Isoflavone Aglycones Research Articles

Effect of storage and heat treatment on the levels of bioactive flavonoids produced in fermented soy beverages

Among vegetable functional products, soy-based foods stand out for their high content in protein and flavonoids, mainly isoflavones. The fermentation of soy beverages with selected bacterial strains is a way to obtain a product enriched in isoflavone aglycones, alongside with other isoflavone derivates and other bioactive flavonoids. Two bacterial strains with high activity on the transformation of these compounds, Limosilactobacillus mucosae INIA P508 and Bifidobacterium pseudocatenulatum INIA P815, were tested for the fermentation of soy beverage. Both strains produced high concentration of the aglycones daidzein and genistein, in addition to a significant increase (P < 0.01) of glycitein, O-desmethylangolensin, 6″-hydroxy-O-desmethylangolensin, tetrahydrodaidzein and other flavonoid aglycones such as kaempferol, naringenin and luteolin. Two alternatives to conserve the developed functional beverages were explored, cold storage and thermal treatment. Refrigeration did not affect the concentration of isoflavones, even observing an increase in aglycones. Similarly, the thermal treatment and further room temperature storage did not reduce the amounts of daidzein and genistein. Therefore, both strains could be used for the development of soy beverages enriched in bioactive isoflavones and other bioactive flavonoids which would maintain their concentrations in refrigeration or at room temperature after heat treatment.

Nutritional evaluation and transcriptome analyses of short-time germinated seeds in soybean (Glycine max L. Merri.)

Germination is a common practice for nutrition improvement in many crops. In soybean, the nutrient value and genome-wide gene expression pattern of whole seeds germinated for short-time has not been fully investigated. In this study, protein content (PC), water soluble protein content (WSPC), isoflavone compositions were evaluated at 0 and 36 h after germination (HAG), respectively. The results showed that at 36HAG, PC was slightly decreased (P > 0.05) in ZD41, J58 and JHD, WSPC and free isoflavone (aglycones: daidzein, genistein, and glycitein) were significantly increased (P < 0.05), while total isoflavone content was unchanged. Transcriptomic analysis identified 5240, 6840 and 15,766 DEGs in different time point comparisons, respectively. GO and KEGG analysis showed that photosynthesis process was significantly activated from 18HAG, and alternative splicing might play an important role during germination in a complex manner. Response to hydrogen peroxide (H2O2) was found to be down regulated significantly from 18 to 36HAG, suggesting that H2O2 might play an important role in germination. Expression pattern analysis showed the synthesis of storage proteins was slowing down, while the genes coding for protein degradation (peptidase and protease) were up regulated as time went by during germination. For genes involved in isoflavone metabolism pathway, UGT (7-O-glucosyltransferase) coding genes were significantly up regulated (40 up-DEGs vs 27 down-DEGs), while MAT (7-O-glucoside-6′′-O-malonyltransferase) coding genes were down regulated, which might explain the increase of aglycones after germination. This study provided a universal transcriptomic atlas for whole soybean seeds germination in terms of nutrition and gene regulation mechanism.

Estimatiom of the effect of plasma and radio wave treatment of seeds on the content of isoflavones in soybean leaves (Glycine max L.)

The effect of treatment of seeds with a high-frequency (HF) electromagnetic field and HF plasma on the qualitative and quantitative composition of isoflavones in the leaves of soybeans in the phases of branching, flowering and seed filling has been studied.It was found that the treatment of soybean seeds leads to a change in the quantitative content of isoflavone aglycones in the leaves, but does not affect their qualitative composition. The maximum content of daidzein was found in the flowering phase when the seeds were treated with an electromagnetic field, genistein ‒ in the branching phase, while a particularly high content of this component was found in plants whose seeds were treated with plasma.

Integrated Metabolomics and Volatolomics for Comparative Evaluation of Fermented Soy Products.

