Impact of High- and Low-Amylose Rice Residues on Gut Microbiota and Metabolic Profiles: Insights from in Vitro Fermentation

Abstract

This study investigated how rice residues from rice varieties with various amylose content (7-41%) modulates gut microbiota composition and metabolite profiles during in vitro fermentation. Using size-exclusion chromatography (SEC) and fecal samples from eight donors, we found that high-amylose residues (AC >25%) exhibited larger hydrodynamic radii (), associating with fewer shorter branches (DP 2-28) but more longer chains (DP 28-1100), primarily consisting of medium-to-long amylopectin branches and shorter amylose chains (DP 100-1100). After 24-h fermentation, high-amylose residues significantly increased butyrate production, with an average value of 5034.1 μg/mL vs 4521.5 μg/mL in low-amylose residues, and enriched beneficial genera including Agathobacter and Lachnospiraceae_NK4A136_group, the bacteria genus that are significantly and positively correlated with the abundance of enterolactone metabolites linked to anti-inflammatory and metabolic benefits. These results highlight the role of starch chain length distribution (CLD) in promoting gut health, suggesting high-amylose rice as a dietary strategy to enhance colonic fermentation.

Keywords: High amylose starch, Rice, Chain length distribution (CLD), Gut microbiota, Short-Chain Fatty Acids (SCFAs), Size-exclusion chromatography (SEC)