Effect of soil organic matter (SOM) on the degradation of polycyclic aromatic hydrocarbons using Pleurotus dryinus IBB 903-A microcosm study

Evaluating efficacy of Pseudomonas sp. EN-4 to lower the toxic potential of 4-bromophenol and assessing its competency in simulated microcosm

An indigenous bacterium Pseudomonas sp. EN-4 had been reported earlier for its ability to co-metabolise 4-bromophenol (4-BP), in presence of phenol (100 mg/L) as co-substrate. The present study was undertaken to validate the efficacy of biotransformation by comparing the toxicity profiles of untreated and EN-4 transformed samples of 4-BP, using both plant and animal model. The toxicity studies in Allium cepa (A. cepa) indicated to lowering of mitotic index (MI) from 12.77% (water) to 3.33% in A. cepa bulbs exposed to 4-BP + phenol, which reflects the cytotoxic nature of these compounds. However, the MI value significantly improves to 11.36% in its biologically treated counterpart, indicating normal cell growth. This was further supported by significant reduction in chromosomal aberrations in A. cepa root cells exposed to biologically treated samples of 4-BP as compared to untreated controls. The oxidative stress assessed by comparing the activity profiles of different marker enzymes showed that the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) were reduced by 56%, 72%, and 37% respectively, in EN-4 transformed samples of 4-BP + phenol compared to its untreated counterpart. Similar trends were evident in the comet assay of fish (Channa punctatus) blood cells exposed to untreated and biologically treated samples of 4-BP. The comparative studies showed significant reduction in tail length (72.70%) and % tail intensity (56.15%) in fish blood cells exposed to EN-4 treated 4-BP + phenol, compared to its untreated counterpart. The soil microcosm studies validated the competency of the EN-4 cells to establish and transform 4-BP in soil polluted with 4-BP (20 mg/kg) and 4-BP + phenol (20 + 100 mg/kg). The isolate EN-4 achieved 98.08% transformation of 4-BP in non-sterile microcosm supplemented with phenol, indicating to potential of EN-4 cells to establish along with indigenous microflora.

Space-specific flux estimation of atmospheric chemicals from point sources to soil

Predicting chemical flux to soil from industrial point sources accurately at a regional scale has been a significant challenge due to high uncertainty in spatial heterogeneity and quantification. To address this challenge, we developed an innovative approach by combining California Air Resources Board Puff (CALPUFF) and mass balance models, leveraging their complementary strengths in quantitative accuracy and spatial precision. Specifically, CALPUFF was used to predict the polycyclic aromatic hydrocarbons (PAHs) flux to soil due to industrial sources. Additionally, the spatial distribution coefficient of PAHs flux (e.g., si for spatial unit i) was calculated by neural network and combined with the mass balance model to obtain the results of total PAHs fluxes, which were then combined with the results predicted by CALPUFF to effectively estimate the contribution of industrial sources to soil PAHs flux. Taking a petrochemical industry region located in Zhejiang province, China as a case study, results showed the input Phenanthrene (Phe) and Benzo(a)pyrene (BaP) fluxes predicted by CALPUFF were generally lower than those by the mass balance model, with slightly different distribution patterns. CALPUFF results, based on 36 industrial sources, partially represent those of the mass balance model, which includes all sources and pathways. It was suggested that industrial sources contributed 49%-89% and 65%-100% of soil Phe and BaP, respectively across the study area. The average Phe flux from point sources by deposition averaged 2.68 mg m-2∙a-1 in 2021, accounting for approximately 60% of the total Phe flux to soil. The average BaP flux from point sources by deposition averaged 0.0755 mg m-2∙a-1, accounting for only 0.1%-3.65% of the total BaP flux to soil. Thereby, our approach fills up a gap between the relevance to point sources and the accuracy of deposition quantification in estimating chemical flux from specific point sources to soil at a regional scale.

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.

