Abstract: In order to solve the intolerance of probiotics to low pH and oxygen, Bifidobacterium longum was microencapsulated using alginate as the wall material in this study. Microcapsules were prepared with alginate alone or with alginate + alginate oligosaccharides (AOS) by emulsification method and then coated with chitosan oligosaccharides (COS) yielding COS-microcapsules and AOS-COS-microcapsules, respectively. In vitro experiments showed that the two marine oligosaccharide coated microcapsules could greatly improve the survival rate of B. longum in simulated digestive juice or during storage at 4 ℃. AOS-COS-microcapsules could maintain a viable cell count of more than 106 CFU/g after simulated gastric digestion. After simulated gastrointestinal digestion, the viable cell count of AOS-COS-microcapsules was about 1 000 times as high as that of the uncoated microcapsules. The two marine oligosaccharide coated microcapsules could maintain a viable cell count of greater than 108 CFU/g after storage for 28 days at 4 ℃. In vivo experiments showed that compared with free B. longum and the bare microcapsules, the coated microcapsules could significantly increase the content of probiotics and reduce the content of opportunistic pathogenic bacteria, and were more effective in regulating the intestinal flora. Therefore, marine oligosaccharide coated microcapsules containing probiotics have a great potential as a new type of functional food.

Key words: probiotics, microcapsules, marine oligosaccharides, intestinal microbiota, high-throughput sequencing