Gasoline-contaminated Soil Research Articles

Biostimulation of a novel native Bacillus strain capable of degrading gasoline

The contamination of soil with hydrocarbons is a significant ecological issue worldwide, posing a threat to the ecosystem. Therefore, it is crucial to develop environmentally friendly and effective techniques to eliminate pollutants using biological agents. This study aimed to isolate, characterize, and evaluate bacteria capable of degrading gasoline. Soil samples contaminated with gasoline were collected and diluted up to 10-10. Pure cultures were obtained by streaking dilutions of 10-7, 10-6, and 10-5 on nutrient agar. These pure cultures were then inoculated on a selective medium (Bushnell Haas minerals agar). The isolates were characterized based on their growth patterns using morphological characteristics, optical density measurement, and biochemical tests. As a result, five gasoline-degrading bacteria were identified as B. mojavensis and B. licheniformis. Two biodegradation experiments were conducted using low and high concentrations of gasoline (0.01/10 and 0.001/10 mL, respectively) over a period of 14 days. Furthermore, the bacterial strains were stimulated by adding nitrogen and phosphorus to evaluate their efficiency in degrading gasoline. The results showed that B. mojavensis has the potential to degrade gasoline more effectively than the other isolate. Additionally, the addition of nitrogen minerals enhanced the ability of this isolate to degrade gasoline. Conversely, the performance of B. licheniformis in degrading gasoline was improved with the addition of nitrogen and phosphorus. This study demonstrates the effectiveness of Gram-positive bacteria in gasoline degradation and highlights the potential of the genus B. mojavensis for in situ remediation of gasoline-contaminated soils.

Energy Quality of Corn Biomass from Gasoline-Contaminated Soils Remediated with Sorbents

Soil contaminated with petroleum-derived products should be used to cultivate energy crops. One such crop is Zea mays. Therefore, a study was performed to determine the suitability of Zea mays biomass obtained from gasoline-contaminated soil for energy purposes. The analysis included determining the heat of combustion and calorific value of the biomass, as well as the content of nitrogen, carbon, hydrogen, oxygen, sulfur, and ash in the biomass. Additionally, the suitability of vermiculite, dolomite, perlite, and agrobasalt for the phytostabilization of gasoline-contaminated soil was evaluated. It was found that the application of sorbents to gasoline-contaminated soil significantly reduced the severe negative effects of this petroleum product on the growth and development of Zea mays. Gasoline contamination of the soil caused a significant increase in ash, nitrogen, and sulfur, along with a decrease in carbon and oxygen content. However, it had no negative effect on the heat of combustion or calorific value of the biomass, although it did reduce the energy production from Zea mays biomass due to a reduction in yield. An important achievement of the study is the demonstration that all the applied sorbents have a positive effect on soil stabilization, which in turn enhances the amount of Zea mays biomass harvested and the energy produced from it. The best results were observed after the application of agrobasalt, dolomite, and vermiculite on gasoline-contaminated soil. Therefore, these sorbents can be recommended for the phytostabilization of gasoline-contaminated soil intended for the cultivation of energy crops.

Diversity of bacterial phenol hydroxylase-encoding genes from gasoline-contaminated silt soil

Abstract. Vasandani SR, Tan WA. 2022. Diversity of bacterial phenol hydroxylase-encoding genes from gasoline-contaminated silt soil. Biodiversitas 23: 5502-5506. Phenol is an aromatic compound often used as a raw material or intermediate in various industries. Improper handling and disposal may lead to the accumulation of this hazardous compound. Bioremediation is the most viable method to remove phenol from contaminated environment. In this study, the diversity of genes that encode for phenol hydroxylase, a key enzyme in phenol degradation, was assessed in gasoline-contaminated soil from a commercial gas station in Central Jakarta, Indonesia. Partial phenol hydroxylase-encoding gene library was constructed using a pair of universal primer in the pGEM®-Teasy vector. A total of 30 recombinant clones were obtained and sequenced to analyze the genetic diversity of this gene. Obtained clones were 86-99% identical to phenol hydroxylase-related proteins. Phylogenetic tree analysis on amino acid sequences derived from our library revealed that 56.7% of the cloned fragments were closely related to Proteobacteriodota and 20.0% of them were clustered with Actinomycetota. The rest 23.3% of the clones formed a cluster separate from any of the reference sequences, possibly indicating the presence of novel phenol hydroxylase genes.

