Ligninolytic Fungi in Bioremediation: Mechanism of Polycyclic Aromatic Hydrocarbon (Pah) Degradation and Field Applications

Background: Polycyclic aromatic hydrocarbons (PAHs) are persistent, hydrophobic and in several cases carcinogenic pollutants of soils and sediments. Bacterial degradation of high-molecular-weight PAHs is slow because of their low bioavailability, which has directed attention to ligninolytic fungi that attack pollutants extracellularly. Scope: This narrative review, based exclusively on published secondary data (1983–2024), examines the diversity of ligninolytic fungi, their enzyme systems, the biochemical mechanisms of PAH transformation, the factors that control degradation in soil, and the evidence from pilot- and field-scale applications. Key findings: Lignin peroxidase, manganese peroxidase (including lipid-peroxidation chemistry), versatile peroxidase and laccase–mediator systems oxidise PAHs to quinones and ring-fission products, while cytochrome P450 monooxygenases and unspecific peroxygenases form dihydrodiols and phenols. Fungi mineralise only part of the oxidised carbon, but their polar products are readily mineralised by soil bacteria. Field trials – from US demonstrations with Phanerochaete sordida to tonne-scale Finnish piles inoculated on pine bark and Danish trials with spent oyster-mushroom substrate – confirm that inoculation and colonisation are feasible, but improvements over indigenous microbial activity have been inconsistent and strongly site-dependent, limited by bioavailability, competition and logistics. Conclusion: Ligninolytic fungi are most promising for soils dominated by high-molecular-weight PAHs and as partners in integrated fungal–bacterial treatment. Soil-competent strains, low-cost lignocellulosic carriers, attention to bioavailability and standardised metabolite and toxicity monitoring are required for reliable field deployment.