Systematic assessment of oat ß-glucan catabolism during in vitro digestion and fermentation.

ß-Glucan as a component of grain cell walls is consumed daily. However, little is known about whether ß-glucan is influenced by the gastrointestinal environment. In this study, we aim to investigate the integrated metabolic process of cereal ß-glucan. In vitro simulated digestion and fermentation combined with microbiome and metabolome analysis were used to profile the metabolism of ß-glucan. Intriguingly, we found that ß-glucan was not hydrolyzed by digestive enzymes but partially degraded by gastric acid environment during in vitro digestion. Moreover, ß-glucan was utilized by gut microbiota to produce acetate, propionate and butyrate, concurrently, the relative abundance of Lactobacillus significantly increased and Escherichia-Shigella significantly decreased. The correlation analysis between metabolomics datasets and microorganisms revealed that ß-glucan catabolism was also accompanied by amino acid catabolism and linoleic acid biosynthesis. Our study offered a forceful basis for the further exploration of the role of ß-glucan and gut microbiota in host health.

Assessment of Techno-Functional and Nutraceutical Potential of Tomato (Solanum lycopersicum) Seed Meal.

Tomato (Solanum lycopersicum) is a widely consumed fruit all around the world. The industrial exploitation of tomato generates a lot of waste. Most of the utilization of tomato seeds waste is focused on animal feeding, as well as a food ingredient aimed to increase the protein content, and raw material for some organic bioactive component extraction. The aim of this work was to evaluate the techno-functional properties of tomato seed meal (TSM) and its nutraceutical properties after applying defatting processing (TSMD), and to evaluate the nutraceutical properties after a fermentation processing (TSMDF) by Lactobacillus sp. The results showed that, at alkaline conditions (pH 8-9), the techno-functional properties for TSM and TSMD improved. In comparison with TSM, TSMD showed higher water holding capacity (WHC ≈32%), higher oil holding capacity (OHC ≈13%), higher protein solubility (49-58%), more than 10 times foaming activity (FA), more than 50 times foam stability (Fst), as well as an improved emulsifying activity (EA) and emulsion stability (Est) wich were better at pH 9. Regarding the nutraceutical properties, after 48 h of fermentation (TSMDF), the antioxidant activity was doubled and a significant increase in the iron chelating activity was also observed. During the same fermentation time, the highest angiotensin-converting enzyme inhibition (ACEI) was achieved (IC50 73.6 µg/mL), more than 10 times higher than TSMD, which leads to suggest that this fermented medium may be a powerful antihypertensive. Therefore, the strategy proposed in this study could be an option for the exploitation of tomato wastes.

In Vitro Evaluation of Probiotic Potential and Safety Assessment of Lactobacillus mucosae Strains Isolated from Donkey's Lactation.

The study, for the first time, reports the efficacy, safety and probiotic properties of two Lactobacillus mucosae strains, Lact. mucosae SRV5 and Lact. mucosae SRV10 isolated from donkey milk. All major in vitro screening assays were employed to evaluate studied strains. Both strains displayed good survivability at gastric pH 2.0, 0.3% bile and simulated oro-gastrointestinal fluid (above 88%). Also, cultures demonstrated good cell surface hydrophobicity and auto-aggregation ability, clearly indicating their effective cell adhesion ability. Furthermore, functional attributes for both strains demonstrated their efficient bile salt hydrolase and cholesterol-reducing ability in spent broth. In addition to this, both strains expressed significant DPPH-radical scavenging ability of both culture supernatant and intact cells. Another auxiliary health benefit exhibited by both these strains is their antimicrobial potential against 18 enteric and 5 multidrug-resistant clinical pathogens with significant inhibition zone size. Extracellular enzyme production such as lipase, amylase, protease and esterase was also studied. Detailed safety evaluation study showed the presence of innate antibiotic resistance and absence of haemolysis, DNAse and gelatinase activity in both the strains. Also, none of the strains possessed toxic mucinolytic activity in mucin degradation assay. To conclude, both donkey milk isolates, Lact. mucosae SRV5[Accession number: MK990014] and Lact. mucosae SRV10 [Accession number: MN064860], exhibited excellent probiotic ability with tolerance to simulated oro-gastrointestinal fluids, cellular hydrophobicity, auto-aggregation, bile salt hydrolase, cholesterol reduction, high antioxidant activity and antimicrobial potential especially against multidrug-resistant pathogens.

