Fermented Soymilk Research Articles

Assessment of Ultrasonic Stress on Survival and β-Glucosidase Activity of Encapsulated Lactiplantibacillus plantarum BCRC 10357 in Fermentation of Black Soymilk.

The enhanced β-glucosidase activity of encapsulated Lactiplantibacillus plantarum BCRC 10357 within calcium alginate capsules was investigated by ultrasonic stimulation to induce the stress response of the bacteria for the biotransformation of isoflavones in black soymilk. The effects of various ultrasound durations, sodium alginate concentrations (% ALG), and cell suspensions on the β-glucosidase activity of encapsulated bacteria were explored. The β-glucosidase activity of encapsulated L. plantarum BCRC 10357 with ultrasonic stimulation (40 kHz/300 W) was greater than that without ultrasound. With 20 min of ultrasonic treatment, the β-glucosidase activity of encapsulated L. plantarum BCRC 10357 from 2% ALG/0.85% NaCl cell suspension was 11.47 U/mL at 12 h, then increased to 27.43 U/mL at 36 h and to 26.25 U/mL at 48 h in black soymilk at 37 °C, showing the high adaptation of encapsulated L. plantarum BCRC 10357 encountering ultrasonic stress to release high β-glucosidase until 48 h, at which point the ratio of isoflavone aglycones (daidzein and genistein) in total isoflavones (daidzin, genistin, daidzein, and genistein) was 98.65%, reflecting the effective biotransformation of isoflavone glycosides into aglycones by β-glucosidase. In this study, the survivability and β-glucosidase activity of encapsulated L. plantarum BCRC 10357 were enhanced under ultrasonic stimulation, and were favorably used in the fermentation of black soymilk.

The stressing life of Lactobacillus delbrueckii subsp. bulgaricus in soy milk

Lactobacillus delbrueckii subsp. bulgaricus is a beneficial lactic acid bacterium and constitutes one of the most used, and thus consumed, dairy starters, worldwide. This homofermentative bacterium was the first lactobacillus described and is involved in the fermentation of yogurt and of diverse other fermented products, including cheeses. It has a long history of safe use, as well as documented probiotic lato sensu effects, including alleviation of lactose intolerance. Plant-based fermented products presently experience a considerable development, as a result of evolution of consumers' habits, in a general context of food transition. This requires research and development, and thus scientific knowledge, to allow such transition, including the development of fermented soy milks. These last indeed offer an alternative source of live and active bacteria. The yogurt starters L. delbrueckii subsp. bulgaricus, together with Streptococcus thermophilus, have been implemented to generate yogurt-type fermented soy milks worldwide. While the adaptation of these starters to the dairy environment has been extensively studied, little is known about L. delbrueckii adaptation to the soy environment. We therefore investigated its adaptation to soy milk and compared it to cow's milk. Surprisingly, it did not grow in soy milk, neither alone, nor in co-culture with S. thermophilus. Acidification of soy milk was however faster in the presence of both species. In order to deepen such adaptation, we then compared L. delbrueckii growth and survival in soy milk ultrafiltrate (SUF, the aqueous phase of soy milk) and compared it to cow's milk ultrafiltrate (MUF, the aqueous phase of cow milk). This comparison revealed major differences in terms of cell morphology and proteome composition. Lactobacilli appeared deformed and segmented in soy. Major differences in both the surface and the cellular proteome indicated upregulation of stress proteins, yet downregulation of cell cycle and division machinery. Altogether, these results suggest that soy milk may be a stressing environment for the yogurt starter L. delbrueckii subsp. bulgaricus.

Changes of hexanal content in fermented soymilk: Induced by lactic acid bacterial fermentation and thermal treatment

