In vitro utilization of gold and green kiwifruit oligosaccharides by human gut microbial populations.

We examined the effects of whole kiwifruit on gut microbiota using an in vitro batch model of gastric-ileal digestion and colonic fermentation. Faecal fermentations of gold and green kiwifruit, inulin and water (control) digests were performed for up to 48 h. As compared to the control, gold and green kiwifruit increased Bifidobacterium spp. by 0.9 and 0.8 log(10) cfu/ml, respectively (P < 0.001), and the Bacteroides-Prevotella-Porphyromonas group by 0.4 and 0.5 log(10) cfu/ml, respectively. Inulin only had a bifidogenic effect (+0.4 log(10) cfu/ml). This was accompanied with increases in microbial glycosidases, especially those with substrate specificities relating to the breakdown of kiwifruit oligosaccharides, and with increased generation of short chain fatty acids. The microbial metabolic activity was sustained for up to 48 h, which we attribute to the complexity of the carbohydrate substrate provided by whole kiwifruit. Kiwifruit fermenta supernatant was also separately shown to affect the in vitro proliferation of Bifidobacterium longum, and its adhesion to Caco-2 intestinal epithelial cells. Collectively, these data suggest that whole kiwifruit may modulate human gut microbial composition and metabolism to produce metabolites conducive to increased bifidobacteria-host association.