Though varying metabolomes are believed to influence distinctive characteristics of different soy foods, an in-depth, comprehensive analysis of both soluble and volatile metabolites is largely unreported. The metabolite profiles of different soy products, including cheonggukjang, meju, doenjang, and raw soybean, were characterized using LC-MS (liquid chromatography–mass spectrometry), GC-MS (gas chromatography–mass spectrometry), and headspace solid-phase microextraction (HS-SPME) GC-MS. Principal component analysis (PCA) showed that the datasets for the cheonggukjang, meju, and doenjang extracts were distinguished from the non-fermented soybean across PC1, while those for cheonggukjang and doenjang were separated across PC2. Volatile organic compound (VOC) profiles were clearly distinct among doenjang and soybean, cheonggukjang, and meju samples. Notably, the relative contents of the isoflavone glycosides and DDMP (2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4-one) conjugated soyasaponins were higher in soybean and cheonggukjang, compared to doenjang, while the isoflavone aglycones, non-DDMP conjugated soyasaponins, and amino acids were significantly higher in doenjang. Most VOCs, including the sulfur containing compounds aldehydes, esters, and furans, were relatively abundant in doenjang. However, pyrazines, 3-methylbutanoic acid, maltol, and methoxyphenol were higher in cheonggukjang, which contributed to the characteristic aroma of soy foods. We believe that this study provides the fundamental insights on soy food metabolomes, which determine their nutritional, functional, organoleptic, and aroma characteristics.

Antioxidant Activity of Isoflavone Aglycone from Fermented Black Soymilk Supplemented with Sucrose and Skim Milk Using Indonesian Indigenous Lactic Acid Bacteria

Background and Objective: Black soybean (Glycine max (L.) Merr.) Detam-1 variety includes high quantities of isoflavone majorly in glucoside form; in which, the biochemical antioxidant activity was lower than that in isoflavone aglycone form. Fermentation by lactic acid bacteria can increase antioxidant activity and isoflavone aglycone of black soymilk. However, the biochemical ability is strain-dependent and sucrose or skim milk supplementation during processing may affect this ability. The objective of the current study was to investigate antioxidant properties of the fermented black soymilk and fermented black soymilk supplemented with 2% sucrose or skim milk using three Indonesian indigenous lactic acid bacteria, namely Lactobacillus plantarum WGK 4, Streptococcus thermophilus Dad 11 and Lactobacillus plantarum Dad 13. Furthermore, cell growth and acid production were investigated. Material and Methods: Fermentation of black soymilk and black soymilk supplemented with 2% sucrose or skim milk was carried out using three indigenous lactic acid bacteria at 37 °C for 18 h. Viable cell, pH, titratable acidity, β-glucosidase activity, isoflavone aglycone, total phenolic content and antioxidant activity of black soymilk were assessed at the beginning of the experiment and after 18 h of fermentation. Results and Conclusion: Results showed that all strains could grow (9 log CFU ml-1) and produce acid in black soymilk and black soymilk supplemented with 2% sucrose or skim milk. Fermentation increased isoflavone aglycone through β-glucosidase activity, which resulted in increased total phenolic content and antioxidant activity. Fermented black soymilk with no sucrose or skim milk exhibited the highest β-glucosidase activity (19.66-21.54 mU ml-1), daidzein formation (62-74%), genistein formation (67-80%) and antioxidant capacity (32.81-38.47%). All three lactic acid bacteria strains enhanced antioxidant activity and isoflavone aglycone of the black soymilk. Sucrose or skim milk addition did not affect the cell growth but increased acid production and decreased β-glucosidase activity and isoflavone aglycone formation. These three lactic acid bacteria included similar abilities to enhance antioxidant activity and isoflavone aglycone formation in fermented black soymilk.

Optimization of Fermentation Process for Improving Soy Isoflavones Aglycone Content in Bean Dregs by Lactobacillus plantarum PL70a

Aglycone-type soy isoflavones have higher biological activity than glycoside-type soy isoflavones. Bean dregs are rich in glycoside-type soy isoflavones. In order to improve the biological activity of soy isoflavones in bean dregs, the Lactobacillus plantarum PL70a was screened and the fermentation process of converting glycoside-type soy isoflavones into aglycone-type in bean dregs was optimized by single-factor experiments and the response surface methodology. The optimal fermentation process was as follows: (NH4)2SO4 was added in an amount of 0.17%, glucoamylase was added in an amount of 0.87%, inoculation amount was 17%, sucrose was added in an amount of 1.3%, and fermentation time was 3 days. Under this process, the content of aglycone-type soy isoflavones in bean dregs significantly increased. Trypsin inhibitors and antigen proteins were almost removed. The fermentation process provides a good reference for the low-cost processing of high-quality soy isoflavone aglycone food.

