β-Glucosidases from Soybeans Hydrolyze Daidzin and Genistin

β-Glucosidases which hydrolyze isoflavone glucosides, daidzin and genistin, were partially purified from soybean cotyledon. Three iso-forms of β-glucosidases (A,B,C) were separated on a CM-Sephadex C-50 ion exchange column. β-Glucosidase-B and C brought about nearly all of the hydrolyzing action on daidzin and genistin. β-Glu-cosidase-B and C were further purified with gel-filtration chromatog-raphy, and the partially purified enzymes were characterized at pH 5.0 and 45°C, (optimum conditions). Adding the β-glucosidase-B and C to soymilk at 45°C, both enzymes hydrolyzed daidzin and genistin and caused an increase in aglycones daidzein and genistein.     

HYDROLYSIS OF ISOFLAVONE PHYTOESTROGENS IN SOYMILK FERMENTED BY LACTOBACILLUS AND BIFIDOBACTERIUM COCULTURES

This study evaluated the hydrolysis of isoflavones in soymilk fermented at 37C for 48 h by four different Lactobacillus and Bifidobacterium cocultures. The hydrolysis of isoflavone β-glucosides significantly increased ( P <  0.05) the bioactive aglycones from 36 to over 90% of total isoflavones in soymilk fermented with any of the four Lactobacillus and Bifidobacterium cocultures as compared with unfermented soymilk. Compared with three other cocultures of Lactobacillus and Bifidobacterium, fermentation of soymilk with the Lactobacillus paracasei/Bifidobacterium longum cocultures yielded better isoflavone hydrolytic potential (Otieno-Shah index) and the highest β-glucosidase activity after 12 h of incubation.

PRACTICAL APPLICATIONS

Isoflavones are known as phytoestrogens because they are present in soy products and have estrogen-like activity. During fermentation, the majority of glucoside isoflavones in soymilk are converted to bioactive aglycones via microorganism-derived β-glucosidase. In human intestines, aglycone isoflavones are absorbed faster and in greater amounts than their glucosides. Using probiotic Lactobacillus and Bifidobacterium cocultures to ferment soymilk efficiently increases the bioactive aglycone concentrations. Hence, fermenting soymilk with this coculture could enhance the nutritional value of the product.     

Isoflavone phytoestrogen degradation in fermented soymilk with selected beta-glucosidase producing L. acidophilus strains during storage at different temperatures

Soymilk fermented with 3 selected Lactobacillus acidophilus strains were stored at various temperatures (-80 degrees C, 4 degrees C, 25 degrees C and 37 degrees C) for 8 weeks and the concentration of isoflavones determined weekly using RP-HPLC. The decreasing concentration of isoflavones in soymilk during storage due to degradation was found to fit the first order kinetics model. Isoflavone aglycones as well as isoflavone glucosides largely appeared to be stable during storage (P<0.01). Interestingly, the aglycone forms showed much smaller degradation as compared to glucoside forms at all the storage temperatures studied. Of the isoflavone aglycones, daidzein was found to be the most stable followed by genistein, while glycitein was least stable. Isoflavone aglycones such as glycitein, daidzein and genistein showed smaller degradation constants in fermented soymilk at lower storage temperatures (-80 degrees C and 4 degrees C) and higher degradation constants at higher storage temperatures (25 degrees C and 37 degrees C) with each strain. In contrast, glucosides glycitin and daidzin showed higher degradation at lower storage temperatures (-80 degrees C and 4 degrees C) and lower degradation at higher storage temperatures (25 degrees C and 37 degrees C). Storage temperature was therefore found to be very important in regulating the rate of degradation soy isoflavones in fermented soymilk.     

Hydrolysis of soybean isoflavone glycosides by a thermostable β-glucosidase from Paecilomycesthermophila

The β-glucosidase from Paecilomyces thermophila J18 was found to be capable of hydrolysing daidzin and genistin in a previous study. This report further evaluated the thermostability and hydrolysis of soybean isoflavone glycosides. The enzyme was found to be very stable at 50 °C, and retained more than 95% of its initial activity after 8 h at 50 °C. It converted isoflavone glycosides, in soybean flour extract and soybean embryo extract, to their aglycones, resulting in more than 93% of hydrolysis of three isoflavone glycosides (namely, daidzin, genistin and glycitin) after 4 h of incubation. Also, addition of the β-glucosidase greatly increased the contents of isoflavone aglycones in the suspended soybean flour and soymilk. The results indicate that the thermostable β-glucosidase may be used to increase the isoflavone aglycones in soy products. This is the first report on the potential application of fungal β-glucosidases for converting isoflavone glycosides to their aglycones in soy products.     

