Reduction of Redox Potential Exerts a Key Role in Modulating Gut Microbial Taxa and Function by Dietary Supplementation of Pectin in a Pig Model

Pectin exists in a vast range of plants and has a long history of acting as a functional food additive with potential prebiotic effects on intestinal health. However, knowledge of how pectin regulates gut microbial communities is still insufficient and limited. Here, metatranscriptome sequencing revealed that a pectin-enriched diet (PEC) decreased the abundances of fungal keystone taxa (e.g., amino acid-producing Kazachstania spp.) and their genes involved in oxidative phosphorylation, while it increased the abundance of sulfate-reducing Desulfovibrio spp., and methane-producing Methanobrevibacter spp. in colon microbiomes. Furthermore, we first confirmed that PEC decreased fecal redox potential in a fistula pig model, which could be supported by the enrichment of antioxidants (e.g., inosine) in feces. Fecal metagenome analysis disclosed that certain microbial taxa promoted inosine biosynthesis from pectin degradation, including Prevotella, which plays an essential role in pectin biodegradation. Overall, these results demonstrate that pectin decreases the redox potential in pig hindgut to modulate microbial composition and functions, and specific microorganisms generate reducing agents in the course of pectin degradation to decrease redox potential of microbial ecosystem. IMPORTANCE Collective studies indicate that pectin degradation promotes extensive microorganisms that can be involved in pectin degradation directly or indirectly, or benefit from the altered physiological conditions caused by pectin ingestions. Our study focuses on effects of pectin on gut microbial taxa and functions, as well as its interactions with altered environmental features. Our results demonstrate pectin-induced proreducing shifts on colon microbial taxa and functions, and first confirm that pectin decreases hindgut redox potential, which is an important environmental feature that can modulate microbial communities. These results infer that there is bidirectional regulation between microbiota and redox potential during pectin degradation. In general, this investigation proposes new insights into the pectin-modulating gut microbial ecosystem and also provides new perspectives for targeting modulation of gut microbiota.