Development of the first fermented soy beverages enriched in equol and 5-hydroxy-equol

Abstract

Daidzin and genistin, present in soy, can be transformed by the intestinal microbiota into equol and 5-hydroxy-equol; compounds beneficial to human health, although these compounds are only produced by a fraction of the population and in low concentrations. Hence, there is an interest in the ingestion of these compounds. Engineered lactic acid bacteria strains harbouring daidzein reductase, dihydrodaidzein reductase, tetrahydrodaidzein reductase and the dihydrodaidzein racemase genes from Slackia isoflavoniconvertens DSM22006 were incubated in five commercial soy beverages with strains with a high capacity to transform glycosylated isoflavones into their aglycones. High equol and 5-hydroxy-equol concentrations were produced in the five commercial soy beverages; the soy beverages from VegeDia and Carrefour being the ones that showed the highest concentrations of equol (456.02 ± 14.62 and 366.07 ± 25.81 μmol/L) and 5-hydroxy-equol (126.07 ± 6.23 and 121.00 ± 9.57 μmol/L). Moreover, dihydrodaidzein racemase and Bifidobacterium pseudocatenulatum INIA P815, with a high capacity to transform isoflavone glycosides into their aglycones, were necessary to achieve high equol and 5-hydroxy-equol concentrations. Bacteria generally recognized as safe produced the first fermented soy beverages enriched in equol and 5-hydroxy-equol. The high concentrations of these compounds attained in these beverages would have great potential for consumer health.