Phenanthrene Degradation Research Articles

Remediation of Various Phenanthrene-contaminated Soils using Persulfate-Pseudomonas aeruginosa GZ7: Soil Properties, Radical Formation, and Microbial Community

In this study, the complex interaction of oxidizing conditions, soil composition, microbial activity, and phenanthrene (PHE) degradation was explored in persulfate (PS)-Pseudomonas aeruginosa GZ7 remediation of four PHE-contaminated soils: Paddy soil (PAS), Saline soil (SS), Red soil (RS), and Cinnamon soil (CS). Batch experiments displayed the optimal PS dosage was 0.750% (w/w), except for CS (0.125%), achieving PHE degradation rates of 54.79% ~ 81.92% on the 27-day. The zeta potential of soil clay component after 0.750% PS oxidation was lower than 0.125% and 2.000% PS, resulting in a higher PHE bioavailability and biodegradation. The electron paramagnetic resonance (EPR) spectroscopy analysis showed that the abundance of dominant hydroxyl radicals (·OH) in CS was 3 times higher than in PAS at 0.750% PS and PS to Fe2+ molar ratio of 2:1, indicating that a higher soil organic matter would decrease the content of ·OH thus diminishing PHE removal. Stepwise linear regression and sensitivity analysis indicated that the key influential factors in the PHE degradation rate were the residual PHE content after oxidation (60.12%) and hydrolase nitrogen content (30.97%). High-throughput sequencing results showed the bacterial diversity and richness in four soils decreased after combined remediation compared to pristine soil. Redundancy analyses revealed that the fluorescein diacetate (FDA) hydrolase enzyme was the key factor effect of soil bacterial community development in SS; and electrical conductivity and FDA hydrolase enzyme were the key factors in RS, CS, and PAS. This study may provide technical support for optimizing chemical conditions for PS-microbial remediation.

An S-scheme TiO2/g-C3N4 nanocomposite effectively degrades phenanthrene under visible light

It is a challenge to effectively degrade phenanthrene (PHE) pollutants, which are widely present in aquatic environments, in order to reduce harm to humans and ecosystems. In this study, an S-scheme TiO2/g-C3N4 photocatalytic system is constructed using 0D TiO2 nanospheres and 2D g-C3N4 nanosheets for the removal of PHE from water under sunlight irradiation. The effects of irradiation time, quality ratio of TiO2 to g-C3N4, and cycle time on the performance of the TiO2/CN photocatalyst are investigated. The experimental results show that the ratio of TiO2 to g-C3N4 significantly affects the photocatalytic activity of the photocatalyst. Under the optimal ratio of TiO2 to g-C3N4 (50 % TiO2/CN), the apparent reaction rate constant for phenanthrene reached 0.00796 min−1, which is 11.5 times higher than that of pure TiO2 (0.00069 min−1). The tests of optical performance and photoelectrochemical properties further confirmed that the construction of the TiO2/g-C3N4 S-type photocatalyst successfully enhanced the spatial separation efficiency of photogenerated carriers and ensured a continuous supply of energy during the redox reaction process. Converting highly toxic phenanthrene into a non-toxic green degradation product provides an practical strategy for the safe treatment of PHE in aqueous environments through the use of visible-light-driven heterojunction photocatalysts. Additionally, the data collected on phenanthrene degradation in this study will provide valuable references for developing degradation methods for other PAHs, such as naphthalene, anthracene, and pyrene.

