Potentiality of Native Ascomycete Strains in Bioremediation of Highly Polychlorinated Biphenyl Contaminated Soils

Abstract

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.

Molecular Characterization of Fungal Biodiversity in Long-Term Polychlorinated Biphenyl-Contaminated Soils

“…Second, among the 16 species, the strains of F. solani, P. canescens, P. citrosulfuratum and P. chrysogenum had already shown interesting abilities for the PCB degradation in liquid medium by displaying biodegradation rates of at least 60% after 7 days of incubation [20,22]. More interestingly, some strains of these species used in consortium in the mycoremediation by bioaugmentation have made it possible to obtain remarkable biodegradation rates using soils highly polluted with PCBs [21,23]. These results suggest that it might be possible to use strains of these 16 species in consortium to potentially effectively remediate PCBcontaminated soils without having to isolate and screen the strains beforehand, without long and tedious steps and without decreasing the efficiency of biodegradation due to a possible lack of growth of bioaugmented strains.…”

“…Mycoremediation strategies primarily use model fungal species of ligninolytic Basidiomycota due to their interesting biochemical potential, particularly their capacity to produce the nonspecific oxidative exoenzymes involved in the degradation of numerous organic pollutants [7,[16][17][18]. Mycoremediation strategies are also based on the use of native fungal species isolated directly from PCB-contaminated soils and generally used in consortium, i.e., a mixture of several strains previously screened for their biodegradation efficiency [19][20][21][22][23]. While the ligninolytic Basidiomycota displayed partial or low PCB degradation rates compared to those expected probably due to their non-telluric origin, their non-adaptation to PCB-polluted soils or their difficulty to grow in soils due to the competition with indigenous microbiota [13,24], native fungal species could be promising [21,23].…”

“…Mycoremediation strategies are also based on the use of native fungal species isolated directly from PCB-contaminated soils and generally used in consortium, i.e., a mixture of several strains previously screened for their biodegradation efficiency [19][20][21][22][23]. While the ligninolytic Basidiomycota displayed partial or low PCB degradation rates compared to those expected probably due to their non-telluric origin, their non-adaptation to PCB-polluted soils or their difficulty to grow in soils due to the competition with indigenous microbiota [13,24], native fungal species could be promising [21,23]. However, even if they have the advantage of being naturally adapted to the soil to be decontaminated, their use to treat a specific soil requires a strain isolation step and a screening procedure, making it long and tedious to obtain the most efficient ones in biodegradation processes.…”