Hydrocarbon Degradation Research Articles

Advances in the Degradation of Polycyclic Aromatic Hydrocarbons by Yeasts: A Review

Polycyclic aromatic hydrocarbons (PAHs) are toxic organic compounds produced during the incomplete combustion of organic materials and are commonly found in the environment due to anthropogenic activities such as industrial and vehicular emissions as well as natural sources, mainly volcanic eruptions and forest fires. PAHs are well known for their bioaccumulative capacity and environmental persistence, raising concerns due to their adverse effects on human health, including their carcinogenic potential. In recent years, bioremediation has emerged as a promising, effective, and sustainable solution for the degradation of PAHs in contaminated environments. In this context, yeasts have proven to be key microorganisms in the degradation of these compounds, owing to their ability to metabolize them through a series of enzymatic pathways. This review explores the advancements in yeast-mediated degradation of PAHs, with a particular focus on the role of enzymes such as cytochrome P450 (CYPs), epoxide hydrolases (EHs), and glutathione S-transferases (GSTs), which facilitate the breakdown of these compounds. The review also discusses the applications of genetic engineering to enhance the efficiency of yeasts in PAH degradation and the use of omics technologies to predict the catabolic potential of these organisms. Additionally, it examines studies addressing the degradation of benzo[a]pyrene (BaP) by yeasts such as Debaryomyces hansenii, and the potential future implications of omics sciences for developing new bioremediation.

Disentangling the microbial genomic traits associated with aromatic hydrocarbon degradation in a jet fuel-contaminated aquifer.

Spills of petroleum or its derivatives in the environment lead to an enrichment of microorganisms able to degrade such compounds. The interactions taking place in such microbial communities are complex and poorly understood, since they depend on multiple factors, including diversity and metabolic potential of the microorganisms and a broad range of fluctuating environmental conditions. In our previous study, a complete characterization, based on high-throughput sequencing, was performed in a jet-fuel plume using soil samples and in in-situ microcosms amended with hydrocarbons and exposed for 120days. Herein, we propose a metabolic model to describe the monoaromatic hydrocarbon degradation process that takes place in such jet-fuel-contaminated sites, by combining genome-centered analysis, functional predictions, and flux balance analysis (FBA). In total, twenty high/medium quality MAGs were recovered; three of them assigned to anaerobic bacteria (Thermincolales, Geobacter and Pelotomaculaceace) and one affiliated to the aerobic bacterium Acinetobacter radioresistens, potentially the main players of hydrocarbon degradation in jet-fuel plumes. Taxonomic assignment of the genes indicated that a putative new species of Geobacteria has the potential for anaerobic degradation pathway, while the Pelotomaculaceae and Thermincolales members probably act via syntrophy oxidizing acetate and hydrogen (fermentation products of oil degradation) via sulfate and/or nitrate reduction.

Screening, Isolation and Hydrocarbon Degradation Characteristics of Yeasts from Mangrove Sediments of Kerala

The aim of the present work was to examine the hydrocarbon degradation potential of yeasts isolated from the mangrove sediments. Mangrove sediments around the world were considered to be heavily polluted with oil contaminants and the microbes dwelling in them were believed to be highly active in metabolizing and detoxifying the oil fractions. In the present study, 70 yeast isolates were screened for their lipolytic activity qualitatively and 35 of them which showed comparatively higher lipolysis were tested for their crude oil degradation ability. Screening of hydro-carbon utilizing isolates was performed on Bushnell Haas agar media overlaid with 1% crude oil and the appearance of colonies were considered a positive. Three isolates were selected based on this and were sequenced using ITS gene of the 18S region of the rDNA and identified to be Candida tropicalis. The extent of crude oil degradation was assessed by growing the isolates in basal medium supplemented with heavy crude oil as the carbon source for 21 days. The residual crude oil fractions were then analyzed using GC-MS to quantitatively measure the degradation potential of each isolate. Our results showed that the yeast strains under study could actively metabolize the crude oil including the higher chain fractions which make them efficient hydrocarbon degraders that can be used in the bioremediation processes.