Design and construction of an artificial labor-division consortium for phenanthrene degradation with three-functional modules

Polycyclic Aromatic Hydrocarbons (PAHs) are highly toxic organic pollutants. Phenanthrene often serves as a model compound for studying PAHs biodegradation. In this work, we firstly engineered Escherichia coli M01 containing seven phenanthrene degradation genes and combined it with existing engineered strains E. coli M2 and M3 to form an artificial three-bacteria consortium, named M0123, which exhibited a degradation ratio of 64.66% for 100 mg/L of phenanthrene over 8 days. Subsequently, we constructed engineered Pseudomonas putida KTRL02 which could produce 928.49 mg/L rhamnolipids and integrated it with M0123, forming a four-bacteria consortium with an impressive 81.62% phenanthrene degradation ratio. Assessment of extracellular adenosine levels during the degradation process indicated high cellular energy demand in the four-bacteria consortium. Then, we introduced Bacillus subtilis RH33, a riboflavin-producing strain, as an energy-supplying bacterium, to create a five-bacteria consortium, which exhibited an 88.19% degradation ratio for phenanthrene. The NADH/NAD+ ratio in the five-bacteria consortium during the degradation process was monitored, which was consistently higher than that of the four-bacteria consortium over the eight-day period, indicating a higher overall intracellular reduction capacity. Furthermore, the five-bacteria consortium displayed good tolerance to phenanthrene, even achieving a degradation ratio of 79.38% for 500 mg/L of phenanthrene. This study demonstrates that designing and constructing artificial consortia from the functional perspective and various angles can effectively enhance the degradation of phenanthrene after the addition of the energy-supplying bacterium. This study demonstrates that designing and constructing artificial labor-division consortia from the functional perspective and various angles can effectively enhance the degradation of phenanthrene.

Green biosynthesis of Ag-doped hetero-metallic oxide nanocomposite for efficient sunlight-driven photo-adsorptive degradation of carcinogenic naphthalene and phenanthrene

One of the most significant issues facing the world today is environmental contamination due to the polycyclic aromatic hydrocarbons, or PAHs release of reactive chemicals into the environment. Here, a green technology was used to synthesis the Ag doped Bi2O3@Co3O4 nanocomposite utilizing an extract from Azadirachta indica leaves. The morphological and structural examination of Ag doped Co3O4@Bi2O3 revealed an image in the form of a hollow spherical or flake adsorbed on a Ag surface with an increase surface area. New peaks in the FT-IR spectra of Ag–O and Co–O–Bi at 678 cm−1 and 1130 cm−1, respectively, show the coupling of Ag. Following this, under various reaction conditions (pollutant: 10–30 mg/L; catalyst: 10–30 mg; pH: 3–11, dark sunlight) the doped nanocomposite was assessed for the efficient removal of NAP and PHE. Ag doped Co3O4@Bi2O3 displayed maximum degradation of NAP (96 %) and PHE (94 %) at 10 mg/L conc. of each PAH with a 25 mg catalytic dose at neutral pH in the presence of direct sunlight. First-order kinetics followed by initial Langmuir adsorption constituted the degradation process. Predominant reactive species and safer metabolite formation in the photocatalysis process of PAHs were studied by scavenger and GC–MS analysis. The green nano photocatalyst that was created demonstrated excellent stability, sensitivity, and reusability (up to 8th cycles) during the degrading process, which likely qualified it for use in industrial uses.

The key monooxygenase involved in phenanthrene degradation of Ruegeria sp. PrR005

As a typical polycyclic aromatic hydrocarbon (PAH), phenanthrene is often present in diverse environments, leading to severe environmental contamination. However, bacterial degradation plays a crucial role in remediating phenanthrene contamination and has been widely adopted. The widely distributed marine Roseobacter-clade bacteria are frequently found in phenanthrene-contaminated environments, but their catalyzing ability and related molecular mechanism have been rarely elucidated. Our previous work showed Ruegeria sp. PrR005 isolated from the Pearl River Estuary sediment could degrade phenanthrene and other PAHs. Integrated approaches including multi-omics and biochemical analysis were applied here to explore its catabolism mechanism. The genomic and transcriptomic analysis indicated that six new P450 monooxygenase proteins could be closely associated with phenanthrene degradation. Heterologous expression of P450 monooxygenase candidates revealed that PrR005_00615, PrR005_04282, PrR005_04577 have considerable activity in phenanthrene removal, with PrR005_00615 being the primary contributor. Further, the biochemical and metabolic analysis revealed that PrR005_00615 could catalyze phenanthrene to phenanthrene-9,10-epoxide by introducing an oxygen atom at 9,10-carbon positions, which functioned as a monooxygenase. The present study provides compelling evidences of a novel enzyme responsible for catalyzing the initial step of phenanthrene transformation in PrR005. These findings hold significant importance in unraveling the mechanism behind phenanthrene degradation by Roseobacter-clade bacteria.

