Constructing a Comprehensive Picture of Miscanthus Cell Wall to Advance its Deconstruction

摘要

Grasses from the genus Miscanthus are among the most promising dedicated lignocellulosic energy crops. Despite their potential, cell wall recalcitrance to deconstruction still hinders widespread use of its biomass as a bioenergy and biomaterial feedstock. Consequently, the advancement of our knowledge concerning the roots of recalcitrance is a pressing matter. To clarify chemical, structural and biological features underpinning recalcitrance in miscanthus cell walls, here are presented the results of an in-depth cell wall analysis following a multidimensional approach, considering: different developmental stages, stem vs. leaf compositional variability and various genotypes. Early results showed inverse correlations between lignin content and ethanol production in stem tissues but not in leaves. FTIR spectroscopy showed that tissue and development-derived compositional differences are mostly associated to structural carbohydrates. Accordingly, subsequent research was shifted to focus on the composition of polysaccharide fractions of the cell wall and on the exploration of structural associations. Glycome profiling allied to glycan immunolocalisation studies further elucidated the nature of compositional variation and provided detailed information about in situ distribution of selected carbohydrate epitopes. Key observations demonstrated that stem and leaf biomass is differently modified throughout development, leading to harvest and tissue-specific features at the level of glycan abundance, distribution, composition and ornamentation. These differences have substantial effects on the amenability to deconstruction; however, the results highlighted the limited predictive power of single traits as indicators of cell wall recalcitrance. Instead, a holistic view of the cell wall is promoted, which considers that different components have variable impacts on recalcitrance depending on overall cell wall assembly. These outcomes effectively emphasised the value of the results-driven approach followed in this thesis. Ultimately, the constructed detailed portrait of the cell wall will help steer breeding and engineering strategies for the development of superior energy crops and help advance biorefining strategies.udKey words: Miscanthus, biofuel, plant cell wall, FTIR, lignin, carbohydrate, glycan, glycome profiling, immunolabelling, antibody, recalcitrance, lignocellulose, biomass.