Dietary fibers (DF) & Fermenting / Fermentation

The availability of fiber diminishes as the intestinal content moves from the proximal to the distal colon. This is potentially further exacerbated with Western diets due to their low fiber content. Consequently, the gut microbiota in the distal colon switches toward undigested peptides and proteins (exogenous, from the diet and endogenous from mucins) as an alternative Energy source.
Larik et al. 2024 Cell Host & Microbe 32(8): 1225

Fermenting / Fermentation of dietary fiber by primary degraders such as Bifidobacterium spp. yields acetate and other intermediate products
Wolter et al. 2021 Nat Rev Gastroenterol Hepatol 18(12): 885-902

To stimulate butyrate production, the activities of additional organisms would be required. These secondary fermenters capture degradation and fermentation products from primary degraders and metabolize them into new molecules, including butyrate. However, if primary degraders use the supplements efficiently, only a fraction of the carbon and energy they contain may become available to the secondary fermenters.
Baxter et al. 2019 mBio 10: e02566-18

Indigestible fiber-rich diets containing complex polysaccharides, including fibers and mucins are metabolized in the cecum and the large intestine by anaerobic cecal and colonic microbiota. Hundreds of gut bacterial species across many taxa share the genes for fermenting carbohydrates into Short-chain fatty acids (SCFAs)
Flint et al. 2015

see also:
Caecum / Cecum & Short-chain Fatty Acids (SCFAs)
Dietary fibers (DF) & Gut microbiota
Energy Source & Short-Chain Fatty Acids (SCFAs)
Fermenting / Fermentation
Fermentation & Plant Polysaccharides / Plant Glycans
Germinated barley foodstuff (GBF) & Ulcerative Colitis (UC)
Resistant starch type 2 (RST2)