Characterization of 2-phenanthroate:CoA ligase from the sulfate-reducing, phenanthrene-degrading enrichment culture TRIP.

Polycyclic aromatic hydrocarbons (PAHs) constitute a class of very toxic and persistent pollutants in the environment. However, the anaerobic degradation of three-ring PAHs such as phenanthrene is barely investigated. The initial degradation step starts with a carboxylation followed by a CoA‑thioesterification reaction performed by an aryl-CoA ligase. The formation of a CoA-thioester is an important step in the degradation pathway of aromatic compounds because the CoA-ester is needed for all downstream biochemical reactions in the pathway. Furthermore, we provide biochemical proof for the identification of the first genes for anaerobic phenanthrene degradation. Results presented here provide information about the biochemical and structural properties of the purified 2‑phenanthroate:CoA ligase and expand our knowledge of aryl-CoA ligases.

Occurrence of polycyclic aromatic hydrocarbons in the Yellow River delta: Sources, ecological risks, and microbial response

This research investigated the distribution, sources, and ecological risks of polycyclic aromatic hydrocarbons (PAHs) in the Yellow River Delta (YRD), China, emphasizing the response of soil microorganisms. The study involved quantitative analyses of 16 PAHs specified by the U.S. Environmental Protection Agency (USEPA) in both water and soil, utilizing metagenomic technique to determine the response of microbial communities and metabolism within the soil. Results noted that PAHs in the water mainly originate from pyrogenic source and in the soil originate from mixture source, with higher concentrations found in wetland areas compared to river regions. The ecological risk assessment revealed low-to-moderate risk. Microbial analysis demonstrated increased diversity and abundance of bacteria associated with PAHs in areas with higher PAHs pollution. Metagenomic insights revealed significant effects of organic carbon on PAHs degradation genes (ko00624 and ko00626), as well as significant differences in specific metabolic pathways including phenanthrene degradation, with key enzymes showing significant differences between the two environments. The study underscores the importance of understanding PAHs distribution and microbial responses to effectively manage and mitigate pollution in estuarine environments.

Methanogenesis coupled hydrocarbon biodegradation enhanced by ferric and sulphate ions

Bioremediation provides an environmentally sound solution for hydrocarbon removal. Although bioremediation under anoxic conditions is slow, it can be coupled with methanogenesis and is suitable for energy recovery. By altering conditions and supplementing alternative terminal electron acceptors to the system to induce syntrophic partners of the methanogens, this process can be enhanced. In this study, we investigated a hydrocarbon-degrading microbial community derived from chronically contaminated soil. Various hydrocarbon mixtures were used during our experiments in the presence of different electron acceptors. In addition, we performed whole metagenome sequencing to identify the main actors of hydrocarbon biodegradation in the samples. Our results showed that the addition of ferric ions or sulphate increased the methane yield. Furthermore, the addition of CO2, ferric ion or sulphate enhanced the biodegradation of alkanes. A significant increase in biodegradation was observed in the presence of ferric ions or sulphate in the case of all aromatic components, while naphthalene and phenanthrene degradation was also enhanced by CO2. Metagenome analysis revealed that Cellulomonas sp. is the most abundant in the presence of alkanes, while Ruminococcus and Faecalibacterium spp. are prevalent in aromatics-supplemented samples. From the recovery of 25 genomes, it was concluded that the main pathway of hydrocarbon activation was fumarate addition in both Cellulomonas, Ruminococcus and Faecalibacterium. Chloroflexota bacteria can utilise the central metabolites of aromatics biodegradation via ATP-independent benzoyl-CoA reduction.Key points• Methanogenesis and hydrocarbon biodegradation were enhanced by Fe3+ or SO42−• Cellulomonas, Ruminococcus and Faecalibacterium can be candidates for the main hydrocarbon degraders• Chloroflexota bacteria can utilise the central metabolites of aromatics degradationGraphical

