Chitin promotes equol production via n-acetylglucosamine in human fecal cultures

Miyuki Kodera; Kohei Nakamura; Shin-Ichiro Yokoyama

doi:10.1016/j.anaerobe.2024.102923

Chitin promotes equol production via n-acetylglucosamine in human fecal cultures

Anaerobe. 2024 Nov 25:102923. doi: 10.1016/j.anaerobe.2024.102923. Online ahead of print.

Authors

Miyuki Kodera¹, Kohei Nakamura², Shin-Ichiro Yokoyama³

Affiliations

¹ The United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan; Gifu Prefectural Research Institute for Food Science, 1-1 Yanagido, Gifu, 501-1112, Japan.
² The United Graduate School of Agricultural Science, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
³ Gifu Prefectural Research Institute for Food Science, 1-1 Yanagido, Gifu, 501-1112, Japan. Electronic address: yokoyama-shinichiro@rd.pref.gifu.jp.

PMID: 39603518
DOI: 10.1016/j.anaerobe.2024.102923

Abstract

Objectives: Equol is a metabolite of isoflavone. Here, we investigated the effect of dietary fiber on equol-producing microbiota.

Methods: Human feces were anaerobically cultured in Gifu Anaerobic Medium (GAM) containing 1 mg/L daidzein supplemented with 1% (w/v) dietary fiber (pectin, chitin, or resistant starch [RS]). The equol conversion rate, number of equol-producing bacteria, pH, short-chain fatty acids (SCFAs), and microbial composition were measured in fecal cultures.

Results: Equol conversion significantly increased by 2.7-fold in the chitin group compared with the control group. Conversely, the conversion rate decreased to one-tenth in the pectin group and one-third in the RS group. The number of equol-producing bacteria also significantly increased in the chitin group compared with the control group. Whereas pH values and acetate/propionate concentrations decreased in the pectin and RS groups compared with the control group, no significant differences were observed in the chitin group. Microbiota analysis indicated that the relative abundances of Bifidobacterium and Lactobacillus increased, whereas those of Dorea, Lachnoclostridium, and Eggerthella decreased in the pectin and RS groups. In contrast, these abundances remained stable in the chitin group. The relative abundances of Adlercreutzia and Slackia remained unchanged across all groups. In vitro cultures of Eggerthella sp. strain YY7918 and Adlercreutzia equolifaicens JCM14793 demonstrated that equol conversion from daidzein was stimulated by the addition of 0.5-1% (w/v) n-acetylglucosamine, a breakdown product of chitin, but not chitin itself.

Conclusions: Our findings suggest that equol production is stimulated by n-acetylglucosamine, derived from decomposed chitin, in certain equol-producing bacteria without affecting their growth.

Keywords: chitin; dietary fiber; equol; microbiota; n-acetylglucosamine; qPCR.