Biodegradation Of Hydrocarbons Research Articles

Biosurfactant Producing Bacteria Capable of Hydrocarbon Biodegradation from the Soils of Hassi-Messaoud Region of Algeria

Biosurfactant Producing Bacteria Capable of Hydrocarbon Biodegradation from the Soils of Hassi-Messaoud Region of Algeria

Biochar inoculated with Pseudomonas putida alleviates its inhibitory effect on biodegradation pathways in phenanthrene-contaminated soil

Controversial results are reported whereby biodegradation of polycyclic aromatic hydrocarbons (PAHs) can be promoted or inhibited by biochar amendment of soil. Metabolomics was applied to analyze the metabolic profiles of amendment with biochar (BB) and biochar inoculated with functional bacteria (Pseudomonas putida) (BP) involved in phenanthrene (PHE) degradation. Additionally, metagenomic analysis was utilized to assess the impact of different treatments on PHE degradation by soil microorganisms. Results indicated that BB treatment decreased the PHE biodegradation of the soil indigenous bacterial consortium, but BP treatment alleviated this inhibitory effect. Metabolomics revealed the differential metabolite 9-phenanthrol was absent in the BB treatment, but was found in the control group (CK), and in the treatment inoculated with the Pseudomonas putida (Ps) and the BP treatment. Metagenomic analysis showed that biochar decreased the abundance of the cytochrome P450 monooxygenase (CYP116), which was detected in the Pseudomonas putida, thus alleviating the inhibitory effect of biochar on PHE degradation. Moreover, a noticeable delayed increase of functional gene abundance and enzymes abundance in the BB treatment was observed in the PHE degradation pathway. Our findings elucidate the mechanism of inhibition with biochar amendment and the alleviating effect of biochar inoculated with degrading bacteria.

Assessment and Biodegradation of Polycyclic Aromatic Hydrocarbons in Soil and Water Around Petroleum Products Depot Suleja, Nigeria.

Petroleum contamination constitutes a frequent incidence in various petroleum depots in Nigeria. In this study, the polycyclic aromatic hydrocarbons (PAHs) present in soil and water in communities around Petroleum Products Marketing Company (PPMC) Suleja, Nigeria, were evaluated and degraded using indigenous microorganisms. The samples sites were divided into 7 plots from where samples of water and soil were obtained: one within the PPMC depot, five from communities surrounding the depot, and the control 93,000km from the depot. The microbial counts were determined using spread plate inoculation technique on minimal salt media. The microbial isolates were characterized and identified based on their cultural, biochemical, and molecular characteristics. The potential of the microbial isolates to utilize 0.05 mL of diesel, kerosene, engine oil, and crude oil was determined in a Bushnell Haas Broth, and the biodegradation was determined by total viable cell counts and spectrophotometry. The ability of the isolates to mineralize PAHs was also evaluated in a minimum salt media. The bacterial isolates were species of Streptococcus, Pseudomonas, Staphylococcus, Proteus, Escherichia, and Bacillus, while species of Penicillium, Aspergillus, Mucor, and Rhizopus were isolated among the fungi. Aspergillus niger strain ATCC 1015 and Bacillus thuringiensis strain M43 showed high capacity to utilize the 16 priority PAHs. The pahE1 gene was used by Bacillus thuringiensis, Pseudomonas aeruginosa and A. niger, while Penicillium notatum used pahE2 gene for the degradation of the PAH. The current study identified microbial isolates that can utilize priority PAHs, making them beneficial for oil spill bioremediation in tropical environments.