Effects of biodegradable microplastics coexistence with biochars produced at low and high temperatures on bacterial community structure and phenanthrene degradation in soil

The increasing use of biodegradable plastics may result in more serious pollution of microplastics which often coexist with biochar in soil, this will affect how organic pollutants move and transform in the soil. This work investigated the effect of biodegradable polybutylene adipate-co-terephthalate (PBAT) coexistence with biochars produced at temperatures of 400 and 700 °C (W4 and W7) on soil bacterial communities and phenanthrene degradation. The results showed that coexistence of PBAT and biochar paticles greatly boosted the relative abundance of Nocardioides while decreased the relative abundance of Sphingomonas as compared to soils with a single addition of PBAT or biochar. Changes in soil Eh values were the most influential factor in bacterial communities (more than 40% contribution). The degradation ratio of phenanthrene when PBAT coexisted with W7 (39.6 ± 3.6%) was not significantly different from the treatment with a single W7 addition (35.0 ± 2.3%, P＞0.05), and was related to phenanthrene degradation in the adsorbed state of W7 in soil. In contrast, the degradation ratio of phenanthrene in PBAT coexisting with W4 (35.1 ± 3.5%) was intermediate between that of single PBAT (49.8 ± 0.9%) and W4 (13.7 ± 5.8%) treatments. This was primarily due to changes in the experiment's initial bioavailable phenanthrene content. Furthermore, after the introduction of earthworms, phenanthrene degradation ratio in coexistence treatments were very similar to that described above in the absence of earthworms. Except for two treatments that contain W7, phenanthrene degradation ratio in the other treatments was increased by the presence of earthworms (up to 23%), which is related to the enhanced relative abundance of polycyclic aromatic hydrocarbon-degraders. Our findings indicated that PBAT coexistence with high-temperature or low-temperature biochar had a completely different impact on bacterial communities and phenanthrene degradation in soil.

Electro-photocatalyst effect of N-S-doped carbon dots and covalent organic triazine framework heterostructures for boosting photocatalytic degradation of phenanthrene in water

In the present study, we introduce a covalent organic triazine framework polymer (COTF-P) using 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) with triazine-based amine. The resulting dark red COTF-P illustrated potential behavior as a photocatalyst under visible light. Due to the inadequate solar energy capture and ultrafast charge recombination of the resulting COTF-P, the prepared COTF-P has been decorated with CQDs (N-CQD and N-S-CQD) to build a Z-scheme CQDs/COTF-P heterojunction photocatalyst and utilizes as photocatalyst for the breakdown of phenanthrene (PHE) exposed to visible light. The prepared COTF-P and CQDs/COTF-P were fully characterized, analyzing the textural (N2 isotherms), structural (XRD and FTIR), chemical (EDX and XPS), morphological (FESEM and TEM), optical (DRS-UV-Vis and photoluminescence), and electrochemical properties (EIS impedance, transient photocurrent, and flat band potential). The prepared N-S-CQD/COTF-P heterojunction displayed optimum activity for the photocatalytic oxidation of PHE from water, owing to an enhanced separation of the photogenerated charges and lower bandgap value, 2.1 vs. 1.9 eV. The N-S-CQD/COTF-P heterojunction showed acceptable stability in terms of activity and structural properties after 5 cycles of reuse. The mechanism of activation highlights the importance played by superoxide radicals and hydroxyl radicals. This project sheds light on the potential use of CQDs for the decoration of polymers, extending the absorbance in the visible region and boosting the migration of charge, which boosts the activity of the resulting material.

Phenanthrene-Degrading and Nickel-Resistant Neorhizobium Strain Isolated from Hydrocarbon-Contaminated Rhizosphere of Medicago sativa L.