Potensi Formulasi Self Microemulsifying Drug Delivery System (SMEDDS) Ekstrak Biji Kedelai (Glycine soja) Terhadap Penurunan Kolesterol pada Penyakit Jantung Koroner

Background: Coronary heart diseases (CHD) is a disorder that caused by blockage of coronary arteries due to the process of atherosclerosis which disrupts the blood supply to the heart muscle. According to Sample Registration System (SRS) Indonesia in 2014, CHD is a second highest cause of death after stroke that is 12,9% of all cause of death in Indonesia. Therefore, this study aims to examining the effect of soybean extract encapsulated with Self Microemulsifying Drug Delivery System (SMEDDS) on LDL levels in coronary heart model rats. Based on various study, isoflavone aglycone genistein is the main flavonoid in soybean seed that has potential as an antioxidant. To increase bioavailability of aglycone isoflavones, a SMEDDS is needed. In this regard, the purpose of this reseach is to examine the potential of soybean seed (Glycine soja) extract to reduced cholesterol in CHD.Methods: The method used is a literature review with literature sources in the form of relevant articles from the search engines, namely Google Scholar, Pubmed, ScienceDirect, and Research Gate. Inclusion criteria included journals containing the keywords “soybean (Glycine soja)”, “Coronary Heart Disease”, “SMEDDS”, and “genistein isoflavone aglycone”.Result: Isoflavone aglycone as an potential antioxidant that is able to bind free radicals and and also lowering LDL, Triglycerides, and glucose levels in hyperglycemic states and increasing HDL.Conclusion : Soybean seed extract with SMEDDS encapsulation have a potential to decrease LDL level in coronary heart disease.

The expression of β-glucosidase during natto fermentation increased the active isoflavone content

Natto is a traditional food fermented by Bacillus subtilis natto with soybean as raw material and contains a variety of active substances, especially flavonoid. Flavonoids in soybean usually exist in the form of inactive glycosides, which can only play biological activities when being decomposed into free isoflavone aglycone by β-glucosidase. In this study, the relationship between the activity of β-glucosidase, the expression of β-glucosidase coding genes and the content and structure of active isoflavones in Bacillus natto was systematically elucidated for the first time. In this research, more than 70 kinds of flavonoids have been identified and the active isoflavones in natto increased by 2.2 times compared with soybeans. Furthermore, the activity of β-glucosidase and the expression level of its coding genes were both increased, which laid a theoretical foundation for further understanding the active substances and physiological functions of natto and the application of β-glucosidase in food industry.

Metabolomic-Based Comparison of Traditional and Industrial Doenjang Samples with Antioxidative Activities.

Numerous varieties of doenjang are manufactured by many food companies using different ingredients and fermentation processes, and thus, the qualities such as taste and flavor are very different. Therefore, in this study, we compared many products, specifically, 19 traditional doenjang (TD) and 17 industrial doenjang (ID). Subsequently, we performed non-targeted metabolite profiling, and multivariate statistical analysis to discover distinct metabolites in two types of doenjang. Amino acids, organic acids, isoflavone aglycones, non-DDMP (2,3-dihydro-2,5-dihydroxy-6-methyl-4H-pyran-4- one) soyasaponins, hydroxyisoflavones, and biogenic amines were relatively abundant in TD. On the contrary, contents of dipeptides, lysophospholipids, isoflavone glucosides and DDMP-conjugated soyasaponin, precursors of the above-mentioned metabolites, were comparatively higher in ID. We also observed relatively higher antioxidant, protease, and β-glucosidase activities in TD. Our results may provide valuable information on doenjang to consumers and manufacturers, which can be used while selecting and developing new products.

