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

A 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 (q_max?) 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.     

Square wave voltammetric determination of methiocarb insecticide based on multiwall carbon nanotube paste electrode

Cyclic voltammogram of methiocarb in 0.1 M H₂SO₄ exhibited an irreversible anodic peak at about +1285 mV versus Ag/AgCl. Electro-oxidation and determination of methiocarb in spiked soil, river water and agrochemical formulation were realized on a newly prepared carbon-nanotube paste electrode by applying square wave voltammetry (SWV). The dE _p /dpH value indicated that the oxidation mechanism involved the coupling of H⁺ with the oxidation process. The peak signals were linearly related to methiocarb concentration in the range of 1.5–59.1 mgL^?1 with a detection limit of 0.45 mgL^?1. The accuracy and selectivity of the proposed method were shown by calculating the recoveries of methiocarb from soil, river water and pesticide formulation Mesurol^®. The calculated percent recoveries for soil and river water samples spiked with 30.0 μg g^?1 and 40.0 μg mL^?1 levels were 99.3 ± 1.2 and 98.5 ± 0.3 at 95 % confidence limit, respectively.     

Biodegradation of Phenol from Wastewater by Microorganism Immobilized in Bentonite and Carboxymethyl Cellulose Gel

This study presents a microbial process for phenol degradation in coking wastewater. The optimum immobilized condition of the strain for degrading phenol was determined through orthogonal experiment. The free and immobilized microorganisms were examined for their capabilities on degrading phenol. Results indicated that the optimum immobilized conditions were 20% microorganism suspension, 5% bentonite, 3% sodium carboxymethyl cellulose content, and 1 h of crosslinking time. The biodegradation rate was optimized at 35°C and 0.23 gmL^?1 of immobilized microorganism bead. The degrading rate for the immobilized microorganism bead was up to 95.96% at an initial phenol concentration of 100 mgL^?1; however, the immobilized microorganism considerably took more time (288 h) to reach 94.6% removal efficiency at a much higher concentration of 1000 mgL^?1. The batch experiment demonstrated that 94.50% of phenol was removed using the beads with the immobilized microorganism at an initial concentration of 500 mgL^?1. By contrast, only 24.60% and 33.88% of phenol were degraded using the gel beads without and with free microorganisms, respectively. The immobilized microorganism beads can used reused for up to nine cycles at the same initial phenol concentration (50 mgL^?1) and can be stored up to 40 d without loss of its degradation capacity.     

Polycyclic Aromatic Hydrocarbons in Residential Soils from an Indian City near Power Plants Area and Assessment of Health Risk for Human Population

This article deals with the distribution, composition profiles, and possible sources of sixteen priority polycyclic aromatic hydrocarbons (PAHs) in residential soils from Korba district in Chhattisgarh State, India. Sixteen priority PAHs in soils were analyzed after ultrasonic extraction, silica gel column chromatographic cleanup, and quantitation was performed using HPLC-DAD. The concentrations of ∑16PAHs were within acceptable limits of soil quality guidelines and the study area got classified as weakly contaminated. The concentration of probable human carcinogenic PAHs in soils accounted for 10% of ∑16PAHs. The concentration of Benzo(a)Pyrene (BaP) accounted 1% to total PAHs. Benzo(a)pyrene Toxicity Equivalency (BaP_TEQ) for 16 PAHs was 30 ± 12 μg BaP_TEQ kg^?1. The composition profiles and molecular ratios of PAHs suggested mixed pyrogenic sources of PAHs from combustion of coal, wood, and vehicular exhaust emissions. Human health risk was assessed by calculating the lifetime average daily dose (LADD) and incremental life time cancer risk (ILCR) for human adults and children. Estimated ILCR was within safe limit (10^?6?10^?5), indicating low risk to human population. Potential risk to contaminated ground water from leaching of carcinogenic PAHs was assessed by estimating the Index of Additive Cancer Risk (IACR).     