Assessment of the bacterial viability of chlorine- and quaternary ammonium compounds-treated Lactobacillus cells via a multi-method approach.

AIMS: The assessment of the bacterial viability of chlorine- and quaternary ammonium compounds (QACs)-treated Lactobacillus cells by culture-dependent and -independent methods. METHODS AND RESULTS: Lactobacillus isolates (Lactobacillus plantarum G1, Lactobacillus plantarum B1, Lactobacillus brevis S1 and Lactobacillus paracasei W1) in biofilm and planktonic cell suspensions were treated with chlorine-based (0·018 and 0·18%) and QACs-based (0·2 and 2·0%) disinfectants for 5 min and then analysed by plate counting, flow cytometry (FCM) and fluorescence activated cell sorting (FACS). The reaction of sessile cells to disinfectants was assessed with the confocal laser scanning microscopy (CLSM). Plate counts revealed L. paracasei W1 to be substantially inactivated by both disinfectants, while counts of the other isolates to be significantly reduced only by QACs, with L. plantarum B1 and L. brevis S1 showing a greater difference between QACs concentrations and cell types. In several cases, the disinfectants caused slightly higher inactivation of planktonic than biofilm cells, with L. plantarum B1 being significantly less sensitive to QACs in biofilm cells (P < 0·05). Following FCM with a Syto® 9/PI assay, which addresses cell membrane integrity, the emergence of damaged (Syto® 9- PI+ ) and injured (Syto® 9+ PI+ ) subpopulations was often observed in cells when they were treated with QACs, whereas intact (Syto® 9+ PI- ) and unstained (Syto® 9- PI- ) subpopulations were mostly encountered in chlorine-treated cells. Except Syto® 9- PI+ , all subpopulations were recovered on agar plates following FACS, with biofilm cells showing higher culturability irrespective of conditions, probably because of the residues of the biofilm matrix which serve as a protective cover for the bacteria. The CLSM revealed a substantial cell membrane damage within the QACs-treated biofilms, however, some cells deep in the biofilm were still intact and thus remained protected against this disinfectant. CONCLUSION: We found that FCM/FACS proved useful in the analysis of lactobacilli membrane integrity in disinfection experiments as well as in recovery evaluation of planktonic-biofilm cell subpopulations. In turn, CLSM was particularly useful in investigating the resistance mechanism when Lactobacillus cells were embedded in biofilms. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the need for treatment optimization on a case-by-case basis to avoid the emergence of cells in intermediate states with recovery potential and to reach and, thus, kill all bacteria in already developed lactobacilli biofilms.

Assessment of selenium bioaccumulation in lactic acid bacteria.

Selenium is an essential micronutrient for living beings, as it helps to maintain the normal physiological functions of the organism. The numerous discoveries involving the importance of this element to the health of human beings have fostered interest in research to develop enriched and functional foods. The present study evaluated the potential for bacterial strains of Enterococcus faecalis (CH121 and CH124), Lactobacillus parabuchneri (ML4), Lactobacillus paracasei (ML13, ML33, CH135, and CH139), and Lactobacillus plantarum (CH131) to bioaccumulate Se in their biomass by adding different concentrations of sodium selenite (30 to 200 mg/L) to the culture medium. Quantification of Se with UV and visible molecular absorption spectroscopy showed that the investigated bacteria were able to bioaccumulate this micromineral into their biomass. Two of the L. paracasei strains (ML13 and CH135) bioaccumulated the highest Se concentrations (38.1 ± 1.7 mg/g and 40.7 ± 1.1 mg/g, respectively) after culture in the presence of 150 mg/L of Se. This bioaccumulation potential has applications in the development of dairy products and may be an alternative Se source in the diets of humans and other animals.

