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，占陆地生物质的约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。木质素的微生物分解是缓慢的，很可能是因为只有一小群微生物具有分解这些复杂生物材料的能力。然而，最近的研究表明，木质素可以通过暴露于太阳辐射（或光降解）而降解，这纯粹是一个物理过程。光降解在木质素分解中的作用，以及该过程如何与微生物分解相互作用，还没有得到很好的理解。本项目的主要目标是研究光降解和微生物分解过程如何联合收割机来确定木质素的化学组成和分解。在这个项目中，一种新的方法，使用二维核磁共振（2D NMR）共振光谱将用于在分子水平上检查木质素的化学组成，提供更清晰的木质素结构，加深我们对木质素在土壤中如何处理的理解。拟议的研究对社会很重要，因为它与我们对碳循环的理解相关，因为木质素分解的动力学对大多数生态系统中土壤中的碳储存具有强烈的影响。这项研究的结果将有助于更好地了解木质素降解，这对更广泛地解锁分解过程至关重要。这项研究还将通过为研究生研究人员和直接由该资金支持的本科生提供培训和教育机会，影响广泛的受众。它还将为本科生或高中生提供机会，通过正在进行的K-12外展活动和与加州大学圣巴巴拉麦克奈尔学者计划的联系，开发相关的独立项目。

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.