Bioremediation of polycyclic aromatic hydrocarbons: An updated microbiological review

Spatial distribution of PAHs and microbial communities in intertidal sediments of the Pearl River Estuary, South China

The exploration of sediment pollution caused by PAHs and its impact on microbial communities can provide valuable insights for the remediation of sediments. The spatial distribution of PAHs and their impact on the microbial community within the Pearl River Estuary were investigated in this study. The findings revealed that the total concentration ranges of 16 PAHs were between 24.26 and 3075.93 ng/g, with naphthalene, fluorene, and phenanthrene potentially exerting adverse biological effects. More PAHs were found to accumulate in subsurface sediments, and their average accumulation rates gradually decreased as the number of rings in PAHs increased, ranging from 180 % for 2-ring to 36 % for 6-ring. The phyla Proteobacteria, Bacteroidetes, Actinobacteria, and Chloroflexi were found to dominate both surface and subsurface sediments The correlation between microbial genera and PAHs contents was weak in sediments with low levels of PAHs contamination, while a more significant positive relationship was observed in sediments with high levels of PAHs contamination. The physicochemical properties of sediments, such as pH, soil structure and Cu significantly influence bacterial community composition in highly contaminated sediments. Additionally, the network analysis revealed that certain bacterial genera, including Novosphingobium, Robiginitalea and Synechococcus_CC9902, played a pivotal role in the degradation of PAHs. These findings are significant in comprehending the correlation between bacterial communities and environmental factors in intertidal ecosystems, and establish a scientific foundation for bioremediation of intertidal zones.

Simultaneous biodegradation of polycyclic aromatic hydrocarbons and phthalates by bacterial consortium and its bioremediation for complex polluted soil and sewage sludge

Simultaneous biodegradation of multiple micropollutantslike polycyclic aromatic hydrocarbons (PAHs) and phthalates (PAEs) by microbial consortia remain unclear. Here, four distinct bacterial consortia capable of degrading PAHs and PAEs were domesticated from sludge and its composts. PAH-degrading consortium HS and PAE-degrading consortium EC2 displayed the highest degradation efficiencies for PAHs (37 %-99 %) and PAEs (98 %-99 %), respectively, being significantly higher than those of individual member strains. Consortia HS and EC2 could simultaneously degrade both PAHs and PAEs. Remarkably, a synthetic consortium Syn by co-culturing consortia HS and EC2 demonstrated proficient simultaneous biodegradation for both PAHs (65 %-98 %) and PAEs (91 %-97 %). These consortia changed their community structure with enriching pollutant-degrading genera and extracellular polymeric substance contents to promote simultaneous biodegradation of multiple pollutants. Moreover, consortium Syn significantly enhanced degradation of both PAHs and PAEs in soil and sludge. This study provides strong candidates for simultaneous bioremediation of complex polluted environments by PAHs and PAEs.

Transfer from ciliate to zebrafish: Unveiling mechanisms and combined effects of microplastics and heavy metals

The impacts and toxicological mechanisms of microplastics (MPs) or heavy metals on aquatic ecosystems have been the subject of extensive research and initial understanding. However, the combined toxicity of co-pollutants on organisms and cumulative toxic effects along the food chain are still underexplored. In this study, the ciliate protozoan Paramecium caudatum and zebrafish Danio rerio were used to represent the microbial loop and the higher trophic level, respectively, to illustrate the progressive exposure of MPs and cadmium (Cd2+). The findings indicate that MPs (ca. 1 ×105 items/L) containing with Cd2+ (below 0.1 µg/L) could permeate the bodies of zebrafish through trophic levels after primary ingestion by ciliates. This could cause adverse effects on zebrafish, including alterations in bioindicators (total sugar, triglycerides, lactate, and glycogen) associated with metabolism, delayed hepatic development, disruption of intestinal microbiota, DNA damage, inflammatory responses, and abnormal cellular apoptosis. In addition, the potential risks associated with the transfer of composite pollutants through the microbial loop into traditional food chain were examined, offering novel insights on the evaluation of the ecological risks associated with MPs. As observed, understanding the bioaccumulation and toxic effects of combined pollutants in zebrafish holds crucial implications for food safety and human health.

Occurrence and distribution of emerging contaminants in wastewater treatment plants: A globally review over the past two decades

Emerging contaminants are pervasive in aquatic environments globally, encompassing pharmaceuticals, personal care products, steroid hormones, phenols, biocides, disinfectants and various other compounds. Concentrations of these contaminants are detected ranging from ng/L to μg/L. Even at trace levels, these contaminants can pose significant risks to ecosystems and human health. This article systematically summarises and categorizes data on the concentrations of 54 common emerging contaminants found in the influent and effluent of wastewater treatment plants across various geographical regions: North America, Europe, Oceania, Africa, and Asia. It reviews the occurrence and distribution of these contaminants, providing spatial and causal analyses based on data from these regions. Notably, the maximum concentrations of the pollutants observed vary significantly across different regions. The data from Africa, in particular, show more frequent detection of pharmaceutical maxima in wastewater treatment plants.