In vitro evaluation of the prebiotic effect of red and white grape polyphenolic extracts.

Nowadays, the strong relationship between diet and health is well known. Although the primary role of diet is to provide nutrients to fulfill metabolic requirements, the use of foods to improve health and the state of well-being is an idea increasingly accepted by society in the last three decades. During the last years, an important number of scientific advances have been achieved in this field and, although in some situations, it is difficult to establish a distinction between "harmful" and "good" bacteria, experts agree in classifying the genera Bifidobacterium and Lactobacillus as beneficial bacteria. Thus, several strategies can be used to stimulate the proliferation of these beneficial intestinal bacteria, being one of them the consumption of prebiotics. The development of new prebiotics, with added functionality, is one of the most serious challenges shared not only by the scientific community but also by the food industry. The objective of this work was to evaluate the potential prebiotic effect of red and white grape residues, both obtained during the winemaking process. For such purpose, an in vitro study with pure cultures of Lactobacillus and Bifidobacterium was first conducted. Secondly, a study with mixed cultures using human fecal inocula was carried out in a simulator of the distal part of the colon. The obtained results showed an increase in the Lactobacillus and Bifidobacterium population, indicating that these ingredients are serious candidates to be considered as prebiotics.

A dynamic regression analysis tool for quantitative assessment of bacterial growth written in Python.

Herein, an open-source method to generate quantitative bacterial growth data from high-throughput microplate assays is described. The bacterial lag time, maximum specific growth rate, doubling time and delta OD are reported. Our method was validated by carbohydrate utilization of lactobacilli, and visual inspection revealed 94% of regressions were deemed excellent.

The effect of sun-dried raisins (Vitis vinifera L.) on the in vitro composition of the gut microbiota.

Modulation of the human gut microbiota has proven to have beneficial effects on host health. The aim of this work was to evaluate the effect of sun-dried raisins (SR) on the composition of the human gut microbiota. A full model of the gastrointestinal tract, which includes simulated mastication, a dynamic gastric model, a duodenal model and a colonic model of the human large intestine, was used. An increase in the numbers of bifidobacteria and lactobacilli was observed by plate-counting in response to the addition of either SR or FOS after 8 and 24 h fermentation. A significant decrease in Firmicutes and Bacteroidetes was observed in SR samples after 8 and 24 h fermentation. FOS resulted in the greatest production of short chain fatty acids. Sun-dried raisins demonstrated considerable potential to promote the colonization and proliferation of beneficial bacteria in the human large intestine and to stimulate the production of organic acids.

Microbiological Cutoff Values: A Critical Issue in Phenotypic Antibiotic Resistance Assessment of Lactobacilli and Bifidobacteria.

The purpose of this study was to assess the antimicrobial resistance profiles of several strains of Lactobacillus and Bifidobacterium spp. of probiotic interest. The International Organization for Standardization method was used to determine the minimal inhibitory concentrations of the antibiotics recommended by the European Food Safety Authority (EFSA). As a result, some of the tested microorganisms showed a visible growth up to the microbiological cutoff values indicated by EFSA guidelines in 2012. We were not able to categorize these strains as susceptible or resistant on the basis of antimicrobial resistance phenotypic testing as EFSA document does not explicitly deal with such a phenotypic condition where strains grow at antibiotic concentrations up to the established cutoff value. Although a few strains have been analyzed for this study, our findings highlight a potential challenge in accurately determining the antibiotic resistance in specific strains relevant for human and animal health.

Comparative proteomics: assessment of biological variability and dataset comparability.