Biodegradation of diesel oil in a baffled roller bioreactor

BACKGROUND: Ex situ bioremediation is a feasible and economical way to remove petroleum pollutants from contaminated soil or water. A baffled roller bioreactor was shown to be effective for biodegradation of diesel oil as a model petroleum pollutant. Microorganisms enriched from an industrially contaminated soil with heavy hydrocarbons were shown to be the best inoculum source for diesel biodegradation. RESULTS: The baffled roller bioreactor demonstrated better performance than control (roller bioreactor without baffles) or bead mill roller (control bioreactor filled partially with spherical beads) bioreactors. Biodegradation consisted of both fast and slow stages for degradation of light and heavy compounds, respectively. Among the tested temperatures ranging from 15 to 35 °C, room temperature (23 °C) was found to be the optimum temperature for biodegradation. The values of maximum specific growth rate and substrate yield (µ_max and Y_XS) for the indigenous microorganisms in the baffled roller bioreactor at room temperature were found to be 0.72 ± 0.08 h^?1 and (7.0 ± 1.0) × 10⁷ cells mg^?1 diesel, respectively. Biodegradation of diesel concentrations up to 200 g L^?1 was achieved with the highest biodegradation rate of 266 mg L^?1 h^?1 at the highest rotation rate of 45 rpm in the baffled roller bioreactor. CONCLUSION: Using indigenous bacteria enriched from industrial contaminated soil at room temperature, a baffled roller bioreactor is able to biodegrade high diesel oil concentrations at high biodegradation rates. Copyright © 2008 Society of Chemical Industry     

Occurrence and Source Apportionment of Polycyclic Aromatic Hydrocarbons in Urban Residential Soils from National Capital Region,Uttar Pradesh,India

This study aims to investigate the level of priority polycyclic aromatic hydrocarbons (PAHs) and identification of their potential sources in residential soils. During the study, a total 36 soil samples collected from twelve residential locations at Sahibabad-Ghaziabad area of western Uttar Pradesh, India, a constituted part of the National Capital Region of India. Samples extracted using ultrasonication, cleaned with silica and analyzed by diode array detector–high-performance liquid chromatography using acetonitrile/water as mobile phase. The 25th and 75th percentile concentration of ∑PAHs was 264 μg kg^?1 and 584 μg kg^?1, respectively, with mean and median of 445 μg kg^?1 and 421 μg kg^?1. The detection frequency of PAHs in all samples was lower for low molecular weight PAHs (19%) than high molecular weight PAHs (81%). The concentration of seven probable carcinogenic PAHs accounted for 67% of the ∑PAHs. PAHs toxicity potential as benzo(a)pyrene toxicity equivalent ranged between 2.52–253 μg BaP_TEQ kg^?1. Composition profile of PAHs with different aromatic rings and selected diagnostic molecular ratios suggested the local pyrogenic sources of PAHs from vehicular emissions, diesel engines, biomass combustion, gasoline, and coal combustions.     

Biodegradation of High Molecular Weight Polycyclic Aromatic Hydrocarbons Mixture by a Newly Isolated Fusarium sp. and Co-Metabolic Degradation with Starch

One native fungal strain, designated ZH-H2, was isolated from an agricultural soil contaminated by HMW-PAHs in a typical coal mining area of Hebei, China. The filamentous fungus was identified as a Fusarium sp. ZH-H2 was able to survive not only in the presence of the individual HMW-PAHs of Chry, BaA, B(K)F, BaP, DB(a,h)A, InP, InP and B(g,h,i)p but in the presence of a mixture of the above seven HMW-PAHs with a total concentration of up to 10 mg L^?1. Biodegradation experiments demonstrated that Fusarium sp. (ZH-H2) was able to degrade the aforementioned individual HMW-PAHs, with a degradation percentage of 77%, 85%, 91%, 42%, 56%, 42% and 38%, respectively, and degrade the aforementioned seven PAHs mixture with a degradation percentage of 48%. The effect of starch addition on the biodegradation efficiency of the PAH mixture was also investigated. The results showed a significant improvement in the degradation extent of the PAH mixture with the increase of starch concentration. The greatest degradation rate (DR; 89%) in 7 d was obtained when starch was added at 1.0 g L^?1, about 2-fold than was achieved without starch. This study implicates that Fusarium sp. (ZH-H2), a potential biodegrader, is suitable for practical field application in effective bioremediation of soils that have been simultaneously contaminated by several HMW-PAHs for a long time.     

