Involvement of singlet oxygen in the fungal degradation of lignin

The possible involvement of singlet oxygen (¹O₂) in the degradation of lignin by $\text{Phanerochaete}\text{chrysosporium}$ was examined. Ligninolytic cultures and photochemically generated ¹O₂ gave the same oxidation products from the lignin substructure model compound 1,2-bis(3-methoxy-4-alkoxyphenyl)propan-1,3-diol. Fluorescence and near UV absorbance of the specific ¹O₂ trapping agent anthracene-9,10-bisethanesulfonic acid (AES) disappeared in ligninolytic cultures, indicating that ¹O₂ was produced. AES strongly inhibited oxidation of ¹⁴C-lignin, but not ¹⁴C-glucose, to ¹⁴CO₂ in cultures, and also strongly suppressed oxidation of the model compound. These results indicate the ¹O₂ plays an integral role in lignin biodegradation.