TIME-RESOLVED STUDIES ON THE BREAKDOWN OF LIGNOCELLULOSIC BIOMASS

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 天然木质纤维素生物质是由结晶纤维素微纤维与半纤维素、果胶和木质素层压而成的复杂材料。纤维素乙醇生产中的限制因素是木质纤维素生物质水解成糖用于发酵的难易性。预处理通常在碱或酸中采用高温（~200 ℃），这些碱或酸容易溶解并经常水解非结晶果胶和半纤维素多糖并破坏纤维素结构。已知这些预处理通过破坏木质纤维素微观结构来增加表面积和可接近性。然而，预处理是从生物质生产乙醇中限速、能量密集和最昂贵的加工步骤，因此，将酶活性与用原位时间分辨SAXS和WAXS观察到的形态和可及性的变化相关联是令人感兴趣的。在橡树岭国家实验室进行的稀酸预处理木质纤维素的非原位SANS表明：（1）纤维素原纤维的横截面半径增加;（2）出现Rg~100的额外结构我们将其与木质素聚集体相关联;和（3）微米级孔的光滑表面没有变化。在BioCAT进行的原位SAXS/WAXS研究中，在温度控制的Linkham阶段使用密封毛细管，结果取得了有限的成功。 挫折的主要问题是（1）样品的辐射损伤和（2）无法测量适当的背景与当前的设置。这些问题的解决方案正在进行中，为未来的现场SAXS的尝试。

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~100150 ¿ 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.