To study the causes of beany off-flavor regeneration after fermented soymilk was thermal treated. Hexanal was soymilk beany off-flavor and analyzed using headspace solid phase microextraction. The hexanal removal and regeneration during fermentation and heat treatment of soymilk and soy protein solutions were analyzed. Soymilk contained both free and protein-bound hexanal. Both 7 S and 11 S could bind to hexanal, and the amount of bound hexanal to 11 S was approximately five times that to 7 S. pH decreased to approximately 4.5 or enzymatic hydrolysis could effectively weaken the binding of hexanal to soy protein, but not capable of dissociating them. Further heat treatment was required for hexanal volatilized from protein. Lactic acid bacteria could completely remove free hexanal, but the removal ability of protein-bound hexanal was weak, which varied among bacterial species. The results will be valuable for improving flavor qualities of fermented soymilk and its beverage products. This result revealed the mechanism behind the fact that the off-flavor of heated fermented soymilk was difficult to be removed. Thus, the results will be valuable for improving flavor qualities of fermented soymilk and its beverage products. Practical applications This result revealed the mechanism behind the fact that the off-flavor of heated fermented soymilk was difficult to be removed. Thus, the results will be valuable for improving flavor qualities of fermented soymilk and its beverage products.

Production and characterization of bioactive peptides in novel functional soybean chhurpi produced using Lactobacillus delbrueckii WS4

A novel soy chhurpi product was developed by fermentation of soymilk using proteolytic Lactobacillus delbrueckii strains isolated from traditional chhurpi production of Sikkim Himalaya. Soymilk fermentation by L. delbrueckii WS4 was associated with the hydrolysis of globulin proteins, with observed antioxidant, and ACE-inhibitory activity which further increased upon simulated in vitro gastrointestinal digestion. Peptidomics analysis of soy chhurpi and its gastrointestinal digest resulted in the identification of bioactive peptides with ACE-inhibitory and antioxidant properties. In silico antihypertensive property prediction followed by molecular docking study demonstrated strong binding affinity of selected peptides with ACE. The glycinin-derived peptide, SVIKPPTDE escaped gastrointestinal digestion and demonstrated strong non-bond interactions with ACE catalytic residues. QSAR models predicted an ACE-inhibitory IC50 of 21.29 µM for SVIKPPTDE. This is the first report on the production of novel functional soy chhurpi cheese using defined starter strains and the identification of bioactive peptides in undigested and gastrointestinal digested soy chhurpi.

Physicochemical Characteristics and Rheological Properties of Soymilk Fermented with Kefir

The objective of this work was to evaluate the physicochemical characteristics and rheological behavior of soymilk fermented with kefir. The titratable acidity ranged from 0.25 to 1.47 %; the pH ranged from 5.06 to 5.89 %. The soluble solids (SS) ranged from 1.82 to 5.38 Brix, while the differences between initial SS and final SS were 0.74 to 7.65 °Brix. The sedimentation percentage of the formulations ranged from 50.15 to 99.40 %. The rheological parameters for the flow behavior of the soymilk fermented with kefir were adjusted by the Herschel-Bulkley model. The 9 assays were characterized as non-Newtonian fluids because the behavior showed no linear relationship between the shear rate and shear stress. In the present work, the beverages were characterized as pseudoplastic fluids. In this work, we carry out the fermentation of soymilk with kefir without using any additional ingredients. The optimal treatment was determined, being a solution with an initial soymilk concentration of 5 g of kefir biomass (-0.5), 8 h (-1) of fermentation time, and 10 Brix of SS (+1).

Riboflavin Bioenriched Soymilk Alleviates Oxidative Stress Mediated Liver Injury, Intestinal Inflammation, and Gut Microbiota Modification in B2 Depletion-Repletion Mice.

Epidemiological evidence emphasizes that ariboflavinosis can lead to oxidative stress, which in turn may mediate the initiation and progression of liver injury and intestinal inflammation. Although vitamin B2 has gained worldwide attention for its antioxidant defense, the relationship between B2 status, oxidative stress, inflammatory response, and intestinal homeostasis remains indistinct. Herein, we developed a B2 depletion-repletion BALB/c mice model to investigate the ameliorative effects of B2 bioenriched fermented soymilk (B2FS) on ariboflavinosis, accompanied by oxidative stress, inflammation, and gut microbiota modulation in response to B2 deficiency. In vivo results revealed that the phenotypic ariboflavinosis symptoms, growth rate, EGRAC status, and hepatic function reverted to normal after B2FS supplementation. B2FS significantly elevated CAT, SOD, T-AOC, and compromised MDA levels in the serum, simultaneously up-regulated Nrf2, CAT, and SOD2, and down-regulated Keap1 gene in the colon. The histopathological characteristics revealed significant alleviation in the liver and intestinal inflammation, confirmed by the downregulation of inflammatory (IL-1β and IL-6) and nuclear transcription (NF-κB) factors after B2FS supplementation. B2FS also increased the abundance and diversity of gut microbiota, increased the relative abundance of Prevotella and Absiella, as well as decreased Proteobacteria, Fusobacteria, Synergistetes, and Cyanobacteria in strong conjunction with antioxidant, anti-inflammatory properties, and gut homeostasis along with the remarkable increase in cecal SCFAs content. We hereby reveal that B2FS can effectively alleviate deleterious ariboflavinosis associated with oxidative stress mediated liver injury, chronic intestinal inflammation, and gut dysbiosis in the B2 depletion-repletion mice model via activation of the Nrf2 signaling pathway.

