremely high (0.086 and 0.156h-1 for acenaphthene and phenanthrene, respectively). The characterization of the microbial communities by next-generation sequencing and fluorescence in situ hybridization showed that the PAH-removing consortium was mainly composed by bacteria affiliated to Diaphorobacter and Paracoccus genera, independently of the PAH tested. Moreover, besides biodegradation, biosorption was a relevant mechanism involved in the removal of both PAHs, which is an important finding since biosorption is less expensive than biodegradation and can be carried out with dead biomass. Although biodegradation is the most commonly reported biological mechanism for PAH removal, this study demonstrated that biosorption by this microbial community may be extremely efficient for their removal. Given the outstanding ability of this microbial consortium to quickly remove the compounds addressed, it could be further applied for the bioremediation of PAHs in refinery wastewaters and other contaminated environments.

Bioremediation of Polycyclic Aromatic Hydrocarbon (PAHs): A Perspective

Hydrocarbon pollution is a perennial problem not only in India but throughout the globe. A plethora of microorganisms have been reported to be efficient degraders of these recalcitrant pollutants. One of the major concerns of environmental problem is the presence of hydrocarbons due to the various anthropogenic activities. PAHs are ubiquitous in naturei.e.present in soil, water and air. Presence of PAHs in environment creates problem as their presence have deleterious effect on human and animals. They also have the ability to cause the tumors in human and animals. Some of the microorganisms are capable of transforming and degrading these PAHs and remove them from the environment. The present review describes about the sources, structure, fate and toxicity of PAHs as well as different bioremediation techniques involved in the removing of contaminants from the environment which are efficient and cost-effective. The conventional approaches used for removal of PAH are not only environment friendly but also are able to reduce the risk to human and ecosystem.

Biosurfactant-Assisted Bioremediation of Polycyclic Aromatic Hydrocarbons (PAHs) in Liquid Culture System and Substrate Interactions

ABSTRACTA lipopeptide biosurfactant was produced by the bacterium Pseudomonas aeruginosa strain LBP9 isolated from petroleum-contaminated soil. Phenanthrene, fluoranthene, and pyrene were used as model polycyclic aromatic hydrocarbons (PAHs) to study the effect of the biosurfactant on the biodegradation of mixed and sole substrate PAHs, and examine substrate interactivity effects on their biodegradation in liquid culture. At 400 mg/L amendment of lipopeptide, the solubility of phenanthrene, fluoranthene, and pyrene were increased to 19, 33, and 45 times their aqueous solubility, respectively, and the extent of substrate utilization rate (qmax ) of PAHs was enhanced up to three-fold in the sole substrate studies in comparison to the unamended controls. In the ternary PAH mixture at total concentration of 300 mg/L, with equal parts of each PAH, 77%, 57%, and 33% degradation of phenanthrene, fluoranthene, and pyrene were observed, respectively, at 400 mg/L lipopeptide amendment on day 30 of incubation. Whereas in the sole substrate experiments at 300 mg/L concentration of each PAH and the same level of lipopeptide amendment more than 98% fluoranthene and 76% pyrene were degraded and phenanthrene removal was so rapid that at day 4 of incubation more than 80% was degraded. Biosurfactants at optimum amounts enhanced biodegradation of PAHs. Lipopeptide amendments of 200 mg/L and 400 mg/L were found out to be optimum amounts for statistically significant (p < 0.05) biodegradation of the PAHs in the experiments. However, despite biosurfactant-enhanced bioavailability of the PAHs, biodegradation rate was competitively inhibited in the multisubstrate microcosms.