Roseomonas aestuarii, as a Potential In Situ Surfactin Producer During Hydrocarbon Biodegradation.

In situ biosurfactant production by hydrocarbon degrader microorganisms is an attractive approach in the bioremediation of oil contamination because of their compatibility, biodegradability, environmental safety, and stability under extreme environmental conditions. Given the high efficiency of bacteria in degrading petroleum hydrocarbons, the present work studied the detection and characterization of a biosurfactant-producing hydrocarbon degrader, Roseomonas aestuarii NB833. This strain was able to synthesize a biosurfactant during the biodegradation of crude oil, which reduced the surface tension of the aqueous system from 70 to 34 mN m-1, with a critical micelle concentration of 200 mg L-1. The emulsification ability of the biosurfactant was sustained at various temperatures, pH values, and salinities. The biosurfactant chemical structure was identified via FT-IR, LC-MS, and NMR analyses. These analyses confirmed the production of surfactin-C14 with a molecular mass of 1007 g mol-1. These results revealed the high potential of R. aestuarii NB833 as an in situ surfactin-producing bacteria for bioremediation applications under extreme environmental conditions.

Two types of microorganisms isolated from petroleum hydrocarbon pollutants: Degradation characteristics and metabolic pathways analysis of petroleum hydrocarbons.

The petroleum hydrocarbons in seawater have been worldwide concern contaminants. Biological method, with the advantages of low cost, minimal environmental impact, and no secondary pollution, is a promising method for petroleum hydrocarbon treatment. In this study, two strains, identified as Stenotrophomonas acidaminiphila and Ochrobactrum, were demonstrated to possess the ability to degrade petroleum hydrocarbons. The mixed culture composed of Stenotrophomonas acidaminiphila and Ochrobactrum at a 2:1 ratio was able to achieve 79.41% degradation of the total petroleum hydrocarbons after 5 days. Besides, the average removal efficiencies of C10-C30 components in petroleum hydrocarbons by Stenotrophomonas acidaminiphila, Ochrobactrum, and mixed culture were 62.98%, 59.14% and 73.30%, respectively. The possible degradation pathways of petroleum hydrocarbons had been speculated through gas chromatography-mass spectrometry (GC-MS) and differential gene expression metabolomics analyses. The toxicity of products from the biodegradation of petroleum hydrocarbons was greatly reduced.

Microbiomes of urban trees: unveiling contributions to atmospheric pollution mitigation.

Urban trees are crucial in delivering essential ecosystem services, including air pollution mitigation. This service is influenced by plant associated microbiomes, which can degrade hydrocarbons, support tree health, and influence ecological processes. Yet, our understanding of tree microbiomes remains limited, thus affecting our ability to assess and quantify the ecosystem services provided by trees as complex systems. The main hypothesis of this work was that tree microbiomes concur to hydrocarbon biodegradation, and was tested through three case studies, which collectively investigated two tree micro-habitats (phyllosphere and tree cavity organic soil-TCOS) under various conditions representing diverse ecological scenarios, by applying different culture-based and molecular techniques and at different scales. The integration of all results provided a more comprehensive understanding of the role of microbiomes in urban trees. Firstly, bacterial strains isolated from the phyllosphere of Quercus ilex were characterized, indicating the presence of Plant-Growth Promoting bacteria and strains able to catabolize PAHs, particularly naphthalene and phenanthrene. Secondly, naphthalene biodegradation on artificially spiked Hedera helix leaves was quantified in greenhouse experiments on inoculated and untreated plants. The persistence of the inoculated strain and community structure of epiphytic bacteria were assessed by Illumina sequencing of V5-V6 hypervariable regions of 16S rRNA gene. Results showed that naphthalene degradation was initially faster on inoculated plants but later the degradation rates became similar, probably because bacterial populations with hydrocarbon-degrading abilities gradually developed also on non-inoculated plants. Finally, we explored bacterial and fungal biodiversity hosted by TCOS samples, collected from six large trees located in an urban park and belonging to different species. Microbial communities were characterized by Illumina sequencing of V5-V6 hypervariable regions of bacterial gene 16S rRNA and of fungal ITS1. Results indicated TCOS as a distinct substrate, whose microbiome is determined both by the host tree and by canopy environmental conditions and has a pronounced aerobic hydrocarbon degradation potential. Overall, a better assessment of biodiversity associated with trees and the subsequent provision of ecosystem services constitute a first step toward developing future new microbe-driven sustainable solutions, especially in terms of support for urban green planning and management policy.