Metabolomics analysis of soymilk fermented by Bacillus subtilis BSNK-5 based on UHPLC-Triple-TOF-MS/MS

Soymilk is an ideal alternative to develop functional soybean foods, and fermentation can effectively enhance the digestibility and nutritional and functional properties of soymilk. In this study, the metabolites changes of soymilk fermented by Bacillus subtilis BSNK-5 were investigated through comparative metabolomics with UHPLC-Triple-TOF-MS/MS. The metabolites were gradually enriched with the extension of fermentation time and stabilized in the fermentation anaphase. In total, 289 differential metabolites were identified as the major chemical components, and they were distributed into 14 categories, mainly involving in three types of metabolites, peptides and amino acids, lipids, and flavonoids. Moreover, the fermented soymilk at 48 h exhibited the highest abundance of metabolites. Based on KEGG analysis, 14 pathways were enriched, associated with 14 specific metabolites, and mainly related to amino acid and lipid metabolism. Thus, BSNK-5 could effectively degrade the macromolecular substances of soymilk into small molecules, synthesize small peptides, small molecular acids, quinones, and isoflavone aglycones to affect the nutritional and functional properties of fermented soymilk. The in-depth analysis of metabolites in BSNK-5-fermented soymilk provides a theoretical foundation for the development of small molecule functional foods in later stages.

Adaptive mechanism of Lactobacillus amylolyticus L6 in soymilk environment based on metabolism of nutrients and related gene-expression profiles.

Lactobacillus amylolyticus L6 isolated from naturally fermented tofu‐whey was characterized as potential probiotics. To give insight into the adaptive mechanism of L. amylolyticus L6 in soymilk, the gene‐expression profiles of this strain and changes of chemical components in fermented soymilk were investigated. The viable counts of L. amylolyticus L6 in soymilk reached 1012 CFU/mL in the stationary phase (10 hr). The main sugars reduced gradually while the acidity value significantly increased from 45.33° to 95.88° during fermentation. About 50 genes involved in sugar metabolization and lactic acid production were highly induced during soymilk fermentation. The concentration of total amino acid increased to 668.38 mg/L in the logarithmic phase, and 45 differentially expressed genes (DEGs) in terms of nitrogen metabolism and biosynthesis of amino acid were detected. Other genes related to lipid metabolism, inorganic ion transport, and stress response were also highly induced. Besides, the concentration of isoflavone aglycones with high bioactivity increased from 14.51 mg/L to 36.09 mg/L during the fermentation, and the expression of 6‐phospho‐β‐glucosidase gene was also synchronously induced. This study revealed the adaptive mechanism of L. amylolyticus L6 in the soymilk‐based ecosystem, which gives the theoretical guidance for the application of this strain in other soybean‐derived products.

Mesenchymal Stem Cells and Selenium Nanoparticles Synergize with Low Dose of Gamma Radiation to Suppress Mammary Gland Carcinogenesis via Regulation of Tumor Microenvironment

Breast cancer is one of the most prevalent and deadliest cancers among women in the world because of its aggressive behavior and inadequate response to conventional therapies. Mesenchymal stem cells (MSCs) combined with green nanomaterials could be an efficient tool in cell cancer therapy. This study examined the curative effects of bone marrow–derived mesenchymal stem cells (BM-MSCs) with selenium nanoparticles (SeNPs) coated with fermented soymilk and a low dose of gamma radiation (LDR) in DMBA-induced mammary gland carcinoma in female rats. DMBA-induced mammary gland carcinoma as marked by an elevation of mRNA level of cancer promoter genes (Serpin and MIF, LOX-1, and COL1A1) and serum level of VEGF, TNF-α, TGF-β, CA15-3, and caspase-3 with the reduction in mRNA level of suppressor gene (FST and ADRP). These deleterious effects were hampered after treatment with BM-MSCs (1 × 106 cells/rat) once and daily administration of SeNPs (20 mg/kg body weight) and exposure once to (0.25 Gy) LDR. Finally, MSCs, SeNPs, and LDR notably modulated the expression of multiple tumor promoters and suppressor genes playing a role in breast cancer induction and suppression.

