Isolation, characterization, and mycostimulation of fungi for the degradation of polycyclic aromatic hydrocarbons at a superfund site

Abstract

Mycoremediation is a biological treatment approach that relies on fungi to transform environmental pollutants into intermediates with lower environmental burden. Basidiomycetes have commonly been used as the target fungal phylum for bioaugmentation in mycoremediation, however this phylum has been found to be unreliable when used at scale in the field. In this study, we isolated, characterized, and identified potential polycyclic aromatic hydrocarbon (PAH) degrading fungal isolates from creosote-contaminated sediment in the Elizabeth River, Virginia. Our goal was to identify non-basidiomycete PAH degrading fungi. A total of 132 isolates were isolated, of which the overwhelming majority belonged to the phylum Ascomycota. Isolates were screened for their ability to produce known PAH degrading enzymes, particularly laccase and manganese-dependent peroxidases, and to transform model PAH compounds [fluoranthene, phenanthrene, pyrene and benzo(a)pyrene]. Fungal isolates were subsequently biostimulated using complex amendments including chicken feathers, wheat seeds, grasshoppers, and maple saw dust. Following biostimulation, laccase expression and PAH transformation were assessed. The grasshopper amendment was found to yield the highest laccase upregulation improvement with a maximum increase of 18.9% for the Paraphaeosphaeria isolate. The Septoriella and Trichoderma isolates exposed to the chitin-based grasshopper amendment demonstrated an increase in PAH removal. Septoriella sp. increased its transformation of fluoranthene (44%), pyrene (54.2%, and benzo(a)pyrene (48.7%), while there was a 58.3% increase in the removal of benzo(a)pyrene by Trichoderma sp. While the results from this study demonstrate the potential of indigenous fungi to be biostimulated for the removal of PAHs, additional investigation is needed to determine if the response to the chitin-based grasshopper mycostimulation can be translated from the bench to the field.