Comparing phenanthrene degradation by alginate‐encapsulated and free Pseudomonas sp. UG14Lr cells in heavy metal contaminated soils

BACKGROUND: Many polycyclic aromatic hydrocarbon (PAH) contaminated sites also contain high levels of toxic heavy metals. The presence of heavy metals can adversely affect PAH biodegradation. Encapsulation of bacterial cells has been shown to improve survival and activity of cells under various environmental stresses. This study examined if encapsulation of a phenanthrene‐mineralizing bacterial strain could improve its survival and phenanthrene degradation in heavy metal contaminated soils. RESULTS: Alginate encapsulation did not improve survival and phenanthrene degradation by Pseudomonas sp. UG14Lr in heavy metal contaminated soil. Phenanthrene degradation by, and survival of, free cells and alginate‐encapsulated cells were similar in soil contaminated with 5 mg kg^?1 dry soil of As, Cd, or Pb. The number of UG14Lr cells decreased to undetectable level when the concentration of each heavy metal was increased to 100 mg kg^?1 dry soil. UG14Lr, when inoculated as free cells, survived the best and they were detected over 60 days of incubation in soil. Cells in both wet and dry alginate beads survived less well than free cells at the higher metal concentrations. Correspondingly, phenanthrene degradation in soil inoculated with free UG14Lr was better than that in soil inoculated with alginate‐encapsulated cells. CONCLUSION: Alginate encapsulation adversely affected the survival and phenanthrene degradation ability of UG14Lr cells in heavy metal contaminated soil. It is postulated that alginate may have concentrated the metals which in turn increased the toxicity to UG14Lr cells. The results are of interest to those interested in the use of encapsulation technology to formulate microbial cells for bioremediation purposes. Copyright © 2009 Society of Chemical Industry     

The Effect of Polycyclic Aromatic Hydrocarbons on the Structure of Organotrophic Bacteria and Dehydrogenase Activity in Soil

The objective of this article was to determine the structure of microbial communities and the activity of dehydrogenases in soil samples contaminated with four polycyclic aromatic hydrocarbons (PAHs), i.e., naphthalene, phenanthrene, anthracene, and pyrene, in the amount of 0, 1000, 2000, and 4000 mg kg^?1soil DM. Organic substances—cellulose, sucrose, and compost—were added to the samples in the amount of 0 and 9 g kg^?1soil DM. The experiment was performed in a laboratory on samples of loamy sand. Indices of colony development (CD) and eco-physiological diversity (EP) of organotrophic bacteria, soil resistance (RS), and soil resilience (RL) were calculated. Soil contamination with PAHs differentiated the structure of organotrophic bacteria, and the lowest CD and EP values were noted in soil samples containing pyrene. PAHs inhibited the activity of dehydrogenases, and pyrene exerted the most inhibitory effect on enzyme activity. Dehydrogenase activity was determined mainly by the applied PAH dose, the date of analysis and the type of organic substance added to soil. Low RL values indicate that exposure to PAHs induces long-term changes in dehydrogenase activity.     

Biosorption of Lead by Immobilized Biomass of Brevundimonas vesicularis: Batch and Column Studies

The objective of the present study was to evaluate the feasibility of a strategy to remove lead [Pb(II)] from aqueous waste using Brevundimonas vesicularis, a bacterial species isolated from contaminated soil. Batch studies were conducted using free and immobilized biomass and the optimum conditions for removal of lead from solutions were determined. The maximum specific lead uptake of the dry biomass was found to be 12.4 mg g^?1. Column study was conducted using immobilized biomass and the maximum specific lead uptake was 74.8 mg g^?1. It is concluded that Brevundimonas vesicularis is a promising biosorbent to remove lead from contaminated wastewater.     

Microbial uptake of diesel oil sorbed on soil and oil spill clean‐up sorbents

Sorbent effects in the microbial uptake of diesel oil were determined for black cotton soil (BCS) and two oil spill clean‐up sorbents, ie peat sorb and spill sorb. Biodegradation studies were conducted in mass transfer limited batch slurry microcosms using microorganisms capable of direct interfacial uptake of diesel oil. Under identical loading conditions, the amounts of diesel oil initially loaded on the various sorbents were 178, 288 and 649 mg g^?1 for BCS, spill sorb and peat sorb, respectively. Total biodegradation of sorbed diesel was comparable for all the sorbents (45–52 mg), however, the biodegradation rates were significantly different. Peat sorb demonstrated a distinct initial lag phase, the biodegradation rate in spill sorb was initially slower, whereas biodegradation at a high rate commenced immediately for BCS. The maximum biodegradation rates observed for BCS, spill sorb and peat sorb microcosms were 7.9, 5, and 2.9 mg day^?1, respectively. Thus, the maximum biodegradation rate increased as the diesel oil loading decreased. Our results indicate that spill clean‐up sorbents have greater bioavailability limitations compared with soils and this is linked with their significantly higher loading capacity and internal porosity. Copyright © 2005 Society of Chemical Industry     

