In vitro fermentation characteristics of galacto-oligosaccharides and manno-oligosaccharides by mucosal microbiota from porcine jejunum and ileum

Abstract:

[Background] Mucosal microbiota from small intestine is an important part of gut microbiota. Many studies had shown that galacto-oligosaccharides (GOS) and manno-oligosaccharides (MOS) can regulate the gut microbiota from large intestine of pigs. However, there are few studies on its regulation of mucosal microbiota from small intestine. [Objective] This study aimed to explore the in vitro fermentation characteristics of GOS and MOS by mucosal microbiota from porcine jejunum and ileum. [Methods] The microbiota samples from the jejunum mucosa and ileum mucosa of growing pigs were used for the anaerobic fermentation of GOS and MOS. Total bacterial number, pH, ammonia nitrogen (NH₃-N), microbial crude protein (MCP), and organic acids were measured at 0, 6, 12, and 24 h during the fermentation. The bacteria were quantified by quantitative PCR after 24 h incubation. [Results] After 24 h incubation, the concentration of NH₃-N in the ileum mucosa group was lower than that in the jejunum mucosa group, while the concentration of MCP showed an opposite trend (P<0.05). After 6 h incubation, the pH changed slightly because of the small amount accumulation of organic acids. After 12 h incubation, lactate, acetate, butyrate, and total short-chain fatty acids in the MOS group were significantly higher than those in the GOS group (P<0.05), and only a small amount of propionic acid was produced in the ileum mucosa group. After 24 h incubation, the MOS group with the microbiota from ileum mucosa showed the highest yield of lactate and the lowest pH (P<0.05). The GOS group had higher propionate yield than the MOS group (P<0.05). The MOS group had higher yield of acetate than the GOS group, as well as that of butyrate and total SCFA in the jejunum mucosa group (P<0.05). After 24 h incubation, Firmicutes showed the close number to total bacteria, being the dominant phylum. Compared with MOS, GOS increased the number of Bacteroidetes, Streptococcus,Veillonella, and Faecalibacterium, as well as that of Clostridiumcluster IV in the jejunum mucosa group and Clostridium cluster XIVa in the ileum mucosa group (P<0.05). Compared with GOS, MOS increased the number of Escherichia coli and Lactobacillus, as well as that of Roseburia in the ileum mucosa group (P<0.05). [Conclusion] The mucosal microbiota from porcine small intestine had different fermentation patterns for GOS and MOS, as manifested by the varied production of organic acids and bacterial proliferation. GOS had an advantage of propionate production and increased the number of Bacteroidetes and Veillonella. MOS promoted the production of acetate, lactate in the ileum mucosa group and butyrate in the jejunum mucosa group, and increased the number of Escherichia coli and Lactobacillus.