Soybean extract modified by Aspergillus awamori stimulates a greater collagen-I synthesis in the intracellular matrix of human fibroblasts.

Aglycone isoflavones are estrogen-like bioactive compounds found in low amounts in soybean, which are increased by biotransformation processes. This study investigated two biotransformation processes of soybean extracts with Aspergillus awamori fungus, evaluating aglycone content and capability of stimulation of collagen-I deposition. Isoflavones were quantified via HPLC; cytotoxicity of biotransformed extracts toward mouse and human fibroblasts was evaluated via NRU and apoptosis/necrosis assays; and collagen-I deposition was measured through Western blot, immunofluorescence, and immunoassay. BSE-2 was the biotransformed soybean extract with the highest aglycone content and did not decrease viability or demonstrated cytotoxicity to either L929 or HDFa cells. BSE-2, at the optimal concentration of 1.33μg/mL, increased substantially collagen-I amount in HDFa intracellular matrix compared to non-biotransformed soybean extract (NBSE) and immunoassay demonstrated that the extracellular deposition was mostly inhibited by BSE-2 concentrations, except at 1.33μg/mL. Hence, biotransformed soybean extract by the enzymatic filtrate of Aspergillus awamori fungus demonstrated a high nutricosmetic potential, showing safeness and effective collagen-I augmentation.

Effects of enzyme-assisted extraction on the profile and bioaccessibility of isoflavones from soybean flour

The effects of enzymatic extraction strategies on extractability, bioconversion, and bioaccessibility of biologically active isoflavone aglycones, total phenolic content, and antioxidant activity of aqueous extracts from full-fat soy flour were evaluated. Protease, tannase, and cellulase enzymes were used individually or in combination. Except for the protease treatment, all enzymatic treatments increased the extraction of biologically active isoflavones (daidzein and genistein) compared with the control. The use of a mixture of protease, tannase, and cellulase resulted in increased extractability and/or bioconversion of aglycones from soy flour, indicating a synergistic effect amongst the enzymes. Daidzein and genistein concentrations increased from 29.0 to 158.2 μg/g and from 27.0 to 156.5 μg/g (compared to the control), respectively. Furthermore, enzymatic extraction followed by in vitro gastrointestinal digestion significantly increased the bioaccessibility of isoflavone aglycones, total phenolic content (by 22–45%), and antioxidant activity (by 15–22%) of the extracts. These results demonstrate that enzyme selection is an efficient strategy to maximize the extraction, bioconversion, and bioaccessibility of bioactive isoflavones from soy flour, which could contribute to health benefits associated with the consumption of soy-rich products.

Optimization of the Bioactivation of Isoflavones in Soymilk by Lactic Acid Bacteria

Soybeans and soy-based products contain isoflavones which can be used for nutraceutical and medical applications. In soybeans and in unfermented soy foods, isoflavones are normally present as glycosides. Isoflavone glycosides can be enzymatically converted to isoflavone aglycones, thus releasing the sugar molecule. The effective absorption of isoflavones in humans requires the bioconversion of isoflavone glycosides to isoflavone aglycones through the activity of the enzyme β-glucosidase. The objective was to assess the capacity of 42 bacterial strains (belonging to Lactobacillus, Streptococcus and Enterococcus) to produce β-glucosidase activity. The strain that showed the highest β-glucosidase activity (Lactobacillus plantarum 128/2) was then used for the optimization of the bioconversion of genistin and daidzin present in commercial soymilk to their aglycone forms genistein and daidzein. The contribution of process parameters (temperature, inoculum size, time) to the efficiency of such bioactivation was tested. Lactobacillus plantarum 128/2 was able to completely bioactivate soymilk isoflavones under the following conditions: 25 °C temperature, 2% inoculum size and 48 h process time. These results confirm the suitability of lactic acid bacteria for the bioactivation of isoflavones present in soymilk and provide an interesting candidate (L. plantarum 182/2) for food industries to perform this transformation.