Arsenic Enhances the Degradation of Middle-Chain Petroleum Hydrocarbons by Rhodococcus sp. 2021 Under Their Combined Pollution.

The efficient and green remediation of petroleum hydrocarbon (PH) contamination has emerged as a viable strategy for environmental management. Here, we investigated the interaction between arsenic and PH degradation by Rhodococcus sp. 2021 under their combined pollution. The strain exhibited disparate responses to varying concentrations and valences of arsenic. The elevated concentration of arsenic (>100 mg/L) facilitated the degradation of PHs, and there was a positive correlation between arsenic-promoted degradation of PHs and their carbon-chain length. The degradation of PHs changed with arsenic conditions as follows: trivalent arsenic groups > pentavalent arsenic groups > arsenic-free groups (control). Arsenite and arsenate significantly promoted the gene expression of arsenic metabolism and alkane degrading. But unlike arsenite, arsenate also significantly promoted the gene expression of phosphate metabolism. And arsenite promoted the up-regulation of the expression of genes involved in the process of PHs oxidation and fatty acid oxidation. These results highlight the potential of Rhodococcus sp. 2021 in the remediation of combined total petroleum hydrocarbon (TPH) and heavy metal pollution, providing new insights into the green and sustainable bioremediation of combined pollution of organic matters such as PHs and heavy metals/heavy metal-like elements such as arsenic.

Comparing theeffect of applying different types of amendments on carbon emissions and kinetics of degrading total petroleum hydrocarbons in artificial petroleum-contaminated soil.

Contamination byspent engine oil represents a significant global environmental challenge as it poses a major hazard to human health, animals, plants, microorganisms, the soil ecosystem, and aquatic ecosystems. This study assumes that some amendments differ significantly in their ability to degrade petroleum hydrocarbons. Therefore, this incubation study was conductedto investigate the effect of different types of inorganic and organic amendments (zeolite, bone char, banana leaves biochar, and wood chips biochar) on carbon emissions (CO2-C) and the kinetics of total petroleum hydrocarbons (TPHC) degradation in artificial petroleum-contaminated soil. These amendments wereadded to the soil under study at adose of 3% (w/w). At the end of the incubation period, applying zeolite, bone char, banana leaves biochar, and wood chips biochar to artificial petroleum-contaminated soil significantly reduced cumulative CO2-C emissions compared to the control. The banana leaves biochar significantly decreased TPHC concentrations in artificial petroleum-contaminated soil compared to the control treatment. At the end of the incubation period, adding banana leaves biochar to the soil showed high degradation efficiencies of TPHC which was36% higher than soil before incubation. The effectiveness of applying amendments used in this experiment on the degradation of TPHC increase was in the order of banana leaves biochar > bone char > wood chips biochar > control > zeolite. The second-order model described the kinetics of total petroleum hydrocarbons better than thefirst-order model. Banana leaves biochar added to the soil resulted in a significant increase in the degradation rate constant of total petroleum hydrocarbons (k2) compared with the control. A higher k2 value indicates that TPHC degrades more rapidly. The half-life of TPHC degradation in the soil was decreased significantly by adding banana leaves biochar. According to the second-order equation, the half-lives of control, zeolite, bone char, banana leaves biochar, and wood chips biochar were 4.0, 5.3, 2.7, 1.0, and 3.6 years, respectively. The banana leaves biochar amendment might be cheaper and more environmentally friendly than other organic amendments because it has the high potential for carbon sequestration and remediate petroleum-contaminated soil, which would increase the sustainable use of petroleum-contaminated soil leading to preserving the environment.

