<em>In vitro</em> fermentation characteristics of guar gum: Particularly enriching <em>Bifidobacterium pseudolongum</em> and <em>Parabacteroides distasonis</em>

Guar gum, a widely used food hydrocolloid, exhibits extensive biological activities and its regulatory effects on the gut microbiota are closely linked to health outcomes. However, its specific enrichment effects on gut microbiota and the interaction modes with the enriched bacteria remain unclear. This study investigated the regulatory effects using an <em>in vitro</em> fermentation model and both single-step and stepwise cultivation methods. Results showed that the gut microbiota degraded guar gum, yielding abundant acetate and propionate. Guar gum suppressed the growth of the potential pathogenic bacteria (Enterobacteriaceae) while enriching the beneficial bacteria (<em>Bifidobacterium </em>and <em>Parabacteroides</em>). Notably, <em>B. pseudolongum </em>and <em>P. distasonis</em> were specifically enriched, although neither could directly utilize guar gum. The primary degrader, such as <em>Bacteroides ovatus</em>, facilitated guar gum breakdown and stimulated the proliferation of <em>B. pseudolongum </em>and <em>P. distasonis</em>. Further analysis revealed that the proliferation of these bacteria may be related to their preferences for utilizing mannose and galactose. Taken together, these findings enhance our understanding of the interactions between guar gum and the microbiota, and contribute to the scientific basis for developing guar gum-based functional foods.