Hydrocarbon-contaminated Soil Samples Research Articles

Assessment of the dibenzothiophene desulfurization potential of indigenously isolated bacterial consortium IQMJ-5: a different approach to safeguard the environment

Biodesulfurization is emerging as a valuable technology for the desulfurization of dibenzothiophene (DBT) and its alkylated substitutes, which are otherwise regarded as refractory to other physical and chemical desulfurizing techniques. The inability of the currently identified pure cultures and artificial microbial consortia due to lower desulfurization rate and product inhibition issues has compelled the researcher to look for an alternative solution. Thus, in the present study, an indigenously isolated microbial consortium was employed to tackle the desulfurization issue. Herein, we isolated several kinds of DBT desulfurizing natural microbial consortia from hydrocarbon-contaminated soil samples by conventional enrichment technique. The most effective desulfurizing microbial consortium was sequenced through illumine sequencing technique. Finally, the effect of the products of the desulfurizing pathway (such as 2-hydroxybiphenyl (2-HBP) and sulfate (SO4-2) was evaluated on the growth and desulfurization capability of the isolated consortium. The outcomes of Gibb's assay analysis showed that six isolates followed the "4S" pathway and converted DBT to 2-HBP. Among the isolates, I5 showed maximum growth rate (1.078g/L dry cell weight) and desulfurization activity (about 77% as indicated by HPLC analysis) and was considered for further in-depth experimentation. The analysis of 16S rRNA by high-throughput sequencing approach of the I5 isolate revealed five types of bacterial phyla including Proteobacteria, Bacteroidetes, Firmicutes, Patescibacteria, and Actinobacteria (in order of abundance). The isolate showed significant tolerance to the inhibitory effect of both 2-HBP and SO4-2 and maintained growth in the presence of even about 1.0mM initial concentration of both products. This clearly suggests that the isolate can be an efficient candidate for future in-depth desulfurization studies of coal and other fossil fuels.

Response of Bacteria Isolated from Spent Engine Oil Contaminated Soil to Hydrocarbons, Metals and Antibiotics

ABSTRACT Automobile Mechanic Workshops (AMWs) in Low- and Middle-Income Countries (LMIC) contribute to the problem of soil contamination with petroleum hydrocarbons and toxic heavy metals as a result of indiscriminate disposal of spent engine oil (SEO). Such contaminated soil ecosystems can serve as reservoirs of bacteria harboring adaptive tolerance to metals and hydrocarbons as well as resistance to antibiotics. This study investigated the growth response of bacteria isolated from spent engine oil contaminated soils collected from AMWs in South-West, Nigeria to different concentrations of petroleum hydrocarbons, heavy metals (Cu, Zn, Pb and their mixture) and clinically relevant antibiotics. Sixty percent of the bacterial isolates (n = 192) from the hydrocarbon contaminated soil samples possess the unique ability to metabolize various hydrocarbons, tolerate heavy metals and resist at least one of the tested antibiotics. The isolates were identified as members of the Genera Pseudomonas, Bacillus, Enterobacter, Burkholderia, Micrococcus, Staphylococcus, Actinomycetes, Citrobacter and Serratia. Significant correlation (p < .05) was observed between hydrocarbon utilization and antibiotic resistance. Results showed SEO contamination plays a role in the development and spread of antibiotic resistance in the soil ecosystem. Thus, it is necessary to enforce stricter regulations on the disposal of SEO and other petroleum hydrocarbons to limit their human and environment associated hazards.

Hydrocarbon Removal in Oil-Contaminated Soil Using In-Vessel Composting with Yard Waste and Rumen Waste

AbstractThis study aimed to determine hydrocarbon removal in oil-contaminated soil using composting with an amendment of yard waste and rumen waste. Hydrocarbon-contaminated soil samples from a pub...

Microbial diversity and hydrocarbon depletion in low and high diesel-polluted soil samples from Keller Peninsula, South Shetland Islands

AbstractThe bioremediation of Antarctic soils is a challenge due to the harsh conditions found in this environment. To characterize better the effect of total petroleum hydrocarbon (TPH) concentrations on bacterial, archaeal and microeukaryotic communities in low (LC) and high (HC) hydrocarbon-contaminated soil samples from the Maritime Antarctic clone libraries (small-subunit rRNA genes) were constructed. The results showed that a high concentration of hydrocarbons resulted in a decrease in bacterial and eukaryotic diversity; however, no effect of the TPH concentration was observed for the archaeal community. The HC soil samples demonstrated a high relative abundance of bacterial operational taxonomic units (OTUs) affiliated with unclassified group TM7 and eukaryotic OTUs affiliated with unclassified fungi from Pezizomycotina subphyla. Chemical analyses of the LC and HC soil samples revealed the presence of negligible amounts of nitrogen, thereby justifying the use of biostimulation to remediate these Antarctic soils. Microcosm experiments showed that the application of fertilizers led to an increase of up to 27.8% in the TPH degradation values. The data presented here constitute the first step towards developing the best method to deploy bioremediation in Antarctic soils and provide information to indicate an appropriate action plan for immediate use in the case of new accidents.

