Application of recombinant lactic acid bacteria and bifidobacteria able to enrich soy beverage in dihydrodaidzein and dihydrogenistein.

Dihydrodaidzein (DHD) and dihydrogenistein (DHG) are intermediate compounds in the production of equol and 5-hydroxy-equol from daidzein and genistein by certain intestinal bacteria. In this work, we explored the heterologous expression of the daidzein reductase gene from Slackia isoflavoniconvertens DSM22006, responsible for the formation of DHD and DHG, in nine lactic acid bacteria and Bifidobacterium strains under a strong constitutive promoter in the plasmid pNZ:TuR.dzr. All the transformed strains showed high production of DHD and DHG both from pure daidzein and genistein and from the isoflavone glycosides present in soy beverage. In addition, Lactococcus lactis MG1363 pNZ:TuR.dzr, expressing the recombinant daidzein reductase, incremented the production of equol by equol-producing intestinal microbiotas in a colonic environment. Nevertheless, other recombinant strains tested showed the opposite effect to L. lactis MG1363 pNZ:TuR.dzr in the production of equol by intestinal microbiota. Here, we describe for the first time the production of 5-hydroxy-equol by human intestinal microbiota, both from genistein and DHG. The use of DHD and DHG as substrates, compared to daidzein and genistein, resulted in an increment of equol and 5-hydroxy-equol production by intestinal microbiota. The recombinant strains developed would be of value for the development of fermented soy beverage enriched in DHD and DHG with the aim of facilitate equol and 5-hydroxy-equol production by intestinal microbiota.

Production of O-desmethylangolensin, tetrahydrodaidzein, 6'-hydroxy-O-desmethylangolensin and 2-(4-hydroxyphenyl)-propionic acid in fermented soy beverage by lactic acid bacteria and Bifidobacterium strains.

Isoflavones intake is associated with health benefits. The metabolism of isoflavones by bacteria plays a key role in their biotransformation. Therefore, commercial soy drink was fermented by 11 lactic acid bacteria (LAB) and 9 bifidobacteria strains. The majority of the strains showed deglycosylation of the isoflavone glycosides present in soy drink and appearance of the aglycones daidzein, genistein and glycitein. Moreover, we observed the further transformation of daidzein into O-desmethylangolensin (O-DMA) and tetrahydrodaidzein, alongside with dihydrodaidzein (DHD) and a putative isomer of DHD. On the other hand, genistein was transformed by nearly all strains into 6-hydroxy-O-desmethylangolensin (6-hydroxy-O-DMA), but no dihydrogenistein production was registered. A high concentration of 2-(4-hydroxyphenyl)-propionic acid was observed, suggesting the degradation of O-DMA and 6-hydroxy-O-DMA. The potential of LAB and Bifidobacterium strains to produce functional soy drink enriched with bioactive isoflavones is demonstrated in this work.