Biological remediation treatments improve the health of a mixed contaminated soil before significantly reducing contaminant levels

The remediation of mixed contaminated soil is challenging as it often requires actions to minimize metal-induced risks while degrading organic contaminants. Here, the effectiveness of different bioremediation strategies, namely, rhizoremediation with native plant species, mycoremediation with Pleurotus ostreatus spent mushroom substrate, and biostimulation with organic by-products (i.e., composted sewage sludge and spent mushroom substrate), for the recovery of a mixed contaminated soil from an abandoned gravel pit was studied. The combination of biostimulation and rhizoremediation led to the most significant increase in soil health, according to microbial indicator values. The application of composted sewage sludge led to the highest reduction in anthracene and polychlorinated biphenyls concentrations. None of the strategies managed to decrease contamination levels below regulatory limits, but they did enhance soil health. It was concluded that the biological remediation treatments improved soil functioning in a short time, before the concentration of soil contaminants was significantly reduced.

Variations of different PAH fractions and bacterial communities during the biological self-purification in the soil vertical profile

Wild PAH-contaminated sites struggle to provide continuous and stable monitoring, resulting in the potential risks of contaminated soil utilization could not be evaluated effectively. This work provided a 9-months laboratory simulation which was close to the natural ecological process. These results believed that PAH-degrading bacteria (PDB) preferred to degrade organic extracted PAH (PAH_OS) and fresh bound-PAH (79.36-99.97%). The formation and migration efficiency of PAH binding with HA humic acid (HA) (PAH_HA) was lower than that of PAH binding with fulvic acid (FA) and humin (HM) (PAH_FA and PAH_HM), leading to PAH_HA had more persistent retention and influenced bacterial communities in shallow soils. Besides, phylum Proteobacteria gradually dominated the bacterial community and decreased 12.05-20.48% diversity at all depths during the biological self-purification process. Although the effect of this process enhanced the abundance of 28 genes 16 s rRNA and three PAH-degrading genes (PDGs) by 5.91-2047.34 times (phe, nahAc and nidA), the top 30 genera maintained their ecological characteristics. This study provided insights into the important influencing factor and mechanism of the biological self-purification processes and discerned the linkages between bacterial communities and environmental variables in the vertical profile, which is important to the isolation and application of PDB and ecological risk assessment.

Evaluating the potential of engineered Trichoderma atroviride and its laccase-mediated system for the efficient bioconversion of 5-hydroxymethylfufural

5-Hydroxymethylfurfural (HMF) is a fermentation inhibitor which is formed during acid-based thermochemical pre-treatment of biomass. The present study involves two approaches for HMF conversion; the first includes screening and identification of fungal strains which produce oxidoreductases for HMF bioconversion, and thereafter evaluating their roles in HMF conversion. Out of the ten fungal strains screened, genetically engineered Trichoderma atroviride (Lac⁺) showed maximum HMF bioconversion and the activities of ligninolytic enzymes produced were noted. Maximum HMF conversion of 99% was achieved at pH 5.0 and 30 °C when 72 h old 10% inoculum of T. atroviride (Lac⁺) was utilized for 6 days. Based on the fungal bioconversion of HMF to 2, 5 diformylfuran with 58% yield, laccase was observed to influence the conversion process. Thus, a comparative study was established on HMF conversion by 100 U/mL of commercial laccases and partially purified laccase from T. atroviride (Lac+). In the presence of TEMPO, T. atroviride laccase showed comparable HMF conversion to commercial laccases, which establishes the efficiency of fungi and ligninolytic enzymes in bioconversion of HMF to value-added products.