Impact of petroleum hydrocarbon contamination on the indigenous soil microbial community

Changes in the microbial community structure in agricultural soils and soils contaminated with hydrocarbons were evaluated using the culture-independent method of 16S rRNA gene sequence analysis. The bacterial composition was more diverse in the agricultural soil (AS) samples in terms of number of species and Shannon diversity index [6.6 vs. 1.94 for the hydrocarbon-contaminated soil (HCS)]. Twelve known bacterial groups were identified in the AS: Proteobacteria (41 % of bacterial community), Actinobacteria (34 %), Acidobacteria (5 %), Firmicutes (4 %), Chloroflexi (4 %), Bacteroidetes (3 %), Gemmatimonadetes, Planctomycetes, Verrucomicrobia, Armatimonadetes, Cyanobacteria, TM7 and Archaea (the latter 7 each accounting for 1–2%) . In comparison, the clonal library from the HCS samples included members from only five groups: Proteobacteria (85 %) and Bacteriodetes, Actinobacteria, Chloroflexi and Verrucomicrobia (the latter four collectively accounting for 15 %). The family Ectothiorhodospiraceae was the most dominant family within the Proteobacteria isolated from the HCS. These microbes are known to synthesize a number of biotechnologically useful products, such as polyhydroxyalkanoates and ectoines, and their dominance in the sampled area suggests the possibility of discovering better adapted novel genes of commercial importance, especially since the site had high alkaline and saline characteristics. Soils (arid, alpine and polar) which are nutrient and moisture limited are typically often dominated by Actinobacteria that are well adapted to low-resource environments and do not show major changes in community structure as a result of hydrocarbon contamination.

Hydrocarbon pollution does not influence bacterial diversity as much as geographic location: a Korean case study

Bacterial diversity of hydrocarbon-contaminated sites in various regions of Korea was investigated to ascertain the influence of hydrocarbon pollution on bacterial diversity using terminal restriction fragment length polymorphism (T-RFLP) and differential gel gradient electrophoresis. Thirty-two hydrocarbon-contaminated soil samples were collected from seven different geographical locations in Korea. A dendrogram of T-RFLP profiles for the bacterial community structure in soil samples using Ward’s method with Jaccard distance showed that samples from the same location clustered together. Principal components analysis (PCA) and self-organizing maps (SOM) of terminal restriction fragments were also used to characterize the associations among samples. PCA and SOM results also showed that soil bacterial communities were classified according to locations, but not by hydrocarbon pollution level. Moreover, correlation analyses prove a direct correlation between bacterial diversity and meteorological parameters, whereas no significant correlation was observed with hydrocarbon contamination levels. These results suggest that geographical origin, rather than soil contamination level, might be more important in determining the bacterial diversity of crude oil-contaminated soils. Environmental factors, which play a major role in determining natural bacterial diversity which in turn should be enriched for effective bioremediation, should be the central dogma while considering bioremediation of hydrocarbon-contaminated sites.

Data Reduction in Comprehensive Two-Dimensional Gas Chromatography for Rapid and Repeatable Automated Data Analysis

A rapid approach for comprehensive two-dimensional gas chromatographic data analysis is introduced, providing important environmental metrics including total petroleum hydrocarbon concentration as well as chemical-class distribution. The approach, comprising transformation of exported data files to two-dimensional retention time arrays, blank subtraction, alignment and projection onto new axes, subdivision of the aligned two-dimensional data matrix, and compilation of summary data is able to be performed without user intervention. The approach satisfies critical goals of rapid batch analysis with repeatability and traceability. Application to assessment of petroleum hydrocarbon contaminated soil samples from Macquarie Island, a remote Southern Ocean island, is shown to illustrate the utility of this new data analysis strategy.