Production of surfactin from novel Bacillus spp. isolated from soil and its antifungal properties

Aim: This research aimed to screen the biosurfactant-producing bacteria from soil, especially for the betterment of the environment in terms of bioremediation and biodegradation of lipids and hydrocarbons. Methodology: Bacillus spp. isolated from the soil was cultured and inoculated into different mineral media such as Glucose, Sawdust, and Bagasse mineral media. The surfactin was extracted and the activity was studied using oil emulsification test, oil spreading assay, and drop collapse assay. Bacillus spp. that provided better results were sequenced and submitted to NCBI. The surfactin of the specific bacteria was characterized using TLC, UV-vis spectra, and FTIR analysis. Finally, the antifungal activity assay was performed against Aspergillus flavus, Rhizopus spp., and Aspergillus niger. Results: Bacillus species subjected to gene sequencing was identified as Bacillus mycoids strain ARJCBNR (On464184). UV-vis spectra and FTIR analyses revealed various functional groups such as 3356.14 cm-1 (N-H stretch), 1635.64 cm-1 (C=O amide), and 1211 cm-1 (C-O stretch) representing the surfactin compound between 4000 and 500 cm-1. Upon antifungal activity, sawdust-extracted surfactin had a higher zone of inhibition against all the tested fungi. Interpretation: This study revealed that Bacillus spp. can utilize agro-industrial waste as substrate to produce surfactin. Also, the surfactin extracted from sawdust mineral media showed higher antifungal activity. Key words: Bacillus spp., Biosurfactant, Mineral media, Soil, Surfactin

Saline wastewater treatment by bioelectrochemical process (BEC) based on Al-electrocoagulation and halophilic bacteria: optimization using ANN with new approach

ABSTRACT In the present study, a bioelectrochemical reactor (BEC) was utilized to treat two types of real saline produced water (PW). BEC was designed based on the combination of electrocoagulation (EC) process with halophilic microorganisms, and it was assessed in terms of biodegradation of hydrocarbons. The effects of various operating parameters including the current density, electrical contact time (On/Off), hydraulic retention time (HRT), and total dissolved solids (TDS) at different levels on the chemical oxygen demand (COD) removal efficiency, settleability, and performance of isolated halophilic microorganisms were examined. Additionally, a novel neural network (ANN) approach modelling using adaptive factors was used to predict and optimize the effects and interactions between operating parameters during BEC process by predicting complicated mechanisms and variations associated with microorganisms. In addition, a new algorithm was developed for the sensitivity analysis to achieve the optimum operating conditions and obtain maximum efficiency in COD removal, sludge volume index (SVI), mixed liquor suspended solids (MLSS), and specific electrical energy consumption (SEEC), simultaneously. BEC was found to be significantly more effective at removing most hydrocarbons, particularly pristine and phytane. In addition, the results showed a significant improvement in settling ability of the biological flocs with average SVI of 91.5 mL/g and a size of 178.25 μm using BEC. Based on estimated operating costs and energy consumption, BEC was more cost-effective and efficient than other bioelectrochemical systems.

Effect of glucose on biodegradation of hydrocarbons in crude-oil polluted soil undergoing bioremediation

Bioremediation of crude oil polluted soil can be enhanced by addition of easily assimilated carbon sources such as glucose. The aim of this study was to determine the effect of increasing concentration of glucose on biodegradation of hydrocarbons in crude-oil polluted soil undergoing bioremediation. Some hydrocarbon utilizing bacteria and fungi were used as bioremediation agents in the study. Soil artificially polluted with crude-oil was divided into 5 setups: CT (control), S1, S2, S4, and S8. Suspension of the bioremediation agents and nutrients were added to the setups. About 5, 10, 20, and 40 g glucose were added to S1, S2, S4, and S8 respectively: equivalent to 1, 2, 4, and 8 % glucose concentration. Soil moisture in the setups was maintained at 10-20 % during the experimental period. Total hydrocarbon concentration (THC), and population of total heterotrophic bacteria (THB), hydrocarbon utilizing bacteria (HUB), total fungi (TF), & hydrocarbon utilizing fungi (HUF) were determined on day 1 and 21. Results obtained showed that increase in HUB occurred only in setup S1, and setup S1 had the highest extent of hydrocarbon degradation (18.93 %). Setup S8 had the lowest extent of hydrocarbon degradation (0.79 %). It is concluded that glucose concentration of 1 % and below will enhance biodegradation of hydrocarbons in crude-oil polluted soils, whereas high glucose concentration will retard hydrocarbon biodegradation. Also, the study indicates the possibility of fungi not partaking in hydrocarbon degradation when glucose is made available.

