(714b) Structural Studies On Recrystallized Ionic-Liquid (IL) Treated Lignocellulosic Biomass

Terrestrial lignocellulosic biomass is composed of three major components; cellulose, a linear polymer of glucose (a hexose sugar); hemicellulose, a complex branched polymer of xylose (a pentose sugar) and other sugar derivatives; and lignin, a polyphenyl propanoid macromolecular assembly that is covalently cross-linked to hemicellulose. These components can serve as a source of carbon based feedstock for fuel and chemical production in much the same way that crude oil serves as the carbon feedstock in petrochemical refineries.

The deconstruction of lignocellulosic biomass into simple sugars constitutes a core barrier for producing value added products from the sugar platform. The cellulosic component has a crystalline and oriented fibrillar structure in biomass, whereas the hemicellulosic and lignin components have less ordered structures that encrust the cellulose fibers. The crystalline structure of native cellulose fibers, called cellulose I, can be a major impediment to its hydrolysis to monomeric sugars. Pretreatment can disorder the crystalline cellulosic component and result in structural changes in the cellulose fibers. These structural changes in cellulose fiber can be achieved by modifying the pretreatment conditions. Depending upon the type of pretreatment, the conversion of cellulose fibers to other crystal forms, such as cellulose II, cellulose III_II and cellulose III_I, or amorphous forms, can greatly improve their susceptibility to hydrolysis. To investigate the effects of varying the parameters of IL pretreatment on the structure of their cellulosic components, X-ray powder diffraction (XRD) and X-ray fiber diffraction from biomass samples was used with unoriented and partially (fiber) orientated cellulosic components . A comparative study on enzymatic hydrolysis and sugar analysis related to the observed changes in cellulose structure to biomass digestibility was also performed. The improvement in hydrolysis is hypothesized to be primarily due to structural changes in the cellulose constituent.