The role of lipopeptide biosurfactant on microbial remediation of aged polycyclic aromatic hydrocarbons (PAHs)-contaminated soil

Polycyclic aromatic hydrocarbons (PAHs) have been recognised as priority pollutants due to their carcinogenic, mutagenic and teratogenic properties. Bioremediation of PAHs is limited by low bioavailability of soil-bound PAHs due to their low aqueous solubility, high hydrophobicity and strong sorption to soil. The purpose of this study was to investigate the biodegradation enhancement potential of a heavy molecular mass lipopeptidal biosurfactant produced by Bacillus cereus SPL-4 on an aged wood treatment plant soil heavily contaminated with PAHs. In the laboratory scale batch treatments conducted (concentration of 6745.5mgkg−1, sum of 13PAHs) the high molecular weight PAHs removal rate was significantly enhanced in the biosurfactant supplemented microcosms than in the surfactant free controls. In the microcosms supplemented with 0.2 and 0.6% (w/w) lipopeptide, 51.2% of 4-ring and 55% of 5- and 6-ring PAHs; 64.1% of 4-ring and 79% of 5- and 6-ring PAHs were removed respectively, compared to 29% of 4-ring and 25.5% of 5- and 6-ring PAHs removal in the surfactant free control after 64daysof incubation. However, there was no statistically significant change in the degradation rates of low molecular weight PAHs in surfactant amended and surfactant free controls. Fitting the experimental data to two compartment model showed that the biosurfactant addition at 0.2 and 0.6% (w/w) increased the fast degradation fraction to 34.2 and 63% respectively, compared to 6% at the surfactant free controls. The degradation of 5 and 6 ring PAHs was significantly enhanced (p<0.05) in the higher surfactant dosage compared to the lower dosage. The results suggest that biosurfactant assisted degradation by microbial consortium may be a promising practical bioremediation strategy for aged PAH-contaminated soils.

Fluoranthene degradation and binding mechanism study based on the active-site structure of ring-hydroxylating dioxygenase in Microbacterium paraoxydans JPM1.

In this study, a gram-positive fluoranthene-degrading bacterial strain was isolated from crude oil in Dagang Oilfield and identified as Microbacterium paraoxydans JPM1 by the analysis of 16S rDNA sequence. After 25days of incubation, the strain JPM1 could degrade 91.78% of the initial amount of fluoranthene. Moreover, four metabolites 9-fluorenone-1-carboxylic acid, 9-fluorenone, phthalic acid, and benzoic acid were detected in the culture solution. The gene sequence encoding the aromatic-ring-hydroxylating dioxygenase was amplified in the strain JPM1 by PCR. Based on the translated protein sequence, a homology modeling method was applied to build the crystal structure of dioxygenase. Subsequently, the interaction mechanism between fluoranthene and the active site of dioxygenase was simulated and analyzed by molecular docking. Consequently, a feasible degrading pathway of fluoranthene in the strain JPM1 was proposed based on the metabolites and the interaction analyses. Additionally, the thermodynamic analysis showed that the strain JPM1 had high tolerance for fluoranthene, and the influence of fluoranthene for the bacterial growth activity was negligible under 100 to 400mgL-1 concentrations. Taken together, this study indicates that the strain JPM1 has high potential for further study in bioremediation of polycyclic aromatic hydrocarbon (PAH)-contaminated sites.

Bioremediation of Polycyclic Aromatic Hydrocarbon Contaminated Soil by a Microbial Consortium through Supplementation of Biosurfactant Produced by Pseudomonas aeruginosa Strain

Lipopeptide biosurfactant produced by Pseudomonas aeruginosa Lbp 3 strain isolated from petroleum contaminated soil was investigated for its potential to enhance bioavailability, and hence, the biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil microcosms. Experiments were conducted on a soil spiked with equal parts of the PAHs Phenanthrene, Fluoranthene, and Pyrene to a final concentration of 1200 mg of total PAHs per kg of dry soil. To evaluate biodegradation enhancement efficiency, 50 g spiked soil samples were supplemented with 50 mgL−1, 100 mgL−1, 300 mgL−1, and 1000 mgL−1of lipopeptide dissolved in 30 mL of MSM, and incubated for 40 days at 30°C in darkness. Statistically significant (P < 0.05) biodegradation rates were observed in all the amended microcosms in comparison to the unamended controls. Maximal biodegradations (> 96% of Phenanthrene and Fluoranthene and > 93% of Pyrene) were observed in the soil microcosms supplemented with 1000 mgL−1and 50 mgL−1 lipopeptide. The effect of substrate interactivity of the PAHs on the biodegradation kinetics was also tested in comparison with sole substrate microcosms. Competitive inhibition of the biodegradation of low molecular weight PAHs was observed as a result of substrate interactivity in the multisubstrate system.