Ecotoxicological and microbiological characterization of soils from heavy-metal- and hydrocarbon-contaminated sites

The aims of this study were to characterize soils from industrial sites by combining physicochemical, microbiological, and ecotoxicological parameters and to assess the suitability of these assays for evaluation of contaminated sites and ecological risk assessment. The soil samples were taken from long-term contaminated sites containing high amounts of heavy metals (sites 1 and 2) or petroleum hydrocarbons (site 3) located in the upper Silesia Industrial Region in southern Poland. Due to soil heterogeneity, large differences between all investigated parameters were measured. Microbiological properties revealed the presence of high numbers of viable hetrotrophic microorganisms. Soil enzyme activities were considerably reduced or could not be detected in contaminated soils. Activities involved in N turnover (N mineralization and nitrification) were significantly (P < 0.05) higher in samples from the metal-contaminated sites than in samples from the hydrocarbon-contaminated site, whereas the opposite was observed for phosphatase activity. The Microtox test system appeared to be the most appropriate to detect toxicity and significant differences in toxicity between the three sites. The Ostracodtoxkit test was the most appropriate test system to detect toxicity in the hydrocarbon-contaminated soil samples. Correlation analysis between principal components (obtained from factor analysis) determined for physicochemical, microbiological, and ecotoxicological soil properties demonstrated the impact of total and water-extractable contents of heavy metals on toxicity.

Growth of Streptomyces spp. from hydrocarbon-polluted soil on diesel and their analysis for the presence of alkane hydroxylase gene (alkB) by PCR

The investigation aimed to examine the Streptomyces flora of hydrocarbon-contaminated soil and study their capability to grow on diesel fuel as a sole carbon source and their analysis for the presence of the alkane hydroxylase gene (alkB) by PCR. A total of 16 Streptomyces isolates were recovered from hydrocarbon-contaminated soil samples on starch casein nitrate agar medium with the ability of 3 isolates to grow on diesel as evaluated by agar plate diffusion method, enzymatic assay and dry weight measurements. PCR analysis of the isolates for the presence of the alkB gene showed two groups with different band size products; group 1 (G1) (316–334 bp) and group 2 (G2) (460–550 bp). Three isolates (SF.1Ac, SF.2Ba, and SF.3Ad) grew around diesel-containing wells and contained the alkB gene with size band ranged between 320 and 550 bp. However; one isolate (SF.1Aa) did not show any PCR product although it was able to grow on diesel. This implies that the alkB gene is not the only gene that is responsible for the degradation of alkanes. Further, the variation in the G2 fragment size probably indicates different related genes that might be involved in alkane degradation rather than a single gene.

Microbial degradation of polycyclic aromatic hydrocarbons in soil by bacterium-fungus co-cultures

Two fungi and the phenanthrene-degrading bacterial strainRhodococcus sp. IC10 were used as inocula for the bioremediation of petroleum hydrocarbon-contaminated soil from a manufactured gas plant area. The two fungi, which were previously isolated from different hydrocarbon-contaminated soil samples, were identified asAspergillus terreus andPenicillium sp. In addition, two types of co-cultures which consist of fungal species includingA. terreus orPenicilium sp. withRhodococcus sp. IC10 were applied. After a 10-week incubation period, the concentrations of anthracene, phenanthrene, and pyrene were totally biodegraded by days 68, 54, and 64, for the 16 polycyclic aromatic hydrocarbons (PAH's) tested. The ecotoxicity of the soil after bioremediation did not show any effect on the survival ofDaphnia magna (24 h-old-daphnids). However, the toxicity on seed germination ofBrassica alba and the oxidoreductase activity ofBacillus cereus declined after 5- and 10-weeks of incubation, respectively. Co-cultures ofPenicillium sp. andRhodococcus sp. IC 10 revealed the best efficiency at reducing ecotoxicity.

Characterization of EPA’s 16 priority pollutant polycyclic aromatic hydrocarbons (PAHs) in tank bottom solids and associated contaminated soils at oil exploration and production sites in Texas

The purpose of this study was to determine the concentration and types of polycyclic aromatic hydrocarbons (PAHs), a group of environmentally toxic and persistent chemicals, at contaminated oil exploration and production (E&P) sites located in environmentally sensitive and geographically distinct areas throughout Texas. Samples of tank bottom solids, the oily sediment that collects at the bottom of the tanks, were collected from inactive crude oil storage tanks at E&P sites and hydrocarbon contaminated soil samples were collected from the area surrounding each tank that was sampled. All samples were analyzed for the 16 PAH priority pollutant listed by US EPA and for total petroleum hydrocarbons (TPH). The results demonstrate that overall average PAH concentrations were significantly higher in tank bottom solids than in contaminated soils. Total PAH concentrations decreased predictably with diminishing hydrocarbon concentrations; but the percent fraction of carcinogenic PAHs per total measured PAH content increased from approximately 12% in tank bottom solids to about 46% in the contaminated soils. These results suggest that the PAH content found in tank bottom solids cannot reliably be used to predict the PAH content in associated contaminated soil. Comparison of PAHs to conservative risk-based screening levels for direct exposure to soil and leaching from soil to groundwater indicate that PAHs are not likely to exceed default risk-based thresholds in soils containing TPH of 1% (10,000 mg/kg) or less. These results show that the magnitude of TPH concentration may be a useful indicator of potential risk from PAHs in crude oil-contaminated soils. The results also provide credibility to the 1% (10,000 mg/kg) TPH cleanup level, used in Texas as a default management level at E&P sites located in non-sensitive areas, with respect to PAH toxicity.