Single and Combined Application of Ozonation and Coagulation/Flocculation for Humic Acid Removal

Humic acids are often found in surface and ground waters as a result of organic matter decay. In this study, water samples containing 50 mgL^?1 humic acid were treated by conventional application of coagulation/flocculation technique. The results showed 70% ±10 turbidity, ≥82% ±10 UV₂₅₄ absorbance and 85% ±10 total organic carbon removal under pH 5–9 and above 5 mgL^?1 Fe³⁺ coagulant doses. Application of post-ozonation significantly increased the UV₂₅₄ absorbance and turbidity removal under low dose Fe³⁺ application. On the other hand ozonation prior to coagulation/flocculation process altered the structure of HA and caused no significant improvement in removal efficiencies.     

Biodegradation Capability and Enzymatic Variation of Potentially Hazardous Polycyclic Aromatic Hydrocarbons—Anthracene and Pyrene by Anabaena fertilissima

This study encompasses the biodegradation capacity of Anabaena fertilissima to model PAH (Polycyclic Aromatic Hydrocarbon) compounds namely Anthracene (ANT) and Pyrene (PYR) at different LC₅₀ concentrations viz., 5.0 mg/L and 3.0 mg/L, respectively, on growth in terms of Chlorophyll-a and protein. Depletion in chlorophyll-a and protein content was registered with rise in PAHs concentration while the inhibition of nitrogen fixing enzymes such as nitrate reductase and glutamine synthetase activity was also concentration dependent and showed more sensitivity for high molecular weight aromatic compound PYR as compared to ANT. GC/MS analysis explained the degradation of ANT by 46% and PYR by 33%, at 5.0 mg/L and 3.0 mg/L, respectively. Moreover, the common degraded product for ANT was 2, 4-Dimethyl-1-heptene and for PYR it was 2, 3, 4-Trimethylhexane. Results indicate that PYR was more stable and recalcitrant compared to ANT. This study suggests that Anabaena fertilissima could be used for bioremediation of ANT and PYR pollution in surface waters and terrestrial environments.     

Sensitive molecular determination of polycyclic aromatic hydrocarbons based on thiolated Calix[4]arene and CdSe quantum dots (QDs)

A novel and sensitive electrochemical sensor based on the cone conformation of the supramolecule 25, 27-(3-thiopropoxy)-p-tert-butyl calix[4]arene has been developed for quantitative determination of polycyclic aromatic hydrocarbons (PAHs). The method works effectively by immobilizing calix[4]arenes on Fe₃O₄ magnetic nanoparticles. CdSe quantum dots were used as electrochemical labels. CdSe quantum dots (QDs) modified PAHs in competition with the sample PAHs were intercalated into calix[4]arenes supramolecules via a host–guest interaction through individual bowl-shaped calix[4]arenes. The stripping analysis of the cadmium dissolved from CdSe nanoparticles provided a sensitive method for the detection of PAHs in the samples. The signal decrease of the QDs was proportional to the increase in the concentration of the PAHs. Under optimal conditions, among the five PAHs, the square wave voltammetry (SWV) response of QDs decreased linearly for anthracene and naphthalene in the range of 2.1 × 10^?7–1.4 × 10^?5 and 1.5 × 10^?6–2.5 × 10^?5 M, respectively. The calculated detection limits (3δ) were 20.1 ng mL^?1 for anthracene and 105.5 ng mL^?1 for naphthalene.     