BACKGROUND: Comparative proteomics in bacteria are often hampered by the differential nature of dataset quality and/or inherent biological deviations. Although common practice compensates by reproducing and normalizing datasets from a single sample, the degree of certainty is limited in comparison of multiple dataset. To surmount these limitations, we introduce a two-step assessment criterion using: (1) the relative number of total spectra (R TS ) to determine if two LC-MS/MS datasets are comparable and (2) nine glycolytic enzymes as internal standards for a more accurate calculation of relative amount of proteins. Lactococcus lactis HR279 and JHK24 strains expressing high or low levels (respectively) of green fluorescent protein (GFP) were used for the model system. GFP abundance was determined by spectral counting and direct fluorescence measurements. Statistical analysis determined relative GFP quantity obtained from our approach matched values obtained from fluorescence measurements. RESULTS: L. lactis HR279 and JHK24 demonstrates two datasets with an R TS value less than 1.4 accurately reflects relative differences in GFP levels between high and low expression strains. Without prior consideration of R TS and the use of internal standards, the relative increase in GFP calculated by spectral counting method was 3.92 ± 1.14 fold, which is not correlated with the value determined by the direct fluorescence measurement (2.86 ± 0.42 fold) with the p = 0.024. In contrast, 2.88 ± 0.92 fold was obtained by our approach showing a statistically insignificant difference (p = 0.95). CONCLUSIONS: Our two-step assessment demonstrates a useful approach to: (1) validate the comparability of two mass spectrometric datasets and (2) accurately calculate the relative amount of proteins between proteomic datasets.

Sweet potatoes as a basic component in developing a medium for the cultivation of lactobacilli.

A sweet potato medium (SPM) was formed with extract from baked sweet potatoes supplemented with 0, 4, or 8 g/L of each nitrogen source (beef extract, yeast extract, and proteose peptone #3) to form SPM1, SPM2, and SPM3 respectively. Lactobacilli MRS was used as control medium. Ten Lactobacillus strains containing an average of 2.34 ± 0.29 log CFU/mL were inoculated individually into batches of MRS, SPM1, SPM2, and SPM3. The growth patterns for the tested Lactobacillus strains growing in SPM2 and SPM3 were found to be similar to that in MRS. The average final population after 24 h of incubation in MRS, SPM2, and SPM3 reached 10.41 ± 0.35, 10.59 ± 0.27, and 10.72 ± 0.19 log CFU/mL respectively. SPM2 and SPM3 maintained higher pH values throughout the incubation period than MRS. These findings indicate that SPM2 can be a suitable medium for the growth of Lactobacillus and can provide an alternative at low-cost.

Stress response assessment of Lactobacillus sakei strains selected as potential autochthonous starter cultures by flow cytometry and nucleic acid double-staining analyses.

AIMS: The aim of this study was to apply the flow cytometry to Lactobacillus sakei strains, selected as potential autochthonous starters, to investigate dynamics and physiological heterogeneity of microbial behaviour under different stress conditions. METHODS AND RESULTS: A simultaneous nucleic acid double-staining assay was applied to discriminate cell populations in different physiological states after exposure to heat (50 and 55°C) and acid (pH 2·5 and 3·0) stresses. Alive cells with intact membranes, damaged cells still alive but with injured membranes, so with even a recovery ability, and dead cells with a permanent membrane damage were differentiated with a significant increase in damaged cells after stronger stress treatments. CONCLUSIONS: The existence and characteristics of subpopulations displaying heterogeneity in particular conditions are highly relevant, because specific subpopulations may show improved survival, changes and dynamics under stress conditions. SIGNIFICANCE AND IMPACT OF STUDY: This assay has potential for physiological research on lactic acid bacteria and for application in the food industry. The assessment of intermediate physiological states in Lb. sakei strains with recovery possibility could be an important criterion for application of potential starter cultures. Application of flow cytometry and characterization of sorted subpopulations may contribute to further understanding of diversity and heterogeneity in physiology of bacterial populations.