Biodegradable Composites Made by Cassava Peels, Residual Glycerin, Bentonite, and Zeolite: The Contribution to the Treatment of BTEX in Gasoline-Contaminated Soils

Biodegradable Composites Made by Cassava Peels, Residual Glycerin, Bentonite, and Zeolite: The Contribution to the Treatment of BTEX in Gasoline-Contaminated Soils

Effects of contamination with gasoline on engineering properties of fine-grained silty soils with an emphasis on the duration of exposure

Leaking tanks may lead to severe contamination of their surrounding soil. The geotechnical behavior of the soil varies with the physicochemical processes that occur between the contaminant and the soil. In this respect, studying the geochemical properties of gasoline-contaminated soils and sediments seems to be important for engineering and especially environmental purposes. In this paper, laboratory tests were carried out to examine the effects of crude gasoline contamination on some of the geotechnical properties of a silty soil sampled from the Mashhad plain, located in the northeast of Iran. Tests consisted of basic properties, Atterberg limits, compaction, direct shear, and uniaxial compression tests, which were carried out on clean and contaminated soil samples at the same densities. The contaminated samples were prepared by mixing the soils with crude gasoline in the amounts of 3%, 6%, 9%, and 12% of dry weight and curing periods of 0, 7, 15, and 30 days. Results indicated a decrease in the friction angle and an increase in the cohesion of the soil by increasing gasoline content. Besides, a reduction in the maximum dry density and optimum moisture content was observed in the compaction test. The increase in gasoline percentage up to 6% also showed a direct effect on increasing the liquid limit and plastic limit of silty soil, which decreased thereafter. Moreover, any increase in gasoline percentage had a reverse effect on the modulus of elasticity of the soil. The increase in gasoline percentage up to 3% also had a direct impact on the uniaxial compressive strength of the soil, exceeding which it started to decline. Finally, the effects of contamination duration were examined by testing contaminated samples in periods of 7, 15, and 30 days under natural conditions. The results showed a reverse relationship with all geotechnical properties due to aging and a reduction in the gasoline content due to the evaporation of volatile compounds. Also, the numerical analysis of the laboratory results indicated an increase in settling and the percentage of shear strain beneath the foundation with increasing the contamination level, confirming the laboratory results.

Stable Isotope Probing Implicates Pseudomonas as the Methanogenic Toluene Degrader in Gasoline-Contaminated Soil

Stable Isotope Probing Implicates Pseudomonas as the Methanogenic Toluene Degrader in Gasoline-Contaminated Soil

Bioremediation of diesel and gasoline-contaminated soil by co-vermicomposting amended with activated sludge: Diesel and gasoline degradation and kinetics

Present study aims to examine the efficiency of co-vermicomposting amended with activated sludge and E. fetida earthworm for bioremediation of diesel and gasoline from contaminated soil. The diesel and gasoline removal efficiency and degradation rates coefficients were estimated with gas chromatography (GC) analysis and first-order kinetics. The removal of gasoline and diesel in different co-vermicomposting processes with and without E. fetida ranged between 65-100% and 24.94–63.93%, respectively within 90- day experiment. Removal of gasoline and diesel increased in soil with addition of earthworm (E. fetida); higher degradation rate coefficients (k) were observed for co-vermicomposting with earthworm compared with co-vermicomposting processes. The highest k (0.014) for diesel degradation was estimated for microcosm reactor 4 (R4), where high numbers of E. fetida accelerate the less biodegradable organic contaminant from the soil matrices. The reasonable survival rates of earthworms in exposure to high concentration of petroleum-derivatives contaminated soils indicated increased activity of ligninolytic diesel–degrading earthworms and microorganisms. Therefore, co-vermicomposting amended with activated sludge is suggested as feasible and promising technologies for bioremediation of high content of organic contaminants from the soil matrices.

