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.

Polycyclic aromatic hydrocarbons (PAHs) are bonded organic compounds with numerous structures with different toxicity levels. They can be of low molecular weight with 2-3 rings or high molecular weight with more than four rings and are persistent in nature. They possess high molecular weight and boiling point, hydrophobic with minimal solubility in water, and lipophilic with high solubility in organic solvents. With the gain in molecular weight, their susceptibility to oxidation-reduction decreases. They are generated during incomplete combustion of organic materials. They can be natural, such as forest fires, or artificial agents, such as coal, oil, wood burning, smoke, and auto-emissions. Due to strong molecular bonds and structural complexity, PAHs are highly malignant under normal conditions. They cause environmental damage due to improper handling and disposal in the surrounding air, water, soil, etc. PAH contamination is highly toxic because of mutagenic and potentially immune toxicants, often resulting in higher workplace casualties. Various physical, biological, and chemical processes remediate the PAHs in contaminated land. Indigenous microbial communities can effectively degrade it in-situ or ex-situ conditions. The degradation process depends on the type of microorganism, its life cycle, PAH substrate, pH, temperature, pressure, and the reaction mechanism. The present article discusses current literature, chemistry, natural and anthropogenic sources of generation, impacts on the environment, biota, etc., merits of physical, biological, and chemical remediation mechanisms with emphasis on microbial degradation, and novel options of technology intermix suitable for sustainable remediation outcomes.

This work is dedicated to the study and investigation of thermoxidation processes in crude oil and petroleum products. The study of thermoxidation processes in crude oil and petroleum products was carried out using various analytical techniques, including IR, NMR, UV, small-batch reactor, TGA, DSC, DTA, thermochemical luminescence and others. One of the key characteristics of crude oil and petroleum products is their thermo-oxidative stability. During thermoxidation, hydrocarbons in the oil oxidize in an oxygen-rich environment, forming undesirable compounds such as hydroperoxides, alcohols, ketones, and others. These changes lead to increased viscosity and alterations in the chemical and physical properties of the product. The hydroperoxides formed during the process play a critical role as free radical initiators, which accelerate oxidation reactions. At higher temperatures, these reactions can produce solid particles, resins, and even sediments. In engines, such sediments can disrupt the normal flow within the fuel system, leading to improper process management, engine damage, increased operational costs, reduced efficiency, and environmental pollution. Effective management of oxidation processes and the implementation of preventive measures are crucial to addressing environmental issues such as soil and water contamination. In the oil industry, it is essential to enhance the understanding and control of oxidation processes to meet both the increasing global demand and the tightening environmental regulations. This approach not only improves production efficiency but also ensures the protection of the environment

A strain of Bacillus licheniformis T5 was isolated from soil contaminated with crude oil due to its efficient degradation of polycyclic aromatic hydrocarbons (PAHs). When subjected to stress metabolism using phenanthrene as a carbon source, significant changes were observed in T5 cells. Infrared spectrum analysis revealed the presence of -C=C- and Ph-O-C (aromatic) groups on the bacterial surface, facilitating the adsorption of PAHs on the phospholipid layer and causing damage to the cell membrane. Scanning electron microscope (SEM) analysis showed the changes of cell morphology, including a large number of folds on the lower surface and the folding of cell membrane. Transmission electron microscope (TEM) observation showed that non-stressed bacteria with adequate nutritional conditions accumulated more lipids. However, the stress group contained more protein. It was found that stress metabolism led to the increase of protein content in T5 cells by 16.4% and the activity of oxidoreductase more than doubled. These physiological and biochemical changes enhance the ability of stressed bacteria to degrade PAHs efficiently, thereby reducing the degradation cycle. The findings offer valuable insights for the remediation of PAHs pollution.

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that pose significant environmental and health risks. These compounds originate from both natural phenomena, such as volcanic activity and wildfires, and anthropogenic sources, including vehicular emissions, industrial processes, and fossil fuel combustion. Their classification as carcinogenic, mutagenic, and teratogenic substances link them to various cancers and health disorders. PAHs are categorized into low-molecular-weight (LMW) and high-molecular-weight (HMW) groups, with HMW PAHs exhibiting greater resistance to degradation and a tendency to accumulate in sediments and biological tissues. Soil serves as a primary reservoir for PAHs, particularly in areas of high emissions, creating substantial risks through ingestion, dermal contact, and inhalation. Coastal and aquatic ecosystems are especially vulnerable due to concentrated human activities, with PAH persistence disrupting microbial communities, inhibiting plant growth, and altering ecosystem functions, potentially leading to biodiversity loss. In plants, PAH contamination manifests as a form of abiotic stress, inducing oxidative stress, cellular damage, and growth inhibition. Plants respond by activating antioxidant defenses and stress-related pathways. A notable aspect of plant defense mechanisms involves plant-derived extracellular vesicles (PDEVs), which are membrane-bound nanoparticles released by plant cells. These PDEVs play a crucial role in enhancing plant resistance to PAHs by facilitating intercellular communication and coordinating defense responses. The interaction between PAHs and PDEVs, while not fully elucidated, suggests a complex interplay of cellular defense mechanisms. PDEVs may contribute to PAH detoxification through pollutant sequestration or by delivering enzymes capable of PAH degradation. Studying PDEVs provides valuable insights into plant stress resilience mechanisms and offers potential new strategies for mitigating PAH-induced stress in plants and ecosystems.

