Petroleum Degradation Research Articles

High pyrolysis temperature biochar reduced the transport of petroleum degradation bacteria Corynebacterium variabile HRJ4 in porous media

Biochar has been widely applied for the remediation of petroleum-contaminated soil. However, the effect of biochar on the transport of petroleum degradation bacteria has not been studied. A typical Gram-positive petroleum degradation bacteria-Corynebacterium variabile HRJ4 was used to study the effect of different biochars on bacterial transport and retention. Results indicated that the addition of biochar in sand was effective for reducing the transport of bacteria and poplar sawdust biochar (PSBC) had a stronger hinder effect than corn straw biochar (CSBC). The hindrance was more evident with pyrolysis temperature of biochar raised from 300°C to 600°C, which was attributed to the increase of specific surface area (309 times). The hindrance effect also enhanced with higher application rate of biochar. Furthermore, the reduction of HRJ4 transport was more obvious in higher (25 mmol/L) concentration of NaCl solution owing to electrostatic attraction enhancement. The adsorption of biochar to HRJ4 was defined to contribute to the hindrance of HRJ4 transport mainly. Combining the influence of feedstocks and pyrolysis temperature on HRJ4 transport, it suggested that specific surface area had the greatest effect on HRJ4 transport, and pore-filling, electrostatic force also contributed to HRJ4 retained in quartz sand column. At last, phenol transportation experiment indicated that the restriction of biochar on HRJ4 enhanced the phenol removal rate in the column. This study provides a theoretical basis for the interaction of biochar and bacteria, which is vital for the remediation of oil-contaminated soil and groundwater in the field.

Newly Isolated Alkane Hydroxylase and Lipase Producing Geobacillus and Anoxybacillus Species Involved in Crude Oil Degradation

Isolation and studies of novel, crude oil biodegrading thermophilic strains may provide a wider knowledge in understanding their role in petroleum degradation. In this study, the screening of ten new thermophilic strains revealed that all strains were alkane hydroxylase producers and seven of them produced lipase concurrently. Three best strains were characterized and identified through 16S rRNA sequence analysis as Geobacillus sp. D4, Geobacillus sp. D7, and Anoxybacillus geothermalis D9 with GenBank accession numbers MK615934.1, MK615935.1, and MK615936.1, respectively. Gas chromatography (GC) analysis showed that all three strains were able to breakdown various compounds in crude oil such as alkanes, toxic poly-aromatic hydrocarbons (PAHs), organosulfur, carboxylic acids, alkene, resins, organosilicon, alcohol, organochlorine, and ester. For the first time, alkane hydroxylase and lipase activity as well as crude oil degradation by A. geothermalis species were reported. Geobacillus sp. D7 is the best alkane degrader followed by A. geothermalis D9 and Geobacillus sp. D4 with 17.3%, 13.1%, and 12.1% biodegradation efficiency (BE%), respectively. The potential of thermophiles isolated can be explored further for bioremediation of sites polluted by petroleum and oil spills.

Bacterial community response to petroleum contamination in brackish tidal marsh sediments in the Yangtze River Estuary, China

The brackish tidal marsh in the Baimaosha area of the Yangtze River Estuary was severely contaminated by 400 tons of heavy crude petroleum from a tanker that sank in December 2012. The spill accident led to severe environmental damage owing to its high toxicity, persistence and wide distribution. Microbial communities play vital roles in petroleum degradation in marsh sediments. Therefore, taxonomic analysis, high-throughput sequencing and 16S rRNA functional prediction were used to analyze the structure and function of microbial communities among uncontaminated (CK), lightly polluted (LP), heavily polluted (HP), and treated (TD) sediments. The bacterial communities responded with increased richness and decreased diversity when exposed to petroleum contamination. The dominant class changed from Deltaproteobacteria to Gammaproteobacteria after petroleum contamination. The phylum Firmicutes increased dramatically in oil-enriched sediment by 75.78%, 346.19% and 267.26% in LP, HP and TD, respectively. One of the suspected oil-degrading genera, Dechloromonas, increased the most in oil-contaminated sediment, by 540.54%, 711.27% and 656.78% in LP, HP and TD, respectively. Spore protease, quinate dehydrogenase (quinone) and glutathione-independent formaldehyde dehydrogenase, three types of identified enzymes, increased enormously with the increasing petroleum concentration. In conclusion, petroleum contamination altered the community composition and microorganism structure, and promoted some bacteria to produce the corresponding degrading enzymes. Additionally, the suspected petroleum-degrading genera should be considered when restoring oil-contaminated sediment.

