This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Natural lignocellulosic biomass is a complex material composed of crystalline cellulose microfibrils laminated with hemicellulose, pectin, and lignin. The limiting factor in cellulosic ethanol production is the recalcitrance of lignocellulosic biomass to hydrolysis into sugars for fermentation. Pretreatments commonly employ elevated temperatures (~200 ?C) in alkali or acids that readily dissolve and often hydrolyze the non-crystalline pectin and hemicellulose polysaccharides and disrupt cellulose structure. These pretreatments are known to increase surface area and accessibility by destruction of the lignocellulose microstructure. Yet, pretreatment is the rate-limiting, energy-intensive, and the most expensive processing step in the production of ethanol from biomass and therefore, it is of interest to correlate enzymatic activity with changes in morphology and accessibility observed with in-situ Time resolved SAXS and WAXS. Ex-situ SANS, performed at HFIR, Oak Ridge National Laboratory of dilute acid pretreated lignocellulose has revealed: (1) increase in the cross-sectional radius of the cellulose fibrils;(2) appearance of an additional structure of Rg~100?150 ? which we associate to lignin aggregates;and (3) no change in the smooth surface of the micron-size pores. In-situ SAXS/WAXS studies performed at BioCAT using sealed capillary tubes in a temperature-controlled linkham stage resulted in limited success. The main problems for the setback were (1) radiation damage to sample and (2) inability to measure proper backgrounds with the current setup. Solutions to these problems are in-progress for future in-situ SAXS attempts.
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