Effects of Solid-State Fermentation with Eurotium cristatum YL-1 on the Nutritional Value, Total Phenolics, Isoflavones, Antioxidant Activity, and Volatile Organic Compounds of Black Soybeans

In this study, black soybean was firstly processed by solid-state fermentation (SSF) with a probiotic fungus Eurotium cristatum YL-1. The effect of SSF on the nutritional components (including proximate, amino acids, minerals, and fatty acids), total phenolics, isoflavones, antioxidant activity, and volatile organic compounds of black soybeans were revealed. Results of this work demonstrated that black soybean processed by SSF with E. cristatum greatly increased the contents of protein, essential amino acids, and some minerals (e.g., calcium, phosphorus, and magnesium). GC results revealed that more than 80% of the total lipids from both fermented and non-fermented black soybeans were unsaturated fatty acids, and SSF influenced the fatty acids composition. Higher contents of total phenolics and aglycone isoflavones (i.e., genistein, daidzein, and glycitein) of fermented black soybeans were achieved by SSF. Furthermore, SSF with E. cristatum considerably augmented the ferric reducing antioxidant power, scavenging effects against ABTS·+ and DPPH radical, reducing power, and chelating ability of black soybeans, which evaluated with various polarity solvent extracts. HS-GC-IMS analysis detected a total of 66 volatile compounds in FBS and BS, and 56 volatile organic compounds were successfully identified. The intensities of main volatile compounds (i.e., 10 esters, 11 alcohols, and 19 aldehydes) differed remarkably by fermentation with E. cristatum. The intensities of seven alcohols and nine aldehydes considerably decreased, whereas higher levels of esters were achieved by SFF. Thus, our results confirmed that black soybeans processed by SSF with E. cristatum is a promising approach to substantially improve its nutritional value, flavor characteristics, and biological effect, and might have great potential in the development of new functional foods or be used as a new nutritional ingredient applied in food design.

Cyclodextrin-Assisted Extraction Method as a Green Alternative to Increase the Isoflavone Yield from Trifolium pratensis L. Extract.

Trifolium pratense L. is receiving increasing attention due to the isoflavones it contains, which have been studied for their benefits to human health. A common problem with isoflavone aglycones is a rather low water solubility and limited pharmaceutical applications. The use of excipients, such as cyclodextrins in the production of isoflavone rich extracts, could become one of the new strategies for the extraction of target compounds. The aim of this study was to evaluate an eco-friendly method using the effects of α-, β- and γ-cyclodextrins for isoflavone solubilization in plant extracts in comparison to a standard extract without excipients. Extractions of red clover were prepared using ultrasound-assisted combined with thermal hydrolysis and heat reflux. It was determined that cyclodextrins significantly increased the isoflavones aglycone yields. By increasing cyclodextrins in the extraction media from 1 to 5%, the daidzin concentration increased on average by 1.06 (α-cyclodextrins), 1.4 (β-cyclodextrins) and 1.25 (γ-cyclodextrins) times. Genistein concentration increased using α- and γ-cyclodextrins (1.28 and 1.12 times, α- and γ-cyclodextrins, respectively), but decreased using β-cyclodextrins. The results showed that the cyclodextrin-assisted extraction enhanced the yields of isoflavones from red clover, which suggests using cyclodextrins as a green alternative and a cost-effective method to increase its pharmaceutical application.

Biotransformation of soy whey into a novel functional beverage by Cordyceps militaris SN-18

Soy whey, a liquid nutritional by-product of soybean manufacture, is rich in proteins, oligosaccharides and isoflavones. Soy whey can be used to produce functional beverages, instead of discarding it as a waste. In this study, unfermented soy whey (USW) and Cordyceps militaris SN-18-fermented soy whey (FSW) were investigated and compared for their physicochemical and functional properties by high performance liquid chromatography (HPLC) and DNA damage assay. Results show that C. militaris SN-18 fermentation could increase the contents of essential amino acids, total phenolic and flavonoid and isoflavone aglycones and eliminate the oligosaccharides in soy whey. Furthermore, C. militaris SN-18 could significantly enhance the ABTS radical scavenging ability, reducing power and ferric reducing power of soy whey, and its fermented products could prominently attenuate Fenton reaction-induced DNA damage. These findings indicate that soy whey can potentially be converted into a novel soy functional beverage by C. militaris SN-18 fermentation.Graphical abstract