Bacterial Degradation of Petroleum Hydrocarbons in Saudi Arabia.

The Kingdom of Saudi Arabia (KSA) is the leading oil-exploring and -exploiting country in the world. As a result, contamination of the environment by petroleum products (mainly hydrocarbons) is common, necessitating strategies for their removal from the environment. Much work has been conducted on bacterial degradation of hydrocarbons in the KSA. This review comprehensively analyzed 43 research investigation articles on bacterial hydrocarbon degradation, mainly polyaromatic hydrocarbons (PAHs) within the KSA. More than 30 different bacterial genera were identified that were capable of degrading simple and complex PAHs, including benzo[a]pyrene and coronene. Different strategies for selecting and isolating these bacterial strains and their advantages and disadvantages were highlighted. The review also discussed the origins of sample inocula and the contributions of various research groups to this field. PAH metabolites produced by these bacteria were presented, and biochemical pathways of PAH degradation were proposed. More importantly, research gaps that could enrich our understanding of petroleum product biodegradation mechanisms were highlighted. Overall, the information presented in this paper will serve as a baseline for further research on optimizing bioremediation strategies in all petroleum-contaminated environments.

Microbe-plant-nanoparticle interactions: role in bioremediation of petroleum hydrocarbons.

Petroleum hydrocarbons (PHCs) are organic substances that occur naturally on earth. PHCs have emerged as one of the most prevalent and detrimental contaminants in regions comprising soil and water resources. The limitations of conventional physicochemical and biological remediation solutions could be solved by combining remediation techniques. An effective, affordable, and environmentally benign method of reducing petroleum toxins is provided by the advanced idea of bioremediation, which has evolved into nanobioremediation. Environments contaminated with PHCs have been restored through microbe-plant-nanoparticle (NP)-mediated remediation, this review emphasizes how various metallic NPs interact with microbes and plants changing both their activity and that of enzymes, therefore accelerating the remediation process. This work further examines the challenges and possible uses of nanobioremediation, as well as the application of novel technologies in the interactions between bacteria, plants, and NPs for the bioremediation of PHCs. Furthermore, it has been shown that the use of plant-based, microbe-based, microbe-plant-based, and microbe-plant-NP-based techniques to remediate contaminated soils or water bodies is economical and environmentally beneficial. Microbial consortia have been reported as the treasure houses for the cleaning and recovery of hydrocarbon-contaminated environments, and the development of technologies for bioremediation requires an understanding of hydrocarbon degradation mechanisms.

Comprehensive effects of biochar-assisted nitrogen and phosphorus bioremediation on hydrocarbon removal and microecological improvement in petroleum-contaminated soil

Biochar is widely used in agricultural soils, but its effects with nitrogen and phosphorus amendments on petroleum-contaminated soil are unclear. This study investigated biochar-assisted biostimulation in a microcosm experiment, focusing on hydrocarbon degradation, nitrogen cycling, and soil properties. Compared to the biostimulation alone (BS), biochar combined biostimulation (BSC) significantly enhanced the abundances of petroleum hydrocarbon degraders including Lysobacter and Brevundimonas, which led to a 17% increase in total petroleum hydrocarbon (TPH) degradation, with 9% and 39% enhancements in saturated hydrocarbon degradation and aromatic hydrocarbon fraction degradation, respectively. Biochar also promoted ammonia and nitrous oxide oxidation by upregulating AOA, AOB, norB, and nosZ genes, while controlling nitrogen loss by downregulating nirK. Soil moisture, oxidation–reduction potential (ORP), dehydrogenase activity (SDHA), and microbial proliferation were significantly enhanced. Structural equation models (SEM) indicated synergistic interactions between nitrogen cycling and hydrocarbon degradation. Biochar enhances hydrocarbon degradation and nitrogen cycling, offering a promising soil remediation approach.

