The secondary cell wall is a sophisticated composite formed by cellulose, hemicellulose and lignin. It is the major constituent of plant biomass and is the central source for biofuel production. Enormous effort has been devoted to understanding the biosynthesis and engineering of carbohydrates and lignins in the interests of post-harvest utilization, but our limited understanding of the cell wall structure, due to the lack of non-destructive and high-resolution characterization methods, has placed a major barrier. Here, we integrated solid-state NMR spectroscopy with cutting-edge, sensitivity-enhancing technique of Dynamic Nuclear Polarization (DNP) to characterize the intact stems of a series of grasses and wood such as maize, switchgrass, poplar and spruce. In grasses, cellulose is found to be spatially separated from lignins, with xylan bridging these two hydrophobic cores in a conformation-dependent manner. In contrast, lignin-cellulose interactions are substantially more pronounced in woods, thus revealing different architectures. Lignin-carbohydrate interactions correlate with the content of methyl ether groups, revealing the central role of electrostatic interactions in maintaining these contacts. These results require a substantial revision of our understanding of the biosynthesis and assembly of secondary cell walls and provide molecular insights into the cell wall recalcitrance to enzymatic/chemical digestions during biofuel production.<br/>

Cellulose structure and lignin-carbohydrate interactions in intact secondary plant cell walls from solid-state NMR

2019 Spring National Meeting

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