Molecular characterization and evaluation of crude oil remediation potential of some rhizobia isolated from plant root nodules

This study aimed to determine the molecular identities and genetic relatedness of rhizobia isolated from pigeon pea and pinto beans, and assess their remediation potential in the presence of 1 %, 3 % and 5 % (w/v) crude oil in minimal medium for 7 days incubation period. Standard microbiological and molecular methods which include amplification and purification of 16S rRNA, agarose gel electrophoresis, and sequencing. Results showed molecular identities of six rhizobia from pigeon peas as Bradyrhizobium diazoefficiens USDA122, Rhizobium leguminosarum WSM2304, Bradyrhizobium japonicum N61, Rhizobium leguminosarum N741, Rhizobium leguminosarum BIHIB1217, and Bradyrhizobium japonicum E109; and three rhizobia obtained from pinto beans were Rhizobium leguminosarum N871, Bradyrhizobium diazoefficiens USDA110 and Bradyrhizobium japonicum SEMIA5079. All tested rhizobia (9) showed petroleum degradation ability, as they all grew in the 1, 3 and 5 % (w/v) crude oil minimal medium under laboratory conditions. B. diazoefficiens USDA122 showed the highest optical density (OD) value of 1.184 ± 0.05 on 7th day at 1 % (w/v) crude oil contamination, while R. leguminosarum N741 has the lowest OD value of 0.372 ± 0.02 at 5 % (w/v) crude oil on 7th day. For all the rhizobia, increase occurred throughout incubation period at 1, 3 and 5 % (w/v) except Rhizobium leguminosarum N741 and R. leguminosarum BIHIB1217. In conclusion, the association of R. leguminosarum BIHIB1217 and R. leguminosarum N871 from pigeon pea and pinto beans respectively, were found most effective in crude oil degradation and thus they are recommended as a promising association for remediation of crude oil spilled soils.

Human and Aquatic Toxicity Potential of Petroleum Biodegradation Metabolite Mixtures in Groundwater from Fuel Release Sites.

The potential toxicity to human and aquatic receptors of petroleum fuel biodegradation metabolites (oxygen‐containing organic compounds [OCOCs]) in groundwater has been investigated as part of a multi‐year research program. Whole mixtures collected from locations upgradient and downgradient of multiple fuel release sites were tested using: 1) in vitro screening assays for human genotoxicity (the gamma‐H2AX assay) and estrogenic effects (estrogen receptor transcriptional activation assay), and 2) chronic aquatic toxicity tests in 3 species (Ceriodaphnia dubia, Raphidocelis subcapitata, and Pimephales promelas). In vitro screening assay results demonstrated that the mixtures did not cause genotoxic or estrogenic effects. No OCOC‐related aquatic toxicity was observed and when aquatic toxicity did occur, upgradient samples typically had the same response as samples downgradient of the release, indicating that background water quality was impacting the results. This information provides additional support for previous work that focused on the individual compounds and, taken together, indicates that OCOCs from petroleum degradation at fuel release sites are unlikely to cause toxicity to human or freshwater receptors at the concentrations present. Environ Toxicol Chem 2020;39:1634–1645. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Microbial communities in petroleum-contaminated seasonally frozen soil and their response to temperature changes

