Further study discounts role for singlet oxygen in fungal degradation of lignin model compounds.

This study reexamined our contention that singlet oxygen (1O2) plays a role in the fungal degradation of lignin (BBRC 102(1981)484). Cultures of Phanerochaete chrysosporium and a photochemical 1O2-generating system (riboflavin/light/O2) cleaved a lignin substructure model compound, 1,2-bis(4-methoxyphenyl)propane-1,3-diol (I), by indistinguishable mechanisms. However, the rate of cleavage of I in D2O was the same as in H2O in the photochemical 1O2-generating system, indicating that 1O2 was not involved. Furthermore, products formed from I in a chemical system for generating 1O2 (H2O2 + NaOCl) differed from those produced by cultures or the photochemical system. It is concluded that 1O2 is not responsible for cleavage of I or related compounds in the fungal cultures or in the photochemical system.