This 2021 in vitro study examined butyrate producers:

“Butyrate produced by gut microbiota has multiple beneficial effects on host health. Oligosaccharides derived from host diets, and glycans originating from host mucus, are major sources of its production.

Butyrate is the major energy source for epithelial cells in the distal colon, induces differentiation of colonic regulatory T cells, and functions as an inhibitor of host histone deacetylase. These activities are essential for documented beneficial properties of butyrate, including anti-inflammation, gut immune homeostasis, inhibition of proliferation, and induction of apoptosis of colorectal cancer cells.

FOS-type oligosaccharides (kestose, nystose, fructooligosaccharide) were metabolized by only 6 of 14 butyrate-producing strains tested:

Faecalibacterium prausnitzii, which is the most abundant butyrate producer in the healthy human gut, metabolized only FOS-type oligosaccharides among tested oligosaccharides. Anaerostipes spp. exhibited a similar pattern, except that A. caccae metabolized kestose but not nystose.

Glycoside hydrolase (GH)32 enzymes exhibiting FOS degradation activities were conserved in all six strains metabolizing FOS, and in three of the eight strains that did not metabolize FOS. This suggests that GH32 enzymes in those three strains are not actively used in metabolism.

The present study highlighted that even if functional genes are present in microbes, they are sometimes unable to metabolize substrates. This should be carefully considered in metagenomic studies to understand metabolic potential of gut microbiota.”

https://www.tandfonline.com/doi/full/10.1080/19490976.2020.1869503 “Characterization of fructooligosaccharide metabolism and fructooligosaccharide-degrading enzymes in human commensal butyrate producers”

These researchers had some work to do to show that selected strains’ characteristics were representative of their species. This post’s title was excerpted from Citation 37.