Biological machinery for polycyclic aromatic hydrocarbons degradation: A review

Zhou

et al. 2022

IJERPH

In this study, 16 PAHs were selected as the priority control pollutants to summarize their environmental metabolism and transformation processes, including photolysis, plant degradation, bacterial degradation, fungal degradation, microalgae degradation, and human metabolic transformation. Meanwhile, a total of 473 PAHs by-products generated during their transformation and degradation in different environmental media were considered. Then, a comprehensive system was established for evaluating the PAHs by-products’ neurotoxicity, immunotoxicity, phytotoxicity, developmental toxicity, genotoxicity, carcinogenicity, and endocrine-disrupting effect through molecular docking, molecular dynamics simulation, 3D-QSAR model, TOPKAT method, and VEGA platform. Finally, the potential environmental risk (phytotoxicity) and human health risks (neurotoxicity, immunotoxicity, genotoxicity, carcinogenicity, developmental toxicity, and endocrine-disrupting toxicity) during PAHs metabolism and transformation were comprehensively evaluated. Among the 473 PAH’s metabolized and transformed products, all PAHs by-products excluding ACY, CHR, and DahA had higher neurotoxicity, 152 PAHs by-products had higher immunotoxicity, and 222 PAHs by-products had higher phytotoxicity than their precursors during biological metabolism and environmental transformation. Based on the TOPKAT model, 152 PAH by-products possessed potential developmental toxicity, and 138 PAH by-products had higher genotoxicity than their precursors. VEGA predicted that 247 kinds of PAH derivatives had carcinogenic activity, and only the natural transformation products of ACY did not have carcinogenicity. In addition to ACY, 15 PAHs produced 123 endocrine-disrupting substances during metabolism and transformation. Finally, the potential environmental and human health risks of PAHs metabolism and transformation products were evaluated using metabolic and transformation pathway probability and degree of toxic risk as indicators. Accordingly, the priority control strategy for PAHs was constructed based on the risk entropy method by screening the priority control pathways. This paper assesses the potential human health and environmental risks of PAHs in different environmental media with the help of models and toxicological modules for the toxicity prediction of PAHs by-products, and thus designs a risk priority control evaluation system for PAHs.

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Potential Toxicity Risk Assessment and Priority Control Strategy for PAHs Metabolism and Transformation Behaviors in the Environment

Zhou

et al. 2022

IJERPH

“…66 Although, aldehyde dehydrogenases have wellestablished involvement in polyaromatic hydrocarbons, studies specifically concentrated on PAD involvement in styrene metabolism are still emerging. 67…”

Section: Interaction Of Pad With Phenylacetaldehydementioning

confidence: 99%

Understanding the in silico aspects of bacterial catabolic cascade for styrene degradation

2022

Styrene is a nonpolar organic compound used in very high volume for the industrial scale production of commercially important polymers such as polystyrene resins as well as copolymers like acrylonitrile butadiene styrene, latex, and rubber. These resins are widely used in the manufacturing of various products including single‐use plastics such as disposable cups and containers, protective packaging, heat insulation, and so forth. The large‐scale utilization leads to the over‐accumulation of styrene waste in the environment causing deleterious health risks including cancer, neurological impairment, dysbiosis of central nervous system, and respiratory problems. To eliminate the accumulating waste. Microbial enzyme‐based system represents the most environmental friendly and sustainable approach for elimination of styrene waste. However, comprehensive understanding of the enzyme–substrate interaction and associated pathways would be crucial for developing large‐scale disposal systems. This study aims to understand the molecular interaction between the protein‐ligand complexes of the styrene catabolic reactions by bacterial enzymes of sty operon. Molecular docking analysis for catalytic enzymes namely, styrene monooxygenase (SMO), styrene oxide isomerase (SOI), and phenylacetaldehyde dehydrogenase (PAD) of the bacterial sty operon was carried out with their individual substrates, that is, styrene, styrene oxide, and phenylacetic acid, respectively. The binding energy, amino acids forming binding cavity, and binding interactions between the protein‐ligand binding sites were calculated for each case. The obtained binding energies showed a stable association of these complexes indicating the future scope of their utilization for large‐scale bioremediation of styrene, and its commercially used polymers and copolymers.

“…The genes coding for these degrading enzymes is expressed in all bacteria populations capable of attaching to the Bay-region and K-region (Kotoky et al, 2022;Wang et al, 2018). The most widely reported PAH genes expressed by most hydrocarbondegrading bacterial populations for the degradation LMW and HMW PAHs are aldehyde dehydrogenase (alkB) (Williams et al, 2022), alkane hydroxylase gene (alkH) (Abbasian et al, 2016;Pacwa-Płociniczak et al, 2019), naphthalene dioxygenase (nahAcR) (Mawad et al, 2020), PAH ring hydroxylating dioxygenase (PAH-RHDα) (Imam et al, 2022;Obi et al, 2020), catechol 1,2-dioxygenase (C12O) (Aravind et al, 2021) and catechol 2,3-dioxygenase (C23O) (Mawad et al, 2020 ). The bacteria gene markers for the aerobic bioconversion/degradation of 16 priority PAHs pollutants are the alkB, alkH, C12O, and C23O.…”

Section: Introductionmentioning

confidence: 99%

MOLECULAR CHARACTERISATION OF BACTERIA MONOOXYGENASE AND DEHYDROGENASE GENES INVOLVED IN PAHs REMEDIATION

Okolafor

Ekhaise

2022

OJER

Bacterial catabolic genes (alkB, alkH, C12O, and C23O) are a good biomarker for choosing the choice of the organism for polycyclic aromatic hydrocarbon (PAH) degradation. Low molecular weight (LMW) and high molecular weight (HMW) PAHs metabolism can be made possible by monooxygenase and dehydrogenase enzymes which code for the catabolic genes. In this study, the monooxygenase and dehydrogenase genes were characterized from the bacterial population isolated from motor mechanic workshop soils and landfill soil artificially polluted with waste engine oil (WEO). Standard microbiological methods were followed for the isolation and characterization of the bacterial population. The PCR cycling for alkB and alkH followed initial denaturation at 94oC for 5 minutes, followed by 35 cycles of denaturation at 95oC for 1 minute, annealing at the correct temperature (alkB 49oC, alkH 72oC). PCR cycling for C12O and C23O genes followed initial denaturation at 95oC for 5 minutes, 35 cycles of denaturation at 94oC for 20 s, annealing at 63oC for 30 s, extension at 60oC for 45 s, with final extension for 5 minutes at 72oC. Final elongation step for all the catabolic genes at 72oC for 10 minutes and holding temperature at 10oC forever. Ampliﬁed fragments were visualized on safe view-stained 1.5% agarose gel electrophoresis. The result of the characterization revealed base pair sizes of the genes; alkB (100 to 300 bp), alkH (< 700 bp), C12O (>250 bp), and C23O (<80 pb). All the bacterial populations invested in this study expressed the monooxygenase and dehydrogenase genes. Monooxygenase and dehydrogenase genes are coding for the enzymes responsible for hydroxylation and intradiol or extradiol ring-cleaving of PAHs.