Microbial diversity changes and enrichment of potential petroleum hydrocarbon degraders in crude oil-, diesel-, and gasoline-contaminated soil.

This study investigated the impacts of crude oil, diesel, and gasoline on the diversity of indigenous microbial communities as well as culturable microorganisms in the studied soil. Oil contamination led to shifts in thediversityofthesoil'smicrobialcommunities, regardless of the contaminant applied. Unpolluted soils were more diverse and evenly distributed than contaminated samples. The domain Bacteria accounted for 65.15% of the whole microbial community. The bacterial phylum Proteobacteria dominated in all samples, followed by Actinobacteria and Acidobacteria. Pseudomonas with 28.15% of reads dominated in Proteobacteria, while Rhodococcus (3.07%) dominated in Actinobacteria, and Blastocatella (2.53%) dominated in Acidobacteria. The dominant fungal phyla across all samples were Ascomycota dominated by Penicillium (50.48% of sequences), and Zygomycota dominated by Mortierella (16.87%). Sequences similar to the archaeal phyla, Euryarchaeota and Thaumarchaeota, were also detected. The number of culturable microorganisms increased following the contamination and was higher in contaminated samples than in clean samples. Oil contamination also resulted in the enrichment of oil-degrading strains. Two bacteria, Serratia marcescens strain PL and Raoultella ornithinolytica PS, which were isolated from crude oil-contaminated soil, exhibited strong crude oil degradation ability. Strain PL was the most efficient strain and degraded 75.10% of crude oil, while strain PL degraded 65.48%, after 20days of incubation. However, the mixed culture of the two strains was more effective than single strain and could achieve up to 96.83% of crude oil degradation, with a complete abatement of straight-chain hydrocarbons (from C12 to C25), and more than 91% removal of highly branched hydrocarbons, phytane and pristane, which are known to be more recalcitrant to biodegradation. Strains PS and PL are two newly isolated crude oil degraders that are not among the most prominent crude oil-degrading strains referenced in the literature. Therefore, their high degradation capacity makes them perfect candidates for the bioremediation of petroleum hydrocarbon contaminated environments.

Sphingobium terrigena sp. nov., isolated from gasoline-contaminated soil.

A Gram-stain-negative, strictly aerobic bacterial strain, designated EO9T, was isolated from gasoline-contaminated soil in the Republic of Korea. Cells were non-motile short rods showing catalase- and oxidase-positive reactions. Growth was observed at 10-37 °C (optimum, 30 °C), at pH 6.0-9.0 (pH 6.5) and in the presence of 0-0.5 % (w/v) NaCl (0 %). Ubiquinone-10 (Q-10) and spermidine were identified as the predominant respiratory quinone and polyamine, respectively. Summed feature 8 (comprising C18:1ω7c/C18:1ω6c), summed feature 3 (comprising C16:1ω7c/C16:1ω6c), C16:0 and C14:0 2-OH were identified as major cellular fatty acids. The major polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, sphingoglycolipid, phosphatidylglycerol and an unidentified phospholipid. The G+C content of the genomic DNA was 62.8 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain EO9T formed a tight phylogenetic lineage with Sphingobium xenophagum NBRC 107872T and Sphingobium hydrophobicum C1T within the genus Sphingobium. Strain EO9T was most closely related to S. xenophagum NBRC 107872T (97.2 %) and S. hydrophobicum C1T (97.2 %), but DNA-DNA relatedness levels between strain EO9T and the type strains of S. xenophagum and S. hydrophobicum were 37.1 and 36.8 % , respectively. Based on its phenotypic, chemotaxonomic and molecular features, strain EO9T clearly represents a novel species of the genus Sphingobium, for which the name Sphingobium terrigena sp. nov. is proposed. The type strain is EO9T (=KACC 19523T=JCM 32762T).

