SusChEM: Integrated Studies on Interactions between Lignocellulosic Fine Structure and Hydrolytic Enzymes toward Efficient Hydrolysis

木质纤维植物生物质，如草秸秆和农用残渣，已被认为是生产燃料酒精和其他增值化学品的低成本、丰富和可再生的可发酵糖来源。目前部署在纤维素生物燃料设施中的工艺使用一种酶的混合物，将纤维素部分转化为可发酵的糖。然而，这一过程仍然相当缓慢，是纤维素生物燃料生产中最昂贵的步骤，部分原因是木质纤维生物质对酶的攻击和分解具有抵抗力。这是由于木质纤维素在分子和微观水平上结构的复杂性造成的。因此，在酶处理之前，木质纤维生物质要进行预处理，通常是用蒸汽和化学物质的组合来打开生物质中的孔，以便酶能更有效地发挥作用。有必要对生物质分解过程有更好的分子水平的了解，以确定新的策略，优化或取消预处理，并提高转化率，以实现成本降低。这个项目的目标是对木质纤维生物质在酶处理过程中如何分解或解构有一个基本的了解，以便能够确定这些新的节约成本的策略。这项研究的创新方面是将分子建模和分子化学成像相结合，以发现关于这一复杂过程的更多信息。与该项目相关的教育活动的特点是编写了一本关于将生物质转化为生物燃料的手册，供夏季青年项目使用。木质纤维素生物质是一种三维生物聚合物基质，由纤维素、半纤维素和木质素在从分子尺度到微尺度的多个尺度上订购。长期以来，木质纤维基质的复杂性一直被认为是其酶解可发酵糖效率的关键限制因素。这项研究将动态建模和分子成像相结合，以获得在利用水解酶的混合物将木质纤维生物质转化为糖的过程中木质纤维的分子和精细结构变化的实时动态。为了实现这一目标，本研究有三个目标。第一个目标是从根本上、定量地了解木质纤维生物质细微结构抵抗酶攻击的分子机制。第二个目标是建立细胞壁组成和分子结构组织与水解处理条件之间的关系，并将这些关系与生物质解构效率相关联。第三个目标是开发一个综合考虑底物形态和组分分布的机制建模框架，能够模拟现实水解条件下的生物质分解。这些目标将通过原子力显微镜(AFM)的单分子成像和酶处理过程中生物质解构过程的受激拉曼散射(SRS)化学成像来实现。建议的研究结果将使酶鸡尾酒和工艺条件的合理设计能够克服减缓水解反应的因素，从而导致水解生物反应器系统的优化设计和纤维素生物燃料制造系统的成本降低。

Lignocellulosic plant biomass such as grass straw and agricultural residues has been recognized a low-cost, abundant, and renewable source of fermentable sugars for production of fuel alcohol and other value-added chemicals. Current processes deployed in cellulosic biofuel facilities use a mixture of enzymes to convert the cellulosic fractions to fermentable sugars. However, this process is still fairly slow and is the most expensive step in cellulosic biofuels production, in part because lignocellulosic biomass is recalcitrant to enzymatic attack and breakdown. This recalcitrance is due to the complexity of lignocellulose structure at the molecular and microscopic levels. Therefore, before enzyme treatment, the lignocellulosic biomass is pretreated, typically with a combination of steam and chemicals, to open up the pores in the biomass so that the enzyme can be more effective. There is a need to develop a better, molecular level understanding of the biomass breakdown processes to identify new strategies optimize or eliminate pretreatment and improve the rate of conversion to realize cost reduction. The goal of this project is to develop a fundamental understanding of how lignocellulosic biomass is broken down, or deconstructed, during enzyme treatment so that these new cost-saving strategies can be identified. The innovative aspect of this study is the combination of molecular modeling and molecular chemical imaging to discover more about this complex process. The educational activities associated with this project feature the development of a workbook on the conversion of biomass to biofuels for use in summer youth programs.Lignocellulosic biomass is a three-dimensional biopolymer matrix of cellulose, hemicellulose, and lignin ordered at multiple scales ranging from the molecular scale to the microscale. The complexity of the lignocellulosic matrix has long been recognized as a key limiting factor in the efficiency of its enzymatic hydrolysis to fermentable sugars. This research will combine dynamic modeling and molecular imaging to gain new insights into the real-time dynamics of lignocellulosic molecular and fine structure changes during the conversion of lignocellulosic biomass to sugars using mixtures of hydrolytic enzymes. To accomplish this goal, the research has three objectives. The first objective is to gain a fundamental, quantitative understanding of the molecular mechanisms underlying the recalcitrance lignocellulosic biomass fine structure to enzymatic attack. The second objective is to establish relationships between cell wall component composition and molecular structural organization with hydrolysis processing conditions and correlate these relationships to biomass deconstruction efficiency. The third objective is to develop a mechanistic modeling framework capable of simulating biomass deconstruction under realistic hydrolysis conditions with comprehensive consideration of substrate morphology and component distribution. These objectives will be enabled through single-molecule imaging via Atomic Force Microscopy (AFM) and chemical imaging via Stimulated Raman Scattering (SRS) of the biomass deconstruction process during enzymatic treatment. Outcomes from the proposed research will enable the rational design of enzyme cocktails and processing conditions to overcome the factors that slow down the hydrolytic reactions, leading to optimal design of the hydrolysis bioreactor systems and cost reduction of cellulosic biofuel manufacturing systems.