Utilization of surface-active compounds derived from biosolids to remediate polycyclic aromatic hydrocarbons contaminated sediment soil

In the present study, surface-active compounds (SAC) were extracted from biosolids using an alkaline treatment process. They were tested for their remediation efficiency of crude oil-contaminated sediment soil and was compared with Triton x-100. The SAC exhibited a similar soil washing efficiency to that of the commercial Triton x-100, and under the optimized soil washing parameters, SAC exhibited a maximum of 91% total polycyclic aromatic hydrocarbons removal. Further, on analysing the toxicity of the soil residue after washing, it was observed that SAC from biosolids washed soil exhibited an average of 1.5-fold lesser toxicity compared to that of Triton x-100 on different test models-earthworm, a monocot, and dicot plants. The analysis of the key soil parameters revealed that the commercial surfactant reduced the soil organic matter and porosity by an average of 1.3-fold compared to SAC. Further, the ability of surfactants to induce toxicity was confirmed by the adsorption of the surfactants on the surface of the soil particles which was in the order of Triton x-100 > SAC. Thus, this study suggests that SAC can be applied as an effective bioremediation approach for contaminated soil for a greener and sustainable ecosystem.

Long-term application of nitrogen fertilizer alters the properties of dissolved soil organic matter and increases the accumulation of polycyclic aromatic hydrocarbons

Soil is a key component of terrestrial ecosystems, as it provides nutrients and energy for all terrestrial organisms and is the site of various physical, chemical, and biological processes. Soil organic matter is particularly important for the role that it plays in element cycling, as well as the adsorption and degradation of soil pollutants. Nitrogen (N) fertilizer is an important nutrient element in the soil microenvironment. Applications of N fertilizer can improve soil quality, but the long-term excessive application of N fertilizer can lead to the deterioration of the soil environment, alter the properties of organic matter, and affect the adsorption and accumulation of soil pollutants. In recent years, several pollutants, especially polycyclic aromatic hydrocarbons (PAHs), have accumulated in farmland soil due to long-term sewage irrigation. However, few studies have examined the response of soil PAHs accumulation to long-term N application, as well as the relationship between this response and changes in soil microenvironmental indicators caused by N application. Here, we conducted field experiments to study changes in soil pH, total organic carbon, and dissolved organic matter (DOM) under long-term N application, as well as their effects on PAHs accumulation. The application of N fertilizer resulted in the aromatization and humification of soil DOM, enhanced the accumulation response ratio (-0.05-0.32) and the amount of PAHs accumulated in soil (more than 30%), and exacerbated the environmental risks of PAHs. Our findings provide new insights that could aid the management and control of PAHs pollution of soil in sewage-irrigated areas.

Microbial degradation and transformation of benzo[a]pyrene by using a white-rot fungus Pleurotus eryngii F032

Polycyclic aromatic hydrocarbons (PAHs) are environmentally recalcitrant contaminants formed from naturally or incomplete combustion of organic materials and some of them are difficult to degrade due to their hydrophobicity and persistency. Benzo [a]pyrene (BaP), is one of PAHs that having five fused benzene and reported as mutagenic, carcinogenic and teratogenic compounds. Biodegradation is one of promising techniques due to its relatively low economic cost and microorganism is a natural capacity to consume hydrocarbons. In this investigation, Pleurotus eryngii F032 was grown in 20 mL of modified mineral salt broth (MSB) supplemented with BaP under static and agitated culture. Within 20 days, static culture removed 59% of BaP, whereas agitated culture removed the highest amount (73%). To expedite BaP elimination, the mechanism and behavior of BaP biosorption and biotransformation by Pleurotus eryngii F032 were additionally examined by gas chromatography-mass spectrometer (GC-MS). The optimal conditions for P. eryngii F032 to eliminate BaP were 25 °C, a C/N ratio of 8, pH 3 and 0.2% inoculum concentration. At an initial BaP content of 10 mg/L, more than 50% was effectively eliminated within 20 days under these conditions. Salinity, glucose, and rhamnolipids were the most important factors impacting BaP biodegradation. GC-MS found degradation products such as BaP-3,6-quinone, indicating plausible metabolic routes. Finally, it may be assumed that the primary mechanism by which white-rot fungi eliminate BaP is by the utilization of biotransformation enzymes such as laccase to mineralize the PAHs. Hence, Pleurotus eryngii F032 could be an ideal candidate to treat PAHs contaminated soils.