Removal of benzo[a]pyrene from the soil by adsorption coupled with degradation on saponin-modified bentonite immobilized crude enzymes

Bentonite is a non-metallic mineral with montmorillonite as the main component. It is an environmentally friendly mineral material with large reserves, wide distribution, and low price. Bentonite can be easily modified organically using the surfactant saponin to obtain saponin-modified bentonite (Sap-BT). This study investigates the immobilization of crude enzymes obtained from Trametes versicolor by physical adsorption with Sap-BT. Thus, saponin-modified bentonite immobilized crude enzymes (CE-Sap-BT) were developed to remove benzo[a]pyrene. Immobilization improves the stability of free enzymes. CE-Sap-BT can maintain more than 80% of activity at 45 °C and after storage for 15 d. Additionally, CE-Sap-BT exhibited a high removal rate of benzo[a]pyrene in soil, with 65.69% after 7 d in highly contaminated allotment soil and 52.90% after 6 d in actual soil contaminated with a low concentration of benzo[a]pyrene at a very low laccase dosage (0.1 U/3 g soil). The high catalytic and removal performance of CE-Sap-BT in contaminated sites showed more excellent practical application value.

Exploring the diversity and functional profile of microbial communities of Brazilian soils with high salinity and oil contamination

Environmental pollution associated with the petroleum industry is a major problem worldwide. Microbial degradation is extremely important whether in the extractive process or in bioremediation of contaminants. Assessing the local microbiota and its potential for degradation is crucial for implementing effective bioremediation strategies. Herein, contaminated soil samples of onshore oil fields from a semiarid region in the Northeast of Brazil were investigated using metagenomics and metataxonomics. These soils exhibited hydrocarbon contamination and high salinity indices, while a control sample was collected from an uncontaminated area. The shotgun analysis revealed the predominance of Actinomycetota and Pseudomonadota, while 16S rRNA gene amplicon analysis of the samples showed Actinomycetota, Bacillota, and Pseudomonadota as the most abundant. The Archaea domain phylotypes were assigned to Thermoproteota and Methanobacteriota. Functional analysis and metabolic profile of the soil microbiomes exhibited a broader metabolic repertoire in the uncontaminated soil, while degradation pathways and surfactant biosynthesis presented higher values in the contaminated soils, where degradation pathways of xenobiotic and aromatic compounds were also present. Biosurfactant synthetic pathways were abundant, with predominance of lipopeptides. The present work uncovers several microbial drivers of oil degradation and mechanisms of adaptation to high salinity, which are pivotal traits for sustainable soil recovery strategies.

Polycyclic aromatic hydrocarbon: underpinning the contribution of specialist microbial species to contaminant mitigation in the soil

The persistence of PAHs poses a significant challenge for conventional remediation approaches, necessitating the exploration of alternative, sustainable strategies for their mitigation. This review underscores the vital role of specialized microbial species (nitrogen-fixing, phosphate-solubilizing, and biosurfactant-producing bacteria) in tackling the environmental impact of polycyclic aromatic hydrocarbons (PAHs). These resistant compounds demand innovative remediation strategies. The study explores microbial metabolic capabilities for converting complex PAHs into less harmful byproducts, ensuring sustainable mitigation. Synthesizing literature from 2016 to 2023, it covers PAH characteristics, sources, and associated risks. Degradation mechanisms by bacteria and fungi, key species, and enzymatic processes are examined. Nitrogen-fixing and phosphate-solubilizing bacteria contributions in symbiotic relationships with plants are highlighted. Biosurfactant-producing bacteria enhance PAH solubility, expanding microbial accessibility for degradation. Cutting-edge trends in omics technologies, synthetic biology, genetic engineering, and nano-remediation offer promising avenues. Recommendations emphasize genetic regulation, field-scale studies, sustainability assessments, interdisciplinary collaboration, and knowledge dissemination. These insights pave the way for innovative, sustainable PAH-contaminated environment restoration.

A commercial humic acid inhibits benzo(a)pyrene biodegradation by Paracoccus aminovorans HPD-2

