Fermented soy beverages as vehicle of probiotic lactobacilli strains and source of bioactive isoflavones: A potential double functional effect

Soy beverages can be a source of bioactive isoflavones, with potential human health benefits. In this work, the suitability of three Lacticaseibacillus and three Bifidobacterium probiotic strains as functional starters for soy beverage fermentation were evaluated, alongside with the effect of refrigerated storage on the viability of the strains and the isoflavone composition of the fermented beverages. The three bifidobacteria strains suffered a decrease in their viability during refrigeration and only Bifidobacterium breve INIA P734 produced high concentrations of bioactive isoflavones. Meanwhile, L. rhamnosus GG and L. rhamnosus INIA P344 produced high levels of aglycones and, with L. paracasei INIA P272, maintained their viability during the refrigeration period, constituting promising starters to obtain functional soy beverages that could gather the benefits of the bioactive isoflavone aglycones and the probiotic strains. Moreover, the three lactobacilli caused an increase in the antioxidant capacity of the fermented beverages, which was maintained over the refrigerated storage.

Production of Bovine Equol-Enriched Milk: A Review

Simple Summary

Milk and dairy products contain many substances beneficial to human health; moreover, the contents of some of these substances can be enhanced. This is also the case of isoflavones which are compounds of plant origin that can be ingested and metabolized by cattle and, subsequently, secreted into bovine milk. An especially healthful substance called equol is ranked among isoflavone metabolites, commonly produced in the digestive tract of cattle. Equol content in milk can be modified by using feedstuffs with different contents of isoflavones or by milk processing and storage.

Abstract

Milk and dairy products are important sources of nutrients in the human diet because they contain a number of essential substances and other biologically active components. Many of these substances can be modified, and thus offer opportunities to use milk and dairy products as functional food. Isoflavones are particularly important in human nutrition due to their diverse pharmacological and antioxidant properties. The clinical effectiveness of isoflavone-rich products is believed to be dependent on their ability to metabolize daidzein to equol, which may directly exert cancer preventive effects. However, only approximately 30–40% of humans are able to produce equol, while animals, in general, produce equol. Equol is the predominant product of bacterial metabolism of isoflavones and can be found in various amounts in some food of animal origin, especially in milk. Therefore, milk and dairy products can be considered to be sources of equol for humans who are not able to produce this metabolite. When the content of isoflavones in milk is to be modified, two groups of factors should be considered, i.e., dietary factors that include the source of isoflavones and the processing effects on feedstuffs and animal factors that include the intake of isoflavones, ruminal and postruminal changes, and the health and physiological status of animals. The approximate content of isoflavones in milk can be predicted using carry-over rates for different dietary sources or using a formula that describes the relationship between equol concentration in milk and formononetin intake. Processing and storage can affect the content and profile of isoflavones in milk and dairy products.

Techno-functional characterization of indigenous Lactobacillus isolates from the traditional fermented foods of Meghalaya, India

The rural tribal people of Meghalaya depend mostly on their ethnic fermented foods as a part of their regular diet and these fermented foods are considered to be a hub of healthy microorganisms. However, the efficacy of probiotic microorganisms is considered to be population-specific because of gut microflora variation in food habits and specific host-microbial interactions. Hence, a strong need for exploring novel indigenous microorganisms with rich probiotic potentiality is required. A few indigenous Lactobacillus isolates (from traditional fermented foods of Meghalaya) were studied extensively for its technological and probiotic attributes. The isolates could survive at pH 2–3 (L. fermentum K16 showed high cell count: pH 2–5.12 log CFU/ml; pH 3–5.76 log CFU/ml), against bile salts (L. fermentum K7 showed high cell count-5.36 log CFU/ml), gastric juices (pepsin and trypsin), and intestinal juice (pancreatin). The isolates showed α-galactosidase activity from 0.104-0.412 μM/ml and β-glucosidase activity ranging from 0.122-0.409 μM/ml. Exopolysaccharide production was in between 410 and 950 mg/L. Cell surface hydrophobicity was 71.57% (L. rhamnosus K4E) and auto-aggregation was 83% (L. fermentum K16) during the study. Highest proteolytic activity (0.671 nm) and cholesterol assimilation (52.57%) was exhibited by L. fermentum K16. The isolates showed high free radical scavenging activity by ABTS method up to 80.78% by isolate L. fermentum K7. Antibacterial activity and co-aggregation efficacy was also tested against B. cereus, E. faecalis, S. dysenteriae, S. aureus, E. coli, L. monocytogenes, S. typhi. These indigenous Lactobacillus isolates with high probiotic potentials could be exploited in the development of the traditional fermented foods of Meghalaya.

