Biodegradation Of Hydrocarbons In Soil Research Articles

Phytochemical effects of Apium graveolens on the abundances of functional genes associated with PAH degradation in soil

The biodegradation of polycyclic aromatic hydrocarbons in soil is enhanced by chemical constituents of various plant species that support the growth and activity of PAH degrading bacteria in the rhizosphere. Here, we investigated the phytochemical effects of celeriac (Apium graveolens var. rapaceum) root tissues, a known stimulator of PAH degradation, on the copy numbers of nahAc, xylE, and 16S rRNA genes to determine the relative contributions of growth-linked degradation versus selective enrichment of PAH degraders. Real-time quantitative PCR analysis showed that the copy numbers of 16S rRNA genes, as a reporter of general bacterial population size, increased approximately 2- to 5-fold in soil amended with celeriac, but were not affected by exposure to naphthalene alone. In contrast, copy numbers of two functional genes (nahAc and xylE), commonly used as reporters for monitoring the population size of PAH degraders, were significantly increased following exposure to naphthalene but were differently affected by soil amendment with celeriac. As compared with the copy numbers of nahAc gene in unamended control soil, the nahAc copy numbers were increased by 460-fold in soil amended with naphthalene alone and by 610-fold in soil amended with both naphthalene and celeriac after 10 days of incubation. The copy numbers of xylE were increased by 20-fold in soil amended with naphthalene alone and increased by 200-fold in soil amended with both naphthalene and celeriac after 10 days of incubation. The result suggests that increased degradation rates of PAHs in the presence of celeriac involves both growth linked processes and selective enrichment of the degrader population.

Bioaccessibility of 14C-phenanthrene from root amended contaminated soil

Plants and their roots, in particular, may be important in stimulating microbial degradation of organic contaminants in soil. It is also known that bioaccessibility is important in controlling the biodegradation of organic contaminants in soil. This study aimed to assess the impact of plant roots on the biodegradation and bioaccessibility of 14C-phenanthrene in soil in the presence of plant root biomass. To do this, changes in the 14C-phenanthrene mineralisable and hydroxypropyl-β-cyclodextrin (HPCD) extractable fractions were evaluated. After 1, 25, 50 and 100 days of PAH-soil contact time, 12/14C-phenanthrene-spiked soil was amended with roots from two grasses and one legume. Mineralisation and HPCD extractability of 14C-phenanthrene were measured after 1, 21 and 42 days PAH-root-soil contact time. Findings revealed that mineralisation of 14C-phenanthrene was enhanced following the amendment with plant root biomass regardless their species or form, especially in the soils that been aged for ≥50 days soil-PAH contact time. Overall, this study showed that greater levels of phenanthrene biodegradation may be achieved by incorporating root biomass into the contaminated soil, particularly where indigenous catabolic activity has developed. The findings reported here contribute to the understanding of how plant root biomass may impact on contaminant bioaccessibility and stimulate the more effective indigenous biodegradation of hydrocarbons in soil.

Optimization of Landfarming Amendments Based on Soil Texture and Crude Oil Concentration

This work examines the rates of bioremediation during a landfarming process. A field study was performed using three types of soil, which were contaminated with two different hydrocarbon concentrations: 20,000 and 50,000 ppm of total petroleum hydrocarbons (TPH). They were subjected to landfarming under the action of different treatments, based on the provision of irrigation, aeration by rototilling, fertilizer, and surfactant. The biodegradation of TPH, considering concentration and families of hydrocarbon compounds (including polycyclic aromatic hydrocarbons, PAHs), was precisely measured for a period of 486 days. The results show how biodegradation rates depend on soil texture, initial contamination level, and type of amendment. Thus, the combination of fertilizer, irrigation, and aeration was the best treatment for treating the soil contaminated with 20,000 ppm of TPH (TPH final concentrations were reduced to a range of 49 to 62% depending on the soil texture). In the case of parcels contaminated with 50,000 ppm of TPH, the most effective treatment combined the supply of fertilizer, surfactant, irrigation, and aeration (TPH final concentrations were reduced to a range of 47 to 63%, depending on the soil texture). The best biodegradation results are obtained for soils with coarser textures and using the treatment with fertilizer, irrigation, and aeration. In addition, the application of surfactant did not imply a significant improvement in the level of biodegradation of hydrocarbons in soil contaminated with 20,000 ppm of TPH, whereas in soils contaminated with 50,000 ppm of TPH, it played a leading role.

