Prebiotic potential of turmeric and fingerroot polysaccharides: modulation of human gut microbiota and metabolite profiles in in vitro colonic fermentation

The prebiotic potential of crude polysaccharide extracts from turmeric ( Curcuma longa ; CP-TM) and fingerroot ( Boesenbergia rotunda ; CP-FR) was investigated using galactooligosaccharides (GOS) as a reference. Extracts were characterized for carbohydrate content and assessed for probiotic stimulation, pathogen inhibition, gastrointestinal resistance, and in vitro colonic fermentation with human fecal microbiota. Both CP-TM and CP-FR stimulated lactic acid bacteria growth in a strain-dependent manner and suppressed Escherichia coli and Bacillus cereus . In simulated digestion, CP-TM showed comparatively higher survival of Lactobacillus casei , while CP-FR conferred moderate tolerance. Fermentation analyses showed that both extracts modulated microbial diversity, enriched beneficial taxa such as Phascolarctobacterium and Collinsella , and reduced Proteobacteria expansion. Functional prediction analyses suggested shifts in carbohydrate metabolism and stress-adaptation pathways. CP-TM showed the highest acetate and butyrate levels, while all supplements maintained low phenol and p-cresol. These findings suggest that crude polysaccharide extracts from turmeric and fingerroot may represent promising candidates for functional food applications targeting gut microbiota modulation.