Elucidation of In Situ Ligninolysis Mechanisms of the Selective White-Rot Fungus Ceriporiopsis subvermispora

Lignin degradation by white-rot fungi is an essential step in terrestrial carbon cycling and has great potential for biotechnological applications. Selective white-rot fungi have been recognized for their ability to effectively delignify lignocellulose, but the underlying mechanisms, particularly in situ, have largely remained elusive to date. In this work, we elucidate specific degradation routes of beta-O-4 aryl ethers in actual lignocellulosic biomass for the industrially relevant selective white-rot fungus Ceriporiopsis subvermispora. Multidimensional NMR and py-GC-MS analyses together with enzymatically synthesized model compounds enabled, for the first time, the identification of various diagnostic lignin cleavage products in residual wheat straw. Our results support that in situ ligninolysis by C. subvermispora is initiated by single-electron transfer, which then cascades into the cleavage of C-alpha-C-beta, C-beta-O, and O-4-aryl bonds of beta-O-4 aryl ethers. The high abundance of 1-(benzyl)-2,3-dihydroxypropan-1-ones indicated that beta-O-|4 cleavage is a more important pathway than previously considered. Our approach highlights key diagnostic substructures for providing mechanistic insight into fungal ligninolysis.