In vitro fermentation of a purified fraction of polysaccharides from the root of Brassica rapa L. by human gut microbiota and its interaction with Bacteroides ovatus

Abstract

In this study, the physicochemical properties, in vitro fermentation, and interaction with Bacteroides ovatus of a purified fraction of polysaccharides from the root of Brassica rapa (BRP2-2) were investigated. It was demonstrated with an in vitro anaerobic fermentation model that BRP2-2 significantly increased (p < 0.05) the relative abundance of Bacteroides spp. After 24 h incubation of BRP2-2 with Bacteroides ovatus alone, 10.24 ± 0.69, 8.76 ± 0.48 and 3.37 ± 0.26 mM of acetate, propionate and isovalerate were produced, respectively. Moreover, transcriptome analysis of B. ovatus showed that 143 genes were up-regulated by BRP2-2, including five discrete polysaccharide utilization loci and two carbohydrate-active enzyme clusters. Based on the annotation of carbohydrate enzyme function, we speculate that BRP2-2 is a pectic polysaccharide containing homogalacturonan, rhamnogalacturonan I and rhamnogalacturonan II domains. These results suggested that BRP2-2 was degraded by B. ovatus, which produced metabolites with beneficial effects on host health.

Keywords: Bacteroides ovatus; Brassica rapa L.; Gut microbiota; Polysaccharides; Transcriptome.