Crop yields and soil organic carbon fractions as influenced by straw incorporation in a rice–wheat cropping system in southeastern China

In agro-ecosystems, the relationship between soil fertility and crop yield is mediated by manure application. In this study, an 8-year field experiment was performed with four fertilizer treatments (NPK, NPKM₁, NPKM₂, and NPKM₃), where NPK refers to chemical fertilizer and M₁, M₂, and M₃ refer to manure application rates of 15, 30, and 45 Mg ha^?1 year^?1, respectively. The results showed that the NPKM (NPKM₁, NPKM₂, and NPKM₃) treatments produced greater and more stable yields (4.95–5.45 Mg ha^?1 and 0.59–0.75) than the NPK treatment (4.01 Mg ha^?1 and 0.50). Crop yields under the NPKM treatments showed two trends, with a rate of decrease of 0.48–0.83 Mg ha^?1 year^?1 during the first 4 years and a rate of increase of 0.10–0.25 Mg ha^?1 year^?1 during the last 4 years. The soil organic carbon (SOC) significantly increased under all treatments. The estimated annual SOC decomposition rate was 0.35 Mg ha^?1 year^?1 and the equilibrium SOC level was 6.22 Mg ha^?1. Soil total nitrogen (N), available N, total phosphorus (P) and available P under the NPKM treatments increased by 0.15–0.26, 15–33, 0.17–0.66 and 45–159 g kg^?1, respectively, compared with the NPK treatment. Manure application mainly influenced crop yield by affecting the soil TN, available N, and available P, which accounted for up to 64% of the crop yield variation. Taken together, applying manure can determine or at least improve the effects of soil fertility on crop yield in acidic soils in South China.     

Biological treatment of high salinity produced water by microbial consortia in a batch stirred tank reactor: Modelling and kinetics study

This study was performed to evaluate the potential of acclimated halophilic microorganisms, commercial microorganisms, and microorganisms from polluted soil to degrade crude oil in high salinity oily wastewater (synthetic produced water) at different salt concentrations ranging from zero to 250,000?mg?L^?1 of total dissolved solids (TDS). The highest degradation of crude oil (>60%) was found for acclimated halophilic microorganisms at TDS of 35,000?mg?L^?1. An increase in the TDS concentrations above 145,000?mg?L^?1 leads to a significant decrease in the growth of microorganisms. The results showed that efficiency of the commercial microorganisms was less than the acclimated halophilic microorganisms. The oil biodegradation followed substrate inhibition kinetics and the specific growth rate were fitted to the Haldane model. The biokinetic constants for the saline oily water at TDS of 35,000?mg?L^?1, i.e., Y, K_s, µ_max, and 1/K_i, were 0.21?mg?MLSS/mg crude oil, 0.27?mg?L^?1, 0.019?h^?1, and 0.002?mg?L^?1, respectively.     

Nitrate leaching from organic and conventional arable crop farms in the Seine Basin (France)

In the Seine Basin, characterised by intensive arable crops, most of the surface and groundwater is contaminated by nitrate (NO₃ ^?). The goal of this study is to investigate nitrogen leaching on commercial arable crop farms in five organic and three conventional systems. In 2012–2013, a total of 37 fields are studied on eight arable crop rotations, for three different soil and climate conditions. Our results show a gradient of soil solution concentrations in function of crops, lower for alfalfa (mean 2.8 mg NO₃-N l^?1) and higher for crops fertilised after legumes (15 mg NO₃-N l^?1). Catch crops decrease nitrate soil solution concentrations, below 10 mg NO₃-N l^?1. For a full rotation, the estimated mean concentrations is lower for organic farming, 12 ± 5 mg NO₃-N l^?1 than for conventional farming 24 ± 11 mg NO₃-N l^?1, with however a large range of variability. Overall, organic farming shows lower leaching rates (14–50 kg NO₃-N ha^?1) than conventional farms (32–77 kg NO₃-N ha^?1). Taking into account the slightly lower productivity of organic systems, we show that yield-scaled leaching values are also lower for organic (0.2 ± 0.1 kg N kg^?1 N year^?1) than for conventional systems (0.3 ± 0.1 kg N kg^?1 N year^?1). Overall, we show that organic farming systems have lower impact than conventional farming on N leaching, although there is still room for progress in both systems in commercial farms.     

