Xanthan Gum Digestion By Human Gut Microbiota

The human gut microbiota is a diverse community of microbes in the lower gastrointestinal tract that is increasingly recognized as playing roles in health and disease. The historically recent inclusion of novel food ingredients could alter diet-microbiota effects on human health or be leveraged to engineer new niches in the microbiome.

Xanthan gum is a bacterial exopolysaccharide and a common food additive used for its thickening properties. Xanthan gum is a polymer of β(1,4)-glucose with alternating glucose units harboring a side chain of α(1,3)-linked mannose, β(1,2)-glucuronic acid, β(1,4)-mannose. The inner and outer mannose possess variable 6-O-acetylation and 4,6-O-pyruvylation, respectively. Although the human microbiota has been shown to degrade and consume xanthan gum, the microbes and enzymatic pathways responsible are still unknown. We surveyed a population of healthy adults and found that over a third had microbial communities that could grow on xanthan gum as a primary carbon source. Metagenomic, transcriptomic, and activity-guided fractionation and proteomic analysis of an active culture revealed a suite of enzymes that appear responsible for the full saccharification of xanthan gum. These enzymes are variably abundant across microbiota metagenomes collected from unique geographies across the world. We are currently working to fully elucidate the enzymatic pathways responsible for xanthan gum catabolism and how cross-feeding on xanthan oligosaccharides affects microbial communities in the gut. We are also investigating how these enzymes may provide utility for applications in industries that use xanthan gum, such as in drilling mud in the petroleum industry.