Benzo(a)pyrene (BaP) is posing serious threats to soil ecosystems and its bioremediation usually limited by environmental factors and microbial activity. Humic acid (HA), a ubiquitous heterogeneous organic matter, which could affect the fate of environmental pollutants. However, the impact of HA on bioremediation of organic contamination remains controversial. In the present study, the biodegradation of BaP by Paracoccus aminovorans HPD-2 with and without HA was explored. Approximately 87.4 % of BaP was biodegraded in the HPD-2 treatment after 5 days of incubation, whereas the addition of HA dramatically reduced BaP biodegradation to 56.0 %. The limited BaP biodegradation in the HA + HPD-2 treatment was probably due to the decrease of BaP bioavailability which induced by the adsorption of HA with unspecific interactions. The excitation-emission matrix (EEM) of fluorescence characteristics showed that strain HPD-2 was responsible for the presence of protein-like substances and the microbial original humic substances in the HPD-2 treatment. Addition of HA would result in the increase of soluble microbial humic-like material, which should ascribe to the biodegradation of BaP and probably utilization of HA. Furthermore, both the growth and survival of strain HPD-2 were inhibited in the HA + HPD-2 treatment, because of the limited available carbon source (i.e. BaP) at the presence of HA. The expression of gene1789 and gene2589 dramatically decreased in the HA + HPD-2 treatment, and this should be responsible for the decrease of BaP biodegradation as well. This study reveals the mechanism that HA affect the BaP biodegradation, and the decrease of biodegradation should ascribe to the interaction of HA and bacterial strain. Thus, the bioremediation strategies of PAHs need to consider the effects of organic matter in environment.

Successful cultivation of edible fungi on textile waste offers a new avenue for bioremediation and potential food production

Textile waste contains both natural fibres such as cotton and bamboo viscose, and synthetic fibres such as elastane and polyester. As a complex mixture, textiles present a challenging pollution issue as breakdown in landfill results in microplastics entering water and soil environments, and incineration results in particulate air pollution. Here the use of edible fungi as bioremediation agents of waste textiles is described for the first time. Three species of filamentous fungi were shown to colonise and grow on mixed fibre textile waste (underpants made from 28% cotton: 68% bamboo viscose: 4% elastane). All three fungi were able to metabolise the common textile dye Reactive Black 5 to some extent. The metabolome was captured to elucidate the dye remediation pathway utilized and to characterise the volatiles released during bioremediation with a view to assessing the safety profile of this process for future industrial applications. The results suggest that edible fungi may be cultivated on textiles, and that some interesting and useful compounds may be produced in the process. This has great biotechnological potential. No mushrooms were produced in this study, suggesting that further work will be needed to optimise conditions for crop production from waste textiles.

PAH bioremediation with Rhodococcus rhodochrous ATCC 21198: Impact of cell immobilization and surfactant use on PAH treatment and post-remediation toxicity

Polycyclic aromatic hydrocarbons (PAHs) are prevalent environmental contaminants that are harmful to ecological and human health. Bioremediation is a promising technique for remediating PAHs in the environment, however bioremediation often results in the accumulation of toxic PAH metabolites. The objectives of this research were to demonstrate the cometabolic treatment of a mixture of PAHs by a pure bacterial culture, Rhodococcus rhodochrous ATCC 21198, and investigate PAH metabolites and toxicity. Additionally, the surfactant Tween ® 80 and cell immobilization techniques were used to enhance bioremediation. Total PAH removal ranged from 70-95% for fluorene, 44-89% for phenanthrene, 86-97% for anthracene, and 6.5-78% for pyrene. Maximum removal was achieved with immobilized cells in the presence of Tween ® 80. Investigation of PAH metabolites produced by 21198 revealed a complex mixture of hydroxylated compounds, quinones, and ring-fission products. Toxicity appeared to increase after bioremediation, manifesting as mortality and developmental effects in embryonic zebrafish. 21198's ability to rapidly transform PAHs of a variety of molecular structures and sizes suggests that 21198 can be a valuable microorganism for catalyzing PAH remediation. However, implementing further treatment processes to address toxic PAH metabolites should be pursued to help lower post-remediation toxicity in future studies.

Insects to the rescue? Insights into applications, mechanisms, and prospects of insect-driven remediation of organic contaminants

Traditional and emerging contaminants pose significant human and environmental health risks. Conventional physical, chemical, and bioremediation techniques have been extensively studied for contaminant remediation. However, entomo- or insect-driven remediation has received limited research and public attention. Entomo-remediation refers to the use of insects, their associated gut microbiota, and enzymes to remove or mitigate organic contaminants. This novel approach shows potential as an eco-friendly method for mitigating contaminated media. However, a comprehensive review of the status, applications, and challenges of entomo-remediation is lacking. This paper addresses this research gap by examining and discussing the evidence on entomo-remediation of various legacy and emerging organic contaminants. The results demonstrate the successful application of entomo-remediation to remove legacy organic contaminants such as persistent organic pollutants. Moreover, entomo-remediation shows promise in removing various groups of emerging contaminants, including microplastics, persistent and emerging organic micropollutants (e.g., antibiotics, pesticides), and nanomaterials. Entomo-remediation involves several insect-mediated processes, including bio-uptake, biotransfer, bioaccumulation, and biotransformation of contaminants. The mechanisms underlying the biotransformation of contaminants are complex and rely on the insect gut microbiota and associated enzymes. Notably, while insects facilitate the remediation of contaminants, they may also be exposed to the ecotoxicological effects of these substances, which is often overlooked in research. As an emerging field of research, entomo-remediation has several knowledge gaps. Therefore, this review proposes ten key research questions to guide future perspectives and advance the field. These questions address areas such as process optimization, assessment of ecotoxicological effects on insects, and evaluation of potential human exposure and health risks.