Insolubilization of Tramates versicolor laccase as cross-linked enzyme aggregates for the remediation of trace organic contaminants from municipal wastewater

The novelty of this study deals with the biocatalytic treatment of trace organic contaminants (TrOCs) from municipal wastewater by insolubilized laccase. Laccase from Trametes versicolor was aggregated by three-phase partitioning technique followed by cross-linking with glutaraldehyde to produce insolubilized laccase as cross-linked enzyme aggregates (CLEAs). The optimal conditions for CLEAs preparation include ammonium sulphate concentration of 83% (w/v), crude to t-butanol ratio of 1.00: 1.05 (v/v), pH 5.3, and glutaraldehyde concentration of 20 mM obtained via statistical design. The efficiency of insolubilization of the CLEAs laccase based on the k_cat/k_m ratio was approximately 4.8-fold greater than that of free laccase. The developed CLEAs showed greater resistance to product inhibition mediated by ABTS than the free enzyme and exhibited excellent catalytic activity even after the tenth successive cycle. Further, free laccase and the synthesized CLEAs laccase were utilized to treat five analgesics, two NSAIDS, three antibiotics, two antilipemics, and three pesticides in the municipal wastewater. Under the batch process with operating conditions of pH 7.0 and 20 °C, 1000 U/L of CLEAs, laccase removed 11 TrOCs in the range of about 20-99%. However, the inactivated CLEAs only adsorbed 2-25% of TrOCs. It was observed that acetaminophen, mefenamic acid, trimethoprim, and metolachlor depicted almost complete removal with CLEAs laccase. The performance of CLEAs laccase in a perfusion basket reactor was tested for the removal of TrOCs from municipal wastewater.

Surfactant-aided mycoremediation of soil contaminated with polycyclic aromatic hydrocarbons

Remediation of persistent polycyclic aromatic hydrocarbons (PAHs) contaminated soil has become a major challenge in recent years. Further, conventional application of bioaugmentation strategies for PAHs remediation require continuous supply of microbial specific nutrients, which makes these processes less feasible. Hence, the present study focused on PAHs remediation using surfactants along with wood assisted fungal system in a microcosm set up. In this study, in absence of surfactants, a saturation in PAHs degradation was noted in bioaugmentation with wood assisted fungal system (BAW) with 61 ± 1.25% degradation, followed by bioaugmentation with free fungi system (BAF) (54 ± 0.46%). However, with addition of 1500 mg/L of surface-active compounds (SAC), a maximum PAHs degradation in BAW (100%) and BAF (86 ± 1.30%) strategies were noted on 21st day. Irrespective of the strategies, presence of SAC and rhamnolipids enhanced PAHs degradation by increasing the enzymes production in Trametes hirsuta when compared to Triton x-100 and sodium dodecyl sulphate (SDS). Among the detected PAHs, 100% degradation within 17 days was noted for naphthalene and acenaphthene in SAC-supplemented BAW system. Further, ecotoxicity analysis established showed the LC50 of sediment soil at 26.5 ± 0.24%, which was reduced by an average of 71% after soil remediation. Hence, the current microcosm system proved that the application of SAC with BAW enhanced the PAHs remediation rate, which supports its application in real time soil remediation.

