COLLABORATIVE RESEARCH EAGER: Sum-frequency generation (SFG) vibration study of structure and enzymatic hydrolysis activities of crystalline cellulose in biomass

为了有效地将生物质转化为其他有用的化学品，有必要理解和克服其对酶解过程的阻碍。生物质研究中涉及的一个关键问题是酶活性和纤维素结构之间的相关性。虽然许多实验研究已经试图回答这个基本问题，答案仍然难以捉摸。困难在于它需要对含有相同有机官能团的无定形基质中的结晶碳水化合物聚合物（纤维素）进行分子分析。目前的分析方法不能提供关于木质纤维素生物质中结晶纤维素的足够细节。在这个EAGER项目中，来自北卡罗来纳州州立大学的PI Sunkyu Park和Seong H。来自宾夕法尼亚州立大学的Kim将探索和频产生（SFG）振动光谱的应用，以发现纤维素晶体结构对酶解过程的影响。纤维素的独特晶体结构使其能够表现出非线性光学性质，如SFG，这在其他生物质组分中是不存在的。SFG是无光学中心对称系统在强激光脉冲作用下的二阶非线性光学响应。基于这种独特的非线性光学选择规则，生物质中的无定形组分如半纤维素和木质素不能产生SFG信号。因此，SFG可以检测生物质中结晶纤维素的结构，而无需对纤维素进行任何化学分离和修饰。此外，结构和酶活性之间的关系的问题可以通过以下纤维素SFG响应的变化进行监测。这项研究产生了许多更广泛的技术影响。通过这项研究获得的分子见解将是有价值的信息，以了解生物质的可再生性和开发更有效的生物质转化过程。具体而言，预期的成果包括：（1）朝着理解纤维素的晶体结构迈出了重要的一步，（2）用于纤维素表征的新工具开发，而无需分离，仅对木质纤维素生物质中的结晶纤维素敏感，（3）对纤维素晶体结构和酶水解之间关系的分子洞察力，以及（4）跨学科领域的学生教育。这种工具，SFG光谱，预计将是有用的其他生物质的应用，如纤维素溶解，生物质热转化，纤维素生物合成等。

1152824Kim In order to efficiently convert biomass to other useful chemicals, it is necessary to understand and overcome its recalcitrance to enzymatic deconstruction processes. One key question involved in a biomass study is the correlation between the enzymatic activity and the cellulose structure. Although many experimental studies have been attempted previously to answer this fundamental question, the answer still remains elusive. The difficulty is that it requires molecular analysis of crystalline carbohydrate polymers (cellulose) in an amorphous matrix containing the same organic functional groups. Current analytical methods cannot provide sufficient details about crystalline cellulose in lignocellulosic biomass. In this EAGER project, the PIs Sunkyu Park from North Carolina State University and Seong H. Kim from Pennsylvania State University will explore the application of sum-frequency generation (SFG) vibration spectroscopy to find the influence of cellulose crystal structure on the enzymatic deconstruction process. The unique crystal structure of cellulose allows it to demonstrate non-linear optical properties such as SFG which are absent in other biomass components. SFG is a second-order nonlinear optical response of a system without optical centrosymmetry when it is irradiated with high-intensity laser pulses. Based on this unique non-linear optical selection rule, amorphous components such as hemicellulose and lignin in biomass cannot generate SFG signals. Thus, SFG can detect the structure of crystalline cellulose in biomass without any chemical isolation and modification of the cellulose. Furthermore, the question of the relation between structure and enzymatic activity can be monitored by following changes in the cellulose SFG response. There are a number of Broader technical impacts that result from this study. The molecular insights that will be obtained through this research will be valuable information to understand the biomass recalcitrance and develop more efficient biomass conversion processes. Specifically the expected outcomes include: (1) a significant step toward understanding of the crystalline structure of celluloses, (2) new tool development for cellulose characterization without separation, which is sensitive only to crystalline cellulose in lignocellulose biomass, (3) a molecular insight into the relationship between cellulose crystalline structure and enzymatic hydrolysis, and (4) student education in cross-disciplinary areas. This tool, SFG spectroscopy, is expected to be useful for other biomass applications such as cellulose dissolution, biomass thermal conversion, cellulose biosynthesis, etc.