Pollutant degradation and heavy-metal resistance may be important features of the rhizobia, making them promising agents for environment cleanup biotechnology. The degradation of phenanthrene, a three-ring polycyclic aromatic hydrocarbon (PAH), by the rhizobial strain Rsf11 isolated from the oil-polluted rhizosphere of alfalfa and the influence of nickel ions on this process were studied. On the basis of whole-genome and polyphasic taxonomy, the bacterium Rsf11 represent a novel species of the genus Neorhizobium, so the name Neorhizobium phenanthreniclasticum sp. nov. was proposed. Analysis of phenanthrene degradation by the Rsf1 strain revealed 1-hydroxy-2-naphthoic acid as the key intermediate and the activity of two enzymes apparently involved in PAH degradation. It was also shown that the nickel resistance of Rsf11 was connected with the extracellular adsorption of metal by EPS. The joint presence of phenanthrene and nickel in the medium reduced the degradation of PAH by the microorganism, apparently due to the inhibition of microbial growth but not due to the inhibition of the activity of the PAH degradation enzymes. Genes potentially involved in PAH catabolism and nickel resistance were discovered in the microorganism studied. N. phenanthreniclasticum strain Rsf11 can be considered as a promising candidate for use in the bioremediation of mixed PAH-heavy-metal contamination.

Photocatalytic Polyaromatic hydrocarbons (PAH) utilizing magnetic CrFe2O4 nanoparticle: Green synthesis, characterization, ab initio studies, electronic, magnetic features and water treatment application

Polyaromatic hydrocarbons (PAHs) are priority pollutants due to their mutagenicity, persistence, and proven carcinogenicity. Consequently, we investigated the photooxidative degradation of prototypical toxic PAHs, namely anthracene (ANTH) and phenanthrene (PHEN), and naphthalene (NAPH) utilizing magnetic CrFe2O4 nanoparticles under visible light LED irradiation. The prepared nanoparticles, characterized by P-XRD, IR, and SEM, reveal a cubic (FCC) structure and an average particle size of 25.6 nm. On Ab initio study we employed spin polarized first-principle calculations using the Full-Potential Linearized Augmented Plane-Wave (FLAPW) method with GGA-mBJ potentials implemented in the Wien2k package to investigate the properties of CrFe2O4 spinel compound; the calculations reveal that CrFe2O4 adopts a cubic crystal structure with space group 227 (Fd-3 m), and exhibits semiconductor characteristics in both spin channels, featuring indirect band gaps of 1.12 eV (spin-up) and 0.43 eV (spin-down) at the Γ-L and K-Γ points, respectively. Furthermore, the material demonstrates ferromagnetic behavior, with a spin magnetic moment of 20 µB per unit cell. Optical spectra analysis concurs with band structure calculations, suggesting the suitability of this material for photovoltaic applications. The CrFe2O4 magnetic nanoparticles were synthesized through an eco-friendly approach using Boswellia carteri resin as a natural surfactant in an aqueous medium. Our synthesized materials exhibited excellent photocatalytic performance, leading to a rapid exponential decay of ANTH and PHEN over 3 h under visible LED light. The effect of different radical scavengers revealed the role of the percentage of active species OH, h+, and ˙O2− in the oxidation of selected PAHs. At neutral pH, the photo-degradation of PAHs (200 g L−1) by CrFe2O4 (10 mg) followed first-order kinetics and the Langmuir model (R2: 0.99). Exceptional degradation efficiencies were achieved, with ANTH exhibiting a removal efficiency of 99 %, PHEN of 90 %, and NAPH of 86 %. These results show the effectiveness of the synthesized materials as benign and environmentally friendly magnetic nanoparticles for removing carcinogenic PAHs, offering a sustainable, green, and reusable (n = 7) catalytic system to address this environmental challenge.