Selective biostimulation of cold‐ and salt‐tolerant hydrocarbon‐degrading Dietzia maris in petroleum‐contaminated sub‐Arctic soils with high salinity

AbstractBACKGROUNDThe dual tolerance of hydrocarbon‐degrading bacteria to low temperatures and salinity has not been extensively reported. This study identifies cold‐ and salt‐tolerant hydrocarbon degraders obtained from petroleum‐contaminated sub‐Arctic soils, with the objective of stimulating target populations and assessing hydrocarbon biodegradation in soils abruptly impacted by salinity.RESULTSHalotolerant Dietzia and Arthrobacter bacteria were isolated from the soils. Dietzia maris strain NWWC4 can grow in the absence and presence of NaCl (≤12.5% w/v), adheres to hydrocarbons, and produces biosurfactant. The nutrient conditions preferred by strain NWWC4 were characterized to stimulate halotolerant hydrocarbon degraders related to strain NWWC4. In soil‐slurry microcosms with the selected nutrient, Terminal Restriction Fragment Length Polymorphism indicated the dominance of alkB‐gene‐harboring NWWC4 relatives. Radiolabeled 14C‐hexadecane mineralization in high‐salinity soil‐slurry microcosms (29 ± 0.33% 14CO2 production) was strikingly comparable with that in non‐saline conditions (35 ± 0.84% 14CO2 production). In nutrient‐amended, Arctic‐diesel‐spiked soil microcosms subjected to dual stresses (10 °C and 5% NaCl, w/v), hydrocarbon removal in the diesel range (C10–C21) was 21 ± 8% after 18 days and was comparable with the removal achieved under non‐saline conditions (37 ± 6% removal).CONCLUSIONThis study reports the unique versatility of cold‐adapted and salt‐tolerant Dietzia maris capable of degrading hydrocarbons in highly saline and non‐saline conditions. © 2017 Society of Chemical Industry

Soil bioremediation approaches for petroleum hydrocarbon polluted environments.

Increasing industrialisation, continued population growth and heavy demand and reliance on petrochemical products have led to unprecedented economic growth and development. However, inevitably this dependence on fossil fuels has resulted in serious environmental issues over recent decades. The eco-toxicity and the potential health implications that petroleum hydrocarbons pose for both environmental and human health have led to increased interest in developing environmental biotechnology-based methodologies to detoxify environments impacted by petrogenic compounds. Different approaches have been applied for remediating polluted sites with petroleum derivatives. Bioremediation represents an environmentally sustainable and economical emerging technology for maximizing the metabolism of organic pollutants and minimizing the ecological effects of oil spills. Bioremediation relies on microbial metabolic activities in the presence of optimal ecological factors and necessary nutrients to transform organic pollutants such as petrogenic hydrocarbons. Although, biodegradation often takes longer than traditional remediation methods, the complete degradation of the contaminant is often accomplished. Hydrocarbon biodegradation in soil is determined by a number of environmental and biological factors varying from site to site such as the pH of the soil, temperature, oxygen availability and nutrient content, the growth and survival of hydrocarbon-degrading microbes and bioavailability of pollutants to microbial attack. In this review we have attempted to broaden the perspectives of scientists working in bioremediation. We focus on the most common bioremediation technologies currently used for soil remediation and the mechanisms underlying the degradation of petrogenic hydrocarbons by microorganisms.

KINETIC MODELLING AND HALF LIFE STUDY OF ADSORPTIVE BIOREMEDIATION OF SOIL ARTIFICIALLY CONTAMINATED WITH BONNY LIGHT CRUDE OIL