The Combination of Buchloe dactyloides Engelm and Biochar Promotes the Remediation of Soil Contaminated with Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) cause serious stress to biological health and the soil environment as persistent pollutants. Despite the wide use of biochar in promoting soil improvement, the mechanism of biochar removing soil PAHs through rhizosphere effect in the process of phytoremediation remain uncertain. In this study, the regulation of soil niche and microbial degradation strategies under plants and biochar were explored by analyzing the effects of plants and biochar on microbial community composition, soil metabolism and enzyme activity in the process of PAH degradation. The combination of plants and biochar significantly increased the removal of phenanthrene (6.10%), pyrene (11.50%), benzo[a]pyrene (106.02%) and PAHs (27.10%) when compared with natural attenuation, and significantly increased the removal of benzo[a]pyrene (34.51%) and PAHs (5.96%) when compared with phytoremediation. Compared with phytoremediation, the combination of plants and biochar significantly increased soil nutrient availability, enhanced soil enzyme activity (urease and catalase), improved soil microbial carbon metabolism and amino acid metabolism, thereby benefiting microbial resistance to PAH stress. In addition, the activity of soil enzymes (dehydrogenase, polyphenol oxidase and laccase) and the expression of genes involved in the degradation and microorganisms (streptomyces, curvularia, mortierella and acremonium) were up-regulated through the combined action of plants and biochar. In view of the aforementioned results, the combined application of plants and biochar can enhance the degradation of PAHs and alleviate the stress of PAH on soil microorganisms.

Phenanthrene metabolism in Panicum miliaceum: anatomical adaptations, degradation pathway, and computational analysis of a dioxygenase enzyme

Polycyclic aromatic compounds (PAHs) are persistent organic pollutants of environmental concern due to their potential impacts on food chain, with plants being particularly vulnerable. While plants can uptake, transport, and transform PAHs, the precise mechanisms underlying their localization and degradation are not fully understood. Here, a cultivation experiment conducted with Panicum miliaceum exposed different concentrations of phenanthrene (PHE). Intermediate PHE degradation compounds were identified via GC-MS analysis, leading to the proposal of a phytodegradation pathway featuring three significant benzene ring cleavage steps. Our results showed that P. miliaceum exhibited the ability to effectively degrade high levels of PHE, resulting in the production of various intermediate products through several chemical changes. Examination of the localization and anatomical characteristics revealed structural alterations linked to PHE stress, with an observed enhancement in PHE accumulation density in both roots and shoots as treatment levels increased. Following a 2-week aging period, a decrease in the amount of PHE accumulation was observed, along with a change in its localization. Bioinformatics analysis of the P. miliaceum 2-oxoglutarate-dependent dioxygenase (2-ODD) DAO-like protein revealed a 299 amino acid structure with two highly conserved domains, namely 2OG-FeII_Oxy and DIOX_N. Molecular docking analysis aligned with experimental results, strongly affirming the potential link and direct action of 2-ODD DAO-like protein with PHE. Our study highlights P. miliaceum capacity for PAHs degradation and elucidates the mechanisms behind enhanced degradation efficiency. By integrating experimental evidence with bioinformatics analysis, we offer valuable insights into the potential applications of plant-based remediation strategies for PAHs-contaminated environments.

Enhanced phenanthrene biodegradation in river sediments by harnessing calcium peroxide nanoparticles and minerals in Sphingomonas sp. DSM 7526 cultivation

Coupling chemical oxidation and biodegradation to remediate polycyclic aromatic hydrocarbon (PAH)-contaminated sediment has recently gained significant attention. In this study, calcium peroxide nanoparticles (nCaO2) were utilized as an innovative oxygen-releasing compound for in-situ chemical oxidation. The study investigates the bioremediation of phenanthrene (PHE)-contaminated sediment inoculated with Sphingomonas sp. DSM 7526 bacteria and treated with either aeration or nCaO2. Using three different culture media, the biodegradation efficiencies of PHE-contaminated anoxic sediment, aerobic sediment, and sediment treated with 0.2% w/w nCaO2 ranged from 57.45% to 63.52%, 69.87% to 71.00%, and 92.80% to 94.67%, respectively. These values were significantly higher compared to those observed in non-inoculated sediments. Additionally, the type of culture medium had a prominent effect on the amount of PHE removal. The presence of minerals in the culture medium increased the percentage of PHE removal compared to distilled water by about 2-10%. On the other hand, although the application of CaO2 nanoparticles negatively impacted the abundance of sediment bacteria, resulting in a 30-42% decrease in colony-forming units after 30 days of treatment, the highest PHE removal was obtained when coupling biodegradation and chemical oxidation. These findings demonstrate the successful application of bioaugmentation and chemical oxidation processes for treating PAH-contaminated sediment.

