Generation of hydroxyl radical and its involvement in lignin degradation by Phanerochaete chrysosporium

Cultures of $\text{Phanerochaete chrysosporium}$ produced ethylene from methional and 2-keto-4-thiomethyl butyric acid (KTBA) only under conditions when the organism was competent to degrade [¹⁴C]-lignin to ¹⁴CO₂. The ability of several mutant strains to produce ethylene reflected their ability to degrade lignin. Hydroxyl radical scavengers including thiourea, salicylate, mannitol, 4-0-methylisoeugenol, as well as catalase, inhibited fungal lignin degradation, fungal ethylene production from methional and KTBA, as well as ethylene generation from KTBA via Fenton's reagent and γ-irradiation. In addition, methional inhibited fungal lignin degradation and lignin inhibited ethylene generation from methional. All of these results indicate that hydroxyl radical plays an important role in lignin degradation by $\text{P. chrysosporium}$.