Effect of oil-contamination and water saturation on the bearing capacity and shear strength parameters of silty sandy soil

This study investigates the effect of oil contamination and water saturation on the geotechnical properties of silty sandy soil. The silty sandy soil (SM) in this study was obtained from Prachuap Khiri Khan Province, Thailand, and the contaminant product was 95 octane gasoline. The SM soils were prepared in a tank model under the conditions of dry soil, soil with a water level, gasoline-contaminated soil of 2%, and gasoline-contaminated soil of 4%. A laboratory experiment (direct shear test) and a field experiment (lightweight penetration test) were performed on SM soil for all conditions. The lightweight penetration test results indicate that the ultimate bearing capacity in the case of soil with water saturation decreases by 90% on average compared to the dry soil condition. The ultimate bearing capacity for the gasoline-contaminated SM soils of 2% and 4% decrease by 30% and 52%, respectively, on average compared to the dry soil condition. Moreover, the internal friction angle obtained from the direct shear test linearly decreases with the gasoline content and reduces by at least half in the case of water saturation. The cohesion of the oil-contaminated SM soils increases with increasing oil content as according to the second-order polynomial regression, and the dry soil and saturated soil have similar cohesions. These results reveal that the oil contamination and water saturation cause the loss of shear strength and reduce the ultimate bearing capacity of SM soil.

Requirement of ecological replication with independent parallel analysis of each replicate plot to support soil remediation

Consequences of pseudoreplication or the sole use of plot averages even within one ecosystem on the reliability of laboratory remediation tests have barely been studied even though they may mask field variability. Soils from three field plots were tested separately to reveal the consequences of inadequate use of replicates. Parallel remediation experiments consisting of treatments control (non-contaminated soil), natural attenuation (gasoline-contaminated soil) and biostimulation (gasoline-contaminated and methylene urea fertilized soil) were conducted to each plot soil. Three destructive sampling days and three pseudoreplicates per treatment, per plot and per sampling day were designed. The concentrations of total and individual gasoline aromatics were followed using both within-plot pseudoreplicates and plot averages. Results showed that natural attenuation of total or individual gasoline aromatics depended on field plots and that fertilization showed enhancing, inhibiting and negligible effects, respectively, also depending on field plots. Additionally, plot averages masked within-treatment variation between field plots. Conclusively, within-plot pseudoreplication using a single field plot or interpretations based solely on plot averages cannot reveal remediation patchiness observed in practice. Due to the high soil heterogeneity, ecological between-plot replication together with the parallel analysis of each replicate is encouraged in laboratory studies aiming to design in situ remediation strategies.

Evaluation of the Potential of Burningbush (Kochia scoparia (L.) Schard) and Maize (Zea mays L.) and the Role of Soil Organic Amendment in Phytoremediation of Gasoline-Contaminated Soils

A greenhouse study was conducted to investigate the performance of burningbush (Kochia scoparia (L.) Schard) and maize (Zea mays L.) in removal of hydrocarbons from soils contaminated with different levels of gasoline. Plants’ capability to grow in gasoline-spiked soils was also evaluated. Additionally, peat fertilizer applied to selected treatments to identify the role of organic amendment of soil on plant growth and remediation potential in contaminated soil. Both studied plant species were found to tolerate gasoline contamination up to the highest applied concentration, i.e., 10,000 mg/kg; however, seedling emergence and subsequent growth were affected in the presence of various levels gasoline in soil. Germination, biomass and root length of burningbush and maize significantly decreased in the presence of higher levels of gasoline (P < 0.05). Positive influence of soil amendment with peat on plant growth and phytoremediation performance was achieved. Remediation ability of both plant species was altered by variation in gasoline content of soil. For instance, increase in gasoline content of unamended soils from 1000 to 10,000 mg/kg reduced hydrocarbon dissipation in the rhizosphere of burningbush from 92.48 to 79.44%. Burningbush and maize demonstrated considerable remediation ability over the course of experiment, with slightly higher effectiveness for burningbush both in amended and in unamended soils. Results indicated that high tolerance and biomass establishment of a given plant species in gasoline-contaminated soil, as observed for burningbush and maize, may imply promising phytoremediation performance.