Soymilk-fermented with Lactobacillus delbrueckii subsp. delbrueckii TUA4408L improves immune-health in pigs.

Lactobacillus delbrueckii subsp. delbrueckii TUA4408L has the ability to grow and ferment soymilk and is able to modulate the innate immune response of intestinal epithelial cells in vitro. These two properties prompt us to evaluate whether the soymilk fermented with the TUA4408L strain can induce beneficial immunomodulatory effects in vivo. For this purpose, pigs were selected as a preclinical model. The studies performed here demonstrated that the L. delbrueckii subsp. delbrueckii TUA4408L-fermented soymilk (TUA4408L FSM) reduced blood markers of inflammation and differentially regulated the expression of inflammatory and regulatory cytokines in the intestinal mucosa. These immunological changes induced by the TUA4408L FSM were associated to an enhanced resistance to pathogenic Escherichia coli and an improved grow performance and meat quality of pigs. The experiments and analysis in our study indicate that the immunobiotic TUA4408L FSM could be an interesting non-dairy functional food to beneficially modulate the intestinal immune system, improve protection against pathogens and reduce inflammatory damage. The preclinical study carried out here in pigs could have a better correlation in humans, compared to a rodent model. However, the clinical relevance of these findings still needs to be confirmed by further research, for example, in controlled human challenge studies.

Genomic characteristics of a novel strain Lactiplantibacillus plantarum X7021 isolated from the brine of stinky tofu for the application in food fermentation

Lactiplantibacillus plantarum X7021 is a novel strain originated from the brine of stinky tofu. In order to investigate the application potential of the strain in food industry, the genomic characteristics as well as some metabolic features were studied using comparison genomics and transcriptional assay. The complete genome of X7021includes a 3,407,054 bp chromosome with 3259 protein coding sequences, and 6 plasmids. L. plantarum strains, WCFS1, JDM1, and ST-III were selected for comparative genomic analysis. Results revealed that X7021 is safe for the application in foods with less antibiotic resistance and virulence genes. The strain has 25 complete phosphotransferase system transporters and strong proteolytic system for its adaptability to various foodstuffs. The strain containes a complete purine metabolic pathway incorporating 4 permeases, resulting in the reductions of 38.9% guanine, 26.1% hypoxanthine and 70.2% xanthine during the soymilk fermentation. Soy isoflavone glycosides could be converted to corresponding aglycones by two β-glucosidases. The strain could grow in 700 mg/L nitrite and entirely degrade 100 mg/L nitrite during 24 h based on highly active nitrite transporter and nitrite reductase. Accordingly, the results suggest that L. plantarum X7021 is a prospect starter candidate for the fermentation of plant foodstuffs.

A review on the functional properties of fermented soymilk

Fermented soybean products have been used for several centuries. Fermented soymilk is one of the known soy products with several health benefits. The current literature review recapitulates the various health benefits of fermented soymilk. In vitro and in vivo studies have shown that the consumption of fermented soymilk protects one from cancer, diabetes, hyperlipidemia, etc. It has also been reported that fermented soymilk has immune-modulatory, memory improvement, anti-colitis, and wound healing activities. However, there are few studies to confirm the health benefits of fermented soymilk for human subjects. The dose and duration of the intervention may vary between the animal model and humans. So, additional studies are obligatory to authorize the proposed health benefits of fermented soymilk.

