Isoflavone Metabolism by Lactic Acid Bacteria and Its Application in the Development of Fermented Soy Food with Beneficial Effects on Human Health

Abstract

Isoflavones are phenolic compounds (considered as phytoestrogens) with estrogenic and antioxidant function, which are highly beneficial for human health, especially in the aged population. However, isoflavones in foods are not bioavailable and, therefore, have low biological activity. Additionally, their transformation into bioactive compounds by microorganisms is necessary to obtain bioavailable isoflavones with beneficial effects on human health. Many lactic acid bacteria (LAB) can transform the methylated and glycosylated forms of isoflavones naturally present in foods into more bioavailable aglycones, such as daidzein, genistein and glycitein. In addition, certain LAB strains are capable of transforming isoflavone aglycones into compounds with a greater biological activity, such as dihydrodaidzein (DHD), O-desmethylangolensin (O-DMA), dihydrogenistein (DHG) and 6-hydroxy-O-desmethylangolensin (6-OH-O-DMA). Moreover, Lactococcus garviae 20-92 is able to produce equol. Another strategy in the bioconversion of isoflavones is the heterologous expression of genes from Slackia isoflavoniconvertens DSM22006, which have allowed the production of DHD, DHG, equol and 5-hydroxy-equol in high concentrations by engineered LAB strains. Accordingly, the consequences of isoflavone metabolism by LAB and its application in the development of foods enriched in bioactive isoflavones, as well as health benefits attributed to their consumption, will be addressed in this work.

Profiling of Metabolites in a Fermented Soy Dietary Supplement Reinforces its Role in the Management of Intestinal Inflammation

“…[53] Soy's reported health effects have been linked to its bioactive metabolite profile, which can be modified by bacterial and fungal metabolism ex situ or in situ. [13,[54][55][56] Using controlled fermentation to produce soy products with predictable and standardized bioactive metabolite profiles could equitize the observed health effects seen from dietary soy, which are thought to vary due to differences in human microflora. [13,[57][58][59][60] GAD, a fermented soy flour sold as a health ingredient, has a long history of use in relieving symptoms associated with gastric upset, heartburn, and ulceration.…”

“…[13,[54][55][56] Using controlled fermentation to produce soy products with predictable and standardized bioactive metabolite profiles could equitize the observed health effects seen from dietary soy, which are thought to vary due to differences in human microflora. [13,[57][58][59][60] GAD, a fermented soy flour sold as a health ingredient, has a long history of use in relieving symptoms associated with gastric upset, heartburn, and ulceration. Previously, the mechanisms through which this product achieves its efficacy were not well understood, as gastric acid buffering by peptides did not, by themselves, explain the reported rapid pain relief and the ulcer healing.…”

“…), can increase the extent of bioavailability and bioactive quality of these estrogenic molecules. [ 4,13 ] Specific fermented soy products (e.g., tempeh, miso, soy sauce) show higher levels of bioavailable aglycone isoflavones compared to raw or cooked soy foods. [ 14–17 ] Further microbiome‐derived bioactivation of primary metabolites in some individuals is possible in the gut prior to absorption across the gut barrier, producing additional estrogenic molecules.…”

“…[ 14–17 ] Further microbiome‐derived bioactivation of primary metabolites in some individuals is possible in the gut prior to absorption across the gut barrier, producing additional estrogenic molecules. [ 13 ]…”

“…[14][15][16][17] Further microbiome-derived bioactivation of primary metabolites in some individuals is possible in the gut prior to absorption across the gut barrier, producing additional estrogenic molecules. [13] Other important soy chemical constituents can help further explain the favorable dietary effects seen in human populations. The fermentation of soy macromolecules into short chain fatty acids (SCFAs) by probiotic bacteria is reported in fermented soy products from south east Asia.…”