STUDY ON ANTIOXIDANT ACTIVITY OF PHYTOESTROGEN EXTRACTS FROM SOY GERM

Soy germ is one of the richest phytoestrogen sources and thus has many benefits for health such as improving bone density, cardiovascular health, cancer prevention, and menopausal treatment. In addition, phytoestrogens are reported to act as antioxidants, removing reactive oxygen species and thereby preventing oxidative damage in living tissue. Phytoestrogens in soy germ include isoflavone compounds and their derivatives: daidzein, genistein, glycitein, daidzin, genistin, glycitin, acetyl daidzin, acetyl genistin, acetyl glycitin, malonyl daidzin, malonyl genistin, malonyl glycitin. Isoflavones aglycone forms comprise only about 2-5% of total isoflavones, however, they express more biological effects than the others. The objective of this study was to compare the antioxidant activity among three extracts: purified isoflavone aglycone extract, crude isoflavone aglycone extract and total phytoestrogen extract. The IC50 value of DPPH free radical scavenging capacity of purified isoflavone aglycone extract, crude isoflavone aglycone extract and total phytoestrogen extract were 0.763 ± 0.016; 3.345 ± 0.076; 6.142 ± 0.050 mg/ml, respectively. The IC50 value of reducing power activity of purified isoflavone aglycone extract, crude isoflavone aglycone extract and total phytoestrogen extract were 1.248 ± 0.024; 3.961 ± 0.172; 9.385 ± 0.272 (mg/ml). As our result, the ranking order of the antioxidant activity (from highest to lowest level) was purified isoflavone aglycone extract &gt; crude isoflavone aglycone extract &gt; total phytoestrogens extract.

Evaluation of Semi-Solid-State Fermentation of Elaeocarpus serratus L. Leaves and Black Soymilk by Lactobacillus plantarum on Bioactive Compounds and Antioxidant Capacity.

Elaeocarpus serratus L. leaves (EL) containing phenolic compounds and flavonoids, including myricitrin with pharmacological properties, could be valorized as nutritional additive in foods. In this study, the semi-solid-state fermentation of EL and black soymilk (BS) by Lactobacillus plantarum BCRC 10357 was investigated. Without adding EL in MRS medium, the β-glucosidase activity of L. plantarum quickly reduced to 2.33 ± 0.15 U/mL in 36 h of fermentation; by using 3% EL, the stability period of β-glucosidase activity was prolonged as 12.94 ± 0.69 U/mL in 12 h to 13.71 ± 0.94 in 36 h, showing positive response of the bacteria encountering EL. Using L. plantarum to ferment BS with 3% EL, the β-glucosidase activity increased to 23.78 ± 1.34 U/mL in 24 h, and in the fermented product extract (FPE), the content of myricitrin (2297.06 μg/g-FPE) and isoflavone aglycones (daidzein and genistein, 474.47 μg/g-FPE) at 48 h of fermentation were 1.61-fold and 1.95-fold of that before fermentation (at 0 h), respectively. Total flavonoid content, myricitrin, and ferric reducing antioxidant power in FPE using BS and EL were higher than that using EL alone. This study developed the potential fermented product of black soymilk using EL as a nutritional supplement with probiotics.

Anti-aging effect of Lactobacillus plantarum HFY09-fermented soymilk on D-galactose-induced oxidative aging in mice through modulation of the Nrf2 signaling pathway

Abstract After soymilk fermented by L. plantarum HFY09, the bound soybean isoflavones content was reduced, but free soybean isoflavones and peptides increased. In vivo results show that L. plantarum HFY09-fermented soymilk increased the T-SOD, MDA, GSH-Px, GSH, CAT, and NO in the serum, liver, and brain tissues of mice. The aforementioned soymilk also increased the Col I and hyaluronic acid, and reduced the contents of Col III, H2O2, and AGEs in the skin. L. plantarum HFY09-fermented soymilk upregulated Nrf2, HO-1, NOS1, NOS3, SOD1, SOD2, CAT, Nqol, Gclm expression in the liver and the spleen, reduced the NOS2 expression, and upregulated SOD1 SOD2, CAT, GSH-Px, TIMP1, and TIMP2 expression in skin, downregulated MMP3, and MMP9 expression. These results show that L. plantarum HFY09-fermented soymilk could effectively alleviate aging in D-galactose-induced aging mice, the mechanism may be related to the activation of Nrf2 signaling pathway by soy isoflavone aglycone and small molecule peptides.

