PNNL

Abstract

Sorghum (Sorghum bicolor L. Moench) is a promising source of lignocellulosic biomass for the production of renewable fuels and chemicals, as well as for forage. Understanding secondary cell wall architecture is key to studying the nature of biomass recalcitrance and identifying impediments to efficient conversion to simple carbon sources. Here, we employed multi-dimensional magic angle spinning solid-state NMR to demonstrate that sorghum xylan is mainly in a three-fold screw conformation due to dense arabinosyl substitutions, which show close proximity to the cellulose in secondary cell walls. We also show that sorghum secondary cell walls present a high ratio of amorphous to crystalline cellulose as compared to dicots. Here, we propose a model of sorghum cell wall architecture, which is dominated by interactions between three-fold screw xylan and amorphous cellulose. This work can guide the design of future bioenergy crops with lower recalcitrance, an important goal for a sustainable bioeconomy.