The distribution of integral indicators of the soil-plant system components contamination with polycyclic aromatic hydrocarbons in the urban area has been considered. An anthropogenically modified natural complex of the RUDN University campus and the adjacent South-Western Forest Park (Moscow) was the object of study. Soils (Albic Retisols (Ochric)) and common plant species were studied. Traffic load was the main pollution source. Emissions from five sections of roads, around and across the territory, formed a specific pattern of pollutants, which was demonstrated by the example of marker compounds, namely, polycyclic aromatic hydrocarbons. Background concentrations of individual polyarenes in the environment, determined by the method of dynamic phase portraits, have been calculated as an approximate safe level of contamination of soils and vegetation. A local redistribution of contamination zones was revealed owing to the migration of polyarenes from snow into soils, and then into root systems, and the above-ground parts of plants distribution. The proposed methodological approach, based on the use of integral indicators, allows us to assess the degree of damage to ecosystems caused by a complex of priority pollutants.

Petroleum hydrocarbon-induced environmental degradation has escalated, necessitating immediate remediation due to the ongoing growth of communities and modernization of civilization. Both carbon and energy can be obtained from hydrocarbons of petroleum, which are decomposed by a wide variety of microorganisms found in nature. Many times, remediation of places damaged by oil using biological means is accomplished by using bacteria that have such characteristics. Hence, this review attempt to highlight on the oil contaminated soil, source of oil pollution, the composition of oil, the impact of oil contamination on the living organisms additionally, the destiny of oil in the environment, how bacteria distributed in the soil and the most common degradable bacteria and their role in oil biodegradation with some attention on the impact of their enzymes. Also, considering the mechanism of biodegradation of aliphatic and aromatic oil hydrocarbon compounds, how bacteria taking up oil hydrocarbons and the influence of several elements on the processes of oil biodegradation. Furthermore, it; reducing pollution contributes to achieving sustainable development goals.

Worldwide, it has been recorded extensively that plants are subjected to severe abiotic and biotic stressors. The scientific research community has widely reported that multi-abiotic stressors cause horticultural crop losses, accounting for at least 50 to 70% of the crop yield and quality losses. Therefore, this review focused on the detrimental effects caused by abiotic stress factors occurring in single-, combined- and multi-cell stresses on horticultural plants worldwide, along with the best production systems practices for mitigation during and post-single and combined abiotic or multi-stress damages. A conclusion and recommendation could be reached using the pool of research material, which constituted research articles, reviews, book chapters, thesis, research short communications and industrial short communications from at least twenty-five years ago. Findings showed that some of the leading abiotic stresses are single- and combined abiotic stressors like water deficit, salinity, soil pH, phosphate deficiency, wounding, soil density and pot size. Established commercial and smallholder farmers are globally adapting to plant growth regulators and biostimulants as part of their production systems. However, as much as the effectiveness of biostimulants containing humic acids, algal extracts, plant growth-promoting microorganisms and phytohormones has been reported to promote plant development under multi-stress, only a few studies are focusing on organic phytohormone-based biostimulants on horticultural crops grown under adverse multi stress factoring. In conclusion, the review recommends alternative solutions for emerging South African farmers and growers who cannot afford agricultural insurance options and energy alternatives on the common single

Plastic pollution is a common concern of global environmental pollution. Polystyrene (PS) and polyethylene (PE) account for almost one-third of global plastic production. However, so far, there have been few reports on microbial strains capable of simultaneously degrading PS and PE. In this study, Microbacterium esteraromaticum SW3, a non-pathogenic microorganism that can use PS or PE as the only carbon source in the mineral salt medium (MM), was isolated from plastics-contaminated soil and identified. The optimal growth conditions for SW3 in MM were 2% (w/v) PS or 2% (w/v) PE, 35 degrees C and pH 6.3. A large number of bacteria and obvious damaged areas were observed on the surface of PS and PE products after inoculated with SW3 for 21 d. The degradation rates of PS and PE by SW3 (21d) were 13.17% and 5.39%, respectively. Manganese peroxidase and lipase were involved in PS and PE degradation by SW3. Through Fourier infrared spectroscopy detection, different functional groups such as carbonyl, hydroxyl and amidogen groups were produced during the degradation of PS and PE by SW3. Moreover, PS and PE were degraded into alkanes, ketones, carboxylic acids, esters and so on detected by GC-MS. Collectively, we have isolated and identified SW3, which can use PS or PE as the only carbon source in MM as well as degrade PS and PE products. This study not only provides a competitive candidate strain with broad biodegradability for the biodegradation of PS and/or PE pollution, but also provides new insights for the study of plastic biodegradation pathways.

Nanobubbles (NBs), given their unique properties, could theoretically be paired with rhamnolipids (RL) to tackle polycyclic aromatic hydrocarbon contamination in groundwater. This approach may overcome the limitations of traditional surfactants, such as high toxicity and low efficiency. In this study, the remediation efficiency of RL, with or without NBs, was assessed through soil column experiments (soil contaminated with phenanthrene). Through the analysis of the two-site non-equilibrium diffusion model, there was a synergistic effect between NBs and RL. The introduction of NBs led to a reduction of up to 24.3 % in the total removal time of phenanthrene. The direct reason for this was that with NBs, the retardation factor of RL was reduced by 1.9 % to 15.4 %, which accelerated the solute replacement of RL. The reasons for this synergy were multifaceted. Detailed analysis reveals that NBs improve RL's colloidal stability, increase its absolute zeta potential, and reduce its soil adsorption capacity by 13.3 %-19.9 %. Furthermore, NBs and their interaction with RL substantially diminish the surface tension, contact angle, and dynamic viscosity of the leaching solution. These changes in surface thermodynamic and rheological properties significantly enhance the migration efficiency of the eluent. The research outcomes facilitate a thorough comprehension of NBs' attributes and their relevant applications, and propose an eco-friendly method to improve the efficiency of surfactant remediation.