Synthesis of Isoflavone Aglycones and Equol in Soy Milks Fermented by Food-Related Lactic Acid Bacteria and Their Effect on Human Intestinal Caco-2 Cells

Abstract

One hundred and three strains of lactic acid bacteria, isolated from various food ecosystems, were assayed for β-glucosidase activity toward p-nitrophenyl-β-D-glucopyranoside substrate. Lactobacillus plantarum DPPMA24W and DPPMASL33, Lactobacillus fermentum DPPMA114, and Lactobacillus rhamnosus DPPMAAZ1 showed the highest activities and were selected as the mixed starter to ferment various soy milk preparations, which mainly differed for chemical composition, protein dispersibility index, and size dimension. The soy milk made with organically farmed soybeans (OFS) was selected as the best preparation. All selected strains grew well in OFS soy milk, reaching almost the same values of cell density (ca. 8.5 log cfu/mL). After 96 h of fermentation with the selected mixed starter, OFS soy milk contained 57.0 μM daidzein, 140.3 μM genistein, 20.4 μM glycitein, and 37.3 μM equol. Fermented and nonfermented OFS soy milks were used for the in vitro assays on intestinal human Caco-2/TC7 cells. Fermented OFS soy milk markedly inhibited the inflammatory status of Caco-2/TC7 cells as induced by treatment with interferon-γ (IFN-γ) (1000 U/mL) and lipopolysaccharide (LPS) (100 ng/mL), maintained the integrity of the tight junctions, even if subjected to negative stimulation by IFN-γ, and markedly inhibited the synthesis of IL-8, after treatment with interleukin-1β (2 ng/mL). As shown by using chemical standards, these effects were due to the concomitant activities of isoflavone aglycones and, especially, equol, which were synthesized in the fermented OFS soy milk preparation.

A new biotechnological process to enhance the soymilk bioactivity

“…This strain showed the highest β-glucosidase activity among the strains studied. Di Cagno et al (15) found similar results in a study in which soymilk with food-related lactic acid bacteria contained 0.9 mg/100 mL of equol after 96 h of fermentation. The authors proposed correlations between the growth characteristics of the bifidobacteria in soymilk, their β-glucosidase activity, and the conversion of isoflavone glycosides into aglycone forms.…”

“…A number of bacteria in intestinal flora have also been reported to be responsible for this conversion (14). However, the formation of equol during soymilk fermentation without the presence of bacteria from intestinal microflora, has also been considered in some studies that correlate the equol formation with the use of enzymes (15,34,35).…”

“…Essentially, these works showed that enterobacteria fermentation processes can lead to conversions of soy isoflavones, leading to the higher bioavailability of these bioactive molecules and formation of equol (5,15). However, because of the nature of the microorganisms and enzyme sources applied, it is difficult to scale up the process.…”

Study on soybean milk fermented by Lactobacillus plantarum YS-1 reduced the H2O2-induced oxidative damage in Caco-2 cells

“…Inhibition of the NF-κB pathway was able to reduce the ROS induced cellular oxidative damage, and reduced the human IBD [34]. In addition, soybean milk fermented by mixed LAB starter that including Lactobacillus plantarum, Lactobacillus fermentum, and Lactobacillus rhamnosus were also markedly inhibited the chemokine IL-8 production in IL-1β treated Caco-2 cells [35].…”

Staying a Step Ahead of Cancer

“…Similarly, a number of the nutrients, e.g. isoflavones from soy, cannot be absorbed without the aid of microbes in the intestine (Di Cagno et al 2010, Ding and Shah 2010, Rekha and Vijayalakshmi 2010. Nonetheless, a healthy diet can reduce the chances of developing cancer.…”