Plant biomass extracted eco-friendly natural surfactant enhanced bio-electrokinetic remediation of crude oil contaminated soil

The current work investigates bioremediation (BIO) and electrokinetic (EK) remediation of crude oil hydrocarbons utilizing the biomass-electrokinetic (BIO-EK) approaches. The use of natural surfactants derived from plant biomass may improve remediation capacity by enhancing the solubility of organic pollutants. Sapindus mukorossi, a natural surfactant producer, was extracted from plant biomass in this study. The crude oil biodegradation efficiency was reported to be 98 %. In nature, FTIR confirms that plant biomass is lipopeptide. GCMS revealed that the crude oil (C7 - C23) was efficiently bio-degraded from lower to higher molecular weight. The application of natural surfactants in electokinetic remediation increased the plant biomass degradation of crude oil polluted soil by 98% compared to electrokinetic 55% in 2 days. Natural surfactant improves hydrocarbon solubilization and accelerates hydrocarbon electro migration to the anodic compartment, as confirmed by the presence of greater total organic content than the electrokinetic. This study proves that BIO-EK compared with a natural surfactant derived from plant biomass may be utilized to improve in situ bioremediation of crude oil polluted soils.

Bacterial response to the combined pollution of benzo[a]pyrene and decabromodiphenyl ether in soil under flooding anaerobic condition

This study investigated the interaction between the co-pollutants of Benzo[a]pyrene (BaP) and decabromodiphenyl ether (BDE-209) and the bacterial community in soil under flooding anaerobic condition. Three levels of combined pollution (at nominal concentrations of 1, 5, and 25 mg/kg, respectively, for each pollutant), their corresponding sterilized controls, and a blank control (CK) were set up. During the incubation time of 270 days, BaP attenuated more easily than BDE-209. The second-order rate constant of BaP attenuation was negatively correlated with the Ln value of initial BaP concentration. Maximal difference in bacterial community occurred between the CK soil and the highly polluted soil. Desulfomonilaceae, Parcubacteria and Rhodanobacter were probably involved in BaP and BDE-209 degradation, while Nitrosomonadaceae, Phenylobacterium and Mitochondria were significantly suppressed by BaP and BDE-209 or their degrading products. Genes narI, bcrC, fadJ, had, dmpC, narG and CfrA were involved in the degradation of BaP and BDE-209. Impacts of BaP and BDE-209 on metabolisms of carbon, nitrogen and sulfur were not significant. The results provide guidance for the management and remediation of the contaminated soil.

Adaptation strategies and functional transitions of microbial community in pyrene-contaminated soils promoted by lead with Pseudomonas veronii and its extracellular polymeric substances

Pyrene was designated as a remediation target in this study, and low contamination of lead (Pb) was set to induce heavy metal stress. Pseudomonas veronii and its extracellular polymeric substances (EPSs) were chosen for biofortification, with the aim of elucidating the structural, metabolic, and functional responses of soil microbial communities. Community analysis of soil microorganisms using high-throughput sequencing showed that the co-addition of P. veronii and EPSs resulted in an increase in relative abundance of phyla associated with pyrene degradation, and formed a symbiotic system dominated by Firmicutes and Proteobacteria, which involved in pyrene metabolism. Co-occurrence network analysis revealed that the module containing P. veronii was the only one exhibiting a positive correlation between bacterial abundance and pyrene removal, indicating the potential of bioaugmentation in enriching functional taxa. Biofortification also enhanced the abundance of functional gene linked to EPS production (biofilm formation-Pseudomonas aeruginosa) and pyrene degradation. Furthermore, 17 potential functional bacteria were screened out using random forest algorithm. Lead contamination further promoted the growth of Proteobacteria, intensified cooperative associations among bacteria, and increased the abundance of bacteria with positive correlation with pyrene degradation. The results offer novel perspectives on alterations in microbial communities resulting from the synergistic impact of heavy metal stress and biofortification.

Endocrine disruptors: Unravelling the link between chemical exposure and Women's reproductive health

An Endocrine Disrupting Chemical (EDC) is any compound that disrupts the function of the endocrine system in humans and is ubiquitous in the environment either as a result of natural events or through anthropogenic activities. Bisphenol A, phthalates, parabens, pesticides, triclosan, polychlorinated biphenyls, and heavy metals, which are frequently found in the pharmaceutical, cosmetic, and packaging sectors, are some of the major sources of EDC pollutants. EDCs have been identified to have a deteriorating effect on the female reproductive system, as evidenced by the increasing number of reproductive disorders such as endometriosis, uterine fibroids, polycystic ovary syndrome, premature ovarian failure, menstrual irregularity, menarche, and infertility. Studying EDCs in relation to women's health is essential for understanding the complex interactions between environmental factors and health outcomes. It enables the development of strategies to mitigate risks, protect reproductive and overall health, and inform public policy decisions to safeguard women's well-being. Healthcare professionals must know the possible dangers of EDC exposure and ask about environmental exposures while evaluating patients. This may result in more precise diagnosis and personalized treatment regimens. This review summarises the existing understanding of prevalent EDCs that impact women's health and involvement in female reproductive dysfunction and underscores the need for more research. Further insights on potential mechanisms of action of EDCs on female has been emphasized in the article. We also discuss the role of nutritional intervention in reducing the effect of EDCs on women's reproductive health. EDC pollution can be further reduced by adhering to strict regulations prohibiting the release of estrogenic substances into the environment.