Anti-Salmonella activity of lactobacilli from different habitats

Lactic acid bacteria (LAB) may contribute to the food safety. In the present study, the antagonistic activity of 45 Bulgarian Lactobacillus homo- and heterofermentative strains of human and dairy origin, and 4 multibacterial formulas against Salmonella enterica subsp. enterica serovar Typhimurium (S. Typhimurium) was assessed. In vitro tests were performed in different model systems - milk, soymilk, De Man Rogose Sharp (MRS) medium, to simulate real conditions in the food chain. The highest antagonistic activity was observed with cell-free supernatants of exponential MRS broth cultures of the strains isolated from breast milk, followed by lactobacilli from white brined and green cheese. The detected antimicrobial activity against the pathogen was strain-specific and depended on the culture conditions. Lactobacillus (reclassified as Lactoplantibacillus) plantarum strains, cultivated in skimmed milk and whey protein medium, were able to inhibit S. Typhimurium growth, while a limited inhibitory activity was detected for fermented soymilks. A bacteriocinogenic Ligilactobacillus (the previous Lactobacillus) salivarius strain reduced the number of living pathogenic cells during co-cultivation in whole milk. The inhibition was significant only when L. salivarius was inoculated in predominance. In case of underrepresented LAB number, S. Typhimurium over-growth was observed. Eight lactobacilli in combination as a multibacterial co-culture expressed synergic antagonistic effect against Salmonella and were pre-selected as promising. Further characterisation of their active metabolites, however, is needed before their classification as bio-protective agents.

Formulating a novel fermented soy milk functional meal replacement among overweight individuals: a preliminary weight loss clinical trial

Meal replacement is an optimising strategy in designing structured diets for weight management. In this study, a novel fermented soy-whey based beverage was fortified with dietary bioactive ingredients containing probiotic strains (Lactobacillus bulgaricus and Streptococcus thermophilus). The aim of this study was to evaluate its efficacy on the body weight loss of participants pre-and post-meal replacement. A total of 20 participants underwent the weight loss program. Over the 14-day trial, women volunteers had a body weight loss of 6.70% of their initial body weight, and men had a comparable body weight reduction of 6.18%. In comparison to the blood glucose baseline level of 3.5420 mmol/L, the meal replacement decreased the level of blood glucose by nearly 50%, reaching 1.7785 mmol/L. Total cholesterol level was reduced by the beverage with a 15.7% reduction. The functional drink also decreased the triglycerides and low-density lipoprotein significantly (p<0.001). A significantly higher level of high-density lipoprotein was obtained at Day 14 (1.73 mmol/L) compared with Day 0 (1.23 mmol/L). The meal replacement was able to provide satiety within the average of 180.7 minutes post-meal. This study supports the soy-based functional milk is of benefit for weight management, glucose homeostasis and blood cholesterol-lowering effect.

Enhancement of Selected Health Benefits in Fermented Cow and Soy Milk Supplemented with Water Soluble Curcumin

Different formulates of fermented cow and soy milk by Lactobacillus plantarum EMCC 1027 with 50, 100, and 150 mg/100 mL curcumin were investigated for antibacterial, antioxidant, anti-colonic cancer, and anti-inflammation activities. Also, the viability of L. plantarum was monitored during cold storage period. Our results showed that values of antibacterial, antioxidant, anti-colonic cancer, and anti-inflammation activities in crude extracts of fermented soy milk were significantly increased in comparison with crude extracts of fermented cow milk. The addition of different concentrations (100 and 150 mg/100 mL) of curcumin had a significant enhancement effect for all selected health benefits properties. The increase in antioxidant capacity of different crude extracts was in a good correlation with their polyphenols content. Addition of water soluble curcumin did not have any adverse effect on the viability of L. plantarum during fifteen days of cold storage. Therefore, the synergistic effect between fermented cow/soy milk and water soluble curcumin could be recommended. Indeed, extensive research is still needed in order to investigate the molecular mechanisms of health a benefit of different formulates of fermented cow/soy milk and water soluble curcumin.