Characterization of a phenanthrene-degrading microbial consortium enriched from petrochemical contaminated environment

In this study, a novel aerobic microbial consortium for the complete degradation of phenanthrene was enriched from petrochemical contaminated soil in Puyang City, Henan Province, China. The consortium, named as ZY-PHE, could degrade more than 96% of 200 mg/L phenanthrene in a minimal salt medium in 3 days. Pyrosequencing analysis of the bacterial 16S rRNA gene suggested that Proteobacteria was the dominant phyla of ZY-PHE consortium representing 56.7% of the total number of detected sequences followed by Actinobacteria (21.7%), Deinococcus-Thermus (14.5%), Bacteroidetes (4.3%) and Firmicutes (0.8%). Several abundant genera, Truepera (14.47%), Starkeya (1.35%), Nitratireductor (1.35%), Legionella (0.71%), Aeromicrobium (0.47%), Phyllobacterium (0.38%) and Cellulosimicrobium (0.31%), have firstly been detected in PAHs contaminated environment. The consortium has the ability to degrade other PAHs such as pyrene and fluorene by utilizing them as sole carbon and energy source. Further, consortium ZY-PHE exhibited an excellent pH adaptation and extensive temperature flexibility, indicating this consortium could function well under a wide range of environmental conditions. Liquid chromatography–quadrupole-time-of-flight mass spectrometry assay revealed accumulation of few intermediate metabolites involved in phenanthrene degradation. The use of this bacterial consortium may be an attractive alternative for the bioremediation of polycyclic aromatic hydrocarbons in the environment.

Current State of Knowledge in Microbial Degradation of Polycyclic Aromatic Hydrocarbons (PAHs): A Review.

Polycyclic aromatic hydrocarbons (PAHs) include a group of organic priority pollutants of critical environmental and public health concern due to their toxic, genotoxic, mutagenic and/or carcinogenic properties and their ubiquitous occurrence as well as recalcitrance. The increased awareness of their various adverse effects on ecosystem and human health has led to a dramatic increase in research aimed toward removing PAHs from the environment. PAHs may undergo adsorption, volatilization, photolysis, and chemical oxidation, although transformation by microorganisms is the major neutralization process of PAH-contaminated sites in an ecologically accepted manner. Microbial degradation of PAHs depends on various environmental conditions, such as nutrients, number and kind of the microorganisms, nature as well as chemical property of the PAH being degraded. A wide variety of bacterial, fungal and algal species have the potential to degrade/transform PAHs, among which bacteria and fungi mediated degradation has been studied most extensively. In last few decades microbial community analysis, biochemical pathway for PAHs degradation, gene organization, enzyme system, genetic regulation for PAH degradation have been explored in great detail. Although, xenobiotic-degrading microorganisms have incredible potential to restore contaminated environments inexpensively yet effectively, but new advancements are required to make such microbes effective and more powerful in removing those compounds, which were once thought to be recalcitrant. Recent analytical chemistry and genetic engineering tools might help to improve the efficiency of degradation of PAHs by microorganisms, and minimize uncertainties of successful bioremediation. However, appropriate implementation of the potential of naturally occurring microorganisms for field bioremediation could be considerably enhanced by optimizing certain factors such as bioavailability, adsorption and mass transfer of PAHs. The main purpose of this review is to provide an overview of current knowledge of bacteria, halophilic archaea, fungi and algae mediated degradation/transformation of PAHs. In addition, factors affecting PAHs degradation in the environment, recent advancement in genetic, genomic, proteomic and metabolomic techniques are also highlighted with an aim to facilitate the development of a new insight into the bioremediation of PAH in the environment.

