CAREER: The Human Gut as an Untapped Reservoir for Bacteria and Enzymes that Degrade Lignin, a Potential Sustainable Source for Critical Chemicals

University Of California-Irvine, Irvine CA

Investigators

Abstract

With the support of the Chemistry of Life Processes (CLP) program in the Division of Chemistry, Elizabeth Bess from the University of California, Irvine, is studying how the human gut microbiota—trillions of bacteria that live in the intestines of human beings—can be leveraged to produce chemicals that are important to society for industrial processes. Such commodity chemicals are typically sourced from fossil fuels, a non-renewable resource. A more sustainable potential feedstock for commodity chemicals is lignin. Lignin is made by plants and is one of Earth’s most abundant and chemically unique polymers. Despite its abundance, efficient methods to convert lignin into useful commodity chemicals are lacking. The work will test the hypothesis that the human gut is an untapped reservoir of bacteria that could efficiently convert lignin into desirable chemicals. The rationale is that lignin is a component of dietary plants, and intestinal bacteria only have hours to deconstruct dietary lignin as it transits the intestines. The project has two aims: (1) identify bacterial species in the human gut that deconstruct lignin and (2) reveal the chemical products of this process. This research project offers an opportunity to engage students from underrepresented groups in scientific inquiry. Specifically, new experiential-learning programs will be implemented in which high school and undergraduate students participate in a lignin-rich diet intervention and subsequently examine the impact of diet on their own gut microbiota. By establishing a personal connection to scientific research, these programs have the goal of enhancing students science self-efficacy. Biological and chemical approaches to deconstruct lignin are needed as existing approaches are limited either by inefficient biocatalytic steps and/or by chemical methods that yield product mixtures and thus require costly purification. The overall objective of this project is to uncover new bacteria to convert lignin to value-added products and to develop reliable tools that could potentially be used to discover such biocatalysts in any biological system. To achieve the goals of this project, a bio-orthogonal noncanonical amino acid tagging (BONCAT) method will be used to identify specific gut bacteria that deconstruct lignin. Lignin-coated magnetic beads will be developed to separate bacterial candidates for lignin degradation from the complex bacterial communities of the gut. Characterization of how human gut bacteria alter the lignin polymer will be performed using 2D nuclear magnetic resonance spectroscopy, and isotope-tracing metabolomics will be implemented to identify the chemical products that result. Discovery of new ways to efficiently deconstruct lignin to lignin has the potential to be useful for sustainable chemistryby opening up new value-added and biorenewable pathways to key chemical building blocks. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.