Bacterial lignin degradation: characterization and biocatalytic applications

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Bacteria are responsible for most of the degradation of natural and human-made compounds in the biosphere. This degradation constitutes an essential link in the global carbon cycle and is critical to sustaining life on our planet. Bacterial degradation activities also represent a rich, barely tapped source of biocatalysts to sustain the emerging global bioeconomy. Over the past two decades, my NSERC-funded research program has provided novel insights into the function of bacterial enzymes involved in the degradation of aromatic compounds and pollutants as well as into how these enzymes are regulated. Over the next five years, I will focus my program on enzymes that degrade lignin, a complex aromatic polymer that comprises about 25% of the land-based biomass. Lignin occurs in tight association with cellulose and hemicellulose to form the strong, rigid structure that is very resistant to degradation. Deconstructing this lignocellulose is critical to using woody biomass as a renewable source of chemicals, materials and other bioproducts. While fungal enzymes that degrade lignin have been studied for years, bacterial lignin-degrading enzymes have been largely overlooked despite being more amenable for industrial processes. My research will focus on two types of bacterial enzymes that: (a) breakdown the polymeric lignin; and (b) degrade the lignin depolymerization products. These enzymes represent important classes of metal-containing enzymes that are not well understood. The proposed research will increase our understanding of what these enzymes do and how they do it. This will in turn provide fundamental insights into the molecular mechanism of important biological processes as well as how Nature uses metals to catalyze these processes. The knowledge gained will also facilitate the engineering of enzymes and bacteria for biotechnological applications. More particularly, it will help in the design of biocatalysts to transform low-value lignin into high-value materials, such lubricants, cosmetics and bioplastics. The research objectives will be achieved using an interdisciplinary approach involving a variety of cutting-edge techniques. The research will benefit from a number of tools and approaches developed in the Eltis lab. Finally, the research program provides trainees with a wide range of skills, preparing them for fulfilling careers in academia, industry and government.