The document proposes a scheme for how Saccharomyces cerevisiae CNCM I-1077 interacts with fiber-degrading gut microbiota. S. cerevisiae colonizes lignin and hemicelluloses in the gut, increasing the density of cellulolytic microbes like Ruminococcus Flavefaecin that break down cellulose. It also boosts hemicellulolytic microbes like Fibrobacter succinogenes that degrade hemicelluloses. This supports fiber degradation in the gastrointestinal tract.