In this study, comparative potential effects of commercial activated carbon (CAC) and plantain peel-derived biochar (PPBC) of different particle sizes and dosage to stimulate petroleum hydrocarbon biodegradation in soil were investigated. Microcosms containing soil were spiked with weathered Bonny light crude oil (WBLCO) (10% w/w) and amended with different particle sizes (0.02, 0.07 and 0.48 mm) and dosage (20, 30 and 40 g) of CAC and PPBC, respectively. The bioremediation experiments were carried out for a period of 28 days under laboratory conditions. The results showed that there was a positive relationship between the rate of petroleum hydrocarbons reduction and presence of the CAC and PPBC in crude oil contaminated soil microcosms. The WBLCO biodegradation data fitted well to the first-order kinetic model. The model revealed that WBLCO contaminated-soil microcosms amended with CAC and PPBC had higher biodegradation rate constants (k) as well as lower half-life times (t1/2) than unamended soil (natural attenuation) remediation system. The rate constants increased while half-life times decreased with decreased particle size and increased dosage of amendment agents. ANOVA statistical analysis revealed that WBLCO biodegradation in soil was significantly (p = 0.05) influenced by the addition of CAC and biochar amendment agents, respectively. However, Tukey’s post hoc test (at p = 0.05) showed that there was no significant difference in the bioremediation efficiency of CAC and PPBC. Thus, amendment of soils with biochar has the potential to be an inexpensive, efficient, environmentally friendly and relatively novel strategy to mitigate organic compound-contaminated soil.

Applicability of non-exhaustive extraction procedures with Tenax and HPCD

Chemical extraction techniques like non-exhaustive extraction with Tenax or hydroxypropyl-β-cyclodextrin (HPCD) have been shown to measure the biodegradable fraction of aromatic contaminants like PAHs in soil. However, there is little research on the chemical prediction of aliphatic hydrocarbon degradation. The aim of this study was to investigate the potential for HPCD and Tenax extractions to predict PAH and petroleum hydrocarbon biodegradation in soil. 11 historically contaminated soils with PAH concentrations between 74 and 680mg/kg and concentrations of petroleum hydrocarbons from 330 to 4704mg/kg were analysed. Both non-exhaustive extraction procedures showed promising results for estimating the available contaminant fraction of both contaminant groups concerning the feasibility, reproducibility and correlation with soil biodegradation applying single point testing. Both methods have the potential to be used to assess the biodegradable hydrophobic organic pollutant fraction in contaminated soils. In a direct comparison of the two extraction procedures, Tenax extraction is assessed to be more time-consuming than HPCD extraction. Furthermore, a sufficient soil/Tenax ratio has to be considered.

Just Add Water and Salt: the Optimisation of Petrogenic Hydrocarbon Biodegradation in Soils from Semi-arid Barrow Island, Western Australia

We investigated the potential of soil moisture and nutrient amendments to enhance the biodegradation of oil in the soils from an ecologically unique semi-arid island. This was achieved using a series of controlled laboratory incubations where moisture or nutrient levels were experimentally manipulated. Respired CO2 increased sharply with moisture amendment reflecting the severe moisture limitation of these porous and semi-arid soils. The greatest levels of CO2 respiration were generally obtained with a soil pore water saturation of 50–70%. Biodegradation in these nutrient poor soils was also promoted by the moderate addition of a nitrogen fertiliser. Increased biodegradation was greater at the lowest amendment rate (100 mg N kg−1 soil) than the higher levels (500 or 1,000 mg N kg−1 soil), suggesting the higher application rates may introduce N toxicity. Addition of phosphorous alone had little effect, but a combined 500 mg N and 200 mg P kg−1 soil amendment led to a synergistic increase in CO2 respiration (3.0×), suggesting P can limit the biodegradation of hydrocarbons following exogenous N amendment.

Biodegradation of petroleum industry oily-sludge using Jordanian oil refinery contaminated soil

The main objective of this study was to evaluate the effect of oily sludge concentration on its biodegradability in soil. Oily sludge was collected and applied to microcosms at full-, half-, or quarter-strength concentrations equivalent to 44.2, 22.2, and 11.1 g kg −1 soil, respectively, of total petroleum hydrocarbons (TPH) contained in oily sludge. The biodegradability of oily sludge was evaluated by measuring CO 2 evolution and by measuring removal of TPH as well as its main composing fractions; namely; alkanes, aromatics, NSO-compounds, and asphaltenes. The collected soil contained 3.63 × 10 6 cfu g −1 soil of hydrocarbon-degrading bacteria, which is satisfactory to drive successful biodegradation of hydrocarbons in soil. These numbers increased significantly with oily sludge addition at a rate proportional to the added TPH reaching 3.35 × 10 7 cfu g −1 soil in the half-strength treatment. TPH mineralization rate followed the same pattern. However, TPH-mineralization efficiency was the greatest in quarter-strength treatment at 18.3%. TPH-removal efficiency was also highest in quarter-strength treatment at 30.9%. Nutrients addition caused mineralization inhibition. Since nutrients were added as a ratio of the added carbon, inhibition was the greatest with the highest TPH treatment. While alkanes were degraded, aromatics and asphaltenes were not, and NSO-compounds were enriched. Although SDS was completely biodegradable in soil, its addition promoted mineralization and removal of TPH from soil.