Performance study of fouling resistant novel ultrafiltration membranes based on the blends of poly (ether ether sulfone)/poly (vinyl pyrrolidone)/nano-titania for the separation of humic acid, dyes and biological macromolecular proteins from aqueous solutions

This study explains the use of a ultrafiltration membrane made of polyvinyl pyrrolidone (PVP) and poly(ether ether sulfone) (PEES)/Nano-titania (n-TiO₂) for the separation of organic compounds. The results of the tests for porosity, water content, surface chemistry, membrane morphology, and contact angle demonstrated that the developed membranes have more hydrophilicity than PEES membranes due to the redundant hydrophilic nature of PVP and n-TiO₂. The membrane pure water flux, which contains 5 wt% PVP and 1.5 wt% n-TiO_2, was 312.76 Lm^-2h^-1, about three-fold higher than that of pristine membrane (95.71 Lm^-2h^-1). Employing bovine serum albumin as a model foulant, the fouling resistance of the PEES/PVP/n-TiO₂ membrane was examined. According to the analysis of flux recovery ratio and irreversible resistance, modified membranes were less likely to foul, and the PEES/n-TiO₂ membrane with 5% PVP addition was recommended as optimal. The fabricated membranes effectively removed more than 95% of various organic compounds such as humic acid, safranin O, egg albumin, pepsin, and trypsin from aqueous solution. Permeability of safranin O and humic acid of PEES/PVP/n-TiO₂ membranes was about 118 Lm^-2h^-1 and 138 Lm^-2h^-1, respectively.

Fabrication of highly permeable and anti-fouling performance of Poly(ether ether sulfone) nanofiltration membranes modified with zinc oxide nanoparticles

Membrane fouling is one of the challenging bottleneck problems in waste water treatment by membrane process. The present study constructed a nanofiltration membrane based on the zinc oxide nanoparticle (n-ZnO) integrated Poly(ether ether sulfone) (PEES) membranes. The developed membranes were characterized by X-ray diffraction (XRD), attenuated total reflectance - fourier transform infrared spectroscopy (AT-FTIR), atomic force microscopy (AFM) and scanning electron microscope (SEM) coupled with energy dispersive X-ray (EDX) analysis. Pure water flux, contact angle, molecular weight cut-off, mean pore size and porosity were determined to investigate the influence of n-ZnO on the properties of the membranes. The characterization showed asymmetric configuration of membranes after n-ZnO incorporation. This incorporation also enhanced the hydrophilicity of PEES membrane. The fouling-resistant potential of the membranes was investigated by the model foulant humic acid (HA) and an enhanced anti-fouling irreversible property with a corresponding flux recovery rate of 92.43 % was noted for the prepared membrane. The rejection performance and permeability of HA was 98.03 % and 166.73 L m^-2 h^-1, respectively, owing to the hydrophilic nature of ZnO particles. Further, modified PEES membrane exhibited superior separation performance for monovalent and divalent anions. PEES/n-ZnO hybrid membrane assisted nanofiltration is an effective process for the improvement of membrane performance and anti-fouling property, demonstrating its immense use in water reclamation.

A latest review on the application of microcosm model in environmental research

Microcosms are used experimentally to simulate ecosystems. This technology has received increasing attention and is widely used for environmental research. This review briefly introduces the origin and development of microcosm theory, summarizes classification and applications of microcosms across decades, and describes the advantages and limitations of microcosm technology in comparison with other methods. Finally, trends in the development of microcosm models are discussed.

Enzyme-assisted bioremediation approach for synthetic dyes and polycyclic aromatic hydrocarbons degradation