Enhanced removal of PHE-Cd2+ co-contamination by the mixed bacterial cultures of Pseudomonas putida and Arthrobacter sp.: Performance and mechanism

The strain species resource is essential for microbial remediation of PHE (phenanthrene)-Cd2+ co-contamination. In this study, the mixed bacterial culture (M) was established to intensively remediate PHE-Cd2+ co-contamination using PAHs-degrading bacteria Pseudomonas putida and Arthrobacter sp. with different Cd2+ tolerance. The PHE degradation efficiency of the mixed bacterial cultures (M) was 65 %-81 % under different Cd2+ concentration of 10–50 mg/L, respectively, which was 1.40–2.98 times that of the individual strains. In addition, strain metabolic enzyme activity, intracellular structure and extracellular polymeric substances (EPS) were carried out under Cd2+ stress. Results showed that the catechol 1,2-dioxygenase enzyme (C120) and the electron transport system activity (ETSA) were less adversely affected by Cd2+ in mixed bacterial cultures. Transmission electron microscopy images showed that the cells surface of the mixed bacterial cultures (M) could be adsorbed more Cd2+ compared to the single strain. The analysis of cell functional groups suggested that C-O-C and C-O groups in EPS mediated the removal of Cd2+ in the mixed bacterial culture. Moreover, the Cd2+ removal proportion by EPS adsorption of the mixed bacterial cultures accounted for 92 %, 67 %, 57 %, and 52 % under Cd2+ stress of 0.5, 10, 25, and 50 mg/L, respectively, which were superior to that of individual strains. This study confirmed the potential application and technical reference of the specific mixed bacterial cultures in the enhanced bioremediation of PHE-Cd2+ co-contamination.

Evaluation of phenanthrene degradation in seawater by an isolated bacterial consortium from the Gulf of Mexico

Evaluation of phenanthrene degradation in seawater by an isolated bacterial consortium from the Gulf of Mexico

Pseudomonas aeruginosa PR23 isolated from oil contaminated soil tolerate and degrades mixture of polyaromatic hydrocarbons and express novel proteins.

Pseudomonas aeruginosa PR23 isolated from the hydrocarbon contaminated soil can tolerate and degrade mixture of polyaromatic hydrocarbons (PAHs) at an initial concentration of 1300ppm. The degradation and intermediates formed were assessed by gas chromatography-mass spectrometry (GC-MS) analysis. The isolated strain was able to degrade 59.2% of the mixture of PAHs in 3days and 71.6% by day 15. Effect of PAHs on protein expression in Pseudomonas aeruginosa PR23 was studied using nano LC-MS/MS. Thirty-six proteins showed a more than 2-fold increase in expression in the presence of mixture of PAHs. Out of these proteins, 7 proteins have been reported for their role in degradation of naphthalene, phenanthrene, and pyrene. The data revealed the presence of 16 proteins that were uniquely expressed in the presence of mixture of PAHs. A twin-arginine translocation signal peptide (Tat system), known for the transportation of folded proteins across the cell membrane, showed more than 8-fold increased expression in the presence of mixture of PAHs. These results indicate that the isolated strain adopts the conditions in the presence of mixture of PAHs by modulating its metabolic and physiological processes. These findings suggest that Pseudomonas aeruginosa PR23 may be a suitable candidate for use in the development of strategies for bioremediation of mixtures of PAHs.

Remediation of phenanthrene contaminated soil by persulphate coupled with Pseudomonas aeruginosa GZ7 based on oxidation prediction model.