Biodegradation of Polycyclic Aromatic Hydrocarbons (PAHs) by Diutina mesorugosa isolated in the Amazon, Brazil

There is a demand for new microorganisms with the potential to degrade recalcitrant petroleum compounds, such as polycyclic aromatic hydrocarbons (PAHs). The objective of this research was to evaluate the potential of the AM15 strain isolated from water samples from the effluent dike of the Urucu petroleum Province, to degrade a mixture of PAHs. After isolation in culture medium, and initial screening by Gram stain, it was found to be yeast. The characterization of the strain was carried out by analysis based on the sequences of the polymorphic regions ITS1/ITS2 and D1/D2 of the 28S rRNA gene, concomitant with the restriction fragment size polymorphism, generated by the Polymerase Chain Reaction-Fragment Length Polymorphism of Restriction (PCR-RFLP). The ability of yeast to degrade petroleum compounds was determined by testing with the redox indicator 2,6-Dichlorophenol Indophenol (DCPIP), and degradation was confirmed and quantified by gas chromatography and mass spectrometry (GC-MS) analyses. Molecular analyzes indicated that the AM15 strain belongs to the Diutina mesorugosa species. The results obtained in the test carried out with DCPIP showed that the AM15 strain has the potential to degrade hydrocarbons present in petroleum and diesel oil. GC-MS analyzes confirmed that the AM15 strain was able to degrade 79.4% of a mixture of PAHs in 21 days. These results suggest that D. mesorugosa AM15 is promising to degrade different types of hydrocarbons, and can be used as a tool in the bioremediation of oil-impacted areas.

Regulating the biodegradation of petroleum hydrocarbons with different carbon chain structures by composting systems

Composting can decrease petroleum hydrocarbons in petroleum contaminated soils, however the microbial degradation mechanisms and regulating method for biodegradation of petroleum hydrocarbons with different carbon chain structures in the composting system have not yet been investigated. This study analyzed variations of total petroleum hydrocarbon concentrations with C ≤ 16 and C > 16, Random Forest model was applied to identify the key microorganisms for degrading the petroleum hydrocarbon components with specific structure in biomass-amended composting. Regulating method for biodegradation of petroleum hydrocarbons with different carbon chain structures was proposed by constructing the influence paths of “environmental factors-key microorganisms- total petroleum hydrocarbons”. The results showed that composting improved the degradation rate of C ≤ 16 fraction and C > 16 fraction of petroleum hydrocarbons by 67.88 % and 61.87 %, respectively. Analysis of the microbial results showed that the degrading bacteria of the C ≤ 16 fraction had degradation advantages in the heating phase of the compost, while the C > 16 fraction degraded better in the cooling phase. Moreover, microorganisms that specifically degraded C > 16 fractions were significantly associated with total nitrogen and nitrate nitrogen. The biodegradation of C ≤ 16 fraction was regulated by organic matter, moisture content, and temperature. The composting system modified by biogas slurry was effective in removing of petroleum hydrocarbons with different carbon chain structures in soil by regulating the metabolic potential of the 46 key microorganisms. This study given their expected importance to achieve the purpose of treating waste with waste and contributing to soil utilization as well as pollution remediation.

Oil-Contaminated Soil Remediation with Biodegradation by Autochthonous Microorganisms and Phytoremediation by Maize (Zea mays).