Environmental protection from emerging pollutants has become a significant challenge for mankind as an increasing number of contaminants, including synthetic dyes and polycyclic aromatic hydrocarbons (PAHs), represent a serious risk to ecological and environmental balance. Most synthetic dyes have complex aromatic structures and are resistant to degrade by classical approaches, such as physical and chemical processes, including adsorption, chemical coagulation, flocculation, ion exchange, membrane separation, froth flotation, and reverse osmosis. Enzymes-assisted catalytic transformation of pollutants has become a potential alternative to classical methods because of their ability to react with complex compounds, a quick degradation rate, and producing less harmful by-products. Plant peroxidases, and microbial laccase and lignin-degrading peroxidases (manganese and lignin peroxidase) have gained significant attention for treating aromatic waste due to their capability of oxidizing and detoxifying a wide range of recalcitrant xenobiotics, including PAHs and synthetic dyes. Peroxidases being efficient biocatalysts detoxify an array of toxic compounds by simple free-radical mechanism resulting in the formation of oxidized and depolymerized products of significantly reduced toxicity. Moreover, it is an ecofriendly and economically favorable approach towards the biodegradation of recalcitrant and toxic industrial waste. Among microbial and plant peroxidases, bacterial enzymes have broad substrate specificity and can transform a wide range of recalcitrant substrates. Ligninolytic enzymes oxidize the aromatic ring into quinones and acids by producing free hydroxyl radicals instead of dihydrodiols and mineralize aromatic hydrocarbon in combination with cytochrome P450, monooxygenases, and epoxide hydrolases. In the review, an attempt has been made to provide detailed knowledge about the availability of inexpensive peroxidases sources, their mechanism of action, and degradation potential. The present review summarizes the exploitation of peroxidases from plants, bacteria, and fungus (manganese peroxidase, lignin peroxidase, and laccases) for detoxification and degradation of textile dyes as well as PAHs. Conclusively, peroxidases have great potential to react with almost all classes of synthetic dyes and most PAHs due to broad substrate specificity and transformed them into less harmful metabolites.

Biodegradation pathway of the organophosphate pesticides chlorpyrifos, methyl parathion and profenofos by the marine-derived fungus Aspergillus sydowii CBMAI 935 and its potential for methylation reactions of phenolic compounds

The indiscriminate use of organophosphate pesticides causes serious environmental and human health problems. This study aims the biodegradation of chlorpyrifos, methyl parathion and profenofos with the proposal of new biodegradation pathways employing marine-derived fungi as biocatalysts. Firstly, a growth screening was carried out with seven fungi strains and Aspergillus sydowii CBMAI 935 was selected. For chlorpyrifos, 32% biodegradation was observed and the metabolites tetraethyl dithiodiphosphate, 3,5,6-trichloropyridin-2-ol, 2,3,5-trichloro-6-methoxypyridine, and 3,5,6-trichloro-1-methylpyridin-2(1H)-one were identified. Whereas 80% methyl parathion was biodegraded with the identification of isoparathion, methyl paraoxon, trimethyl phosphate, O,O,O-trimethyl phosphorothioate, O,O,S-trimethyl phosphorothioate, 1-methoxy-4-nitrobenzene, and 4-nitrophenol. For profenofos, 52% biodegradation was determined and the identified metabolites were 4-bromo-2-chlorophenol, 4-bromo-2-chloro-1-methoxybenzene and O,O-diethyl S-propylphosphorothioate. Moreover, A. sydowii CBMAI 935 methylated different phenolic substrates (phenol, 2-chlorophenol, 6-chloropyridin-3-ol, and pentachlorophenol). Therefore, the knowledge about the fate of these compounds in the sea was expanded, and the marine-derived fungus A. sydowii CBMAI 935 showed potential for biotransformation reactions.

Performance evaluation of biocatalytic and biostimulation approaches for the remediation of trace organic contaminants in municipal biosolids

Trace organic contaminants (TrOCs) in biosolids is creating potential threats for reuse of biosolids. Out of the tested 64 trace organic contaminants, seven pharmaceutically active compounds (PhACs), and three pesticides were detected in biosolids from a municipal wastewater treatment plant. This study encompasses the removal of TrOCs and improvement in the aerobic digestion of biosolids by various pretreatments including utilization of indigenous microbes present in biosolids (T1), the effect of an enzymatic pretreatment (T2), biostimulation by the addition of an external carbon source (T3) and the synergic effect of biostimulation and enzymatic pretreatment (T4). After 28 days of aerobic digestion, total PhACs removal was 44% with T1, which improved to 51%, 54% and 62% in T2, T3 and T4, respectively. Also, total pesticides removal was 10% in T1, which enhanced to 44%, 14% and 54% in T2, T3 and T4, respectively. The extracellular enzyme activities were also monitored in all the treatments and the maximum activities (114 ± 11 U/L lipase, 382 ± 29 U/L phosphatase, 155 ± 8 U/L protease, 304 ± 26 U/L amylase, 108 ± 7 U/L laccase, and 63 ± 2 U/L lignin peroxidase) were observed in T4 after 28 days of digestion. Thus, this study aids in providing changing aspects of enzyme profiles during these processes and the enhanced bioremediation of biosolids through the hydrolytic and oxidoreductase enzymes produced by the indigenous microorganisms.