Chemical oxidation coupled with microbial remediation has attracted widespread attention for the removal of polycyclic aromatic hydrocarbons (PAHs). Among them, the precise evaluation of the feasible oxidant concentration of PAH-contaminated soil is the key to achieving the goal of soil functional ecological remediation. In this study, phenanthrene (PHE) was used as the target pollutant, and Fe2+-activated persulphate (PS) was used to remediate four types of soils. Linear regression analysis identified the following important factors influencing remediation: PS dosage and soil PHE content for PHE degradation, Fe2+ dosage, hydrolysable nitrogen (HN), and available phosphorus for PS decomposition. A comprehensive model of "soil characteristics-oxidation conditions-remediation effect" with a high predictive accuracy was constructed. Based on model identification, Pseudomonas aeruginosa GZ7, which had high PAHs degrading ability after domestication, was further applied to coupling repair remediation. The results showed that the optimal PS dose was 0.75% (w/w). The response relationship between soil physical, chemical, and biological indicators at the intermediate interface and oxidation conditions was analysed. Coupled remediation effects were clarified using microbial diversity sequencing. The introduction of Pseudomonas aeruginosa GZ7 stimulated the relative abundance of Cohnella, Enterobacter, Paenibacillus, and Bacillus, which can promote material metabolism and energy transformation during remediation.

Determination of soil phenanthrene degradation through a fungal-bacterial consortium.

Fungal-bacterial consortia enhance organic pollutant removal, but the underlying mechanisms are unclear. We used stable isotope probing (SIP) to explore the mechanism of bioaugmentation involved in polycyclic aromatic hydrocarbon (PAH) biodegradation in petroleum-contaminated soil by introducing the indigenous fungal strain Aspergillus sp. LJD-29 and the bacterial strain Pseudomonas XH-1. While each strain alone increased phenanthrene (PHE) degradation, the simultaneous addition of both strains showed no significant enhancement compared to treatment with XH-1 alone. Nonetheless, the assimilation effect of microorganisms on PHE was significantly enhanced. SIP revealed a role of XH-1 in PHE degradation, while the absence of LJD-29 in 13C-DNA indicated a supporting role. The correlations between fungal abundance, degradation efficiency, and soil extracellular enzyme activity indicated that LJD-29, while not directly involved in PHE assimilation, played a crucial role in the breakdown of PHE through extracellular enzymes, facilitating the assimilation of metabolites by bacteria. This observation was substantiated by the results of metabolite analysis. Furthermore, the combination of fungus and bacterium significantly influenced the diversity of PHE degraders. Taken together, this study highlighted the synergistic effects of fungi and bacteria in PAH degradation, revealed a new fungal-bacterial bioaugmentation mechanism and diversity of PAH-degrading microorganisms, and provided insights for in situ bioremediation of PAH-contaminated soil.IMPORTANCEThis study was performed to explore the mechanism of bioaugmentation by a fungal-bacterial consortium for phenanthrene (PHE) degradation in petroleum-contaminated soil. Using the indigenous fungal strain Aspergillus sp. LJD-29 and bacterial strain Pseudomonas XH-1, we performed stable isotope probing (SIP) to trace active PHE-degrading microorganisms. While inoculation of either organism alone significantly enhanced PHE degradation, the simultaneous addition of both strains revealed complex interactions. The efficiency plateaued, highlighting the nuanced microbial interactions. SIP identified XH-1 as the primary contributor to in situ PHE degradation, in contrast to the limited role of LJD-29. Correlations between fungal abundance, degradation efficiency, and extracellular enzyme activity underscored the pivotal role of LJD-29 in enzymatically facilitating PHE breakdown and enriching bacterial assimilation. Metabolite analysis validated this synergy, unveiling distinct biodegradation mechanisms. Furthermore, this fungal-bacterial alliance significantly impacted PHE-degrading microorganism diversity. These findings advance our understanding of fungal-bacterial bioaugmentation and microorganism diversity in polycyclic aromatic hydrocarbon (PAH) degradation as well as providing insights for theoretical guidance in the in situ bioremediation of PAH-contaminated soil.

