Isolation of Ascomycota fungi with capability to transform PAHs: Insights into the biodegradation mechanisms of Penicillium oxalicum

- Ten fungi were isolated and identified from a hydrocarbon-polluted pond.
- The most efficient fungus in anthracene conversion was Penicillium oxalicum.
- P. oxalicum completely removed anthracene and dibenzothiophene within 4 days.
- Induction of oxygenase enzymes was detected during transformation.
- Transformation was proven by the identification of 13C-labelled metabolites.

The aim of this study was to gain insight into the ability of fungi present in a polycyclic aromatic hydrocarbon (PAH)-contaminated pond as remediation agents. Eight of the 10 strains isolated belonging to Ascomycota fungi and were able to remove anthracene after 21 days. Among them, Penicillium oxalicum was selected for further studies. Time course experiments showed that P. oxalicum completely removed anthracene and dibenzothiophene within 4 days, as well as phenanthrene and dibenzofuran, although at slower rates. Induction of oxygenase activity in the subcellular fraction of the fungal mycelium exposed to these aromatic compounds was deeply studied. Besides, the reduction of the conversion rate in the presence of a cytochrome P450 (CYP) inhibitor indicates a role in the first step of transformation of PAHs. The use of a defined growth medium with low carbon content for stable isotope tracer experiments using 13C6-anthracene showed that glucose was required to proceed with anthracene degradation by P. oxalicum. Mineralization of anthracene could not be proved in these experiments, but 13C-labelled oxy- and hydroxy-derivatives were identified by nuclear magnetic resonance (NMR) as major metabolites. These results show the potential application of the isolated fungus P. oxalicum in biotechnological pollutant removal processes.

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