Petroleum has contaminated microbial habitats in some parts of permafrost. The microbial community has probably undergone great changes due to the differential sensitivity of bacteria to petroleum contamination, making the seasonally frozen ground ecosystem even more fragile. In this study, we analyzed the microbial community structure and function at different soil depths and petroleum contaminant levels, and studied their relationship with environmental factors through correlation analysis, the random forest algorithm and co-occurrence network analysis. We found that microbial community composition and function mainly varied in response to concentrations of petroleum and sulfates in the environment. The microbial community was divided into six modules as functional groups. Among them, sulfate-reducing bacteria and sulfite-oxidizing bacteria play important roles in module0 and module4, respectively, which were possibly responsible for the degradation of petroleum in permafrost zone. The microbial ability to degrade petroleum decreased and glycan metabolism decreased and then increased through the temperature rise-fall process as a result of microbial stress tolerance mechanisms to pollution and temperature changes. The impact on microbial community structure and function, as well as the responses to petroleum pollution and temperature changes, are revealed in this study.

Maximization of the petroleum biodegradation using a synthetic bacterial consortium based on minimal value algorithm

Petroleum pollution is a global concern because it causes serious environmental and human health problems. Microbial communities play important roles in petroleum biodegradation. In this study, a synthetic bacterial consortium for efficiently degrading ability was constructed on the basis of a minimal value algorithm running on MATLAB. Functional microbial diversity-based screening of three petroleum-degrading strains, Achromobacter sp. P3, Sphingobium sp. P10 and Rhizobium sp. P14, enabled the initial synthesis of the bacterial consortium in combination with a previously used bacterial consortium PDM. When 27.0% of P3, 21.0% of P10, 28.0% of P14 and 24.0% of consortium PDM were inoculated to a petroleum medium, 78.9% of petroleum was degraded under the optimal conditions. The synthetic bacterial consortium has 34.8% higher petroleum degradation than the original bacterial community PDM. Total 40% of the petroleum in the contaminated soil was removed after 20 days of soil bioremediation using the reconstructed consortium. This is an attempt to remediate petroleum-contaminated pollution with synthetic biology via reconstructing a synthetic bacterial community, providing a new idea for the remediation of other pollution problems.

Bacterial Separation and Community Diversity Analysis of Petroleum Contaminated Soil in Yumen Oilfield

The problem of environmental pollution caused by the development and use of petroleum is increasingly obvious, which is a serious threat to human health. The use of microbial degradation to treat oil pollution is one of the environmentally effective, economical and practical methods.In order to explore the soil microbial diversity in the desert area of Northwest China, this paper analyzes the soil bacterial diversity of soil samples collected from different oil-contaminated areas in Yumen Oilfield for the oil pollution problem in the Yumen Oilfield in the northwest desert area, and selects the high efficiency through pure culture technology. Petroleum degradation bacteria, and research on the biological characteristics of degrading bacteria. The composition, abundance and diversity of bacterial communities in oil-contaminated soil in Yumen Oilfield were analyzed. The culturable bacteria in western oil-contaminated desert soil were separated by coating plate method. The bacterial morphology and 16S rRNA gene system development analysis were studied. The structure and diversity of bacterial community could be cultured, and the oil utilization and degradation ability of the strain could be analyzed. The microbial diversity of Yumen oil-contaminated desert soil was analyzed by Illumina Miseq high-throughput sequencing. Through research, it is found that there are abundant bacterial groups in the oil-contaminated desert soil, and there are obvious diversity. The genetic material in the variable regions of the six soil samples detected a total of 3943 0TU at 97% similarity level, and obtained the soil microbial community. Doors, 48 classes, 78 orders, 179 families and 471 genera, including most common high-efficiency petroleum-degrading bacteria. Petroleum hydrocarbon pollution can change the microbial diversity and community structure of the original soil. The size of microbial diversity in the six soil samples is B2]A1]B1]A2]C1]C2, the diversity of B2 is the highest, the diversity of C2 is the lowest, and the microbial diversity differed greatly between groups, and there was no difference in the group. Among the dominant bacteria isolated from contaminated soil, 8 strains of oil have a degradation rate of more than 30%, including the species of the genus Rhodococcus and Pseudomonas. Soil desertification in western China has a great impact on the local ecological environment. Studying the microbial diversity of desert soils and separating high-efficiency petroleum-degrading strains is of great significance for strengthening the ecological restoration of oil-contaminated environment in desert areas.