Transfer and Degradation of PAHs in the Soil-Plant System: A Review

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic, persistent organic pollutants that threaten ecosystems and human health. Consistent monitoring is essential to minimize the entry of PAHs into plants and reduce food chain contamination. PAHs infiltrate plants through multiple pathways, causing detrimental effects and triggering diverse plant responses, ultimately increasing either toxicity or tolerance. Primary plant detoxification processes include enzymatic transformation, conjugation, and accumulation of contaminants in cell walls/vacuoles. Plants also play a crucial role in stimulating microbial PAHs degradation by producing root exudates, enhancing bioavailability, supplying nutrients, and promoting soil microbial diversity and activity. Thus, synergistic plant-microbe interactions efficiently decrease PAHs uptake by plants and, thereby, their accumulation along the food chain. This review highlights PAHs uptake pathways and their overall fate as contaminants of emerging concern (CEC). Understanding plant uptake mechanisms, responses to contaminants, and interactions with rhizosphere microbiota is vital for addressing PAH pollution in soil and ensuring food safety and quality.

Microbes and microbial strategies in carcinogenic polycyclic aromatic hydrocarbons remediation: a systematic review

Degradation, detoxification, or removal of the omnipresent polycyclic aromatic hydrocarbons (PAHs) from the ecosphere as well as their prevention from entering into food chain has never appeared simple. In this context, cost-effective, eco-friendly, and sustainable solutions like microbe-mediated strategies have been adopted worldwide. With this connection, measures have been taken by multifarious modes of microbial remedial strategies, i.e., enzymatic degradation, biofilm and biosurfactant production, application of biochar-immobilized microbes, lactic acid bacteria, rhizospheric-phyllospheric-endophytic microorganisms, genetically engineered microorganisms, and bioelectrochemical techniques like microbial fuel cell. In this review, a nine-way directional approach which is based on the microbial resources reported over the last couple of decades has been described. Fungi were found to be the most dominant taxa among the CPAH-degrading microbial community constituting 52.2%, while bacteria, algae, and yeasts occupied 37.4%, 9.1%, and 1.3%, respectively. In addition to these, category-wise CPAH degrading efficiencies of each microbial taxon, consortium-based applications, CPAH degradation-related molecular tools, and factors affecting CPAH degradation are the other important aspects of this review in light of their appropriate selection and application in the PAH-contaminated environment for better human-health management in order to achieve a sustainable ecosystem.

Microalgae mediated bioremediation of polycyclic aromatic hydrocarbons: Strategies, advancement and regulations

Polycyclic aromatic hydrocarbons (PAHs) are pervasive in the atmosphere and are one of the emerging pollutants that cause harmful effects in living systems. There are some natural and anthropogenic sources that can produce PAHs in an uncontrolled way. Several health hazards associated with PAHs like abnormality in the reproductive system, endocrine system as well as immune system have been explained. The mutagenic or carcinogenic effects of hydrocarbons in living systems including algae, vertebrates and invertebrates have been discussed. For controlling PAHs, biodegradation has been suggested as an effective and eco-friendly process. Microalgae-based biosorption and biodegradation resulted in the removal of toxic contaminants. Microalgae both in unialgal form and in consortium (with bacteria or fungi) performed good results in bioaccumulation and biodegradation. In the present review, we highlighted the general information about the PAHs, conventional versus advanced technology for removal. In addition microalgae based removal and toxicity is discussed. Furthermore this work provides an idea on modern scientific applications like genetic and metabolic engineering, nanomaterials-based technologies, artificial neural network (ANN), machine learning (ML) etc. As rapid and effective methods for bioremediation of PAHs. With several pros and cons, biological treatments using microalgae are found to be better for PAH removal than any other conventional technologies.

Optimisation of PAHs biodegradation by Klebsiella pneumonia and Pseudomonas aeruginosa through response surface methodology

Response Surface Methodology (RSM) with Box-Behnken Design (BBD) is used to optimise the Phenanthrene (PHE) degradation process by Klebsiella pneumoniae (K bacteria) and Pseudomonas aeruginosa (P bacteria). Wherein substrate concentration, temperature, and pH at three levels are used as independent variables, and degradation rate of PHE as dependent variables (response). The statistical analysis, via ANOVA, shows coefficient of determination R2 as 0.9848 with significant P value 0.0001 fitting in second-order quadratic regression model for PAHs removal by Klebsiella pneumonia, and R2 as 0.9847 with significant P value 0.0001 by P bacteria. According to the model analysis, temperature (P < 0.0006) is the most influential factor for PHE degradation efficiency by K bacteria, while pH (P < 0.0001) is the most influential factor for PHE degradation by P bacteria. The predicted optimum parameters for K bacteria, namely, temperature, substrate concentration, and pH are found to be 34.00℃, 50.80 mg/L, and 7.50, respectively, and those for P bacteria are 33.30℃, 52.70 mg/L, and 7.20, respectively. At these optimum conditions, the observed PHE removal rates by two bacteria are found to be 83.36% ± 2.1% and 81.23% ± 1.6% in validation experiments, respectively. Thus RSM can optimise the biodegradation conditions of both bacteria for PHE.