Characterization of biochemical properties and biological activities of biosurfactants produced by Pseudomonas aeruginosa mucoid and non-mucoid strains isolated from hydrocarbon-contaminated soil samples

Biochemical and pharmacological properties of biosurfactants produced at 45 degrees C temperature by Pseudomonas aeruginosa mucoid (M) and non-mucoid (NM) strains, isolated from hydrocarbon-contaminated soil samples, were characterized. Both the strains secreted appreciable amount of biosurfactants (5.0-6.5 g/l), responsible for the reduction of surface tension of the medium from 68 to 29 +/- 0.5 mN/m post 96 h of growth. Maximum yield of biosurfactants was observed following the supplementation of NH(4)Cl and glycerol as nitrogenous source and carbon source, respectively. These thermostable biosurfactants exhibited strong emulsifying property and could release appreciable amount of oil from saturated sand-pack column. Pharmacological characterization of these biosurfactants revealed that they induced dose-dependent hemolysis and coagulation of platelet-poor plasma but were non-detrimental to chicken lung, liver, heart and kidney tissues. Our study has documented that biosurfactants from P. aeruginosa M and NM strains could be exploited for use in petroleum sectors as well in pharmaceutical industries.

Biodegradation of hydrocarbons in soil by microbial consortium

The bioremediation of hydrocarbon in contaminated soils by mixed cultures of hydrocarbon-degrading bacteria was investigated. The mixtures or consortia of bacteria, denoted as Consortium 1 and Consortium 2 consisted of 3 and 6 bacterial strains, respectively. Bacterial strains used in this study were from the Center for Research in Enzymes and Microbiology (CREAM) collection of strains, at Universiti Putra Malaysia, and were isolated from hydrocarbon-contaminated soil samples by enrichments on either crude oil or individual hydrocarbons as the sole carbon source. The strains were selected based on the criteria that they were able to display good growth in crude oil, individual hydrocarbon compounds or both. Their ability to degrade hydrocarbon contamination in the environment was investigated using soil samples that were contaminated with diesel, crude oil or engine oil. Consortium 2, which consisted of 6 bacterial strains, was more efficient at removing the medium- and long-chain alkanes in the diesel-contaminated soil compared to Consortium 1. Further, Consortium 2 could effectively remove the medium- and long-chain alkanes in the engine oil such that the alkanes were undetectable after a 30-day incubation period. Consortium 2 consisted predominantly of Bacillus and Pseudomonas spp.

Bioremediation treatability assessment of hydrocarbon-contaminated soils from Eureka, Nunavut

The bioremediation potential of three hydrocarbon-contaminated soil samples with diverse soil physical/chemical characteristics from Eureka, Ellesmere Island, Nunavut, was assessed. Microbial enumeration by viable plate counts and MPN analyses combined with molecular analysis (PCR and colony hybridization) for hydrocarbon catabolic genes ( alkB +, xylE +, ndoB +) demonstrated the presence of significant numbers of aerobic cold-adapted hydrocarbon-degrading organisms in the three contaminated soils. The degradative activities of the indigenous microbial populations were assessed by mineralization of 14C-labelled hexadecane (C16) and naphthalene at 5°C or 23°C in untreated and treated soil microcosms. Although very low rates of C16 and naphthalene mineralization were observed in untreated microcosms, nutrient supplementation with a commercial inorganic fertilizer (20:20:20) markedly increased mineralization in the soil microcosms, indicating that these soil are nutrient-deficient. Increasing the incubation temperature to 23°C markedly decreased the acclimation period and increased the rate of mineralization in soil microcosms supplemented with 20:20:20. Optimal treatments resulting in the greatest rates and levels of mineralization for each soil were determined: Soil #1, 20:20:20+tilling; Soil #2, 20:20:20+peat moss; Soil #3, 20:20:20+water to 60% WHC. Total petroleum hydrocarbon (TPH) analysis of cold soil microcosms revealed that, similar to the soil mineralization assays, the optimal treatments increased TPH degradation compared with fertilizer treatment alone. TPH levels in the contaminated Eureka soils were reduced from 5166 to 2966 ppm in Soil #1, from ∼4256 to 2466 ppm in Soil #2, and from 4500 to 1933 ppm in Soil #3 following the appropriate treatment after 16 weeks incubation at 5°C. These results indicate that the bioremediation potential of the Eureka soils at low ambient summer temperatures is considerable. It is suggested that the on-site treatment planned for the 2000 summer include the application of a commercial fertilizer and, if feasible, additional treatments such as tilling, addition of peat moss, or water, depending on the contaminated soil's physical/chemical characteristics.