Effects of digested flours from four different sweet potato (Ipomoea batatas L.) root varieties on the composition and metabolic activity of human colonic microbiota in vitro

Abstract

This study evaluated the effects of flours from four different sweet potato root (SPR) varieties, being two with white peel and two with purple peel, on the composition and metabolic activity of human colonic microbiota in vitro. The capability of these SPR flours (20 g/L) to cause alterations in relative abundance of different bacterial groups found as part of human colonic microbiota, as well as in lactic acid and short-chain fatty acid production was evaluated during 48 hr of an in vitro colonic fermentation. The SPR flours were submitted to a simulated gastrointestinal digestion prior to use in experiments. The four SPR flours increased the relative abundance of Lactobacillus/Enterococcus (range: 0.49-4.48%) and Bifidobacterium (range: 0.32-3.27%) and decreased the relative abundance of Bacteroides/Prevotella (range: 0.29-7.49%), Clostridium histolyticum (range: 0.15-2.08%), and Eubacterium rectale/Clostridium coccoides (range: 0.28-3.86%) during the 48 hr of colonic fermentation. The four SPRF flours had positive prebiotic indexes (> 0.38) after 24 and 48 hr of colonic fermentation, reinforcing the occurrence of selective stimulatory effects on colonic microbiota. An increased metabolic activity of human colonic microbiota was caused by tested SPR flours, which was evidenced by decreased pH (range: 3.20-3.83) and increased lactic acid and short chain fatty acid production during the 48 hr of colonic fermentation. The four examined SPR flours were capable of causing positive alterations in composition and driving the metabolic activity of human colonic microbiota during in vitro colonic fermentation, which should be linked to their prebiotic properties. PRACTICAL APPLICATION: The four examined sweet potato root flours (SPRF) caused beneficial alterations in composition besides of driving the metabolic activity of human colonic microbiota in vitro. These results characterize the examined SPRF as candidates for use as prebiotic ingredients by food industry for formulation of value-added functional foods or dietary supplements.

Keywords: colonic fermentation; gut microbiota; modulatory effects; potato; prebiotic effects.