Plant Biomass Characterization: Application of Solution- and Solid-State NMR Spectroscopy

Releasing fermentable sugars from lignocellulosic materials remains challenging due to resistance of plants to breakdown. A pretreatment stage is required to reduce this recalcitrance, which is considered to be the most intensive operating cost component of cellulosic ethanol production. There are different features that make plant biomass resistant to chemical and biological degradation, such as lignin content/structure, lignin-carbohydrate complexes (LCCs), hemicellulose content, as well as cellulose ultrastructure and degree of polymerization (DP). Research on this subject is therefore focused on understanding the effects of pretreatment technologies on the reduction of biomass recalcitrance as well as on fundamental structural characteristics of biomass that impact pretreatment and subsequent enzymatic hydrolysis. Improving our fundamental knowledge of pretreatment technologies will lead to significant advances in the field of sustainable low-cost cellulosic biofuels production [1]. Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for detailed structural elucidation of the major constitutes of plant biomass, lignin, hemicellulose, and cellulose [2–8]. Many of the structural details/characteristics of biopolymers (especially lignin) in native and transgenic plant biomass we know of today were revealed with NMR measurements, in addition to key information about lignin/hemicellulose synthesis in plants as well as plant genetic engineering [2,3]. This chapter focuses on the application of solutionand solid-state NMR spectroscopy techniques to characterize the structural features of cellulose