Bioremediation of oil-contaminated soil by combination of soil conditioner and microorganism

Oil hydrocarbons are widespread pollutants in soil which pose serious threats to ecological environment. Thus, this study carried out the bioremediation of oil-contaminated soil by using the efficient petroleum-degrading bacteria and soil conditioner, to investigate the changes of physicochemical properties of contaminated soil during bioremediation, reveal the relationship among the exogenous degradation strains and indigenous microbe, and finally illuminate the effects of soil conditioner and microbe on the bioremediation of oil-contaminated soil. A PAH-degrading strain named Stenotrophomonas maltophilia was used in this study, which was isolated from an e-waste dismantling area. The soil conditioner in this present study was developed previously by using agricultural wastes, which was in a powdered form and rich in N, P, and K. The simulated experiments were conducted under the control environmental conditions of greenhouse, to study the effects of inoculation and soil conditioner on bioremediation of oil-contaminated soil. Then, the physicochemical properties of soil and the degradation rates of oil were measured at different set times to evaluate the bioremediation effect. Adding 1% soil conditioner could significantly improve the soil conditions and offer microorganism enough N, P, and K, which would promote microbial growth and played a key role on bioremediation of oil-contaminated soil. Although in polluted soil, the microorganism could maintain metabolic activity and use the petroleum as carbon source. The soil indigenous microbe was more easily to adapt to the contaminated surrounding. However, when both of them co-existed in soil, they would restrain each other, and go against the oil decomposition. Thus, making two types of microorganisms work to achieve synergy was the key to gain much better remediation effect. Because the indigenous microbe was good at decomposing low molecular compounds and saturated hydrocarbons, while the oil-degrading strains can effectively decompose high molecular weight aromatics. The soil nutrient and microorganism, including the exogenous oil-degrading strains and the soil indigenous microbe, had an important effect on degradation of petroleum. The addition of soil conditioner, presence of indigenous microbe, and inoculation of oil-degrading strains all were conducive to bioremediation of oil-contaminated site, but the key was to control the proportion and relationship of the three.

Transcriptome profiling reveals the molecular processes for survival of Lysinibacillus fusiformis strain 15-4 in petroleum environments.

A bacterial strain designated Lysinibacillus fusiformis 15-4 was isolated from oil-free soil on the Qinghai-Tibet Plateau, which can grow well utilizing petroleum hydrocarbons as a carbon source at a lower temperature. To deeply characterize the molecular adaptations and metabolic processes of this strain when grown in a petroleum-containing environment, transcriptome analysis was performed. A total of 4664 genes and the expression of 3969 genes were observed in strain 15-4. When the strain was grown in petroleum-containing medium, 2192 genes were significantly regulated, of which 1312 (60%) were upregulated and 880 (40%) were downregulated. This strain degraded and adapted to petroleum via modulation of diverse molecular processes, including improvements in transporter activity, oxidoreductase/dehydrogenase activity, two-component system/signal transduction, transcriptional regulation, fatty acid catabolism, amino acid metabolism, and environmental stress responses. Many strain-specific genes were involved in the oxidation of hydrocarbon compounds, such as several luciferase family alkane monooxygenase genes, flavin-utilizing monooxygenase family genes, and flavoprotein-like family alkanesulfonate monooxygenase genes. Several cold shock protein genes were also induced suggesting adaptation to cold environments and the potential for petroleum degradation at low temperatures. The results obtained in this study may broaden our understanding of molecular adaptation of bacteria to hydrocarbon-containing environments and may provide valuable data for further study of L. fusiformis.

