Abstract: The aim of this study was to investigate the utilization patterns of galactomannan by microbiota from different gut segments. Anaerobic fermentation was performed utilizing the ileal and colonic microbiota from growing pigs as inoculants with galactomannan as the sole carbon source. The results showed that the utilization efficiency of galactomannan by the microbiota in the ileum and colon was higher from 6 to 12 h of fermentation (P < 0.05). During this period, the pH of the fermentation broth was significantly decreased, while the contents of short-chain fatty acids, amino nitrogen, and microbial protein were significantly increased (P < 0.05). Compared with the ileal microbiota, the colonic microbiota showed a stronger capacity to utilize galactomannan. Meanwhile, lactic acid and acetic acid were the primary organic acid metabolites produced by both microbial groups during anaerobic fermentation, and propionic acid and butyric acid were identified as differential organic acid metabolites. Furthermore, galactomannan altered the beta diversity of microbial communities in both ileal and colonic fermentation broth, leading to a significant increase in the relative abundance of Lactobacillus (P < 0.05) and a significant decrease in the relative abundance of Escherichia-Shigella (P < 0.05). Galactomannan also increased the relative abundance of Acinetobacter in the ileal fermentation broth (P < 0.05) and significantly decreased the relative abundance of Megasphaera, Enterococcus, Veillonella, Solobacterium and Phascolarctobacterium in the colonic fermentation broth (P < 0.05). In conclusion, galactomannan possesses prebiotic potential and is capable of optimizing microbial community structure and driving short-chain fatty acid production. The colonic microbiota has a stronger capacity to utilize galactomannan compared with the ileal microbiota.

Key words: galactomannan; intestinal microbiota; in vitro fermentation; ileum; colon