Functional redundancy enables a simplified consortium to match the lignocellulose degradation capacity of the original consortium

The relationship between structure and function in microbial communities is intriguing and complex. In this study, we used single-carbon source domestication to derive consortium YL from the straw-degrading consortium Y. Y and YL exhibited similar straw degradation capabilities, yet YL harbored only half the species diversity of Y, with distinct dominant species. The most enriched microorganisms in Y were Ureibacillus, Acetanaerobacterium, and Hungateiclostridiaceae, whereas Bacillaceae, Bacillus, and Peptostreptococcales-Tissierellales were most enriched in YL. In-depth analysis revealed that Y and YL had comparable abundances of core lignocellulose-degrading genes, as validated by lignocellulolytic enzyme activity assays. However, the number of species harboring these key lignocellulose-degrading genes (K01179, K01181, K00432) in YL was reduced by over 50%, suggesting that functional redundancy enabled YL to maintain similar degradation capabilities to Y despite reduced diversity. Further analyses of key degradative species and co-occurrence networks highlighted the critical functional roles of dominant degradative species within these communities. An analysis of the overall functional pathways in the two microbial consortia revealed distinct metabolic characteristics between them. Pathways such as polycyclic aromatic hydrocarbon degradation and fluorobenzoate degradation were down-regulated in YL compared to Y, a finding corroborated by the metabolomic data. These results suggest a coupling between community structure and functional capacities within these microbial consortia. Overall, our findings deepen our understanding of the structure-function relationship in microbial communities and provide valuable insights for the design of lignocellulose-degrading consortia.

Microbial colonization on four types of microplastics to form biofilm differentially affecting organic contaminant biodegradation

Different types of microplastics (MPs) concentrated specific functional microorganisms in aquatic environments, potentially influencing the mineralization of coexisting compounds through ecological niche differentiation. Four distinct MPs, polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), and polylactic acid (PLA), were selected to assess their surface biofilms-induced 2,4-dichlorophenol (DCP) biodegradation differences depending on their molecular structure distinction. Microbial colonization on the surfaces of MPs significantly affects the biodegradation of DCP, with a degradation period of 4 to 20 days. For different types of MPs, the improved logistic model calculates the degradation delay parameters as 46.3, 23.3, 52.2, and 19.8 for PVC, PS, PLA, and PET, respectively. PS −, PLA −, and PET biofilm complete the biodegradation of DCP at least 13 days earlier than the free microbiome. Conversely, the potential toxicity and non-biodegradability of PVC inhibited DCP degradation in the PVC-biofilm treatment group. The microorganisms colonized on PS and PET enhanced the ecological niche function for plastic and aromatic hydrocarbon degradation. Furthermore, PS and PET biofilms show similar microbial community structures, with average co-occurrence networks of 16.24 and 16.36, respectively, higher than PLA and PVC (15.92 and 16.16), enhancing community translocation and specialized energy metabolism. PVC and PLA biofilms show upregulation of metabolism related to cell proliferation and apoptosis, leading to a decreased DCP degradation rate. The results demonstrated that microbial colonization on non-toxic and bioavailable MPs facilitated the biodegradation of coexisting chlorinated hydrocarbons. The molecular similarity between MPs and hydrocarbons had the most significant impact on the biodegradation rate of hydrocarbons.

Arctic's hidden hydrocarbon degradation microbes: investigating the effects of hydrocarbon contamination, biostimulation, and a surface washing agent on microbial communities and hydrocarbon biodegradation pathways in high-Arctic beaches

