Fig. 6
Diagram illustrating the experimental design. Fresh stool samples from three healthy donors with different fecal pH values (6.4, 6.8, and 7.2, respectively) were collected, and three dynamic pH programs during 24 h of fermentation were designed which represent the low (5.2-6.4), medium (5.6-6.8) and high (6.0-6.8) pH changes from the proximal to the distal colon. Single substrates (inulin, lactose, GOS, or FOS) were added to each chamber for colonic fermentation. Metabolite outcomes after 24 h of fermentation for each fecal slurry under the corresponding pH and abnormal colonic pHs were detected by 1H NMR, and GM shifts were traced using the V3 region of the 16S rRNA gene amplicon sequencing by Illumina, NextSeq. D, donor