Paraburkholderia aromaticivorans sp. nov., an aromatic hydrocarbon-degrading bacterium, isolated from gasoline-contaminated soil.

A Gram-stain-negative, facultatively aerobic, aromatic hydrocarbon-degrading bacterium, designated strain BN5T, was isolated from gasoline-contaminated soil. Cells were motile and slightly curved rods with a single flagellum showing catalase and oxidase activities. Growth was observed at 20-37 °C (optimum, 25-30 °C), pH 3-7 (optimum, pH 5-6) and 0-2 % NaCl (optimum, 0 %). Ubiquinone-8 was the predominant respiratory quinone. The major fatty acids were C16 : 0, cyclo-C19 : 0ω8c and summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c). Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified phosphoamino lipid, three unidentified amino lipids and eight unidentified lipids were the identified polar lipids. The DNA G+C content was 62.93 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain BN5T formed a phylogenic lineage with members of the genus Paraburkholderia and showed the highest 16S rRNA gene sequence similarities to Paraburkholderia phytofirmans PsJNT (99.4 %), Paraburkholderia dipogonis DL7T (98.8 %) and Paraburkholderia insulsa PNG-AprilT (98.8 %). The average nucleotide identity and in silico DNA-DNA hybridization (DDH) values between strain BN5T and P. phytofirmans PsJNT were 88.5 and 36.5 %, respectively. The DDH values for strain BN5T with P. dipogonis LMG 28415T and P. insulsa DSM 28142T were 41.0±4.9 % (reciprocal, 33.0±4.3 %) and 47.1±6.6 % (reciprocal, 51.7±5.4 %), respectively. Based on its physiological, chemotaxonomic and phylogenetic features, we conclude that strain BN5T is a novel species of the genus Paraburkholderia, for which the name Paraburkholderia aromaticivorans sp. nov. is proposed. The type strain is BN5T (=KACC 19419T=JCM 32303T).

Soil vapor extraction of wet gasoline-contaminated soil made possible by electroosmotic dewatering\u2013lab simulations applied at a field site

PurposeSoil restoration is still mainly carried out ex situ by excavating and replacing the contaminated soil. In situ remediation would reduce the costs of soil transportation and this way, the problem is not merely transferred elsewhere. The present study introduces a field case where the aged, oil-contaminated soil in a former fuel station in Finland was treated in situ sequentially with different methods.Materials and methodsSeveral approaches, including soil vapor extraction and biostimulation with electrokinetic pumping, were performed in the field. After these treatments, the dense original portion of the soil beneath the gasoline pump location, ca 100 m3, was still contaminated with petroleum-derived volatile organic compounds (VOCs), with concentrations of nearly 10,000 mg kg−1 measured at some hotspots. After a period of electroosmotic water circulation, the electrical field (0.5 V cm−1, DC) was kept connected for 6 months without addition of water, leading to dewatering and warming of the soil.Results and discussionIn contrast to the situation with the original wet soil, VOCs, in lab conditions, were found to volatilize very efficiently from the dewatered soil. When the soil vapor extraction treatment was renewed using perforated tubing installed horizontally at ca 1 m depth in the dewatered soil at the contaminated site, the treatment was efficient and the soil was decontaminated in 5 months. The final VOC concentrations were on average 190 mg kg−1 (n = 13) with the highest value of 700 mg kg−1 at one hotspot. After a risk evaluation, the site was concluded to be sufficiently clean for industrial use.ConclusionsSince with many former fuel stations, the contamination consists of both volatile fractions that are difficult to degrade by biological means and heavier compounds for which biostimulation is often suitable, a combination of different methods may be worth pursuing.

Changes in the microbial community during bioremediation of gasoline-contaminated soil.