BackgroundCanadian Arctic summer sea ice has dramatically declined due to global warming, resulting in the rapid opening of the Northwest Passage (NWP), slated to be a major shipping route connecting the Atlantic and Pacific Oceans by 2040. This development elevates the risk of oil spills in Arctic regions, prompting growing concerns over the remediation and minimizing the impact on affected shorelines.ResultsThis research aims to assess the viability of nutrient and a surface washing agent addition as potential bioremediation methods for Arctic beaches. To achieve this goal, we conducted two semi-automated mesocosm experiments simulating hydrocarbon contamination in high-Arctic beach tidal sediments: a 32-day experiment at 8 °C and a 92-day experiment at 4 °C. We analyzed the effects of hydrocarbon contamination, biostimulation, and a surface washing agent on the microbial community and its functional capacity using 16S rRNA gene sequencing and metagenomics. Hydrocarbon removal rates were determined through total petroleum hydrocarbon analysis. Biostimulation is commonly considered the most effective strategy for enhancing the bioremediation process in response to oil contamination. However, our findings suggest that nutrient addition has limited effectiveness in facilitating the biodegradation process in Arctic beaches, despite its initial promotion of aliphatic hydrocarbons within a constrained timeframe. Alternatively, our study highlights the promise of a surface washing agent as a potential bioremediation approach. By implementing advanced -omics approaches, we unveiled highly proficient, unconventional hydrocarbon-degrading microorganisms such as Halioglobus and Acidimicrobiales genera.ConclusionsGiven the receding Arctic sea ice and the rising traffic in the NWP, heightened awareness and preparedness for potential oil spills are imperative. While continuously exploring optimal remediation strategies through the integration of microbial and chemical studies, a paramount consideration involves limiting traffic in the NWP and Arctic regions to prevent beach oil contamination, as cleanup in these remote areas proves exceedingly challenging and costly.

Insights into the low-temperature rapid catalytic pyrolysis and remediation mechanism of weathered petroleum-contaminated saline-alkali soil using Beta zeolite

Pyrolysis technique is considered to have great potential in the remediation of petroleum-contaminated soil, but it still has difficulties such as high energy consumption for the degradation of complex petroleum hydrocarbons and the deterioration of soil quality after treatment. In this study, the low-temperature rapid catalytic pyrolysis was realized using Beta zeolite to assist in remediating weathered petroleum-contaminated saline-alkali soil. Under the action of Beta zeolite, the removal efficiency of petroleum hydrocarbons reached 81% after pyrolysis treatment for 10 min at 250 °C, which was reduced to regulatory standard. The pyrolysis behavior and mechanism revealed that the addition of Beta zeolite effectively reduced the activation energy of C-C and C-O bonds cleavage in petroleum hydrocarbon macromolecules due to the strong acidity of Beta, meanwhile the quality of recovered oil from pyrolysis was improved. Additionally, the analyses of soil physicochemical property indicated that the harmless graphitic C generated from the degradation of petroleum hydrocarbons increased the organic matter in the soil, and the addition of Beta zeolite enhanced soil water retention capacity and reduced the soil alkalinity, thus improving the ecological function of saline-alkali soil. This study provides a new strategy for the removal of organic pollutants under special soil media conditions.

Biocatalytic Potential of Pseudomonas Species in the Degradation of Polycyclic Aromatic Hydrocarbons.

Polycyclic aromatic hydrocarbons (PAHs), one of the major environmental pollutants, produced from incomplete combustion of materials like coal, oil, gas, wood, and charbroiled meat, that contaminate the air, soil, and water, necessitating urgent remediation. Understanding the metabolic pathways for PAHs degradation is crucial to preventing environmental damage and health issues. Biological methods are gaining increasing interest due to their cost-effectiveness and environmental friendliness. These methods are particularly suitable for remediating PAHs contamination and mitigating associated risks. The paper also outlines the processes for biodegrading PAHs, emphasizing the function of Pseudomonas spp., a kind of bacterium recognized for its capacity to degrade PAHs. To eliminate PAHs from the environment and reduce threats to human health and the environment, Pseudomonas spp. is essential. Understanding the mechanism of PAH breakdown by means of microbes could lead to effective clean-up strategies. The review highlights the enzymatic capabilities, adaptability, and genetic versatility of the genes like nah and phn of Pseudomonas spp., which are involved in PAHs degradation pathways. Scientific evidence supports using Pseudomonas spp. as biocatalysts for PAHs clean-up, offering cost-effective and eco-friendly solutions.