Rhamnolipid-assisted mycoremediation of polycyclic aromatic hydrocarbons by Trametes hirsuta coupled with enhanced ligninolytic enzyme production

The present study deals with the development of a wood assisted fungal system (WAFS) from wood chips using Trametes hirsuta to remove polycyclic aromatic hydrocarbons (PAHs) in BRW. The WAFS exhibited a 1.4-fold higher ligninolytic enzyme production than free fungi in the effluent. Further, to understand PAHs bioremediation by T. hirsuta, biodegradation along with biosorption were studied in model PAHs, phenanthrene (Phe) and benzo (a) pyrene (BaP), in the presence of synthesized rhamnolipids. The WAFS mineralized up to an average of 91.26% Phe and 87.72 % BaP along with biosorption of 12.35% Phe and 18.36 % BaP within 12 days. Thus, the addition of rhamnolipids showed 1.2-fold enhanced biodegradation. However, rhamnolipid concentrations beyond 50 ppm reduced the degradation efficiency of WAFS. Moreover, the degradation capability of total aromatic hydrocarbon (TAH) in biorefinery wastewater by WAFS is 1.8-fold higher than that of free fungi, which confirms the effectiveness of the system. Implications: Simultaneous application of white-rot fungus along with surfactant into a pollutant environment affects the microenvironment of the fungus and reduces the production of their degradative enzymes. In addition, the requirement of periodical supplement of external nutrient in the real-time matrix for the growth of white rot fungi may trigger competitive growth of indigenous microorganisms. Considering this glitch, the current work utilizes the carpenter waste for the strategical develop a wood assisted fungal system to protect the microenvironment of the fungi in the presence of rhamnolipids and contribute to their survival in real time matrix, with enhanced PAHs degradation efficiency.

Insights into the mechanisms underlying efficient Rhizodegradation of PAHs in biochar-amended soil: From microbial communities to soil metabolomics

The combined effects of biochar amendment and the rhizosphere on the soil metabolic microbiome during the remediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soil remain unknown. In this study, we attempted to characterize a PAH degradation network by coupling the direct PAH degradation with soil carbon cycling. From microbial community structure and functions to metabolic pathways, we revealed the modulation strategies by which biochar and the rhizosphere benefited PAH degradation in soil. Firstly, some PAH degraders were enriched by biochar and the rhizosphere, and their combination promoted the cooperation among these PAH degraders. Simultaneously, under the combined effects of biochar and the rhizosphere, the functional genes participating in upstream PAH degradation were greatly upregulated. Secondly, there were strong co-occurrences between soil microbial community members and metabolites, in particular, some PAH degraders and the metabolites, such as PAH degradation products or common carbon resources, were highlighted in the networks. It shows that the overall downstream carbon metabolism of PAH degradation was also greatly upregulated by the combined effects of biochar and plant roots, showing good survival of the soil microbiome and contributing to PAH biodegradation. Taken together, both soil carbon metabolism and direct contaminant biodegradation are likely to be modulated by the combined effects of biochar and plant roots, jointly benefitting to PAH degradation by soil microbiome. Our study is the first to link PAH degradation with native carbon metabolism by coupling sequencing and soil metabolomics technology, providing new insights into a systematic understanding of PAH degradation by indigenous soil microbiome and their networks.