Assessment of the in vitro inhibitory activity of specific probiotic bacteria against different Escherichia coli strains.

BACKGROUND: Lactobacilli and bifidobacteria are often associated with health-promoting effects. These live microorganisms, defined as probiotics, are commonly consumed as part of fermented foods, such as yoghurt and fermented milks, or as dietary supplements. Escherichia coli is a gram-negative, rod-shaped bacterium commonly found in the lower intestine of warm-blooded organisms. As a part of the normal gut microbiota, this microorganism colonizes the gastrointestinal tract of animals and humans within a few hours after birth. All E. coli strains can produce a wide variety of biogenic amines responsible for potentially harmful systemic intoxications. Enterohemorrhagic E. coli serotype O157:H7 is a pathotype of diarrhoeagenic strains with a large virulence plasmid pO157 able to produce 1 or more Shiga toxins. METHODS: The overall aim of this study was to determine the inhibitory effects of different strains of probiotics on E. coli serotypes, including E. coli O157:H7 (CQ9485). In particular, the antagonistic activity of 4 Bifidobacterium strains (Probiotical SpA, Italy) and 16 lactic acid bacteria, more specifically 14 Lactobacillus spp. and 2 Streptococcus spp., was assessed against selected E. coli biotypes (ATCC 8739, ATCC 10536, ATCC 35218, and ATCC 25922). The diarrhoeagenic serotype O157:H7 was also tested. RESULTS: The experimental data collected demonstrated an in vitro significant inhibitory effect of 6 Lactobacillus strains, namely L. rhamnosus LR04, L. rhamnosus LR06, L. plantarum LP01, L. plantarum LP02, L. pentosus LPS01, and L. delbrueckii subsp. delbrueckii LDD01, and 2 Bifidobacterium strains, B. breve BR03 and B. breve B632. The inhibiting extent was slightly different among these strains, with L. delbrueckii subsp. delbrueckii LDD01 showing the highest activity on E. coli O157:H7. CONCLUSIONS: Most of the probiotics studied are able to antagonize the growth of the 5 strains of E. coli tested, including the O157:H7 biotype, well known for their characteristic to produce a wide variety of biogenic amines considered responsible for dangerous systemic intoxications.

Mutans streptococci and lactobacilli colonization in predentate children from the neonatal period to seven months of age.

BACKGROUND/AIMS: The aim of this study was to investigate the colonization of mutans streptococci (MS) and lactobacilli (LB) in predentate children from the neonatal period to 7 months. METHODS: A total of 957 mother-and-child pairs were recruited from birth and followed up at 7 months. The 283 children who did not have erupted teeth at the second visit were included in the study. Oral mucosal swabs were taken, and the presence of MS and LB was determined using a commercial microbiological culture kit. RESULTS: At mean ages of 34 days and 7 months, 9 and 11% of the infants, respectively, showed the presence of MS. In contrast, LB presence increased from 24 to 47% (p < 0.0001). MS presence in the neonatal period was associated with maternal MS counts of >10(5) CFU/ml (p = 0.05), while LB presence was associated with natural birth (p = 0.03) and maternal LB presence (p = 0.02). At 7 months, MS presence was associated with maternal MS counts (p = 0.02) and LB counts of >10(5) CFU/ml (p = 0.007). Additional predictors of MS presence at 7 months were a child's MS counts of >10(5) CFU/ml at the neonatal visit (p = 0.019) and nighttime bottle feeding (p = 0.024). LB presence at 7 months was associated with maternal LB (p < 0.001) and MS presence (p = 0.02). CONCLUSIONS: MS and LB can be detected by culture in the oral cavity as early as 34 days after birth. Their infection rates increase to 11 and 47%, respectively, by the time the children reach the end of the predentate stage of oral development.

Development of a probiotic delivery system from agrowastes, soy protein isolate, and microbial transglutaminase.