Biological methods are currently the most commonly used methods for removing hazardous substances from land. This research work focuses on the remediation of oil-contaminated land. The biodegradation of aliphatic hydrocarbons and PAHs as a result of inoculation with biopreparations B1 and B2 was investigated. Biopreparation B1 was developed on the basis of autochthonous bacteria, consisting of strains Dietzia sp. IN118, Gordonia sp. IN101, Mycolicibacterium frederiksbergense IN53, Rhodococcus erythropolis IN119, Rhodococcus globerulus IN113 and Raoultella sp. IN109, whereas biopreparation B2 was enriched with fungi, such as Aspergillus sydowii, Aspergillus versicolor, Candida sp., Cladosporium halotolerans, Penicillium chrysogenum. As a result of biodegradation tests conducted under ex situ conditions for soil inoculated with biopreparation B1, the concentrations of TPH and PAH were reduced by 31.85% and 27.41%, respectively. Soil inoculation with biopreparation B2 turned out to be more effective, as a result of which the concentration of TPH was reduced by 41.67% and PAH by 34.73%. Another issue was the phytoremediation of the pre-treated G6-3B2 soil with the use of Zea mays. The tests were carried out in three systems (system 1-soil G6-3B2 + Zea mays; system 2-soil G6-3B2 + biopreparation B2 + Zea mays; system 3-soil G6-3B2 + biopreparation B2 with γ-PGA + Zea mays) for 6 months. The highest degree of TPH and PAH reduction was obtained in system 3, amounting to 65.35% and 60.80%, respectively. The lowest phytoremediation efficiency was recorded in the non-inoculated system 1, where the concentration of TPH was reduced by 22.80% and PAH by 18.48%. Toxicological tests carried out using PhytotoxkitTM, OstracodtoxkitTM and Microtox® Solid Phase tests confirmed the effectiveness of remediation procedures and showed a correlation between the concentration of petroleum hydrocarbons in the soil and its toxicity. The results obtained during the research indicate the great potential of bioremediation practices with the use of microbial biopreparations and Zea mays in the treatment of soils contaminated with petroleum hydrocarbons.

Co-culture of Acinetobacter sp. and Scedosporium sp. immobilized beads for optimized biosurfactant production and degradation of crude oil

The widespread exploration and exploitation of crude oil has increased the prevalence of petroleum hydrocarbon pollution in the marine and coastal environment. Bioremediation of petroleum hydrocarbons using cell immobilization techniques is gaining increasing attention. In this study, the crude oil degradation performance of bacterial and fungal co-culture was optimized by entrapping both cells in sodium-alginate and polyvinyl alcohol composite beads. Results indicate that fungal cells remained active after entrapment and throughout the experiment, while bacterial cells were non-viable at the end of the experimental period in treatments with the bacterial-fungal ratio of 1:2. A remarkable decrease in surface tension from 72 mN/m to 36.51 mN/m was achieved in treatments with the bacterial-fungal ratio of 3:1. This resulted in a significant (P < 0.05) total petroleum hydrocarbon (TPH) removal rate of 89.4%, and the highest degradation of n-alkanes fractions (from 2129.01 mg/L to 118.53 mg/L), compared to the other treatments. Whereas PAHs removal was highest in treatments with the most fungal abundance (from 980.96 μg/L to 177.3 μg/L). Furthermore, enzymes analysis test revealed that catalase had the most effect on microbial degradation of the target substrate, while protease had no significant impact on the degradation process. High expression of almA and PAH-RHDa genes was achieved in the co-culture treatments, which correlated significantly (P < 0.05) with n-alkanes and PAHs removal, respectively. These results indicate that the application of immobilized bacterial and fungal cells in defined co-culture systems is an effective strategy for enhanced biodegradation of petroleum hydrocarbons in aqueous systems.

Biodegradation of saturate fraction of crude oil and production of signature carboxylic acids

Bacteria degrading large portion of saturated hydrocarbons are important for crude oil bioremediation. This study investigates Novosphingobium sp. S1, Gordonia amicalis S2 and Gordonia terrae S5 capability of degrading wide range of saturated hydrocarbons from Congo Bilondo crude oil and discusses the degradation pathway. A parallel analytical approach combining GC-MS and LC-HRMS enabled characterization of saturated hydrocarbons and comprehensive determination of carboxylic acid metabolites produced during biodegradation, respectively. Results showed that the three strains could efficiently degrade the n-alkanes (C10–C28) as well as methyl-substituted alkanes (C11–C26). The series of mono-, hydroxy- and dicarboxylic acids identified in this study confirmed the active biodegradation of the saturate fraction and suggest their degradation was via the bi-terminal oxidation pathway. This is the first study linking these bacterial species to bi-terminal oxidation of the saturated hydrocarbons. The study highlights the potential application of the bacterial strains in the bioremediation of crude oil contaminated sites. Additionally, while carboxylic acids is indicated as a suitable and valuable metabolic biomarker, its application is considered feasible and cost effective for rapid monitoring and evaluation of hydrocarbon biodegradation.