Transformation of isoflavone phytoestrogens during the fermentation of soymilk with lactic acid bacteria and bifidobacteria

In the present study, soymilk is fermented with lactic acid bacteria (Streptococcus thermophilus BCRC 14085, Lactobacillus acidophilus BCRC 14079) and bifidobacteria (Bifidobacterium infantis BCRC 14633, B. longum B6) individually, and in combination. The change in the content of various isoflavones (aglycones, glucoside, acetyl- and malonyl-glucosides) and the beta-glucosidase activity in soymilk during fermentation is investigated. It is observed that fermented soymilk contains a lower total isoflavone content (81.94-86.61 microg/ml) than soymilk without fermentation (87.61 microg/ml). Regardless of starter organism employed, fermentation causes a major reduction in the contents of glucoside, malonylglucoside and acetylglucoside isoflavones along with a significant increase of aglycone isoflavones content. The level of change in the content of various isoflavones and beta-glucosidase activity after fermentation varies with the starter organism. Among all the fermented soymilks tested, soymilk fermented with S. thermophilus showed the highest beta-glucosidase activity and the greatest increase in the contents of aglycones. The percentage of daidzein, genistein and glycitein to total isoflavone content in S. thermophilus-fermented soymilk increases from an initial 14.24%, 6.89% and 2.45%, respectively, to 36.20%, 28.80% and 12.44% after 24h of fermentation. Finally, the increase of aglycones and decrease of glucoside isoflavones during fermentation coincides with the increase of beta-glucosidase activity observed in fermented soymilk.     

大豆异黄酮组分在腐乳后酵过程中的变化

研究腐乳后酵过程中大豆异黄酮组成和含量的变化。结果表明：在腐乳后酵过程中,大豆异黄酮总含量呈下降趋势;当食盐含量较低时,糖苷(daidzin 和genistin)分解较快;大豆异黄酮糖苷形式(daidzin 和genistin)转化为苷元形式(daidzein 和genistein)。说明腐乳后酵有效提高了大豆异黄酮的生物活性。     

Bioactive action of β‐glucosidase enzyme of Bifidobacterium longum upon isoflavone glucosides present in soymilk

Bioconversion of isoflavone glucosides and antioxidant activity by probiotic strain (Bifidobacterium longum) during soymilk fermentation was investigated, as well as partial characterisation of the produced enzyme β‐glucosidase. The enzyme has higher affinity for genistin than for other substrates assayed. Maximum activity occurred at 42 °C and at pH 6.0; keeping 70–80% of activity for 60 days stored at low temperatures. Bifidobacterium longum grew well in soymilk (8.26 log CFU mL^?1 and pH of 3.9 at 24 h) and were produced in good quantities of organic acids. High hydrolysis degree of isoflavone glucosides (81.2%) was observed at 24 h. Enhancements in bioactivity were assessed in fermented soymilk by monitoring the radical‐scavenging activity, antioxidant activity and DNA protective action. The use of probiotic Bifidobacterium strain as β‐glucosidase producer increased bioactive isoflavone content and demonstrated that this enzyme plays a key role in the bioavailability of soymilk isoflavones, reducing the bioconversion time compared to other studies.     

Effect of Lactic Acid Fermentation on Enrichment of Antioxidant Properties and Bioactive Isoflavones in Soybean

ABSTRACT: The antioxidant properties of 80% ethanolic extracts from soybean obtained with lactic acid fermentation using ABTS•⁺ [2,2'-azinobis (3-ethylbenzothiazoline-6-sulphonicacid) diammonium salt] free radical decolorization assay and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging assay were measured, and the relationship between the observed antioxidant properties and the compositional changes in the isoflavone isomers was evaluated. Fermentation of soybean with 4 bacterial strains producing β-glucosidase for 48 h at 37°C— Lactobacillus plantarum KFRI 00144, Lactobacillus delbrueckii subsp. latisKFRI01181, Bifidobacteriathermophilum KFRI00748, and Bifidobacteria breve K-101—resulted in a significant increas (P < 0.05) in the antioxidant capacity expressed as Trolox equivalent antioxidant capacity (TEAC) (mM) and % scavenging activity. The significant bioconversion (P < 0.001) of the isoflavone glucosides (daidzin + genistin) into their responding bioactive aglycones (daidzein + genistein) during soy fermentation was observed. There was a good linear correlation between the concentration of isoflavone aglycones and the scavenging activity of ABTS ( R = 0.9045) assay, and DPPH ( R = 0.8299) assay in each extract. Among each extract, B. thermophilum KFRI 00748 showed a particularly high antioxidant activity (19.8 mM TEAC) and increased by 4.1 times compared with that of the control (4.8 mM TEAC), which fermented without strains. These results indicated that fermented soybean could be regarded as a potent antioxidant and radical scavenging dietary source due to their remarkable content of bioactive isoflavones.     

