Ecologically adaptable Populus simonii is specific for recalcitrance‐reduced lignocellulose and largely enhanced enzymatic saccharification among woody plants

Abstract

AbstractWoody plants provide enormous biomass resource convertible for biofuels and bioproducts, but they are of typical lignified secondary cell walls with strong recalcitrance against biomass degradation. It thus becomes critical to find out the desirable woody plant enabled for efficient biomass enzymatic saccharification. In this study, we collected totally seven biomass samples from three major hardwood species showing worldwide geographic distributions and diverse cell wall compositions. Under acid (H2SO4) and alkali (NaOH, CaO) pretreatments, all biomass samples showed remarkably enhanced enzymatic saccharification, but the Populus simonii species had the highest hexoses yields from all pretreatments performed. In particular, the mild and green‐like pretreatment (10% CaO, 50°C) could lead to more than 70% cellulose degradation into fermentable hexoses in the P. simonii species, but only 24%–38% cellulose digestions were examined in the other six samples. Importantly, the P. simonii species is of the lowest ratios of lignin S/G and hemicellulose Xyl/Ara among seven samples, being two major factors accountable for much improved lignocellulose recalcitrance. These consequently caused the most reduced cellulose DP in the pretreated P. simonii residues for enhanced biomass saccharification. Furthermore, this study performed a genome‐wide profiling of gene expression to confirm distinct wall polymer biosynthesis and biomass metabolism in the P. simonii species, consistent with its significantly improved lignocellulose recalcitrance. Therefore, this study has found out the desirable model of woody plants for efficient biomass enzymatic saccharification under cost‐effective and green‐like pretreatments, providing a powerful strategy for genetic lignocellulose modification in woody plants and beyond.