Update on new trend and progress of the mechanism of polycyclic aromatic hydrocarbon biodegradation by Rhodococcus, based on the new understanding of relevant theories: a review.

Rapid industrial and societal developments have led to substantial increases in the use and exploitation of petroleum, and petroleum hydrocarbon pollution has become a serious threat to human health and the environment. Polycyclic aromatic hydrocarbons (PAHs) are primary components of petroleum hydrocarbons. In recent years, microbial remediation of PAHs pollution has been regarded as the most promising and cost-effective treatment measure because of its low cost, robust efficacy, and lack of secondary pollution. Rhodococcus bacteria are regarded as one of main microorganisms that can effectively degrade PAHs because of their wide distribution, broad degradation spectrum, and network-like evolution of degradation gene clusters. In this review, we focus on the biological characteristics of Rhodococcus; current trends in PAHs degradation based on knowledge maps; and the cellular structural, biochemical, and enzymatic basis of degradation mechanisms, along with whole genome and transcriptional regulation. These research advances provide clues for the prospects of Rhodococcus-based applications in environmental protection.

Efficient and eco-friendly mixed bacterial consortium for petroleum wastewater treatment: Effect of the bio-augmentation and biosurfactant addition on hydrocarbon biodegradation

In the present investigation, we aimed to study biological petroleum wastewater treatment. A bioprocess based on the use of a mixed bacterial consortium along with the addition of Biosurfactant (BioS) and bioaugmentation with BioS producing strains were evaluated. The consortium was the combination of two bacterial strains with the capacity to metabolize hydrocarbons, Baci and B201. Two other strains BH1 and BSS2 selected for their ability to degrade hydrocarbons as well as to produce BioS were also exploited. The effect of ex-situ and in-situ produced BioS on hydrocarbon biodegradation were compared. Obtained results demonstrated a moderate capacity to remove crude oil from contaminated water of about 47% for the consortium. The best improvement of hydrocarbon biodegradation of about 84% was obtained when adding BH1 derived BioS solely. However, ex-situ produced BioS exhibited better results. Regarding the wastewater characteristics, we note a decrease of the COD/BOD5 Ratio to reach 2.64. Thus, the wastewater became easily biodegradable. The described bioprocess is of great interest for the bioremediation of petroleum effluents. BioS addition as well as bioaugmentation enhanced crude oil removal.

Ribosomal RNA gene operon copy number, a functional trait indicating the hydrocarbon degradation level of bacterial communities

The lack of universal indicators for predicting microbial biodegradation potential and assessing remediation effects limits the generalization of bioremediation. The community-level ribosomal RNA gene operon (rrn) copy number, an important functional trait, has the potential to serve as a key indicator of the bioremediation of organic pollutants. A meta-analysis based on 1275 samples from 26 hydrocarbon-related studies revealed a positive relationship between the microbial hydrocarbon biodegradation level and the community-level rrn copy number in soil, seawater and culture. Subsequently, a microcosm experiment was performed to decipher the community-level rrn copy number response mechanism during total petroleum hydrocarbon (TPH) biodegradation. The treatment combining straw with resuscitation-promoting factor (Rpf) exhibited the highest community-level rrn copy number and the most effective biodegradation compared with other treatments, and the initial TPH content (20,000 mg kg-1) was reduced by 67.67% after 77 days of incubation. TPH biodegradation rate was positively correlated with the average community-level rrn copy number (p = 0.001, R2 = 0.5781). Both meta and community analyses showed that rrn copy number may reflect the potential of hydrocarbon degradation and microbial dormancy. Our findings provide insight into the applicability of the community-level rrn copy number to assess bacterial biodegradation for pollution remediation.