Effects of lactiplantibacillus plantarum X7021 on physicochemical properties, purines, isoflavones and volatile compounds of fermented soymilk

The capability of Lactiplantibacillus plantarum X7021, which was isolated from the stinky tofu brine and completely sequenced, in soymilk fermentation was evaluated based on the study of growth, acidification, viscosity generation, purine ingestion and soy isoflavones glycosides bioconversion, as well as the volatile compounds production of the strain during soymilk fermentation. The yoghurt starter culture was used as a comparison and co-starter. Rapid growth of the strain increasing from 7.0–8.7 lg CFU/mL and pH dropping from 6.6 to 5.3 happened during the first 8 h, accompanying with the viscosity of soymilk raised to 1391 mPa⋅s. Three major purines, guanine, hypoxanthine and xanthine, in soymilk were significantly decreased 38.8 %, 26.1 % and 65.3 % respectively, due to the abundant purine permease systems of the strain. Furthermore, total isoflavones were reduced (147.6 mg/L → 57.1 mg/L) with an increase of aglycone contents and the percentage composition of aglycone increased from 2.7 %–67.5 % after fermentation. Thirty-three volatile compounds were detected in the fermented soymilk versus 12 volatile compounds in soymilk. L. plantarum X7021 displayed higher degradation of the main beany flavor compounds, hexanal, 1-octen-3-ol and 2-pentyl furan than yoghurt starter. Besides, significant increase of volatile compounds, acetate, acetoin and 2,3-butanedione were observed because of the complete pyruvate metabolic pathway of the strain.

Effects of Germination Black Soy Milk Fermented with Lactobacillus plantarum TWK10 on Anti-Oxidative and Anti-Melanogenesis

Black soybean germination or fermentation increases active ingredient bioavailability and anti-oxidative activity. This study investigated the effects of fermented and germinated black soy milk on anti-oxidation and melanogenesis inhibition. The total phenolic content (TPC; 42.66 ± 1.65 mg gallic acid equivalent/g) and total flavonoid content (TFC; 5.43 ± 0.54 mg quercetin equivalent (QE)/g) in ethanol extracts from Lactobacillus plantarum TWK10 (TWK10)-fermented nongermination black soy milk (FNGB) were significantly (p < 0.05) higher than those in ethanol extracts from nonfermented-nongermination black soy milk (NNGB). Although the TPC of ethanol extracts from nonfermented-germination black soy milk (NGB) and fermented-germination black soy milk (FGB) were not significantly different (p > 0.05), the TFC of FGB (1.79 ± 0.08 mg QE/g) was significantly higher than that of NGB (p < 0.05). The 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity of ethanol extracts from NNGB, FNGB, NGB, and FGB was significantly higher than that of water extracts at 10 mg/mL (p < 0.05). Furthermore, ethanol extracts from both FNGB and FGB significantly reduced the melanin content in zebrafish embryos at 100 µg/mL (p < 0.05) without causing death, malformation or bradycardia. Overall, the antioxidant activity of black soy milk significantly increased after TWK10 fermentation; moreover, ethanol extracts from FNGB and FGB could inhibit melanogenesis, indicating their potential as whitening ingredients.

BIOTECHNOLOGY OF SOYA MULTI-COMPONENT FUNCTIONAL INGREDIENTS

The materials of the article present analytical and scientific-practical results of research of soy multi-component functional ingredients. Soy extract (or soy milk) is a valuable and cheap source of protein and other nutritious and biologically active components, like lipids, vitamins, mineral elements, isoflavones, flavonoids, saponins etc. But the presence of indigestible oligosaccharides and a bean flavor limit the consumption of soy milk. The soy oligosaccharides are known to be prebiotic for intestinal microbiota, particularly for probiotic microorganisms that hydrolyze them with the enzyme α-galactosidase. Isoflavones are known as phytoestrogens since they are similar to human estrogen in structure and function, and are recommended to prevent many hormonedependent diseases. In soy beans and unfermented soy products, isoflavones are present mainly as biologically inactive glycoside conjugates. Biologically active aglycones of soy isoflavones are substances that are assimilated by human organism from soy products faster and in higher amounts than their corresponding glycosides. The members of intestinal microbiota are predicted to play an important role also in the metabolism and bioavailability of isoflavones since they, synthesizing β-glycosidase, cause hydrolysis of glycoside components, thus releasing the bioavailable and biologically active form of aglycone. In this work, we estimated the potential of some Lactobacillus and Bifidobacterium strains to synthesize α-galactosidase and β-glycosidase, and to reduce respectively the amount of galactooligosaccharides and to convert isoflavones into their active forms, when growing in soy milk. Simultaneously, the profile of soy milk fermentation by the chosen probiotics was studied, as well as the proteolytic activity and accumulation of lactic acid by those probiotics, i. e. the possibility to produce soy-based polyfunctional fermented food products was investigated.