Production of beta-glucosidase and hydrolysis of isoflavone phytoestrogens by Lactobacillus acidophilus, Bifidobacterium lactis, and Lactobacillus casei in soymilk

ABSTRACT:  The study determined β-glucosidase activity of commercial probiotic organisms for hydrolysis of isoflavone to aglycones in fermenting soymilk. Soymilk made with soy protein isolate (SPI) was fermented with Lactobacillus acidophilus LAFTI^® L10, Bifidobacterium lactis LAFTI^® B94, and Lactobacillus casei LAFTI^® L26 at 37 °C for 48 h and the fermented soymilk was stored for 28 d at 4 °C. β-Glucosidase activity of organisms was determined using ρ-nitrophenyl β-D-glucopyranoside as a substrate and the hydrolysis of isoflavone glycosides to aglycones by these organisms was carried out. The highest level of growth occurred at 12 h for L. casei L26, 24 h for B. lactis B94, and 36 h for L. acidophilus L10 during fermentation in soymilk. Survival after storage at 4 °C for 28 d was 20%, 15%, and 11% greater ( P < 0.05) than initial cell counts, respectively. All the bacteria produced β-glucosidase, which hydrolyzed isoflavone β-glycosides to isoflavone aglycones. The decrease in the concentration of β-glycosides and the increase in the concentration of aglycones were significant ( P < 0.05) in the fermented soymilk. Increased isoflavone aglycone content in fermented soymilk is likely to improve the biological functionality of soymilk.     

Profiling and quantification of isoflavones in soymilk from soy protein isolate using extracted ion chromatography and positive ion fragmentation techniques

Dietary supplements on soy based foods and beverages are increasingly gaining prominence all over the world. In this study, liquid chromatography coupled with positive electrospray ionisation tandem mass spectrometry (LC-ESI-MS) and diode array detection was used for the quantitation and characterisation of isoflavones in fermented and unfermented soymilk made from soy protein isolate SUPRO 590. Bifidobacterium animalis ssp. lactis Bb12 was used for the fermentation of soymilk. The isoflavones were found to produce characteristic radical ions as well as molecules of H₂O, CO₂, a sugar unit, and an alcohol through collision-induced fragmentation. Product ion fragments revealed unique fragmentation pathways for each isoflavone compound. Characteristic fragmentation of different isoflavones were unequivocally identified and differentiated. The occurrence of aldehydes such as pentanal, ethanal and methanal was shown to be specifically linked with isoflavone aglycones, daidzein, genistein and glycitein, respectively. Main glycosides such as genistin, daidzin and glycitin as well as the acetyl-, and malonyl forms also showed respective aglycone ions in their spectra fragmentation. Thus positive ion fragmentation was important in the absolute confirmation of isoflavones and to reveal the occurrence of other related compounds such as aldehydes in soymilk.     

Fermentation characteristics and transit tolerance of probiotic Lactobacillus casei Zhang in soymilk and bovine milk during storage

Lactobacillus casei Zhang is a novel strain that was screened out of koumiss collected in Inner Mongolia, and our previous research showed that L. casei Zhang has health benefits such as cholesterol-reducing and immunomodulating effects. The fermentation characteristics of L. casei Zhang in soymilk and bovine milk and the transit tolerance of L. casei Zhang in fermented milk products during refrigerated storage for 28 d were assessed. A faster decrease in pH and faster growth of L. casei Zhang during fermentation were observed in soymilk compared with bovine milk at various inoculation rates, probably because of the low pH buffering capacity of soymilk. The fermented bovine milk samples had much higher final titratable acidity (TA) values (between 0.80 and 0.93%) than the soymilk samples (between 0.40 and 0.46%). Dramatic increases in TA values in the fermented soymilk samples during storage were observed, and the TA values of the fermented soymilk samples changed from <0.56% to values between 0.86 and 0.98%. On the other hand, only slight increases in TA were observed in the bovine milk samples during the 28 d of storage. The survival rates of freshly prepared cultures of L. casei Zhang in simulated gastric juice at pH 2.0 and 2.5 were 31 and 69%, respectively, and the delivery of L. casei Zhang through fermented soymilk and bovine milk significantly improved the viability of L. casei Zhang in simulated gastric transit. Lactobacillus casei Zhang showed good tolerance to simulated gastric juice and intestinal juice in the fermented soymilk and bovine milk samples, and maintained high viability (>10⁸ cfu/g) during storage at 4°C for 28 d. Our results indicated that both soymilk and bovine milk could serve as vehicles for delivery of probiotic L. casei Zhang, and further research is needed to elucidate the mechanism of the change in pH and TA of L. casei Zhang in fermented milk samples during fermentation and storage and to understand the difference between soy- and milk-based systems.     

