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

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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.