Abstract:

Lignin is a polyphenolic plant fiber that makes up approximately 25% of our daily fiber intake. Polyphenols are a large family of plant-derived metabolites that contribute to human health via anti-oxidant, anti-inflammatory, and anti-cancer activities. Therefore, the deconstruction of lignin by human gut microbiota is an important source of these health-promoting metabolites. However, whether or not lignin is degraded as it transits the human gastrointestinal tract has been debated for over a century. The prevailing argument has been that the anaerobic conditions of the human gut are incompatible with the oxygen-dependent mechanisms of known lignin-degrading enzymes. I have coupled anaerobic microbial culturing techniques with mass spectrometric analyses to obtain evidence that human gut microbiota anaerobically deconstruct lignin. I proposed, for the first time, a plausible structure of a large lignin oligomer and mapped a network of 20 plausible metabolites that result when this oligomer is degraded and depolymerized by human gut microbiota. I have contributed to the growing body of scientific evidence that anaerobic lignin deconstruction is occurring, thereby laying the foundation upon which future scientists can elaborate by identifying the microbiota, enzymes, and biochemical mechanisms that mediate this process. The study of the gut microbiome is a new frontier in the science and medicine of human health, and the discovery that human gut microbiota can anaerobically deconstruct lignin helps to define a new paradigm of biochemical potential for the multitude within.