Abstract:

An intestinal bacterial strain with the ability to metabolize soy isoflavone to equol was isolated from vegetarian
feces. Qualitative and quantitative analysis of equol was performed by ultraviolet spectrophotometry. The isolated strain was
identified through naked-eye observation, scanning electron microscope, physiological and biochemical characterization and
16S rDNA full-length sequencing. The results showed that Makanke medium, BHI medium and anaerobic plate streaking
cultivation method were suitable for isolating intestinal bacteria producing equol. The optimal culture conditions for
enhanced equol production were 10 g of fecal sample diluted in advance to 10-5 inoculated into 6 mg of substrate at an initial
medium pH of 7.3, followed by anaerobic culture at pH 7.3 for 36 h. The strain was identified as LJ-G1, a Gam-negative
bacillus. According to physiological and biochemical properties and referring the Common Bacterial System Identification
Manual, LJ-G1 belonged to Enterobacter amnigenus. The results of 16S rDNA full-length sequencing showed 99%
homology with the intestinal bacterium.

Key words: vegetarian, intestinal bacteria, equol, isolation, identification