Isolation and characterization of the equol-producing bacterium Slackia sp. strain NATTS

Several kinds of carbohydrates such as sorbose, adonitol, and melezitose were found to enhance equol production from daidzein in an in vitro human fecal culture. Sorbose, one of the most effective carbohydrates, was used as a carbohydrate source for isolating the NATTS strain, which was a Gram-positive, non-spore-forming rod bacterium with high ability to convert daidzein to equol isolated from the 7th maintenance culture. The strain was found to belong to the genus Slackia family Coriobacteriaceae by 16S rRNA sequence-based analysis, and the prevalence of the Slackia sp. in Japanese adults was examined by reverse transcription-quantitative PCR (RT-qPCR), which was found to be 40% at a mean population level of 10⁶ cells per gram of feces.