The Ozone Treatment for Nitrogen Removal from Liquid Wastes at High Salinity: Full-Scale Optimization and Economical Aspect

The study involved the optimization of the flow scheme of a full-scale platform for industrial liquid wastes. Non-hazardous liquid wastes from natural gas extraction (spent brine) represent 26% of the total influent wastes. For elevated salinity this waste is strongly inhibitory for traditional biological processes. The implementation of the treatment solution is represented by advanced oxidation with ozone in a separate line to remove the ammonia nitrogen with the direct transformation in nitrogen gas. The ratio of bromides/nitrogen greater than 0.4 was evaluated as being the determining factor to activate the process. Ammonia, without the formation of secondary nitrogen compounds, decreases up to 21 mgL^?1 dosing 300 mgO₃ L^?1 and equal to 0 mgL^?1 at maximum ozone. In addition, the catalytic effect of bromides determines a reduction of nitrate to final concentrations of 5 mgL^?1. Any carcinogenic compounds, such as bromates, or residual stripped ammonia were not noted. The economical evaluation was reported.     

Indoor Polycyclic Aromatic Hydrocarbon Concentration in Central India

The indoor burning of different materials like fuels, incense, mosquito coil, candles etc. results in generation of polycyclic aromatic hydrocarbons (PAHs) in an uncontrolled manner. The PAH, i.e., Benzo(a)pyrene (BaP) is considered as most toxic or carcinogenic and the toxicity of other PAHs is related to this compound. Therefore, the concentration and emission fluxes of polycyclic aromatic hydrocarbons (PAHs) emitted during burning of commonly used indoor materials, i.e., 15 fuels (i.e., biomass (BM), coal (C), cow dung (CD), kerosene (K)), 4 incense (IS) and mosquito coil (MC) in Raipur district, Chhattisgarh, central India is described. The samples were taken in September 2013 in indoor environments and respective smoke emitted were collected using high volume United State of America (USA) air sampler on quartz fiber filters. The concentration of total 13 PAHs (∑PAH₁₃) (i.e., phenanthrene, anthracene, fluoranthene, pyrene, benz(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)-pyrene, dibenz(ah)anthracene, benzo(ghi) perylene, indeno1,2,3-(cd)pyrene, and coronene) in particulate matter (PM₁₀) in the indoor air during burning of the fuels, IS and MC materials ranged from 367–92052 ng m^?3, 4089–14047 ng m^?3, and 66–103 ng m^?3 with mean values of 7767 ± 11809 ng m^?3, 9977 ± 4137 ng m^?3, and 74 ± 20 ng m^?3, respectively. The mean concentration of the ∑PAH₁₃ present in indoor environment is much higher than the WHO limit value of 1.0 ng m^?3. The sources and toxicities of PAHs are discussed.     

Removal of polycyclic aromatic hydrocarbons from soil using surfactant and the white rot fungus Phanerochaete chrysosporium

The bioremediation of soil contaminated with polycyclic aromatic hydrocarbons (PAH) is often limited by a low bioavailability of the contaminants. Non‐ionic surfactants, such as Tween 80, when above their critical micelle concentration (CMC), can efficiently enhance the bioavailability of PAHs in contaminated soil by increasing solubility and dissolution rates. However, disposing of this micelle‐contaminated spent washwater can be a major problem. The aim of this study was to combine surfactant soil washing techniques using Tween 80 with the versatile lignin‐degrading system of the white rot fungus, Phanerochaete chrysosporium, to bioremediate PAH‐contaminated soil. Approximately 85% (w/w) of a total of nine PAHs in an aged (1 month) contaminated soil (total PAH concentration = 403.61 µg g⁻¹) could be solubilized in a 2.5% (w/v) Tween 80 solution at a soil/water ratio of 1:10. The washwater was then catabolized by a 3‐day‐old culture of P chrysosporium under a stationary condition. The disappearance of most PAHs tested (molecular weight ≥ 178) correlated well with their ionization potentials and 66.4% (w/w) of the total PAHs in washwater with 2.5% (w/v) Tween 80 was catabolized after 11 days of culture. The catabolism was enhanced to 86% (w/w) using a lower concentration of 0.5% (w/v) Tween 80. The initial oxidation rate of total PAHs based on the first 4 days of culture remained almost constant at approximately 1.88 µg cm⁻³day⁻¹ when the Tween 80 concentration in washwater was increased from 0.5% to 2.5% (w/v). The combination of soil washing and white rot fungus catabolization of PAH using 2.5% (w/v) Tween 80 eliminated the total PAH concentration in the contaminated soil by 56.4% (w/w) after 11 days. The results suggest that PAH‐contaminated soil may be cleansed by using a combination of surfactant soil washing and white rot fungus catabolism. © 2000 Society of Chemical Industry