Enhanced Biodegradation of Hydrocarbons in Soil by Microbial Biosurfactant, Sophorolipid

Effectiveness of a microbial biosurfactant, sophorolipid, was evaluated in washing and biodegradation of model hydrocarbons and crude oil in soil. Thirty percent of 2-methylnaphthalene was effectively washed and solubilized with 10 g/L of sophorolipid with similar or higher efficiency than that of commercial surfactants. Addition of sophorolipid in soil increased biodegradation of model compounds: 2-methylnaphthalene (95% degradation in 2 days), hexadecane (97%, 6 days), and pristane (85%, 6 days). Also, effective biodegradation method of crude oil in soil was observed by the addition of sophorolipid, resulting in 80% biodegradation of saturates and 72% aromatics in 8 weeks. These results showed the potentials of the microbial biosurfactant, sophorolipid, as an effective surfactant for soil washing and as an in situ biodegradation enhancer.

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.

Assessing the role of Pseudomonas aeruginosa surface-active gene expression in hexadecane biodegradation in sand.

Low pollutant substrate bioavailability limits hydrocarbon biodegradation in soils. Bacterially produced surface-active compounds, such as rhamnolipid biosurfactant and the PA bioemulsifying protein produced by Pseudomonas aeruginosa, can improve bioavailability and biodegradation in liquid culture, but their production and roles in soils are unknown. In this study, we asked if the genes for surface-active compounds are expressed in unsaturated porous media contaminated with hexadecane. Furthermore, if expression does occur, is biodegradation enhanced? To detect expression of genes for surface-active compounds, we fused the gfp reporter gene either to the promoter region of pra, which encodes for the emulsifying PA protein, or to the promoter of the transcriptional activator rhlR. We assessed green fluorescent protein (GFP) production conferred by these gene fusions in P. aeruginosa PG201. GFP was produced in sand culture, indicating that the rhlR and pra genes are both transcribed in unsaturated porous media. Confocal laser scanning microscopy of liquid drops revealed that gfp expression was localized at the hexadecane-water interface. Wild-type PG201 and its mutants that are deficient in either PA protein, rhamnolipid synthesis, or both were studied to determine if the genetic potential to make surface-active compounds confers an advantage to P. aeruginosa biodegrading hexadecane in sand. Hexadecane depletion rates and carbon utilization efficiency in sand culture were the same for wild-type and mutant strains, i.e., whether PG201 was proficient or deficient in surfactant or emulsifier production. Environmental scanning electron microscopy revealed that colonization of sand grains was sparse, with cells in small monolayer clusters instead of multilayered biofilms. Our findings suggest that P. aeruginosa likely produces surface-active compounds in sand culture. However, the ability to produce surface-active compounds did not enhance biodegradation in sand culture because well-distributed cells and well-distributed hexadecane favored direct contact to hexadecane for most cells. In contrast, surface-active compounds enable bacteria in liquid culture to adhere to the hexadecane-water interface when they otherwise would not, and thus production of surface-active compounds is an advantage for hexadecane biodegradation in well-dispersed liquid systems.