UNLABELLED: Probiotic delivery system was developed via the use of microbial transglutaminase (MTG) cross-linked soy protein isolate (SPI) incorporated with agrowastes such as banana peel (BE), banana pulp (BU), and pomelo rind (PR). Inoculums of Lactobacillus bulgaricus FTDC 1511 were added to the cross-linked protein matrix. The incorporation of agrowastes had significantly (P<0.05) reduced the strength, pH value, and the lightness of the SPI gel carriers, while sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles revealed that the occurring cross-links within the SPI gel carriers were attributed to the addition of MTG. Scanning electron microscope micrographs illustrated that SPI carriers containing agrowastes have exhibited a less-dense protein matrix. All the SPI carriers possessed maximum swelling ratio at 4 to 4.5 within 15 min in simulated gastric fluid (SGF), whereas the maximum swelling ratios of SPI/BE, SPI/BU, and SPI/PR were higher compared to that of control in simulated intestinal fluid (SIF). Additionally, SPI carriers in SGF medium did not show degradation of structure, whereas a major collapse of network was observed in SIF medium, indicating controlled-release in the intestines. The addition of agrowastes into SPI carriers led to a significantly (P<0.0001) lower release of L. bulgaricus FTDC 1511 in SGF medium and a higher release in SIF medium, compared to that of the control. SPI carriers containing agrowastes may be useful transports for living probiotic cells through the stomach prior to delivery in the lower intestines. PRACTICAL APPLICATION: Agrowastes could be utilized as a new probiotic carrier for enhanced gastrointestinal transit and during storage. This also reduces the amount of agrowastes accumulated.

Probiotics from an industrial perspective.

Probiotic products have gained popularity with consumers that expect that the products they consume are healthy and help them maintain health. Hence, the need and preferences of the consumers are translated into a product format concept. Probiotics have been used for a long time as natural components in supplements and functional foods, mainly in fermented dairy products. Most of the strains used as probiotics belong to the genera Lactobacillus and Bifidobacterium. By definition, a strain has to have documented health benefits, in order to be called a probiotic. Although each bacterial strain is unique, there are some points that are essential when selecting a probiotic regarding the genetic stability, survival, and technical properties of a strain. Proper components, food matrices and production processes need to be selected since the matrices may affect the viability of the strain in the product and the intestine. Survival in the product is considered a requirement for the beneficial effects of probiotics.

Use of whey lactose from dairy industry for economical kefiran production by Lactobacillus kefiranofaciens in mixed cultures with yeasts.

To evaluate the feasibility of producing kefiran industrially, whey lactose, a by-product from dairy industry, was used as a low cost carbon source. Because the accumulation of lactic acid as a by-product of Lactobacillus kefiranofaciens inhibited cell growth and kefiran production, the kefir grain derived and non-derived yeasts were screened for their abilities to reduce lactic acid and promote kefiran production in a mixed culture. Six species of yeasts were examined: Torulaspora delbrueckii IFO 1626; Saccharomyces cerevisiae IFO 0216; Debaryomyces hansenii TISTR 5155; Saccharomyces exiguus TISTR 5081; Zygosaccharomyces rouxii TISTR 5044; and Saccharomyces carlsbergensis TISTR 5018. The mixed culture of L. kefiranofaciens with S. cerevisiae IFO 0216 enhanced the kefiran production best from 568 mg/L in the pure culture up to 807 and 938 mg/L in the mixed cultures under anaerobic and microaerobic conditions, respectively. The optimal conditions for kefiran production by the mixed culture were: whey lactose 4%; yeast extract 4%; initial pH of 5.5; and initial amounts of L. kefiranofaciens and S. cerevisiae IFO 0216 of 2.1×10(7) and 4.0×10(6)CFU/mL, respectively. Scaling up the mixed culture in a 2L bioreactor with dissolved oxygen control at 5% and pH control at 5.5 gave the maximum kefiran production of 2,580 mg/L in batch culture and 3,250 mg/L in fed-batch culture.

