Administration of equol-producing bacteria alters the equol production status in the Simulator of the Gastrointestinal Microbial Ecosystem (SHIME)

The intestinal microbial transformation of daidzein, one of the principal isoflavones from soy, into the isoflavan equol is subjected to a high interindividual variability. The latter compound is considered to have a higher biological activity than its precursor; hence, there is interest in dietary applications that modulate this important biotransformation. In 2 separate experiments, we administered a mixed microbial culture (EPC4), which we had isolated previously and which efficiently transforms daidzein into equol, to the Simulator of the Human Intestinal Microbial Ecosystem (SHIME). The SHIME was fed soy germ powder and inoculated with fecal samples from two nonequol-producing individuals. Equol production was induced in the distal colon compartments in both experiments, 5-6 d after the start of the treatment; 2 wk after interrupting the addition of EPC4, equol was still produced in high amounts. There are large interregional differences in daidzein metabolism in the simulated colon. Furthermore, no major shifts in the composition and activity of the microbial communities were caused by the supplementation with the microbial consortium. Although further confirmation in in vivo studies is required, these results validate the concept that administering EPC4 could constitute a novel means for converting a nonequol-producer into a producer.