Mesocosm experiments to better understand hydrocarbon half-lives for oil and oil dispersant mixtures.

Concerns on the timing and processes associated with petroleum degradation were raised after the use of Corexit during the Deepwater Horizon oil spill. There is a lack of understanding of the removal of oil associated with flocculate materials to the sediment. Mesocosm studies employing coastal and open-ocean seawater from the Gulf of Mexico were undertaken to examine changes in oil concentration and composition with time. The water accommodated fractions (WAF) and chemically enhanced WAF (CEWAF) produced using Macondo surrogate oil and Corexit were followed over 3–4 days in controlled environmental conditions. Environmental half-lives of estimated oil equivalents (EOE), polycyclic aromatic hydrocarbons (PAH), n-alkanes (C10-C35), isoprenoids pristane and phytane, and total petroleum hydrocarbons (TPH) were determined. EOE and PAH concentrations decreased exponentially following first-order decay rate kinetics. WAF, CEWAF and DCEWAF (a 10X CEWAF dilution) treatments half-lives ranged from 0.9 to 3.2 days for EOE and 0.5 to 3.3 days for PAH, agreeing with estimates from previous mesocosm and field studies. The aliphatic half-lives for CEWAF and DECWAF treatments ranged from 0.8 to 2.0 days, but no half-life for WAF could be calculated as concentrations were below the detection limits. Biodegradation occurred in all treatments based on the temporal decrease of the nC17/pristane and nC18/phytane ratios. The heterogeneity observed in all treatments was likely due to the hydrophobicity of oil and weathering processes occurring at different rates and times. The presence of dispersant did not dramatically change the half-lives of oil. Comparing degradation of oil alone as well as with dispersant present is critical to determine the fate and transport of these materials in the ocean.

The Role of Aspergillus parasiticus NRRL:3386 Strain on Petroleum Biodegradation and Biosorption Processes

Objective: Fungi play an important role in the removal of hazardous organic compounds from the environment with their extracellular multiple enzyme systems. In the bioremediation processes, fungi act as a bioreactor by breaking down or are biosorbent by accumulating organic pollutants. Materials and Methods: The aim of this study was to investigate and to compare the biodegradation and biosorption capacities of different amounts of live and dead biomasses and different concentrations of culture supernatants of Aspergillus parasiticus NRRL:3386 with gravimetric, gas chromatography-mass spectrometry (GC/MS) and scanning electron microscope (SEM) analyses. Results: This study indicated that 1 g of live biomass degraded 80% of petroleum within 4-days of incubation. The cellfree culture supernatant was not as effective as the live biomass in petroleum degradation. The petroleum biosorption was achieved at over 50% by 1 g and 2.5 g; over 70% by 5 g and 7.5 g, and over 80% by 10 g of dead biomasses. The petroleum removal efficiencies of 2 g of live and 10 g of dead biomasses were over 80%. GC/MS analysis demonstrated that C10-C18 n-alkanes (except C11 and C13) and C11, C13, C19-C26 n-alkanes were degraded 47-77% and over 80%, respectively. The moststriking result was that C27-C33 n-alkanes were efficiently degraded over 90% in a short incubation period. SEM analysis showed that gaps between fungal hyphae were clear and bright before biosorption of petroleum, whereas gaps between fungal hyphae were closed after biosorption of petroleum. Conclusion: The results clearly pointed out that A. parasiticus will make a significant contribution to advanced mycoremediation studies.