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

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

Specific adsorption of cadmium on surface-engineered biocompatible organoclay under metal-phenanthrene mixed-contamination

Bioremediation of polycyclic aromatic hydrocarbons (PAHs) is extremely challenging when they coexist with heavy metals. This constrain has led to adsorption-based techniques that help immobilize the metals and reduce toxicity. However, the adsorbents can also non-selectively bind the organic compounds, which reduces their bioavailability. In this study we developed a surface-engineered organoclay (Arquad® 2HT-75-bentonite-palmitic acid) which enhanced bacterial proliferation and adsorbed cadmium, but elevated phenanthrene bioavailability. Adsorption models of single and binary solutes revealed that the raw bentonite adsorbed cadmium and phenanthrene non-selectively at the same binding sites and sequestrated phenanthrene. In contrast, cadmium selectively bound to the deprotonated state of carboxyl groups in the organoclay and phenanthrene on the outer surface of the adsorbent led to a microbially congenial microenvironment with a higher phenanthrene bioavailability. This study provided valuable information which would be highly important for developing a novel clay-modulated bioremediation technology for cleaning up PAHs under mixed-contaminated situations.

Application of backpropagation artificial neural network prediction model for the PAH bioremediation of polluted soil

The backpropagation (BP) artificial neural network (ANN) is a renowned and extensively functional mathematical tool used for time-series predictions and approximations; which also define results for non-linear functions. ANNs are vital tools in the predictions of toxicant levels, such as polycyclic aromatic hydrocarbons (PAH) potentially derived from anthropogenic activities in the microenvironment. In the present work, BP ANN was used as a prediction tool to study the potential toxicity of PAH carcinogens (PAHcarc) in soils. Soil samples (16 × 4 = 64) were collected from locations in South-southern Nigeria. The concentration of PAHcarc in laboratory cultivated white melilot, Melilotus alba roots grown on treated soils was predicted using ANN model training. Results indicated the Levenberg-Marquardt back-propagation training algorithm converged in 2.5E+04 epochs at an average RMSE value of 1.06E-06. The averagedR2 comparison between the measured and predicted outputs was 0.9994. It may be deduced from this study that, analytical processes involving environmental risk assessment as used in this study can successfully provide prompt prediction and source identification of major soil toxicants.

Enhanced Soil Remediation via Plant-Based Surfactant Compounds from Acanthophyllum Laxiusculum

Abstract In the present study, an aqueous root-extract of Acanthophyllum laxiusculum (AREAL) was evaluated for phenanthrene removal from two samples of contaminated soil. AREAL showed a linear solubilization enhancement for phenanthrene with a weight solubilization ratio of 0.05. Batch soil washing experiments caused the removal of phenanthrene with efficiencies of 96.7 % and 78 % from soils with 0.78 % and 2.73 % organic carbon, respectively. Desorption kinetics of phenanthrene exhibited a two-phase pattern, namely, a rapid release as the initial phase and a slower removal as a subsequent phase. A two-compartment exponential model could adequately represent the two phases of the kinetic pattern of phenanthrene desorption. The rise of pH from acidic to basic levels, decreased phenanthrene removal due to changes in the micelle number of the surfactant phase. Maximum achievable yield of removal was 82 % phenanthrene in a column experiment at defined operational conditions. High removal efficiencies show the potential application of AREAL for improving the bioremediation of polycyclic aromatic hydrocarbons (PAHs) from contaminated soils.

