Environmental Processes | 2021
Biodegradation Pathway of Polycyclic Aromatic Hydrocarbons by Ligninolytic Fungus Podoscypha elegans Strain FTG4 and Phytotoxicity Evaluation of their Metabolites
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are a type of persistent toxic organic pollutants with potential carcinogenicity and mutagenicity, therefore, dangerous for the safety of human and animal health. The present study investigated the biodegradation of phenanthrene (PHE) and pyrene (PYR) in in-vitro and in-vivo conditions, by the white rot fungus Podoscypha elegans strain FTG4, isolated from an old rotten wood log through the lignin enrichment method. The ligninolytic enzyme production was periodically checked during PHE and PYR degradation under the influence of different physical parameters viz. pH, temperature, and salinity. PHE and PYR degradation by P. elegans were estimated by HPLC and produced degradation metabolites were identified by GC-MS. Structural changes in PHE and PYR during its degradation were observed by FTIR. The assessment of PHE and PYR removal in in-vivo condition was analyzed in the soil system and phytotoxicity evaluation of degradation metabolites was tested on Vigna radiata by the seed germination method. It was found that in in-vitro condition, P. elegans strain FTG4 removed about 99% of PHE and 98.9% of PYR from the degradation medium (20 mg/L concentration individually), although in the in-vivo condition, it reached up to 50.6% of PHE and 48% of PYR (50 mg/kg concentration individually). The metabolites produced during the degradation were the result of oxidation, dehydrogenation, and ring cleavage reactions, confirming the ligninolytic enzyme activity of P. elegans. Phytotoxicity results indicated that P. elegans strain FTG4 mediated PHE and PYR degradation enhanced the germination index, which ultimately reduced the phytotoxicity. Highlights • We report on the biodegradation of PAHs by ligninolytic fungus Podoscypha elegans • In-vitro P. elegans removed 99% of PHE and 98.9% of PYR from degradation medium • In-vivo P. elegans shows promising results for PHE and PYR degradation • PHE and PYR were degraded by oxidation, dehydrogenation, and ring cleavage reactions • P. elegans mediated PHE and PYR degradation shows reduction in phytotoxicity. Graphical abstract