Photocatalytic degradation of phenol and polycyclic aromatic hydrocarbons in water by novel acid soluble collagen-polyvinylpyrrolidone polymer embedded in Nitrogen-TiO2

The photocatalytic degradation of phenol, naphthalene, fluoranthene, phenanthrene, pyrene, benz[a]anthracene, and anthracene was investigated using a novel nitrogen-doped TiO2/acid-soluble collagen-polyvinyl pyrrolidone nanocomposite (N-TiO2/ASC-PVP). Characterization through X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed that the nanocomposite consists of spheroidal particles smaller than those of undoped TiO2. X-ray photoelectron spectroscopy (XPS) confirmed the incorporation of nitrogen within the TiO2 lattice, appearing as both substitutional nitrogen (OTiN) and interstitial nitrogen (TiON). The degradation process followed apparent first-order kinetics, with the N-TiO2/ASC-PVP calcined at 200°C and 400°C demonstrating high photocatalytic degradation efficiencies. The nanocomposite achieved a remarkable 98.6% degradation of the targeted compounds within 120 minutes at a concentration of 10 mg/L. The enhanced photocatalytic activity under visible light can be attributed to several factors: the smaller crystal size, increased surface hydroxyl groups, improved visible light absorption, and a reduced band gap energy. This N-TiO2/ASC-PVP photocatalyst shows significant potential for applications in materials science and nanotechnology, supporting advancements in environmental and energy-related fields.

Innovative strategy for the treatment of oily wastewater by in-situ synthesis of nitrogen-doped biochar supported FeS for activation of peroxymonosulfate

ABSTRACT Disposing of oily wastewater poses a significant challenge in treating oilfield-produced wastewater treatment. This study developed a FeSNC-9/PMS system for the effective degradation of total petroleum hydrocarbons (TPHs) in oily wastewater, while increasing the value of excess sludge, thus achieving the dual purpose of waste treatment. This work involved the in-situ preparation of a porous nitrogen-doped biochar-supported iron sulphide catalyst material using surplus sludge from SBR. Compared to undoped FeS (NC-9), FeSNC-9 exhibited excellent pore structure and abundant functional groups. Fe-Nx served as an effective connecting site between FeS species and the graphite network of biochar. The FeSNC-9/PMS system significantly degraded 74.21% of TPHs within 300 min. The FeSNC-9/PMS system demonstrated remarkable TPHs degradation efficiency across a wide temperature range and under both weak acidity and near-neutral conditions The dominant reactive oxygen species were identified as SO4 •− and •OH, with O2 •− and 1O2 also confirmed as active species. Gas chromatography semi-quantitative analysis showed that the long-chain alkanes of C20-C30 in total petroleum hydrocarbons were significantly degraded into short-chain alkanes or completely mineralized. This work provides new insights for the low-cost and high-efficiency treatment of TPHs in oilfield-produced water, and delves into the activation mechanism of PMS and the degradation pathways of TPHs.

Improved chickpea growth, physiology, nutrient assimilation and rhizoremediation of hydrocarbons by bacterial consortia.