Enhancement of solubilization and biodegradation of petroleum by biosurfactant from Rhodococcus erythropolis HX-2

The demand to repair areas contaminated with hydrocarbon products has led to the development of new technologies for the treatment of contaminants in an unconventional method, that is, no physical or chemical methods are used. Biosurfactants are amphiphilic biomolecules produced by microorganisms that can be used in environments contaminated by petroleum products due to their unexceptionable tensile properties. Petroleum degrading strain Rhodococcus erythropolis HX-2 was found to be an effective producer of biosurfactants. The resulting biosurfactant (named NK) exhibits high physicochemical properties in terms of surface activity. It is capable of reducing surface tension from 54.99 to 28.89 mN/m and critical micelle concentration (CMC) is 100 mg/L. NK was found to be a substitute for chemically synthesized surfactants because of its higher solubilization efficiency for petroleum and polycyclic aromatic hydrocarbons, superior to SDS, Tween 80, Triton X-100 and Rhamnolipid (a wide used biosurfactant). In addition, it exhibits favorable emulsion stability over a wide range of pH (3–10), temperature (20–100 °C) and salinity ranges (5–20 g/L). It was found that the addition of biosurfactant can improve the efficiency of petroleum degradation, therefore it has potential applications in bioremediation.HighlightsRhodococcus erythropolis HX-2 is an effective petroleum degrading strain.HX-2 is a potential source of biosurfactant production.The biosurfactant NK reduces surface tension and exhibits high emulsification activity.The biosurfactant NK is effective over a wide range of temperatures, pH and salinity.The biosurfactant NK shows high solubilization efficiency for petroleum as well as polycyclic aromatic hydrocarbons.

Oxygen‐Containing Compounds Identified in Groundwater from Fuel Release Sites Using GCxGC‐TOF‐MS

AbstractThis research continues a 7‐year study of oxygen‐containing organic compounds present in groundwater at gasoline and diesel fuel release sites that are quantified as diesel‐range “total petroleum hydrocarbons” when measured by methods utilizing solvent extraction and gas chromatography. Two‐dimensional gas chromatography with time‐of‐flight mass spectrometry was used to tentatively identify 1162 compounds (TICs) in 113 groundwater samples from 22 sites. Samples were collected from wells either upgradient of the release, within the source zone, or downgradient of the source but still within the plume of dissolved organics associated with release. The names and formulas of all TICs found in samples from each well type are presented and the results from upgradient and downgradient locations are compared in detail. About 60% of the most frequently detected TICs in downgradient wells were also detected in upgradient wells. A majority of these were saturated straight chain alkyl acids, commonly called fatty acids, or fatty acid esters. Of TICs frequently detected in downgradient wells but not upgradient wells, over half were branched alkyl alcohols. Hierarchical cluster analysis results suggest about 80% of the chemical composition of downgradient samples is more similar to upgradient samples than to source area samples. This similarity is due to the presence of the same types of fatty acids and esters. Principal component analysis indicates a continuum of biodegradation between the source area and downgradient samples with the latter becoming more consistent with upgradient samples. Results suggest some TICs may not be petroleum degradation intermediates but compounds synthesized by microorganisms through secondary production and carbon cycling.

The influence of multiple-stage oil emplacement on deeply buried marine sandstone diagenesis: A case study on the Devonian Donghe sandstones, Tabei Uplift, Tarim Basin, NW China

