Wheat-based food form has a greater effect than amylose content on fermentation outcomes and microbial community shifts in an in vitro fermentation model

Abstract

Starches with high amylose content resist complete digestion in the small intestine with a fraction (resistant starch) entering the large intestine, where it is fermented by the human gut microbiota resulting in perceived beneficial health effects. However, the effects of food form on the large intestinal digestion of products with different amounts of resistant starch are unknown. Here, wheat flours with 32%, 71%, 74% and 84% amylose content were used to prepare bread, tortillas and noodles, and after in vitro treatment simulating small intestinal digestion, were subjected to in vitro fermentation with a pooled human faecal inoculum. The results showed that food form rather than initial amylose content significantly affected both fermentation rates and short chain fatty acid (SCFA) production. Acetate concentrations were significantly greater in the noodle-based fermentations, whereas propionate concentrations were significantly greater in the tortilla-based fermentations (p < 0.05). Butyrate concentrations were also significantly increased for both the noodle and tortilla-based fermentations when compared to bread (p < 0.05). The microbial communities supported by these different food forms were examined by metagenomic sequencing (MGS) of fermentation samples collected over 48 h. Among the top 20 most abundant species, Enterococcus faecium was significantly increased by bread and tortilla, whereas Ruminococcus spp. and Faecalibacterium prausnitzii were increased for noodles. Although the amount of resistant starch reaching the large intestine is a relevant consideration in pursuit of promoting digestive health, our findings suggest that food form has a major influence on the gut microbiota that is reflected in substantive changes in SCFA profiles.