PAH biodegradation by telluric saprotrophic fungi isolated from aged PAH-contaminated soils in mineral medium and historically contaminated soil microcosms.

Purpose: Remediation of contaminated soils is of high relevance considering losses of this limited resource in most countries through erosion or through destruction for societal purposes. Most physicochemical remediation techniques lead to soil destruction avoiding reuse of the sites and loss of soil functions including ecological services like water retention/filtration, plant needs, carbon sequestration, or atmosphere restoration. This study aims to find out efficient telluric PAH-degrading fungi to both remediate soils and preserve their functioning. Materials and methods: Fifty telluric saprotrophic fungi were thus isolated from different aged PAH-contaminated soils sampled from four brownfields in the North of France. Thirty of these isolates were screened in a mineral medium for their ability to degrade benzo[a]pyrene (BaP) used as a model of HMW PAH. After 9 days of incubation, the remaining BaP was quantified through HPLC analysis. Then, a set of microcosms was performed with an aged PAH-contaminated non-sterile soil encompassing different approaches with bioaugmentation using mycelia of three strains pre-established on expanded clay particles and, for one of these strains, biostimulation strategies including nitrogen or nitrogen/phosphorous supplementations or aeration by stirring. After an incubation time of 30 days, remaining PAH were quantified through GC-MS and evolution of fungal populations evaluated through qPCR. Results and discussion: Isolated Penicillium canescens, Cladosporium cladosporioides, Fusarium solani, and Talaromyces helicus degraded more than 30% of the initial 500 μg of BaP after 9 days of incubation. The three latest strains were thus inoculated in aged PAH-contaminated soil microcosms. After 30 days, PAH quantitative analyses showed that the highest degradation was obtained by bioaugmentation with T. helicus (26% of the initial total PAH content: 321.7 mg kg −1 ), which seems high considering an aged industrial contamination. Biostimulation approaches coupled to the inoculation of this strain did not improve the degradation. DNA quantification of the inoculated species confirmed their enrichment in the soil revealing the interest of the used inoculation strategy. We discuss bioaugmentation and biostimulation approaches in the case of the considered pollutants and soil. Conclusions: A strain identified as T. helicus appears interesting for its HMW PAH degradation capacities both in mineral medium with pure BaP and in industrial non-sterile soil microcosms contaminated with a hydrocarbon complex mixture. This study also confirms the efficiency of a well-studied BaP-degrading strain of F. solani. These results indicate the potentialities of the used bioaugmentation approach and underline the necessity of scale-up strategies to apply this kind of technique on site

Energy-dependent uptake of benzo[a]pyrene and its cytoskeleton-dependent intracellular transport by the telluric fungus <em>Fusarium solani.</em>

In screening indigenous soil filamentous fungi for polycyclic aromatic hydrocarbons (PAHs) degradation, an isolate of the Fusarium solani was found to incorporate benzo[a]pyrene (BaP) into fungal hyphae before degradation and mineralization. The mechanisms involved in BaP uptake and intracellular transport remain unresolved. To address this, the incorporation of two PAHs, BaP, and phenanthrene (PHE) were studied in this fungus. The fungus incorporated more BaP into cells than PHE, despite the 400-fold higher aqueous solubility of PHE compared with BaP, indicating that PAH incorporation is not based on a simple diffusion mechanism. To identify the mechanism of BaP incorporation and transport, microscopic studies were undertaken with the fluorescence probes Congo Red, BODIPY&reg;493/503, and FM&reg;4-64, targeting different cell compartments respectively fungal cell walls, lipids, and endocytosis. The metabolic inhibitor sodium azide at 100&nbsp;mM totally blocked BaP incorporation into fungal cells indicating an energy-requirement for PAH uptake into the mycelium. Cytochalasins also inhibited BaP uptake by the fungus and probably its intracellular transport into fungal hyphae. The perfect co-localization of BaP and BODIPY reveals that lipid bodies constitute the intracellular storage sites of BaP in F. solani. Our results demonstrate an energy-dependent uptake of BaP and its cytoskeleton-dependent intracellular transport by F. solani

Magnetic properties of nanostructured thin films of transition metal obtained by low energy cluster beam deposition

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Microstructure of nodular cast iron after excimer laser surface processing

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Plasma source ion-implantation technique for surface modification of materials

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