Modification of isoflavone profiles in a fermented soy food with almond powder

Isoflavone profiles of a fermented soy food, cheonggukjang, were modified using almond powder. Isoflavones were analyzed by high performance liquid chromatography (HPLC) with an ultraviolet detector. Malonyl derivatives of isoflavones decreased and aglycones of isoflavones increased in samples with almond powder for 48 h. As added, almond powder increased from 0%, 5%, and 10% (w/w), amounts of aglycones increased to 21.11%, 26.63%, and 32.45% for 48 h, respectively. β-Glucosidase activity in 5% and 10% almond added samples was significantly higher than samples without addition of almond (P < 0.05). The content of succinyl daidzin and succinyl genistin, new metabolites from isoflavones, in almond-added cheonggukjang was significantly lower than control samples, implying that β-glucosidase activity from almond affected negatively the formation of succinyl derivatives (P < 0.05). Principal component analysis (PCA) for isoflavone distribution showed that first principal component (PC1) and second principal component (PC2) expressed 64.78% and 22.26% of the data variability, respectively. Biotransformation of isoflavones in any fermented soy foods can be achieved using natural products containing high β-glucosidase activity such as almond. PRACTICAL APPLICATION: The results of this study can help to modify the structural transformation of phytochemicals in any fermented soy foods using natural products. Adjusting the content of almond powder can achieve wanted profiles, for example, high aglycones content. Also, content of metabolites such as succinyl derivatives can be controlled using proper amounts of almond and fermentation time.     

Identification and Characterization of Lactic Acid Bacteria Involved in Natural and Lactic Acid Bacterial Fermentations of Pastes of Soybeans and Soybean-Maize Blends Using Culture-Dependent Techniques and Denaturing Gradient Gel Electrophoresis

Pastes of soybeans and soybean-maize blends were fermented with inoculum through back-slopping using lactic acid bacteria (LAB) fermented cereal gruel, thobwa and without inoculum (naturally). LAB involved in the fermentations were characterized using culture-dependent and culture-independent analyses. Decreases in pH from 6.4 to 3.9–4.2 and from 6.9 to 5.4–5.8 after 72 h were observed in LAB fermented pastes (LFP) and in naturally fermented pastes (NFP), respectively. LAB increased from 5.0 to 8.7–9.6 log₁₀ cfu/g in NFP and from 8.1 to 9.3 log₁₀ cfu/g in LFP. LAB in both fermentations were heterofermentative lactobacilli (82.4%) and homofermentative cocci (17.6%), of which 44.7% and 42.9% were exopolysaccharide producers, respectively. Principal component analysis based on carbohydrate fermentation, CO₂ production and arginine hydrolysis showed four clusters dominated by Lactobacillus fermentum, Weissella confusa, Lactobacillus brevis 1 and Pediococcus pentosaceus, respectively. Sequencing of 16S rDNA gene confirmed Lb. fermentum, W. confusa/W. cibaria, and P. pentosaceus as identities of species in three clusters. Denaturing gradient gel electrophoresis (DGGE) confirmed these species as the dominant microbiota. DGGE showed higher similarity in microbial profiles of LFP throughout fermentation and low similarity in NFP during early and late stages of fermentation.     