Abstract Understanding the oil emplacement influence on diagenesis is one of the most key factors of reservoir quality prediction. The Devonian Donghe sandstones are deeply buried to 5700～6000 m, and they are important exploration target in the Tarim Basin, additional the reservoirs experienced multi-phase hydrocarbon accumulation and destruction. The Donghe sandstones contain various diagenetic minerals, which are mainly composed of calcite cement, a small amount of quartz overgrowth and pyrite, trace ankerite and ferrocalctie. The current study investigates the influence of multiple-stage oil emplacement on the diagenesis with particular attention to calcite and quartz cementation of marine clastic reservoir interval of the Donghe sandstones in the Tarim Basin. The samples in the oil leg and water leg have been collected and a series of studies were performed, including thin section petrography, scanning electron microscopy (SEM), carbon and oxygen isotopes and cathodoluminescence (CL) analysis. The δ13CV-PDB values of calcite cement from the oil leg and water leg between −4.73 and −1.21‰ and −3.81 to −0.86‰, respectively. The δ18OV-PDB values of calcite cement from the oil leg and water leg range from −15.59 to −6.61‰ and −14.97 to −7.76‰, respectively. Both of them display no obviously different in the oil leg and water leg. All of the δ13CV-PDB values in the whole interval of the Donghe sandstones show lightly depletion was explained mixing from marine carbon and carbon produced from bacterial sulfate reduction (BSR) that happens during petroleum degradation associated with sulfate reduced by hydrocarbons bacterially. Two dull-luminescence zones, trace Fe and Mn content, and high Fe accompanied by low Mn content, and orange-red- and bright-orange-yellow-luminescence zones in oil leg indicate four generations of calcite occurred, whereas two generations of calcite occurs in water leg, which are dull- and orange-red-luminescence zones. Two origins of calcite cement were clearly identified: marine biogenic carbonates and hydrocarbon-related from palaeo-reservoir BSR during uplift. The first generation of calcite cement originated from biogenic carbonate, the second and third generations of calcite cement were mixing from predate carbonate cement dissolved and re-precipitated, and calcite precipitated by BSR directly. Some quartz grains and K-feldspars were dissolved by residual organic acids that remained in the irreducible water, and following replaced by the fourth generation of calcite cement. Some calcite cement in the oil leg precipitated in a temperature higher than the homogeneous temperature of fluid inclusion, which indicates oil emplacement has no influence on calcite cementation. The quartz overgrowth postdate the first hydrocarbon accumulation and predate the second hydrocarbon accumulation, which originated from quartz grains dissolved by organic acids that produced from BSR and re-precipitated at a low temperature ( The current study can promote the understanding of the influence of multiple-stage hydrocarbon accumulation on diagenesis, and it can also inspire the diagenesis process of other Paleozoic hydrocarbon reservoirs in the Tarim Basin.

Paleo-Hydrothermal Predecessor to Perennial Spring Activity in Thick Permafrost in the Canadian High Arctic, and Its Relation to Deep Salt Structures: Expedition Fiord, Axel Heiberg Island, Nunavut

Paleo-Hydrothermal Predecessor to Perennial Spring Activity in Thick Permafrost in the Canadian High Arctic, and Its Relation to Deep Salt Structures: Expedition Fiord, Axel Heiberg Island, Nunavut

Study of microbial combination and nutrients in remediation of petroleum-contaminated soil

In this study, degradation of polluted soil (with 1, 4 and 9% petroleum contamination) was performed using different microbial combinations and nutrients. Biosurfactant production and lipase production of the isolated microbes were also tested. A5 and A14 (isolated from petroleum-contaminated soil (PCS)) and G1 and G6 (isolated from garden soil) showed a positive result in the biosurfactant production test. A1, A5, A6, A13, A14, A15, A16, G1 and G5 showed zones around agar wells; these bacterial strains produced lipase. Combinations of microbes were applied in treatment of 1% PCS; the combination of only bacteria and the combination of bacteria and fungi showed petroleum degradation of 71 and 73·17%, respectively. In 4 and 9% PCS, the degradation activities of microbes decreased; the microbes needed a longer time to activate the large amount of petroleum. Furthermore, tests with and without nutrients were conducted to determine the effect of using nutrients in bioremediation of PCS. The results showed that petroleum degradation percentages from the treatment using nutrients were about 5% higher than the degradation percentages from treatments without nutrients.