Heterologous expression of a new manganese-dependent peroxidase gene from Peniophora incarnata KUC8836 and its ability to remove anthracene in Saccharomyces cerevisiae

The white rot fungus Peniophora incarnata KUC8836 has received an attention as the greatest degrader of polycyclic aromatic hydrocarbons (PAHs), which are hazardous xenobiotics and recalcitrant pollutants. To characterize the mechanisms through which MnP degrades PAHs, heterologous expression of manganese-dependent peroxidase (MnP) gene pimp1 was performed in Saccharomyces cerevisiae BY4741 via the pGEM-T Easy vector, resulting in the recombinant plasmid pESC-URA/pimp1 containing the MnP signal peptide. MnP was significantly secreted into the culture medium with galactose as an active protein with higher efficiency (3.58UmL-1)by transformants than by the wild-type S.cerevisiae. The recombinant MnP protein was shown to have a molecular weight of 44kDa by western blotting analysis. With regard to enhancing the bioremediation of PAHs in the environment, anthracene was effectively degraded by the MnP encoded by pimp1, with a degradation rate of 6.5% when Tween 80 was added. In addition, the MnP activity of the transformant exhibited the highest efficiency (2.49UmL-1) during the degradation. These results show that pimp1 might be useful for biodegradation and gene expression technologies at a transcriptional level, and genetic approaches can be improved by incorporating the highly ligninolytic gene pimp1 and the fungus P.incarnata KUC8836.

English

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant contaminants which are routinely found in numerous environmental matrices, contributing to ecological degradation. In this study, the removal of LMW and HMW PAHs with 4- and 5-benzene rings, by Bacillus licheniformis STK 01, Bacillus subtilis STK 02 and Pseudomonas aeruginosa STK 03, was evaluated in silty soil for a period of 60 days. Subsequently, a biosurfactant produced from Beta vulgaris agrowaste was used to augment the removal of the aforementioned PAHs in mono- and co-cultures. The isolates proved to be proficient in removing the contaminants, with B. licheniformis STK01 cultures achieving the highest removal rates. Biosurfactant supplementation significantly enhanced the removal of benzo(a)pyrene- a 5-ring benzene HMW PAH. The highest removal rates achieved in biosurfactant-supplemented cultures were: 100% for phenanthrene, 95.32% for pyrene, 82.71% for benz(a)anthracene and 86.17% for benzo(a)pyrene. The kinetic data used to simulate removal rates were suitably described by first-order kinetics, with the rate constants showing that phenanthrene removal was rapid in cultures without biosurfactant (k = 0.0620 day-1) as well as with biosurfactant (k = 0.0664 day-1), while the removal rates for others followed in the order of their increasing molecular weight. The synergy of the bacterial isolates and the biosurfactant produced from B. vulgaris agrowaste could be used in environmental bioremediation of PAHs even in silty soil. Key words: Benz(a)anthracene, benzo(a)pyrene, bioremediation, biosurfactant, Beta vulgaris, polycyclic aromatic hydrocarbons.

Heavy metals species affect fungal-bacterial synergism during the bioremediation of fluoranthene.

The co-occurrence of polycyclic aromatic hydrocarbons (PAHs) with heavy metals (HMs) is very common in contaminated soils, but the influence of HMs on fungal-bacterial synergism during PAH bioremediation has not been investigated. The bioremediation of fluoranthene-contaminated sand using co-cultures of Acremonium sp. P0997 and Bacillus subtilis showed increases of 109.4 and 9.8% in degradation compared to pure bacterial and fungal cultures, respectively, removing 64.1±1.4% fluoanthene in total. The presence of Cu(2+) reduced fluoranthene removal to 53.7±1.7%, while inhibiting bacterial growth, and reducing translocation of bacteria on fungal hyphae by 49.5%, in terms of the bacterial translocation ratio. Cu(2+) reduced bacterial diffusion by 46.8 and 31.9%, as reflected by D (a bulk random motility diffusional coefficient) and D eff (the effective one-dimensional diffusion coefficient) compared to the control without HM supplementation, respectively. However, Mn(2+) resulted in a 78.2±1.9% fluoranthene degradation, representing an increase of 21.9%, while enhancing bacterial growth and bacterial translocation on fungal hyphae, showing a 12.0% increase in translocation ratio, with no observable impact on D and D eff. Hence, the presence of HMs has been shown to affect fungal-bacterial synergism in PAH degradation, and this effect differs with HM species.