Evaluation of enzymic potential for biotransformation of isoflavone phytoestrogen in soymilk by Bifidobacterium animalis,Lactobacillus acidophilus and Lactobacillus casei

Three strains of Lactobacillus acidophilus, two of Lactobacillus casei and one of Bifidobacterium were screened for β-glucosidase activity using ρ-nitrophenyl-β-d-glucopyranoside as a substrate and their potential for the breakdown of isoflavone glucosides to the biologically active aglycones in soymilk. Isoflavones quantification with HPLC and β-glucosidase activity were performed after 0, 12, 24, 36, and 48 h of incubation in soymilk at 37 °C. All six micro-organisms produced β-glucosidase, which hydrolysed the predominant isoflavone β-glucosides. There was a significant increase and decrease (P < 0.05) in the concentration of isoflavone aglycones and glucosides, respectively, in fermented soymilk. Based on the concentration of isoflavones during peak β-glucosidase activity, the hydrolytic potential was calculated. L. acidophilus 4461 had the highest aglycone concentration of 76.9% after 24 h of incubation, up from 8% in unfermented soymilk (at 0 h). It also had the best isoflavone hydrolytic index of 2.01, signifying its importance in altering the biological activity of soymilk.     

Phytase Activity from Lactobacillus spp. in Calcium-Fortified Soymilk

Abstract: The presence of phytate in calcium-fortified soymilk may interfere with mineral absorption. Certain lactic acid bacteria (LAB) produce the enzyme phytase that degrades phytates and therefore may potentially improve mineral bioavailability and absorption. This study investigates the phytase activity and phytate degradation potential of 7 strains of LAB including: Lactobacillus acidophilus ATCC4962, ATCC33200, ATCC4356, ATCC4161, L. casei ASCC290, L. plantarum ASCC276, and L. fermentum VRI-003. Activity of these bacteria was examined both in screening media and in calcium-fortified soymilk supplemented with potassium phytate. Most strains produced phytase under both conditions with L. acidophilus ATCC4161 showing the highest activity. Phytase activity in fortified soymilk fermented with L. acidophilus ATCC4962 and L. acidophilus ATCC4161 increased by 85% and 91%, respectively, between 12 h and 24 h of fermentation. All strains expressed peak phytase activity at approximately pH 5. However, no phytate degradation could be observed.     

Effect of electroporation on viability and bioconversion of isoflavones in mannitol‐soymilk fermented by lactobacilli and bifidobacteria

BACKGROUND: The aim of this study was to evaluate the effect of electroporation (2.5–7.5 kV cm^?1 for 3.0–4.0 ms) on the growth of lactobacilli and bifidobacteria, membrane properties and bioconversion of isoflavones in mannitol‐soymilk. RESULTS: The viability of lactobacilli and bifidobacteria decreased immediately after electroporation. This was attributed to lipid peroxidation, which led to alterations in the membrane phospholipid bilayer, specifically at the polar head, interface and apolar tail regions. Such alterations also resulted in decreased membrane fluidity and increased membrane permeability upon electroporation (P < 0.05). However, the effect was reversible and treated cells showed better growth than the control upon fermentation for 24 h at 37 °C (P < 0.05). Additionally, electroporation increased the bioconversion of glucosides to bioactive aglycones in mannitol‐soymilk, which was attributed to increased intracellular and extracellular β‐glucosidase activities of cells upon treatment (P < 0.05). CONCLUSION: Application of electroporation on lactobacilli and bifidobacteria could be beneficial for the development of fermented soymilk with enhanced bioactivity. Considering the enhanced bioactive aglycones, this soymilk could be useful for the prevention of hormone‐dependent disorders. Copyright © 2012 Society of Chemical Industry     

Effects of riboflavin photosensitization on the changes of isoflavones in soymilk

Effects of riboflavin photosensitization on the distribution of isoflavones in commercially available soymilk were analyzed using high-performance liquid chromatography (HPLC). Total isoflavones (TI) in soymilk with riboflavin (1000 ppm, w/v) under light were significantly different from those stored in the dark for 24 h (P < 0.05), while TI in samples with 0 and 1000 ppm added riboflavin were not significant from each other in dark conditions (P > 0.05). To test the effects of the concentration of riboflavin on TI, soymilk was mixed with riboflavin to make 0, 100, 250, and 500 ppm (w/v) and stored under light at 25 degrees C for 24 h. TI in soymilk with 100 ppm riboflavin under light significantly decreased by 13.5% for 24 h (P < 0.05) compared to control samples and were not significantly different from those with 250 or 500 ppm samples (P > 0.05). Daidzin and genistin were predominant isoflavones in soymilk, and the rate of photo degradation of genistin was higher than that of daidzin for 24 h in soymilk under riboflavin photosensitization.     