Anaerobic biodegradation of pyrene and benzo[a]pyrene by a new sulfate-reducing Desulforamulus aquiferis strain DSA

The study of anaerobic high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) biodegradation under sulfate-reducing conditions by microorganisms, including microbial species responsible for biodegradation and relative metabolic processes, remains in its infancy. Here, we found that a new sulfate-reducer, designated as Desulforamulus aquiferis strain DSA, could biodegrade pyrene and benzo[a]pyrene (two kinds of HMW-PAHs) coupled with the reduction of sulfate to sulfide. Interestingly, strain DSA could simultaneously biodegrade pyrene and benzo[a]pyrene when they co-existed in culture. Additionally, the metabolic processes for anaerobic pyrene and benzo[a]pyrene biodegradation by strain DSA were newly proposed in this study based on the detection of intermediates, quantum chemical calculations and analyses of the genome and RTqPCR. The initial activation step for anaerobic pyrene and benzo[a]pyrene biodegradation by strain DSA was identified as the formation of pyrene-2-carboxylic acid and benzo[a]pyrene-11-carboxylic acid by carboxylation Thereafter, CoA ligase, ring reduction through hydrogenation, and ring cracking occurred, and short-chain fatty acids and carbon dioxide were identified as the final products. Additionally, DSA could also utilize benzene, naphthalene, anthracene, phenanthrene, and benz[a]anthracene as carbon sources. Our study can provide new guidance for the anaerobic HMW-PAHs biodegradation under sulfate-reducing conditions.

Cell toxic damages during polycyclic aromatic hydrocarbons biodegradation by Pseudomonas aeruginosa G24

Many microorganisms are capable of degrading polycyclic aromatic hydrocarbons (PAHs), but the extent of toxicity of PAHs on these degraders is not yet fully understood. In this study, the physicochemical responses of the PAH-degrading strain Pseudomonas aeruginosa (P. aeruginosa) G24 under PAHs stress were investigated. After 21 days of incubation, the total removal rates of phenanthrene (Phe) and pyrene (Pyr) by P. aeruginosa G24 were 43.8 % and 36.8 %, respectively. Among them, about 11 % of PAHs were absorbed by pellets in the molecular form, resulting in net biodegradation rates of 32.9 % and 25.2 % for Phe and Pyr, respectively. Further investigations revealed that the surface zeta potential of the P. aeruginosa G24 increased from 16.78 to 19.31 mV to 30.32–33.59 mV, the percentage of permeable cells increased from 24.5 %–32.5 % to 52.4 %–56.2 %, and the EPS contents decreased from 2.34 to 3.37 mg L−1 to 0.63–1.80 mg L−1 in the “Phe–MSM + P. aeruginosa G24” and “Pyr–MSM + P. aeruginosa G24” systems. The damages of P. aeruginosa G24 during PAH degradation included increased zeta potential and permeability on the bacterial surface, increased cell apoptosis, reduced EPS contents, as well as injured cell membrane structures. The findings of the study suggest that the damages or apoptosis of P. aeruginosa G24 may inhibit the continuous degradation of residual PAHs during the late stage of incubation.

Improved degradation of petroleum contaminants in hydraulic fracturing flowback and produced water using laccase immobilized on functionalized biochar

Large quantities of hydraulic fracturing flowback and produced water (HF-FPW) represent an important environmental issue owing to their inclusion of toxic petroleum contaminants. Enzymatic degradation is a promising approach for treating these pollutants. However, the low stability and poor reusability of free enzymes greatly inhibit their applications. This study investigated the effect of biochar-immobilized laccases on the biodegradation of petroleum contaminants in HF-FPW. Acid functionalization of corn straw biochar increased its surface area and pore volume, allowing it to adsorb additional laccase on the surface. Biochar-immobilized laccase exhibited a high tolerance to a low pH and high temperatures and retained >81.0% of its relative activity at 4 °C for 20 d. In addition, the immobilized laccase displayed reusability after six reaction cycles, retaining 40.9% of its activity. Supplementation with immobilized laccase substantially improved microbial growth and fluorescein diacetate hydrolase activity in HF-FPW, which were up to 25.5 times and 4.9 times higher than those of the free laccase treatment, respectively. The immobilized laccase also elevated the transcription levels of degradation genes such as rub and xylE, and greatly enhanced the biodegradation of n-alkanes (reduction from 112.4 mg/L to 41.9 mg/L) and polycyclic aromatic hydrocarbons (reduction from 2606.2μg/L to 1526.6μg/L). Full-length 16S rRNA gene sequencing revealed that Pseudomonas stutzeri, Pseudomonas balearica, and Stenotrophomonas maltophilia dominated the microbial community and were potential functional populations. This study represents the first attempt of utilizing biochar-immobilized laccase to treat HF-FPW and has important implications for efforts to develop strategies for HF-FPW remediation.

