Search

Polychlorinated biphenyls (PCBs) are organic pollutants that are harmful to environment and toxic to humans. Numerous studies, based on basidiomycete strains, have reported unsatisfactory results in the mycoremediation of PCB-contaminated soils mainly due to the non-telluric origin of these strains. The abilities of a five-Ascomycete-strain consortium in the mycoremediation of PCB-polluted soils and its performance to restore their sound functioning were investigated using mesocosm experiments associated with chromatography gas analysis and enzymatic activity assays. With the soil H containing 850 ppm PCB from which the strains had been isolated, a significant PCB depletion of 29% after three months of treatment was obtained. This led to an important decrease of PCBs from 850 to 604 ppm. With the soil L containing 36 ppm PCB, biodegradation did not occur. In both soils, the fungal biomass quantified by the ergosterol assay, did not increase at the end of the treatment. Biodegradation evidenced in the soil H resulted in a significantly improved stoichiometry of N and P acquiring enzymatic activities. This unprecedented study demonstrates that the native Ascomycetes display remarkable properties for remediation and restoration of functioning of the soil they originated from paving the way for greater consideration of these strains in mycoremediation.

Polychlorinated biphenyls (PCBs) are widespread persistent pollutants deleterious for environment and very dangerous for human kind. As the bioremediation of PCB polluted sites by model white-rot fungi is still unsatisfactory, the use of efficient native strains which have the natural capacity to develop on polluted sites may constitute a relevant alternative strategy. In this study, we isolated 12 fungal strains from PCB contaminated soil and sediment, improved the screening method to obtain the most efficient ones in biodegradation and detoxification of PCBs and characterized potential underlying enzymatic activities. Four strains Penicillium chrysogenum, P. citreosulfuratum, P. canescens and Aspergillus jensenii, showed remarkable biodegradation capacities, greater than 70%. The remaining PCB-toxicity of their culture, including that of Trametes versicolor and Acremonium sclerotigenum, which present interesting ecological and metabolic properties, was studied. Only P. canescens was able to significantly reduce the toxicity related to PCBs and their metabolites. The enzymatic activities induced by PCBs were different according to the strains, namely laccases in T. versicolor and peroxidases in Ac. sclerotigenum. Our promising results show that the use of native fungal strains can constitute an effective strategy in the depollution of PCB polluted sites.

Polychlorinated biphenyls (PCBs) represent a large group of recalcitrant environmental pollutants. Up to now, many studies have focused on bioremediation of PCBs by fungal strains; however, the mechanisms of adaptation of these strains towards PCBs remain unknown despite their importance in developing effective bioremediation processes. We studied five species, each consisting of two strains isolated either from PCB-polluted or PCB-unpolluted substrates (control strains). We investigated their responses to PCB contamination by studying their tolerance to PCBs, their ability to reduce these pollutants, and their expression level of Laccase genes. In Thermothelomyces thermophila, Thermothelomyces heterothallica, Thermoascus crustaceus, and Fusarium solani, all the studied strains showed a similar tolerance and PCB degradation regardless of their origin. In Schizophyllum commune, while both strains showed similar resistance to PCBs, i.e., PCBs and their degradation products presented no toxicity for these strains, the rate of PCB degradation of the strain from a PCB-polluted environment was significantly slightly higher. The PCB degradation did not correlate with the expression level of genes encoding Laccases. These results demonstrate that the tolerance and PCB degradation by the fungal strains, which did not involve Laccase genes, required different adaptation systems which seem to be constitutive or rapidly inducible by PCB according to the fungal species.