Rhamnogalacturonan-I domains from red dragon fruit pectin promote the proliferation of Bifidobacterium animalis

Pectin-derived oligosaccharides, an important source of the new generation of prebiotics, have aroused widespread research. As per our previous study report, the rhamnogalacturonan-I (RG-I) type pectin of dragon fruit positively affects the proliferation of Bifidobacterium animalis subsp. Lactis 3296. However, the pectin region that primarily produces prebiotic effects is not clear. To further investigate the promotion of the dragon fruit pectin RG-I domain on the proliferation of B. animalis subsp. Lactis 3296, we first obtained pectin (DP-AC-A2a) with a higher proportion of the RG-I region through gel purification and enzyme digestion. Then, monosaccharide components and Fourier transform infrared were analyzed to identify the pectin structures preliminarily. The results demonstrated that DP-AC-A2a with a backbone consisting of repeated -> (4) GalpA (1-2) Rhap (1) -> and the branches are mainly composed of 1,4-linked galactose. Furthermore, the bacterial proliferation experiment proved the contribution of galactan on the pectin's branch to the proliferation of B. animalis. The enzyme activity showed that the addition of DP-AC-A2a can promote the production of beta-d-galactosidase by B. animalis. These data provide effective information for the potential application of red dragon fruit pectin.