•

Technological and probiotic attributes (in vitro) of eight indigenous Lactobacillus strains were studied.

•

Lactobacillus strains were isolated from the traditional fermented foods of Meghalaya, India.

•

L. rhamnosus K4E, L. fermentum K16, L. fermentum K7 and L. plantarum RD7 were considered predominant over the rest of the strains.

•

The isolates could be employed for development of novel functional fermented foods.

Influence of natural coagulants on isoflavones and antioxidant activity of tofu

Tofu (instead of preparing using synthetic coagulant) was prepared using coagulants of plant origin (Citrus limonum, Garcinia indica, Tamarindus indica, Phyllanthus acidus and Passiflora edulis). Total crude protein and fat contents were highest in tofu prepared using G. indica and T. indica (72.5% dbw) compared to synthetic coagulant. Tofu prepared with natural coagulants had signifi cantly higher antioxidant activity compared to synthetic coagulant. Bioconversion of isoflavone glucosides (daidzin and genistin) into their corresponding bioactive aglycones (daidzein and genistein) was observed in tofu. The difference between glucosides and aglycones contents in soy milk was significant but there was not much difference in tofu coagulated with synthetic and natural coagulants.

Fermentation of calcium-fortified soymilk with Lactobacillus: effects on calcium solubility, isoflavone conversion, and production of organic acids

The objective of this study was to enhance calcium solubility and bioavailability from calcium-fortified soymilk by fermentation with 7 strains of Lactobacillus, namely, L. acidophilus ATCC 4962, ATCC33200, ATCC 4356, ATCC 4461, L. casei ASCC 290, L. plantarum ASCC 276, and L. fermentum VRI-003. The parameters that were used are viability, pH, calcium solubility, organic acid, and biologically active isoflavone aglycone content. Calcium-fortified soymilk made from soy protein isolate was inoculated with these probiotic strains, incubated for 24 h at 37 degrees C, then stored for 14 d at 4 degrees C. Soluble calcium was measured using atomic absorption spectrophotometry (AA). Organic acids and bioactive isoflavone aglycones, including diadzein, genistein, and glycetein, were measured using HPLC. Viability of the strains in the fermented calcium-fortified soymilk was > 8.5 log(10) CFU/g after 24 h fermentation and this was maintained for 14-d storage at 4 degrees C. After 24 h, there was a significant increase (P < 0.05) in soluble calcium. L. acidophilus ATCC 4962 and L. casei ASCC 290 demonstrated the highest increase with 89.3% and 87.0% soluble calcium after 24 h, respectively. The increase in calcium solubility observed was related to lowered pH associated with production of lactic and acetic acids. Fermentation significantly increased (P < 0.05) the level of conversion of isoflavones into biologically active aglycones, including diadzein, genistein, and glycetein. Our results show that fermenting calcium-fortified soymilk with the selected probiotics can potentially enhance the calcium bioavailability of calcium-fortified soymilk due to increased calcium solubility and bioactive isoflavone aglycone enrichment.

Endogenous β-glucosidase and β-galactosidase activities from selected probiotic micro-organisms and their role in isoflavone biotransformation in soymilk

AIM

To compare endogenous beta-glucosidases and beta-galactosidases for hydrolysis of the predominant isoflavone glycosides into isoflavone aglycones in order to improve biological activity of soymilk.

