Prebiotic stimulation of human colonic butyrate-producing bacteria and bifidobacteria,<i>in vitro</i>

TLDR

Dietary macronutrients influence gut microbiota composition, and prebiotics are employed to promote a healthy gut, yet their effects on non‑bifidobacterial dominant bacteria remain understudied. This study aims to characterize carbohydrate utilization by representative butyrate‑producing Firmicutes (Lachnospiraceae and Ruminococcaceae) compared with selected Bacteroides and Bifidobacterium species. Growth was assessed using anaerobic Hungate tubes and a rapid microtitre plate assay, which showed good agreement between the two methods. Butyrate‑producing strains displayed distinct growth profiles on starch, inulin, FOS, GOS, and XOS, with selective utilization of short‑chain FOS, long‑chain inulin by Roseburia inulinivorans, and XOS by only six of eleven Firmicutes, illustrating prebiotic selectivity and explaining butyrogenic potential.

Abstract

Dietary macronutrients affect the composition of the gut microbiota, and prebiotics are used to improve and maintain a healthy gut. The impact of prebiotics on dominant gut bacteria other than bifidobacteria, however, is under-researched. Here, we report carbohydrate utilisation patterns for representative butyrate-producing anaerobes, belonging to the Gram-positive Firmicutes families Lachnospiraceae and Ruminococcaceae, by comparison with selected Bacteroides and Bifidobacterium species. Growth assessments using anaerobic Hungate tubes and a new rapid microtitre plate assay were generally in good agreement. The Bacteroides strains tested showed some growth on basal medium with no added carbohydrates, utilising peptides in the growth medium. The butyrate-producing strains exhibited different growth profiles on the substrates, which included starch, inulin, fructooligosaccharides (FOS), galactooligosaccharides (GOS) and xylooligosaccharides (XOS). Eleven were able to grow on short-chain FOS, but this number decreased as the chain length of the fructan substrates increased. Long-chain inulin was utilised by Roseburia inulinivorans, but by none of the Bifidobacterium species examined here. XOS was a more selective growth substrate than FOS, with only six of the 11 Firmicutes strains able to use XOS for growth. These results illustrate the selectivity of different prebiotics and help to explain why some are butyrogenic.