Microbiome based approaches for the degradation of polycyclic aromatic hydrocarbons (PAHs): A current perception

Globally, polycyclic aromatic hydrocarbons (PAHs) pollution is primarily driven by their release into the air through various combustion processes, including burning fossil fuels such as coal, oil, and gas in motor vehicles, power plants, and industries, as well as burning organic matter like wood, tobacco, and food in fireplaces, cigarettes, and grills. Apart from anthropogenic pollution sources, PAHs also occur naturally in crude oil, and their potential release during oil extraction, refining processes, and combustion further contributes to contamination and pollution concerns. PAHs are resistant and persistent in the environment because of their inherent features, viz., heterocyclic aromatic ring configurations, hydrophobicity, and thermostability. A wide range of microorganisms have been found to be effective degraders of these recalcitrant contaminants. The presence of hydrocarbons as a result of numerous anthropogenic activities is one of the primary environmental concerns. PAHs are found in soil, water, and the air, making them ubiquitous in nature. The presence of PAHs in the environment creates a problem, as their presence has a detrimental effect on humans and animals. For a variety of life forms, PAH pollutants are reported to be toxic, carcinogenic, mutation-inducing, teratogenic, and immune toxicogenics. Degradation of PAHs via biological activity is an extensively used approach in which diverse microorganisms (fungal, algal, clitellate, and protozoan) and plant species and their derived composites are utilized as biocatalysts and biosurfactants. Some microbes have the ability to transform and degrade these PAHs, allowing them to be removed from the environment. The goal of this review is to provide a critical overview of the existing understanding of PAH biodegradation. It also examines current advances in diverse methodologies for PAH degradation in order to shed light on fundamental challenges and future potential.

Recent trends in polycyclic aromatic hydrocarbons pollution distribution and counteracting bio-remediation strategies

Polycyclic aromatic hydrocarbons (PAHs) are distributed worldwide due to long-term anthropogenic pollution sources. PAHs are recalcitrant and highly persistent in the environment due to their inherent properties, such as heterocyclic aromatic ring structures, thermostability, and hydrophobicity. They are highly toxic, carcinogenic, immunotoxic, teratogenic, and mutagenic to various life systems. This review focuses on the unique data of PAH sources, exposure routes, detection techniques, and harmful effects on the environment and human health. This review provides a comprehensive and systematic compilation of eco-friendly biological treatment solutions for PAH remediation, such as microbial remediation approaches utilizing microbial cultures. In situ and Ex situ bioremediation of PAH methods, including composting land farming, biopiles, bioreactors bioaugmentation, and phytoremediation processes, are discussed in detail, as is a summary of the factors affecting and limiting PAH bioremediation. This review provides an overview of emerging technologies that use multi-process combinatorial treatment approaches and answers to generating value-added by-products during PAH remediation.

Exploiting fungi in bioremediation for cleaning-up emerging pollutants in aquatic ecosystems

Aquatic pollution negatively affects water bodies, marine ecosystems, public health, and economy. Restoration of contaminated habitats has attracted global interest since protecting the health of marine ecosystems is crucial. Bioremediation is a cost-effective and eco-friendly way of transforming hazardous, resistant contaminants into environmentally benign products using diverse biological treatments. Because of their robust morphology and broad metabolic capabilities, fungi play an important role in bioremediation. This review summarizes the features employed by aquatic fungi for detoxification and subsequent bioremediation of different toxic and recalcitrant compounds in aquatic ecosystems. It also details how mycoremediation may convert chemically-suspended matters, microbial, nutritional, and oxygen-depleting aquatic contaminants into ecologically less hazardous products using multiple modes of action. Mycoremediation can also be considered in future research studies on aquatic, including marine, ecosystems as a possible tool for sustainable management, providing a foundation for selecting and utilizing fungi either independently or in microbial consortia.