METHODS AND RESULTS

beta-glucosidase and beta-galactosidase activities of probiotic organisms including Lactobacillus acidophilus ATCC 4461, Lactobacillus casei 2607 and Bifidobacterium animalis ssp. lactis Bb12 in soymilk were evaluated and correlated with the increase in concentration of isoflavone aglycones during fermentation. The concentrations of isoflavone compounds in soymilk were monitored using a Varian model high-performance liquid chromatography (HPLC) with an amperometric electrochemical detector. In all micro-organisms, beta-glucosidase activity was found greater than that of beta-galactosidase. There was an increase in the aglycone concentration with incubation time because of the apparent hydrolytic action on isoflavone glycosides. Aglycone concentration in the soymilk with L. acidophilus 4461, L. casei 2607 and B. animalis ssp. lactis Bb12, increased by 5.37-, 5.52- and 6.10-fold, respectively, after 15 h of fermentation at 37 degrees C. The maximum hydrolytic potential was also observed at 15 h of fermentation for the three micro-organims coinciding with peak activities of the two enzymes.

CONCLUSIONS

beta-glucosidase activity was more than 15 times higher than beta-galactosidase activity in soymilk for each of the micro-organisms during fermentation. beta-glucosidase played a greater role in isoflavone glycoside hydrolysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Screening for beta-glucosidase and beta-galactosidase activities among probiotics in soymilk is important for the improvement of biological activity of soymilk and in the selection of micro-organisms for use in the growing industry of functional foods and beverages.

A comparison of changes in the transformation of isoflavones in soymilk using varying concentrations of exogenous and probiotic-derived endogenous ?-glucosidases

AIMS

To compare endogenous and exogenous beta-glucosidases for the hydrolysis of the predominant isoflavone glucosides in soymilk in order to improve the biological activity.

METHODS AND RESULTS

beta-glucosidase activity of probiotic organisms, including Bifidobacterium animalis ssp. lactis Bb12, Lactobacillus acidophilus ATCC 4461 and Lactobacillus casei 2607 in soymilk, was evaluated and was related to the increase in the concentration of isoflavone aglycones during fermentation. The concentrations of isoflavone compounds in soymilk were monitored using a Varian model HPLC with an Amperometric electrochemical detector. The aglycone composition, also known as aglycone equivalent ratio, has been considered to be important for the delivery of health benefits of isoflavones, and was monitored during the fermentation of soymilk. Comparison of the hydrolytic effectiveness of both exogenous and endogenous enzyme during 4-h incubation in soymilk was conducted using the Otieno-Shah (O-S) index. Results showed that exogenous enzyme exhibited faster rate of isoflavone glucoside hydrolysis than that by endogenous enzyme. Highest O-S indices were obtained after 4, 3 and 2 h of incubation with enzyme solution having beta-glucosidase activity of 0.288 U ml(-1), 0.359 U ml(-1) and 0.575 U ml(-1), resulting into aglycone concentration increments of 5.87-, 6.07- and 5.94-fold, respectively. Conversely, aglycone concentration in the soymilk with B. animalis ssp. lactis Bb12, L. casei 2607 and L. acidophilus 4461 increased by 3.43-, 2.72- and 3.03-fold, respectively, after 4 h of fermentation at 37 degrees C. In addition, the O-S index of endogenous enzyme was much lower than that of the exogenous enzyme over the same 4-h incubation period. Optimum aglycone equivalent ratios coincided with highest O-S indices and highest aglycone concentrations in soymilk hydrolysed with exogenous enzyme. The same correlation of O-S indices and highest aglycone concentrations occurred for endogenous enzyme during the 24 h of fermentation.

CONCLUSIONS

Obtaining highest aglycone concentration and optimum aglycone equivalent ratio could provide a critical beginning point in clinical trials for the realization of unique health benefits of soy isoflavones.

SIGNIFICANCE AND IMPACT OF THE STUDY

Screening for beta-glucosidase activities of probiotics in soymilk and comparing their hydrolytic potentials with that of exogenous beta-glucosidase could find wide applications in the development of different aglycone-rich functional soy beverages.