Coupling structural characterization with secretomic analysis reveals the mechanism of disruption of the cross-linked structure of bamboo culms

White-rot fungi can overcome biomass recalcitrance and accelerate the conversion of lignocellulose into biofuelsviaa large number of specific extracellular lignocellulolytic enzymes. This study coupled the comparative analysis of fungal secretomes and 2D HSQC NMR analysis of lignocellulose fractions to elucidate the role of the extracellular enzymes ofEchinodontium taxodiiin the disruption of the resistant cross-linked structure of bamboo culms. The high expression levels of carboxylesterases, alcohol oxidases and class-II peroxidases were consistent with the cleavage of the cross-linked structures, including the ester and ether linkages of lignin-carbohydrate complexes (LCCs) and interunit linkages of lignin, which contribute to biomass resistance removal and cellulose exposure during the early stage of fungal decay. Moreover, the rapid oxidation of C-alpha-OH was found to contribute to lignin biodepolymerization. These findings revealed the detailed mechanisms underlying the reduction in biomass recalcitrance by fungal pretreatment and provided new insights for the development of efficient lignocellulosic biomass conversion.