# Makgeolli Lees as a Novel Prebiotic Candidate: Effects on Human Gut Microbiota and Metabolites

## TL;DR

Makgeolli lees, a byproduct of Korean rice wine, may act as a prebiotic by promoting beneficial gut bacteria and metabolites.

## Contribution

The study identifies makgeolli lees as a novel prebiotic candidate based on its effects on gut microbiota and metabolite production.

## Key findings

- Makgeolli lees fermentation increased Bifidobacterium bifidum, Prevotella copri, and Bacteroides uniformis.
- Short-chain fatty acid concentrations, including acetate, propionate, and butyrate, were elevated after fermentation.
- The prebiotic effects of makgeolli lees were comparable to those of fructooligosaccharides (FOS).

## Abstract

Makgeolli lees (ML), an underutilized byproduct of traditional Korean rice wine production, contains abundant indigestible carbohydrates and microbial residues. This study evaluates the prebiotic potential of ML using a simulated human digestion and in vitro fecal fermentation model. In vitro digestion showed that 61.30% of total carbohydrates and 89.92% of crude protein remained undigested. During in vitro fecal fermentation, treatment with ML induced compositional changes in the gut microbiota, including increased abundances of Bifidobacterium bifidum (Δ 0.37 ± 0.09%), Prevotella copri (Δ 0.98 ± 0.24%), and Bacteroides uniformis (Δ 0.46 ± 0.06%), along with a decrease in Bacteroides ovatus (Δ –2.14 ± 1.51%). In addition, SCFA concentrations were elevated after 12 h of fermentation, with acetate at 84.80 ± 4.88 mM, propionate at 43.75 ± 2.74 mM, and butyrate at 20.22 ± 0.71mM. The alterations in microbial composition and associated metabolite profiles were comparable to those observed following fructooligosaccharides (FOS) supplementation. These findings indicate that ML function as a fermentable substrate that selectively enriches health-associated gut microbiota and enhances the production of beneficial microbial metabolites, thereby supporting their potential application as a sustainable and cost-effective prebiotic candidate in dietary applications.