Metabolic fate of ¹³C-labelled polydextrose and impact on the gut microbiome: A triple-phase study in a colon simulator

The present study introduces a novel triple-phase (liquids, solids and gases) approach, which employed uniformly labelled [U-¹³C] polydextrose (PDX) for the selective profiling of metabolites generated from dietary fiber fermentation in an in vitro colon simulator using human fecal inocula. Employing ¹³C NMR spectroscopy, [U-¹³C] PDX metabolism was observed from colonic digest samples. The major ¹³C-labelled metabolites generated were acetate, butyrate,
propionate, and valerate. In addition to these short-chain fatty acids (SCFAs), ¹³C-labelled lactate, formate, succinate, and ethanol were detected in the colon simulator samples. Metabolite formation and PDX substrate degradation were examined comprehensively over time (24 and 48 hours). Correlation analysis between ¹³C NMR spectra and gas production confirmed the anaerobic fermentation of PDX to SCFAs. In addition, 16S rRNA gene analysis showed that the
level of Erysipelotrichaceae was influenced by PDX supplementation and Erysipelotrichaceae level were statistically correlated with SCFA’s formation. Overall, our study demonstrates a novel approach to link substrate fermentation and microbial function directly in a simulated colonic environment.