Soil pollution by petroleum hydrocarbons (PHCs) reduces yield by changing the physico-chemical properties of soil and plants due to PHCs' biotoxicity and persistence. Thus, removing PHCs from the soil is crucial for ecological sustainability. Microbes-assisted phytoremediation is an economical and eco-friendly solution. The current work aimed to develop and use bacterial consortia (BC) for PHCs degradation and plant growth enhancement in hydrocarbon-contaminated soil. Initially, the enriched microbial cultures (that were prepared from PHCs-contaminated soils from five distinct regions) were obtained via screening through microcosm experiments. Afterward, two best microbial cultures were tested for PHCs degradation under various temperature and pH ranges. After culture optimization, isolation and characterization of bacterial strains were done to construct two BC. These constructed BC were tested in a pot experiment for hydrocarbons degradation and chickpea growth in PHCs contaminated soil. Findings revealed that PHCs exerted significant phytotoxic effects on chickpea growth and physiology when cultivated in PHCs contaminated soil, reducing agronomic and physiological traits by 13-29% and 12-43%, respectively. However, in the presence of BC, the phytotoxic impacts of PHCs on chickpea plants were reduced, resulting in up to 24 - 35% improvement in agronomic and physiological characteristics as compared to un-inoculated contaminated controls. Furthermore, the bacterial consortia boosted chickpea's nutritional absorption and antioxidant mechanism. Most importantly, chickpea plants phytoremediated 52% of the initial PHCs concentration; however, adding BC1 and BC2 with chickpea plants further increased this removal and remediated 74% and 80% of the initial PHCs concentration, respectively. In general, BC2 outperformed BC1 (with few exceptions) in promoting plant growth and PHCs elimination. Therefore, using multi-trait BC for PHCs degradation and plant growth improvement under PHCs stress may be an efficient and environmentally friendly strategy to deal with PHCs pollution and toxicity.

Synergistic use of cattle bile, compost and fertilizer amendments in enhancing the bioremediation of hydrocarbon-contaminated soils

This study investigated the degradation of hydrocarbon-contaminated soil using compost, NPK 20:10:10 fertilizer, and cattle bile as biostimulants. In this study, 1000 g of homogenized contaminated soil was amended with 10.50 g of NPK fertilizer and 107.50 g of compost to achieve a nitrogen concentration of 0.2 %. To establish a 0.4 % nitrogen concentration, 23.90 g of NPK fertilizer, 243.54 g of compost, and 2 ml of cattle bile were used. These amendments were applied in various combinations to create the following microcosm treatments: A, B, C, D, A2, B2, C2, D2, and a control. The microcosms, along with the control were incubated for 6 weeks in triplicate. Throughout this period, several parameters were monitored every two weeks, including pH, nitrogen (N), potassium (K), phosphorus (P), moisture content, organic carbon, organic matter, total heterotrophic bacterial count (THBC), and total petroleum hydrocarbon (TPH) concentration. The results showed significant differences (p < 0.05) in TPH content across the microcosms during the four sampling periods. By the end of the 6-week incubation, the TPH residual concentration varied between 1.58 mg kg-1 and 20.61 mg kg-1, corresponding to degradation rates of 98.43 % and 79.58 %, respectively, from an initial TPH concentration of 100.91 mg kg-1. Microcosm B2 demonstrated the highest hydrocarbon removal efficiency (98.43 %), while the control showed the lowest efficiency. The order of degradation efficiency among the microcosms was B2 > B (94.89 %) > C (94.64 %) > A (94.13 %) > D2 (93.62 %) > A2 (93.51 %) > C2 (92.45 %) > D (91.44 %). The study also found that pH and nitrogen levels were related to the reduction in hydrocarbon content. Microcosms with a 0.4 % nitrogen concentration showed a higher rate of nitrogen consumption compared to those with a 0.2 % concentration. Additionally, changes in pH were observed as hydrocarbon degradation progressed. This study further applied cluster analysis, Bayesian statistics, and multiple linear regression to evaluate the effects of treatments on soil quality over time. Cluster analysis showed increasing dissimilarity between merged clusters, while Bayesian analysis revealed positive trends in parameter estimates in Weeks 2 and 4. Regression analysis indicated significant impacts of Weeks 2, 4, and 6 on Week 0, with F-statistics of 8.475 (p = 0.016), 9.804 (p = 0.004), and 3.759 (p = 0.037), though multicollinearity reduced the predictive power of individual coefficients. Overall, Microcosm B2 emerged as the most effective treatment option. The findings suggest that biostimulation using a combination of moisture, compost, NPK fertilizer, and cattle bile is an effective approach to achieving high efficiency in TPH degradation in hydrocarbon-contaminated soils.