We aimed to verify the changes in the microbial community during bioremediation of gasoline-contaminated soil. Microbial inoculants were produced from successive additions of gasoline to municipal solid waste compost (MSWC) previously fertilized with nitrogen-phosphorous. To obtain Inoculant A, fertilized MSWC was amended with gasoline every 3 days during 18 days. Inoculant B received the same application, but at every 6 days. Inoculant C included MSWC fertilized with N–P, but no gasoline. The inoculants were applied to gasoline-contaminated soil at 10, 30, or 50 g/kg. Mineralization of gasoline hydrocarbons in soil was evaluated by respirometric analysis. The viability of the inoculants was evaluated after 103 days of storage under refrigeration or room temperature. The relative proportions of microbial groups in the inoculants and soil were evaluated by FAME. The dose of 50 g/kg of inoculants A and B led to the largest CO2 emission from soil. CO2 emissions in treatments with inoculant C were inversely proportional to the dose of inoculant. Heterotrophic bacterial counts were greater in soil treated with inoculants A and B. The application of inoculants decreased the proportion of actinobacteria and increased of Gram-negative bacteria. Decline in the density of heterotrophic bacteria in inoculants occurred after storage. This reduction was bigger in inoculants stored at room temperature. The application of stored inoculants in gasoline-contaminated soil resulted in a CO2 emission twice bigger than that observed in uninoculated soil. We concluded that MSWC is an effective material for the production of microbial inoculants for the bioremediation of gasoline-contaminated soil.

Stenotrophomonas maltophilia isolated from gasoline-contaminated soil is capable of degrading methyl tert-butyl ether

Background: Methyl tert-butyl ether (MTBE) is a pollutant that causes deleterious effects on human and environmental health. Certain microbial cultures have shown the ability to degrade MTBE, suggesting that a novel bacterial species capable of degrading MTBE could be recovered. The goal of this study was to isolate, identify and characterize the members of a bacterial consortium capable of degrading MTBE. Results: The IPN-120526 bacterial consortium was obtained through batch enrichment using MTBE as the sole carbon and energy source. The cultivable fraction of the consortium was identified; of the isolates, only Stenotrophomonas maltophilia IPN-TD and Sphingopyxis sp. IPN-TE were capable of degrading MTBE. To the best of our knowledge, this report is the first demonstrating that S. maltophilia and Sphingopyxis sp. are capable of degrading MTBE. The degradation kinetics of MTBE demonstrated that S. maltophilia IPN-TD had a significantly higher overall MTBE degradation efficiency and rate (48.39 ± 3.18% and 1.56 ± 0.12 mg L -1 h -1 , respectively) than the IPN-120526 consortium (38.59 ± 2.17% and 1.25 ± 0.087 mg L -1 h -1 , respectively). The kinetics of MTBE removal by both cultures fit first-order and pseudo-first-order reaction models. Conclusions: These findings suggest that S. maltophilia IPN-TD in axenic culture has considerable potential for the detoxification of MTBE-contaminated water. Normal 0 21 false false false ES-TRAD JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria,serif; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:ES-TRAD;}

Phytoremediation of contaminated soils containing gasoline using Ludwigia octovalvis (Jacq.) in greenhouse pots.

Greenhouse experiments were carried out to determine the phytotoxic effects on the plant Ludwigia octovalvis in order to assess its applicability for phytoremediation gasoline-contaminated soils. Using plants to degrade hydrocarbons is a challenging task. In this study, different spiked concentrations of hydrocarbons in soil (1, 2, and 3g/kg) were tested. The results showed that the mean efficiency of total petroleum hydrocarbon (TPH) removal over a 72-day culture period was rather high. The maximum removal of 79.8% occurred for the 2g/kg concentration, while the removal rate by the corresponding unplanted controls was only (48.6%). The impact of gasoline on plants included visual symptoms of stress, yellowing, growth reduction, and perturbations in the developmental parameters. The dry weight and wet weight of the plant slightly increased upon exposure to gasoline until day 42. Scanning electron microscopy (SEM) indicated change to the root and stem structure in plant tissue due to the direct attachment with gasoline contaminated compared to the control sample. The population of living microorganisms in the contaminated soil was found to be able to adapt to different gasoline concentrations. The results showed that L. octovalvis and rhizobacteria in gasoline-contaminated soil have the potential to degrade organic pollutants.

