Abstract: in vitro fermentation technology was used to evaluate the effects of soybean oligosaccharides (SBOS) on fermentation kinetic parameters and fermentation products, which also used to explore its action mechanisms as food or feed additives. Sterile jejunum, ileum, cecum or colon chyme as the inoculum were collected from Huanjiang normal pigs to conduct in vitro fermentation using SBOS at the concentrations of 50, 100, 200, 500 mg/L and 800 mg/L, and glucose as the substrates. The gas production, pH, and the contents of NH3-N, acetic acid, propanoic acid and butyric acid in the fermentation broth were determined after 48h fermentation in an anaerobic system. Results indicated that the maximum amount and rate of gas production in the fermentation broth of ileum group supplemented with SBOS were higher than those of the control group (P＜0.05), while an obvious lag in gas-producing time was observed in fermentation broth of colon or cecal group supplemented with SBOS and glucose. Compared with the control group, the lower gas-producing amount and rate was observed in fermentation broth of colon or cecum group supplemented with SBOS and glucose (P＜0.05). The fermentation kinetic parameters at the condition of 200 mg/L SBOS were the best. The pH and NH3-N content in fermentation broth of colon or cecum group supplemented with 200 mg/L SBOS were lower (P＜0.05) when compared with the control group, but higher (P＜0.05) when compared with the ileum group supplemented with glucose. The proportion of short chain fatty acids (SCFA) in the groups supplemented with SBOS and glucose was higher than that of the control group (P＜0.05). The content of acetic acid was decreased due to the addition of SBOS, while the contents of propionate acid and butyrate acid exhibited a gradual increase. The maximum content of butyrate acid was observed in the fermentation broth of colon group supplemented with 200 mg/L SBOS. Therefore, SBOS is beneficial to gut health as functional food or feed additives to modulate SCFA production patterns in intestinal microflora. Its optimal level is 200 mg/L.

Key words: soybean oligosaccharides, fermentation characteristics, short chain fatty acids (SCFA)