Role of Selective Fungal Delignification in Overcoming the Saccharification Recalcitrance of Bamboo Culms

Abstract

White-rot fungi with selective lignin-degrading ability can improve the conversion efficiency of lignocellulose to biofuels. Understanding the fungal deconstruction process is critical for developing efficient and mild fungal pretreatment technologies. This study reveals the role of selective delignification with Echinodontium taxodii in overcoming saccharification recalcitrance of bamboo culm through cellulase adsorption experiments, surface-property and porosity measurements, and chemical structural analysis. Selective removal of hydrophobic lignin coating cellulose increased substrate hydrophilicity and enlarged the volume of accessible pores of 5–10 nm diameter, and both interunit linkages of lignin and cross-linkages between lignin and xylan were extensively cleaved by E. taxodii . This allowed more cellulase to infiltrate the lignocellulosic matrix to access the cellulose, thus markedly improving the saccharification of the bamboo culms. Fungal delignification increased nonproductive adsorption of cellulase onto residual lignin, but not sufficiently to inhibit saccharification. Compared to harsh thermochemical processes, this natural system for delignification provides a deconstruction strategy that can significantly reduce the rigid lignin barrier of recalcitrant biomass without increasing cellulase inhibition by residual lignin.