Influence of condensed tannins on in vitro fermentation of maize and potato starches using diverse human microbiomes

Abstract

Condensed tannins are non-hydrolyzable polyphenols with well-documented effects on the gut microbiome, including stimulation of beneficial bacteria such as Faecalibacterium. This study evaluated the impact of tannin supplementation on the in vitro fermentation of various starch substrates, both purified (high-amylose maize, corn starch, potato starch) and whole grain flours (K55, K55AE, and Waxy maize), using fecal samples from nine individual human microbiomes. After 16 hours of anaerobic fermentation, short-chain fatty acid (SCFA) concentrations and Faecalibacterium duncaniae growth were measured. Tannins consistently decreased butyrate and acetate production across treatments, while propionate remained relatively stable. Notably, the growth of Faecalibacterium was enhanced in whole grain treatments with tannins, while in the case of purified starches, the tannins negatively affected the microbial growth, resulting in reduced growth of Faecalibacterium duncaniae. These results indicate that the microbial response to tannins is strongly influenced by the food matrix, likely due to physical and chemical interactions with proteins and fibers that modulate tannin bioactivity. These findings provide valuable insights into how dietary components, such as tannins, influence the composition and function of the gut microbiome. Moreover, these findings have implications for the design of functional foods that promote gut health by modulating the microbiome. This study contributes to the understanding of diet-microbiome interactions and supports the development of strategies to design foods that optimize human gut health.