Production of isoflavones-enriched soy yogurt through soymilk fermentation using probiotic bacteria

Background and objective Fermented soy products were regarded as healthy foods and hence are considered an essential part of the diet. Lactic acid bacteria isolated from naturally fermented Egyptian food products were screened for their ability to produce β-glucosidase, isoflavone aglycone, phenolics, and antioxidant activity during the formation of soy yogurt. The present research is a preliminary attempt to ascertain soy yogurt production by different strains of lactic acid bacteria and their efficacy for the production of the aforementioned products. Materials and methods A total of 16 probiotic lactic acid bacteria were used for the preparation of soy yogurt and tested for their probiotic properties. Soymilk was prepared and inoculated (1% v/v) with the probiotic strains previously activated in the MRS medium. After fermentation, cell viability, pH, titratable acidity, total phenolic compounds concentration, antioxidant activity, isoflavones aglycone (daidzein and genistein), and extracellular and cell membrane-bound β-glucosidase activity were determined. Results and conclusion A total of 16 probiotic lactic acid bacteria were used for the preparation of soy yogurt. The final pH of the fermented soymilk ranged from 4.92 to 6.6, and their titratable acidity (lactic acid %) ranged from 0.5 to 0.99%. Changes in β-glucosidase, isoflavone aglycone, total phenolics content, and antioxidant activity during the formation of soy yogurt were determined. All bacterial isolates showed positive cell-bound and extracellular β-glucosidase. Their activities ranged from 308.65 to 553 mU/ml. The Lactobacillus strains showed lower extracellular than their cell-bound β-glucosidase, and the opposite was true for the other group. An increase in the content of isoflavone aglycones in soy yogurt could be achieved by aging with bacterial fermentation. Soymilk fermented with Lactobacillus strains showed the highest bioconversion of isoflavone glucosides into isoflavone aglycones than other strains, although they produced less β-glucosidase enzymes. The antioxidant activity is related to changes in total phenolics. All microorganisms were able to increase the total phenols, whereas some Lactobacillus strains were unable to release more phenols compared with unfermented soymilk.

Effect of Kefir on Soybean Isoflavone Aglycone Content in Soymilk Kefir.

Kefir is a traditional fermented milk originating in the Caucasus area and parts of Eastern Europe. In this study, the kefir culture, which is modified upon the addition of lactic acid bacteria (LAB) cells, specifically for soymilk kefir fermentation with the highest capacity of isoflavone biotransformation, was successfully produced, and the metagenomics composition of soymilk or milk fermented using these kefir cultures was investigated. The metagenome analysis showed that the microbiota of kefir in M-K (milk inoculated with kefir), SM-K (equal volumes of soymilk and milk inoculated with kefir), and S-K (pure milk inoculated with kefir) were related to the addition of soymilk or not. Furthermore, the HPLC chromatogram revealed that Guixia 2 (Guangzhou, China) may be a good source of soymilk kefir fermentation due to its high isoflavone aglycone content (90.23 ± 1.26 μg/g in daidzein, 68.20 ± 0.74 μg/g in genistein). Importantly, the starter culture created by adding 1.5 g probiotics (Biostime®, Guangzhou, China) to Chinese kefir showed a significant increase in the levels of isoflavone aglycones (72.07 ± 0.53 μg/g in isoflavone aglycones). These results provided insight into understanding the suitable soybean cultivar and starter cultures, which exhibit promising results of isoflavone biotransformation and flavor promotion during soymilk kefir fermentation.