Heavily polluted mechanic workshop soil and its phenanthrene-degrading Bacillus thuringiensis

Mechanic workshops in residential areas are sites referenced for small-scale chronic contamination with petroleum hydrocarbons (HC) and associated pollutants like heavy metals. The main aim of this study was to isolate from a mechanic workshop soil in Lagos a novel indigenous bacterium with potential for degradation of phenanthrene, a model polyaromatic compound. Gas chromatographic analysis revealed concentrations of HC (20,055 mg kg-1), lead (156.19 mg kg-1) and zinc (202.005 mg kg-1) in excess of regulatory limits in the soil. Continuous enrichment resulted in the isolation of a bacterium strain ALSL2, which was identified by 16S rRNA gene sequencing as Bacillus thuringiensis. Strain ALSL2 showed broad specificity for a range of HCs including phenanthrene, anthracene, biphenyl, dibenzothiophene, crude oil, diesel and kerosene and also showed biosurfactant production with emulsification index 55.2 %, 65.7 % and 58.7 % on crude oil, kerosene and vegetable oil respectively. The isolate showed evidence of dioxygenase activity and utilized metabolites of aromatic hydrocarbon degradation including 1-naphthol and O-phthalate. At the end of 10 days 51.45 % of phenanthrene was degraded at the rate of 7.922 mg l−1 d−1, degradation constant 0.073 d−1, and half-life 9.864 d. The corresponding values for anthracene were 69.11 %, 9.92 mg l−1 d−1., 0.11 d−1, and 5.924 d respectively. Our findings represent a remarkable addition to available indigenous bioresources with potential for application in bioremediation, and further highlight mechanic workshop soils as veritable source of such isolate.

Promotion and mechanism of defective hematite on the power generation and phenanthrene degradation of soil microbial fuel cells

Iron minerals can significantly impact the performance of soil microbial fuel cells (Soil-MFCs) through extracellular electron transfer (EET). Introducing defects into iron minerals has been shown to reinforce the microbial dissolution process. In this study, oxygen-rich vacancy defects were successfully incorporated into hematite (DHem), resulting in enhanced Soil-MFCs performance. Voltage measurement and Polarization curves demonstrated that the addition of DHem yielded the highest electricity output of 408.96 mV and the highest power density of 324.97 mW/m2. Liquid chromatography revealed that the system with DHem exhibited the most effective phenanthrene degradation at 61.42%, with a 40.70% increase in degradation near cathode areas. The introduction of defects led to increased dissolution of Fe(II) in hematite. The dissolved Fe(II) showed a significant positive correlation with both electricity generation and phenanthrene degradation, confirming that the introduction of defects strengthened the long-distance electron transfer capability by enhancing the dissolution of hematite. In addition, after adding iron minerals, the abundance of Petrimonas, Pseudomonas, Trichococcus, and Azoarcus was increased, which were all important function microorganisms in the system. We concluded that the introduction of defects in hematite can enhance the overall performance of Soil-MFCs by enhance electron transfer and microbial community structure.

Organic radicals driving polycyclic aromatic hydrocarbon polymerization with peracetic acid activation in soil

The use of peracetic acid (PAA) in advanced oxidation processes has gained significant attention recently, but the knowledge of activating PAA to degrade polycyclic aromatic hydrocarbons (PAHs) is limited due to the variety and selectivity of reactive substances in PAA oxidation system. This paper presented the first systemically study on the degradation of PAHs by PAA activation in soil. It was found that heat-activated peracetic acid (heat/PAA) was capable of degrading phenanthrene (PHE) efficiently with degradation efficiency > 90 % within 30 min. Experimental results demonstrated that a series of reactive oxygen species (ROS) including organic radicals (RO•), hydroxyl radicals (HO•) and singlet oxygen (1O2) were generated, while acetylperoxyl (CH3C(O)OO•) and acetyloxyl (CH3C(O)O•) radicals were primarily responsible for PHE degradation in soil. Further analysis shows that polymerization products such as diphenic acid, 2′-formyl-2-biphenylcarboxylic acid and other macromolecules were dominant products of PHE degradation, suggesting polymerization driving PHE degradation instead of the conventional mineralization process. Toxicity analysis shows that most of the polymerization products had less toxicity than that of PHE. These results indicate that PAA activation was a highly effective remediation method for PAHs contaminated soil, which also provided a novel mechanism for pollutant degradation with the PAA activation process for environmental remediation.