DISSERTATION RESEARCH:Quantifying Changes in Lignin Chemistry During Photodegradation Versus Biotic Decomposition Using 2D NMR Spectroscopy

木质素是植物合成的第二丰富的化合物，约占陆地生物量的15%-40%。因此，木质素的分解是影响陆地生态系统碳储存和固存的重要过程。微生物分解木质素的速度很慢，很可能是因为只有一小部分微生物有能力消耗这些复杂的生物材料。然而，最近的研究表明，木质素可以通过暴露在太阳辐射(或光降解)下降解，这纯粹是一个物理过程。光降解在木质素分解中的作用，以及这一过程如何与微生物分解相互作用，还不是很清楚。这个项目的主要目标是研究光降解和微生物分解过程如何结合来确定木质素的化学成分和分解。在这个项目中，将使用一种新的方法，使用二维核磁共振(2D核磁共振)光谱在分子水平上检测木质素的化学组成，提供更清晰的木质素结构图像，加深我们对其在土壤中的处理方式的理解。由于木质素分解的动力学对大多数生态系统中土壤的碳储量有很大的影响，因此该研究对社会具有重要意义，因为它与我们对碳循环的理解有关。这项研究的结果将有助于更好地理解木质素降解，这对更广泛地揭示分解过程至关重要。这项研究还将通过为一名研究生研究员和一名由这笔资金直接支持的本科生提供培训和教育机会，影响广泛的受众。它还将通过正在进行的K-12外展活动以及与加州大学圣巴巴拉分校麦克奈尔学者计划的链接，为本科生或高中生提供发展相关独立项目的机会。

Lignin is the second most abundant compound synthesized by plants, comprising approximately 15-40% of terrestrial biomass. Decomposition of lignin, therefore, is an important process influencing carbon storage and sequestration in terrestrial ecosystems. Microbial decomposition of lignin is slow, most likely because only a small group of microorganisms have the capacity to comsume these complex biological materials. Recent studies, however, suggest that lignin can be degraded by exposure to solar radiation (or photodegradation), which is purely a physical process. The role of photodegradation in lignin decomposition, and how this process interacts with microbial decomposition, are not well understood. The primary goal of this project is to examine how photodegradation and microbial decomposition processes combine to determine lignin chemical composition and decomposition. In this project, a novel approach using two dimensional nuclear magnetic (2D NMR) resonance spectroscopy will be used to examine the chemical composition of lignin at a molecular level, providing a clearer picture of the structure of lignin, deepening our understanding of how it is processed in the soil.The proposed study is important to society because of its relevance to our understanding of the carbon cycle, since the dynamics of lignin decomposition have a strong influence on carbon storage in soils in most ecosystems. Results of this research will contribute to a better understanding of lignin degradation, which is critical to unlocking decomposition processes more broadly. This study will also impact a broad audience by providing training and education opportunities for a graduate student researcher and an undergraduate student directly supported by this funding. It will also provide opportunities for undergraduates or senior high school students to develop related independent projects through ongoing K-12 outreach activities and links to the McNair Scholars Program at the University of California, Santa Barbara.