Isolation, Characterization, and Mycostimulation of Fungi for the Degradation of PAHs at US Superfund Site

Abstract

Mycoremediation is a biological treatment approach that relies on fungi to transform environmental pollutants into intermediates with lower environmen- tal burden. Traditionally, Basidiomycetes were the target fungal phylum used in mycoremediation, however this phylum was found to be unsuccessful when scaled up. 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. 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 com- plex amendments including chicken feathers, wheat seeds, grasshoppers, and maple saw dust. Following biostimulation, laccase expression and PAH transfor- mation was assessed. The grasshopper amendment was found to yield the best results in terms of laccase upregulation with a maximum observed upregulation 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 saw an increase of 44% FLA, 54.2% PYR, and 48.7% BaP, while the Trichoderma isolate saw an increase removal of 58.3% BaP. While the results from this study demonstrate the poten- tial of local Superfund site soil fungi to be used for the removal of PAH, additional invesitgation is need to determine if the response to the chitin-based grasshopper mycostimulation can be translated from in vitro to in vivo.