Characterization of the Probiotic Potential of Lactic Acid Bacteria Isolated from Kimchi, Yogurt, and Baby Feces in Hong Kong and Their Performance in Soymilk Fermentation.

Background: There are several potential healthy or nutritional benefits from the use of lactic acid bacteria (LAB) in foods. This study aimed to characterize the LAB isolates from kimchi, yogurt, and baby feces in the Hong Kong area and evaluate their performance in fermented soymilk, which allowed us to assess their potential use in future experiments. Methods: General characteristics including tolerance to acid, NaCl, bile salts and phenol, antimicrobial activity to various pathogens, and adhesive ability to Caco-2 cells were evaluated using 18 LAB in this study. To further demonstrate the influence of such isolates in soymilk fermentation, we measured viability by plating and noting changes in pH, amino acid content, aglyconic isoflavones content and antioxidant capacities in vitro, such as scavenging ability, and iron chelating ability. Results: In this study, various LAB isolates belonging to Lactobacillus rhamnosus, Lactobacillus sakei, Lactiplantibacillus plantarum, and Leuconostoc mesenteroides isolated in Hong Kong were evaluated. L. plantarum isolates R7, AC12, and AC14.1, and L. rhamnosus AC1 showed higher tolerance to acid, NaCl, bile salts, and phenol as compared to the other isolates tested. L. plantarum isolates AC12, AC13 and AC14.1, and L. rhamnosus AC1 harbored strong antimicrobial activity. L. plantarum isolates R7, AC12, AC13 and AC14.1, and L. paracasei isolates R6 and R8 showed higher adhesive ability than the other tested isolates. In soymilk, the viable numbers of L. paracasei R5, L. plantarum R7, L. rhamnosus AC1, L. sakei AC2, and Leu. mesenteroides AC5 were much higher than the other tested isolates after 48 h of fermentation. The pH value measuring the lactic acid level in soymilk fermented by L. plantarum AC14.1 was the lowest in comparison to those in soymilk fermented by other isolates. In addition, the levels of free amino acids and isoflavones in the aglycone forms of L. rhamnosus AC1-fermented soymilk were the highest. L. rhamnosus AC1-fermented soymilk also showed the highest antioxidant potential, including DPPH scavenging ability and iron chelating ability. Conclusions: In general, L. plantarum isolates R7 and AC14.1 and L. rhamnosus AC1 exhibited higher tolerance to challenging conditions as compared to the other isolates. Moreover, L. rhamnosus AC1 exhibited superior performance in soymilk fermentation and potential as a starter and probiotic culture.

Lactobacillus paracasei M11-4 isolated from fermented rice demonstrates good antioxidant properties in vitro and in vivo.

Probiotics are defined as microorganisms that can exert health benefits for the host. Among the recognized probiotics, Lactobacillus paracasei are one of the most frequently used probiotics in humans. The L.paracasei strain M11-4, isolated from fermented rice (which could ferment soymilk within a short curd time) and fermented soymilk presented high viability, acceptable flavor, and antioxidant activity, which revealed that the strain maybe have a potential antioxidant value. Therefore, it is necessary to further explore the antioxidant activity of L.paracasei strain M11-4. The radical scavenging activities, lipid peroxidation inhibition, and reducing power of L.paracasei M11-4 were the highest in the fermentation culture without cells, whereas the activities of other antioxidant enzymes of L.paracasei M11-4 were high in the cell-free extract and bacterial suspension. Moreover, L.paracasei M11-4 exerted its antioxidant effect by upregulating the gene expression of its antioxidant enzymes - the thioredoxin and glutathione systems - when hydrogen peroxide existed. Supplementation of rats with L.paracasei M11-4 effectively alleviated d-galactose-induced oxidative damage in the liver and serum and prevented d-galactose-induced changes to intestinal microbiota. Supplementation with L.paracasei M11-4 also reduced the elevated expression of thioredoxin and glutathione system genes induced by d-galactose. L.paracasei M11-4 has good antioxidant properties both in vitro and in vivo, and its antioxidant mechanism was studied at the molecular level. © 2021 Society of Chemical Industry.