Enrichment of the soil microbial community in the bioremediation of a petroleum-contaminated soil amended with rice straw or sawdust

Two common organic wastes from agriculture (rice straw) and forestry (sawdust) were applied to a petroleum-contaminated soil to estimate their effectiveness in the removal of total petroleum hydrocarbons (TPHs) and polycyclic aromatic hydrocarbons (PAHs). Rice straw was the more effective amendment than the other treatments in reducing TPH contents and addition of sawdust resulted in a significant decrease in PAH removal, particularly high-molecular-weight (5–6 ring) PAHs. Principal coordinates analysis (PCoA) indicates that rice straw treatment separated only the bacterial community but sawdust greatly affected both the soil bacterial and fungal communities. Moreover, the abundance of some petroleum degraders such as the bacteria Sphingomonas, Idiomarina and Phenylobacterium and the fungi Humicola, Wallemia and Graphium was promoted by inputs of the two agricultural and forestry wastes. These results highlight the potential of waste applications in accelerating hydrocarbon biodegradation which may be attributed to the enrichment of keystone taxa that show strong positive associations with hydrocarbon degradation.

Vertical response of microbial community and degrading genes to petroleum hydrocarbon contamination in saline alkaline soil

A column microcosm was conducted by amending crude oil into Dagang Oilfield soil to simulate the bioremediation process. The dynamic change of microbial communities and metabolic genes in vertical depth soil from 0 to 80 cm were characterized to evaluate the petroleum degradation potential of indigenous microorganism. The influence of environmental variables on the microbial responds to petroleum contamination were analyzed. Degradation extent of 42.45% of n-alkanes (C8–C40) and 34.61% of 16ΣPAH were reached after 22 weeks. Relative abundance of alkB, nah, and phe gene showed about 10-fold increment in different depth of soil layers. Result of HTS profiles demonstrated that Pseudomonas, Marinobacter and Lactococcus were the major petroleum-degrading bacteria in 0–30 and 30–60 cm depth of soils. Fusarium and Aspergillus were the dominant oil-degrading fungi in the 0–60 cm depth of soils. In 60–80 cm deep soil, anaerobic bacteria such as Bacteroidetes, Lactococcus, and Alcanivorax played important roles in petroleum degradation. Redundancy analysis (RDA) and correlation analysis demonstrated that petroleum hydrocarbons (PHs) as well as soil salinity, clay content, and anaerobic conditions were the dominant effect factors on microbial community compositions in 0–30, 30–60, and 60–80 cm depth of soils, respectively.

Influence of graphene oxide and biochar on anaerobic degradation of petroleum hydrocarbons

The anaerobic degradation of petroleum is an important process in natural environments. So far, few studies have considered the response of the microbial community to nanomaterials during this process. This study explored the potential effects of graphene oxide and biochar on the anaerobic degradation of petroleum hydrocarbons in long-term experiments. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that the addition of carbon-based materials promoted the electrochemical activity of anaerobic cultures that degrade petroleum hydrocarbons. The maximum degradation rates for benzene, toluene, ethylbenzene, and xylene (BTEXs) in the cultures incubated for 10 weeks with graphene oxide (0.02mg/L) and biochar (20mg/L) were 76.5% and 77.6%, respectively. The maximum degradation rates of n-alkanes in the cultures incubated for 10 weeks with graphene oxide (2mg/L) and biochar (100mg/L) were 70.0% and 77.8%, respectively. The 16S rDNA copy numbers in the treatments with 0.02mg/L graphene oxide and 20mg/L biochar were significantly higher than others during the process (P < 0.05). In the 2nd week, the maximum copy numbers of the masD and bamA genes in the treatments with biochar were 349 copies/mL (20mg/L) and 422 copies/mL (20mg/L), respectively, and in the treatments with graphene oxide were 289 copies/mL (0mg/L) and 366 copies/mL (0.02mg/L). The contents of carbon-based materials had slight effects on the microbial community structure, whereas the culture time had obvious effects. Paracoccus denitrificans, Pseudomonas aeruginosa, and Hydrogenophaga caeni were the dominant microorganisms in the culture systems under all treatments.