Potential application of a biosurfactant in phytoremediation technology for treatment of gasoline-contaminated soil

Biosurfactants are amphiphilic compounds excreted extracellularly that contain hydrophobic and hydrophilic moieties, allowing them to accumulate between the fluid phases on an organism and thus reduce the surface and interfacial tension. The objectives of this study were to evaluate the potential application of a biosurfactant to the phytoremediation of gasoline-contaminated soil and compare it to other additives such as hydrocarbon degrading bacteria, sodium dodecyl sulphate (SDS) and bacterial culture supernatant. The results showed that the biosurfactant removed a significant amount (up to 93.5%) of the total petroleum hydrocarbons (TPH) compared with the other additives that removed only 85.4% (bacteria), 70.3% (culture supernatant) and 86.3% (SDS). Kinetic analysis showed that the phytoremediation of gasoline-contaminated soils by the biosurfactant fitted pseudo-second-order kinetics with a coefficient of determination (R2) of 0.9318 and a second-order rate constant (k2) of 0.0032 (g TPH/kg plant d). Thus, biosurfactants have strong potential as supporting biocatalysts to increase the performance of phytoremediation technology for soil treatment.

Biodegradation of fuel oxygenates and their effect on the expression of a newly identified cytochrome P450 gene in Achromobacter xylosoxidans MCM2/2/1

Achromobacter xylosoxidans MCM2/2/1 was enriched and isolated from gasoline-contaminated soil and was found to degrade ethyl tert-butyl ether (ETBE) and methyl tert-butyl ether (MTBE) by 41.48% and 34.15%, respectively, in 6 days. Furthermore, the effect of MTBE and TBA on the expression of cytochrome P450 (CYP) of A. xylosoxidans MCM2/2/1 was examined. The presence of the CYP gene in this organism was first confirmed by amplification of a putative 350bp CYP gene fragment followed by identification of the entire gene by genome walking and DNA-sequencing. The identified CYP gene of A. xylosoxidans MCM2/2/1 shares a high similarity of about 88% with the thcB gene of A. xylosoxidans A8. Gene expression studies have shown that the CYP gene is expressed in A. xylosoxidans MCM2/2/1; however, the expression of this gene was altered at different concentrations of MTBE.

Surveillance of the condition of bacteria and Amaranthus viridis in a gasoline contaminated soil

The condition of bacteria and Amaranthus viridis in gasoline-contaminated soil was surveyed. The soil was treated with different concentrations of petrol oil: 0 ml (control), 18, 56, 112, 168 and 224 ml. Each of the concentrations was in triplicates. Seventeen (17) bacterial isolates were recovered from the control soil while twenty (20) bacterial isolates were recovered from the polluted soil. A total of twenty four (24) different genera were recovered from the soil. The organisms areAcinetobacter ceticus, Actinomyces sp, Aerococcus viridians, Alcaligenes paradoxus, Arthrobacter, Bacillus cereus, Bacillus polymxa, Bacillus subtilis, Chromobacterium violaceum, Clostridium sp., Corynebacterium hydrocarbodastus, Corynebacterium kutsceri, Corynebacterium xerosis, Cytophaga sp., Erwinia sp., Flavobacterium sp., Micrococcus luteus, Proteus vulgaris, Pseudomonas fluorescens, Pseudomonas putida, Sarcina ventricule, Serratia sp., Staphylococcus aureus, and Streptococcus sp. The pH, temperature, organic matter content, moisture content and water holding capacity of the soil were determined. A. viridis had 100% germination in both the control (0 ml) and 18 ml gasoline-treated soils while it had delayed germination in the other treatments (56, 112, 168 and 224 ml). The results obtained in this study showed that gasoline spillage posses a great threat to the survival and development of plants. It also revealed that certain bacteria could survive the gasoline-contaminated soil and thus may be useful in biodegradation and/or bioremediation of gasoline contaminated soils. Key words: Surveillance, bacteria, Amaranthus viridis, gasoline, contaminated soil.