Study of polycyclic aromatic hydrocarbons accumulation in bioretention facilities and its influence on microbial community structure

Bioretention facilities are one of the most widely used measures for urban stormwater control and utilization. In this study, the accumulation characteristics of polycyclic aromatic hydrocarbons (PAHs) in bioretention facilities and the effects of PAHs on the structure of microbial communities were explored by combining on-site monitoring and water distribution simulation experiments. The correlation between pollutant accumulation and dominant microorganisms in the bioretention systems was also clarified. The results showed that all 16 priority PAHs were detected in the bioretention facilities in the sponge city pilot area. The PAH concentrations in the soil during the non-rainy season were higher than those in the rainy season and medium- and high-ring PAHs dominated. PAHs in the study area were mainly derived from coal and biomass combustion. The potential carcinogenic risk of PAHs accumulated in the bioretention facilities in the study area was low. The microbial diversity during the non-rainy season was greater than that during the rainy season. Firmicutes, Bacteroidetes, Bacteroides, and Massilia were strongly correlated with naphthalene (NAP), pyrene (PYR), fluoranthene (FLT), and benzo[a]pyrene (BaP). According to the results of the small-scale water distribution test, the addition of PAHs had little effect on the decline in water quantity, and there was no significant regularity in the reduction of water quality including TP, NH4+-N, NO3-N, and TN. The addition of PAHs had a significant effect on the microbial community structure and an inhibitory effect on enzyme activity.

Metabolic capacity to alter polycyclic aromatic hydrocarbons and its microbe-mediated remediation

The elimination of contaminants caused by anthropogenic activities and rapid industrialization can be accomplished using the widely used technology of bioremediation. Recent years have seen significant advancement in our understanding of the bioremediation of coupled polycyclic aromatic hydrocarbon contamination caused by microbial communities including bacteria, algae, fungi, yeast, etc. One of the newest techniques is microbial-based bioremediation because of its greater productivity, high efficiency, and non-toxic approach. Microbes are appealing candidates for bioremediation because they have amazing metabolic capacity to alter most types of organic material and can endure harsh environmental conditions. Microbes have been characterized as extremophiles that can survive in a variety of environmental circumstances, making them the treasure troves for environmental cleanup and the recovery of contaminated soil. In this study, the mechanisms underlying the bioremediation process as well as the current situation of microbial bioremediation of polycyclic aromatic hydrocarbon are briefly described.

Determining the degradation mechanism and application potential of benzopyrene-degrading bacterium Acinetobacter XS-4 by screening

In industrial wastewater treatment, organic pollutants are usually removed by in-situ microorganisms and exogenous bactericides. Benzo [a] pyrene (BaP) is a typical persistent organic pollutant and difficult to be removed. In this study, a new strain of BaP degrading bacteria Acinetobacter XS-4 was obtained and the degradation rate was optimized by response surface method. The results showed that the degradation rate of BaP was 62.73% when pH= 8, substrate concentration was 10 mg/L, temperature was 25 °C, inoculation amount was 15% and culture rate was 180 r/min. Its degradation rate was better than that of the reported degrading bacteria. XS-4 is active in the degradation of BaP. BaP is degraded into phenanthrene by 3, 4-dioxygenase (α subunit and β subunit) in pathway Ⅰ and rapidly forms aldehydes, esters and alkanes. The pathway Ⅱ is realized by the action of salicylic acid hydroxylase. When sodium alginate and polyvinyl alcohol were added to the actual coking wastewater to immobilize XS-4, the degradation rate of BaP was 72.68% after 7 days, and the removal effect was better than that of single BaP wastewater (62.36%), which has the application potential. This study provides theoretical and technical support for microbial degradation of BaP in industrial wastewater.

Water a major source of endocrine-disrupting chemicals: An overview on the occurrence, implications on human health and bioremediation strategies

Endocrine disrupting chemicals (EDCs) are toxic compounds that occur naturally or are the output of anthropogenic activities that negatively impact both humans and wildlife. A number of diseases are associated with these disruptors, including reproductive disorders, cardiovascular disorders, kidney disease, neurological disorders, autoimmune disorders, and cancer. Due to their integral role in pharmaceuticals and cosmetics, packaging companies, agro-industries, pesticides, and plasticizers, the scientific awareness on natural and artificial EDCs are increasing. As these xenobiotic compounds tend to bioaccumulate in body tissues and may also persist longer in the environment, the concentrations of these organic compounds may increase far from their original point of concentrations. Water remains as the major sources of how humans and animals are exposed to EDCs. However, these toxic compounds cannot be completely biodegraded nor bioremediated from the aqueous medium with conventional treatment strategies thereby requiring much more efficient strategies to combat EDC contamination. Recently, genetically engineered microorganism, genome editing, and the knowledge of protein and metabolic engineering has revolutionized the field of bioremediation thereby helping to breakdown EDCs effectively. This review shed lights on understanding the importance of aquatic mediums as a source of EDCs exposure. Furthermore, the review sheds light on the consequences of these EDCs on human health as well as highlights the importance of different remediation and bioremediation approaches. Particular attention is paid to the recent trends and perspectives in order to attain sustainable approaches to the bioremediation of EDCs. Additionally, rigorous restrictions to preclude the discharge of estrogenic chemicals into the environment should be followed in efforts to combat EDC pollution.