Potential for biodegradation of hydrocarbons in soil from the Ross Dependency, Antarctica

Oil spills occur in the Antarctic when fuel oils such as JP8 jet fuel are moved or stored. Hydrocarbons, both n-alkanes and aromatic compounds, have been detected in oil-contaminated soils of the Ross Dependency. In such areas hydrocarbon-degrading microbes, if naturally occurring, could be used for clean-up. Soil samples from oil-impacted and control sites were analysed for hydrocarbon-degrading microbes and for a range of parameters known to limit biodegradative activity. Soils were analysed for water content, pH, concentrations of nutrients (N and P) and electrical conductivity. Numbers of culturable heterotrophic bacteria and hydrocarbon degraders were greater in some of the oil-contaminated samples. Mineralisation studies with 14C-radiolabelled hexadecane and naphthalene demonstrated that nitrogen amendments significantly enhanced hydrocarbon mineralisation rates in an oil-impacted soil.

Surfactant enhances biodegradation of hydrocarbons: Microcosm and field study

The purpose of the present study was to provide new methods that would increase the rates of biodegradation of petroleum hydrocarbons in soil, thus reducing the time required to achieve a satisfactory level of residual hydrocarbon in an ex situ bioremediation. Results of laboratory studies on several techniques were used to guide our implementation of these methods in controlled field studies. Soils contaminated with nonvolatile hydrocarbons were treated with various combinations of (1) an anionic surfactant guanidinium cocoate (CGS), (2) a consortium of hydrocarbon‐degrading microorganisms, (3) a slow‐release form of nitrogen:urea, and (4) the bulking agent vermiculite. Laboratory results describing the activity of CGS have been presented previously (Jain et al., 1992). The amount and rate of hydrocarbon loss in treated soil was compared with hydrocarbon lost in soil that received no amendment other than water (water only). We also used a sheen screen method (Nelson et al., 1995), to assess the effectiveness of our field application of microorganisms.

Effects of ryegrass on biodegradation of hydrocarbons in soil

The effects of growing ryegrass ( Lolium perenne L.) on the biodegradation of hydrocarbons was studied in laboratory scale soil columns. Degradation of hydrocarbons as well as bacterial numbers, soil respiration rates and soil dehydrogenase activities were determined. In the rhizosphere soil system, aliphatic hydrocarbons disappeared faster than in unvegetated columns. Abiotic loss by evaporation was of minor significance. Elimination of pollutants was accompanied by an increase in microbial numbers and activities. The microbial plate counts and soil respiration rates were substantially higher in the rhizosphere than in the bulk soil. The results indicate that biodegradation of hydrocarbons in the rhizosphere is stimulated by plant roots.

Biodegradation of polycyclic aromatic hydrocarbons in soil around Mathura oil refinery, India

Six polycyclic aromatic hydrocarbons [naphthalene, anthracene, phenanthrene, pyrene, chrysene and benzo(a)-pyrene] were detected in soil receiving effluents from an oil refinery. Biodegradation studies revealed a time-dependent disappearance of these polycyclic aromatic hydrocarbons when they were added to soil samples: naphthalene disappeared completely in 60 days, whereas phenanthrene, anthracene, pyrene, chrysene and benzo(a)pyrene decreased by 87%, 34%, 21%, 5% and 40%, respectively, in 120 days.

Pore Structures of Oil-Contaminated, Aggregated Oil-Contaminated and Uncontaminated Soils in Relation to Microbial Activities

Soil pore structure is one of the most important characteristics which influence the biodegradation of hydrocarbons in soil. The objective of this study was to quantify and compare the inter- and intra-aggregate pore structures of oil-contaminated, aggregated oil-contaminated and uncontaminated soils and their effects on microbial biomass and activities. The inter-aggregate and intra-aggregate porosity of the untreated oil-contaminated soil was less than that of the uncontaminated soil indicating the oil-contaminated soil was more compacted, which reduced the microbial activity. The microbial biomass and activity in the aggregated oil-contaminated soil was greater than in the untreated oil-contaminated soil indicating the aggregation process improved the physical environment for microorganisms and enhanced the biodegradation of hydrocarbons in soil.

Effects of Lead on Biodegradation of Hydrocarbons in Soil

The possible effects of lead on biodegradation of oily wastes in soil were studied in model experiments. It was found that addition of lead caused certain changes in the soil microflora: a general reduction of the bacterial populations and proliferation of a few fungal species. Simple alkanes were readily decomposed in presence of high concentrations of lead, but decomposition of complex mixtures of hydrocarbons (heavy fuel oil) was significantly retarded. The importance of these observations for the use of the soil cultivation process for disposal of oily waste is discussed.