Impact of natural weathering on source rocks: ESI FT-ICR MS evidence from Triassic Chang 7 outcrop profile in Tongchuan City, Southern Ordos Basin (China)

Atmospheric, water, and biological interactions with source rocks exposed at or near the surface due to tectonic uplift can result in both the loss of quantity and variability in the chemical composition of organic matter (OM) in source rocks during natural weathering, especially in extractable organic matter (EOM). Most of the research work on weathering has focused on characterization of the changes of saturated and aromatic hydrocarbon fractions in EOM at molecular level. However, few studies have reported how weathering affects polar compounds in EOM. In this work, a series of source rock samples with varying degrees of weathering were obtained from the Yishicun Profile of Triassic Chang 7 member in Tongchuan City of the Ordos Basin, providing an opportunity to study the weathering mechanisms of EOM in weathered source rocks. Gas chromatography-mass (GC-MS) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) were used to analyze the chemical composition and variations in the characteristics of EOM. Asphaltenes, resin fractions, and the slightly oxygenated heteroatomic species (O1–O3) identified by positive- and negative-ion ESI showed a clearly pronounced enrichment trend during weathering due to the oxidation of saturated and aromatic hydrocarbons (biodegradation and photo-oxidation). While saturated, aromatic fractions and the highly oxygenated heteroatomic species (O5–O6) showed a declining trend. Additionally, it was also observed that the highly oxygenated heteroatomic species with low carbon number (CN) showed a more significant loss trend than their high CN counterparts during weathering. This may be due to depletion by surface water leaching due to the high water solubility of these compounds. Therefore, both the oxidation and surface water leaching can play important roles in regulating the OM chemical composition of source rocks during natural weathering.

Correlating the succession of microbial communities from Nigerian soils to petroleum biodegradation

Whilst biodegradation of different hydrocarbon components has been widely demonstrated to occur by specialist oil-degrading bacteria, less is known about the impact on microbial communities as a function of oil composition by comparing the biodegradation of chemically complex fuels to synthetic products. The objectives of this study were (i) to assess the biodegradation capacity and succession of microbial communities isolated from Nigerian soils in media with crude oil or synthetic oil as sole sources of carbon and energy, and (ii) to assess the temporal variability of the microbial community size. Community profiling was done using 16 S rRNA gene amplicon sequencing (Illumina), and oil profiling using gas chromatography. The biodegradation of natural and synthetic oil differed probably due to the content of sulfur that may interfere with the biodegradation of hydrocarbons. Both alkanes and PAHs in the natural oil were biodegraded faster than in the synthetic oil. Variable community responses were observed during the degradation of alkanes and more simple aromatic compounds, but at later phases of growth they became more homogeneous. The degradation capacity and the size of the community from the more-contaminated soil were higher than those from the less-contaminated soil. Six abundant organisms isolated from the cultures were found to biodegrade oil molecules in pure cultures. Ultimately, this knowledge may contribute to a better understanding of how to improve the biodegradation of crude oil by optimizing culturing conditions through inoculation or bioaugmentation of specific bacteria during ex-situ biodegradation such as biodigesters or landfarming.

Distribution and biodegradation of nonextractable polycyclic aromatic hydrocarbons in particle-size aggregates of field-contaminated soils

Distribution and biodegradation of nonextractable polycyclic aromatic hydrocarbons in particle-size aggregates of field-contaminated soils