Formation of Succinyl Genistin and Succinyl Daidzin by Bacillus Species

ABSTRACT:  6"- O -Succinyl-4'-hydroxyisoflavone-7- O -β-D-glucopyranoside (succinyl-β-daidzin) and 6"- O -succinyl-6,4'-dihydroxyisoflavone-7- O -β-D-glucopyranoside (succinyl-β-genistin), 2 new isoflavone metabolites, are found in  cheonggukjang  or  natto , traditional soy-based foods fermented with  Bacillus  species. Standard isoflavones including daidzin, genistin, daidzein, and genistein, and mixtures of isoflavones extracted from roasted soybeans were added to the medium growing  Bacillus subtilis  or  B. subtilis  natto and formation of succinyl-β-daidzin and succinyl-β-genistin were monitored by high-performance liquid chromatography (HPLC). Samples containing  Bacillus  with daidzin and genistin produced succinyl-β-daidzin and succinyl-β-genistin, respectively, while those with daidzein and genistein did not produce succinyl derivatives. Daidzin in samples with  B. subtilis  and  B. subtilis  natto decreased by 39.7% and 10.7%, respectively, for 4 h incubation while genistin decreased by 66.8% and 17.6%, respectively. Genistein decreased faster than daidzein during incubation with  B. subtilis  or  B. subtilis  natto without formation of succinyl derivatives. In the case of mixture of isoflavones, succinyl derivatives increased and β-glucosides and aglycones of isoflavones decreased significantly for 8 h incubation ( P  < 0.05).     

Oat-based Symbiotic Beverage Fermented by Lactobacillus plantarum, Lactobacillus paracasei ssp. casei, and Lactobacillus acidophilus

ABSTRACT: Oats and probiotics have long been recognized for their health benefits. The objectives of this study were (1) to study the ability of Lactobacillus plantarum (B-28), Lactobacillus paracasei ssp. casei (B-29) isolated from a traditional Bulgarian cereal-based fermented beverage, and Lactobacillus acidophilus from Chr. Hansen, Milwaukee, Wis., U.S.A., to remove cholesterol from the media and to adhere to the Caco-2 cell line, (2) to optimize the fermentation conditions to develop a beverage using these probiotics and oats with acceptable sensory and nutritional qualities, and (3) to assess the quality and shelf-life of this beverage and survivability of probiotics in the beverage. Lactobacillus acidophilus , B-28, and B-29 were found to remove 70.67%± 2.35%, 20.26%± 2.63%, and 16.75%± 3.83% of cholesterol from media and the percentage of adhesion was 4.69%± 0.78%, 1.92%± 0.78%, and 8.36%± 0.78%, respectively. The blend of oat flour, sugar, inulin, and whey protein concentrate was cooked in water and fermented for 12 h at 37°C by 2 ± 10⁶ colony-forming units (CFU) /mL each of B-28 and B-29 and 2 ± 10⁸ CFU/mL of L. acidophilus . The beverage had 0.87%± 0.03% of dietary fiber and had better sensory qualities compared with the commercially available similar product. The probiotics survived for 10 wk of storage at 4°C, except for L. acidophilus , which survived for about 4 wk. The population of B-28 was 1.77 ± 10⁶ to 1.29 ± 10⁷ CFU/mL and that of B-29 was 7.39 ± 10⁷ to 4.49 ± 10⁸ CFU/mL throughout the storage period. The oat-based symbiotic beverage is a functional drink providing both probiotics and prebiotics at the same time.     

Enrichment of isoflavone aglycones in soymilk by fermentation with single and mixed cultures of Streptococcus infantarius 12 and Weissella sp. 4

Soymilk was fermented with either Streptococcus infantarius 12 (Si 12), Weissella sp. 4 (Ws 4), or their mixed cultures with different mixing ratios (Si 12:Ws 4 = 1:1, 1:3, 1:5, and 1:10, v/v) for 12 h at 37 °C. All cultures in soymilk readily proliferated and reached about 10^8–9 CFU/mL. After 12 h, pH and titratable acidity of soymilk ranged 4.19–4.47 and 0.57%–0.64%, respectively. The pH of soymilk fermented with Si 12 was the lowest while that obtained with Ws 4 the highest. A sharp increase in β-glucosidase (β-glu) activity corresponded well with a rapid decrease in isoflavone glucosides and an increase in aglycone contents. The rate of hydrolysis of isoflavone glucosides was the least with Si 12 while the highest with Ws 4, resulting in about 23%–33% and 98%–99% hydrolysis of the glucosides with Si 12 and Ws 4, respectively, after 12 h. Mixed cultures with 1:3, 1:5, and 1:10 ratios seem to be more effective starters for bioactive fermented soymilk with more aglycones and appropriate acidity in a short time than single cultures.