Bioconversion of renewable resources into lactic acid: an industrial view.

Lactic acid, an anaerobic product of glycolysis, can be theoretically produced by synthetic route; however, it is commercially produced by homo-fermentative batch mode of operations. Factors affecting its production and strategies improving it are considered while devising an optimized protocol. Although a hetero-fermentative mode of production exists, it is rarely used for commercial production. Attempts to use Rhizopus sp. for lactic acid production through either hetero-fermentative or thermophilic conditions were not economical. Since almost 70% of the cost of its production is accounted by raw materials, R & D efforts are still focused to find economically attractive agri-products to serve as sources of carbon and complex nitrogen inputs to meet fastidious nutrient needs for microbial growth and lactic acid production. Therefore, need exists for using multi-pronged strategies for higher productivity. Its present production and consumption scenario is examined. Its optically active isomers and chemical structure permit its use for the production of several industrially important chemicals, health products (probiotics), food preservatives, and bio-plastics. In addition, its salts and esters appear to have a variety of applications.

Enhanced growth of lactobacilli in soymilk upon immobilization on agrowastes.

Cell immobilization is an alternative to microencapsulation for the maintenance of cells in a liquid medium. The objective of this study was to evaluate the effects of agrowastes from durian (Durio zibethinus), cempedak (Artocarpus champeden), and mangosteen (Garcinia mangostana) as immobilizers for lactobacilli grown in soymilk. Rinds from the agrowastes were separated from the skin, dried, and ground (150 microm) to form powders and used as immobilizers. Scanning electron microscopy revealed that lactobacilli cells were attached and bound to the surface of the immobilizers. Immobilized cells of Lactobacillus acidophilus FTDC 1331, L. acidophilus FTDC 2631, L. acidophilus FTDC 2333, L. acidophilus FTDC 1733, and L. bulgaricus FTCC 0411 were inoculated into soymilk, stored at room temperature (25 degrees C) and growth properties were evaluated over 168 h. Soymilk inoculated with nonimmobilized cells was used as the control. Utilization of substrates, concentrations of lactic and acetic acids, and changes in pH were evaluated in soymilk over 186 h. Immobilized lactobacilli showed significantly better growth (P < 0.05) compared to the control, accompanied by higher production of lactic and acetic acids in soymilk. Soymilk containing immobilized cells showed greater reduction of soy sugars such as stachyose, raffinose, sucrose, fructose, and glucose compared to the control (P < 0.05).

Fermentation characteristics of exopolysaccharide-producing lactic acid bacteria from sourdough and assessment of the isolates for industrial potential.

Lactic acid bacteria (LAB) with antimicrobial activity and high exopolysaccharide (EPS) production ability isolated from sourdough were studied for their fermentation characteristics as potential new starter cultures. The values of pH, titratable acidity, and viable cell counts were 4.06+/-0.009-4.50+/- 0.015, 0.787+/-0.020%-1.172+/-0.018%, and 8.78+/-0.08-8.98+/- 0.06 log CFU/ml, respectively. In order to select probiotics with a high survival rate in the gut, isolates were tested to assess resistance against the artificial gastric acid and bile juice. Viable LAB counts were significantly (p<0.05) affected by the acidity. At pH 2.0, the total declines in the initial bacterial counts were 4.52+/-0.07 log for S. thermophilus St-Body-1, >7.98+/-0.03 log for E. flavescens DU-10, >7.95+/-0.05 log for E. faecium DU-12, and 3.15+/- 0.06 log for L. amylovorus DU-21. Among the strains, L. amylovorus DU-21 was the only strain that had bile tolerance under simulated gastrointestinal conditions. In order to improve EPS production by L. amylovorus DU- 21, the influence of carbon source was studied. When glucose was used as a carbon source, EPS production dramatically increased to 17.19+/-0.28 g/l (p<0.05). The maximum cell growth (10.012+/-0.012 log CFU/ml) and EPS production (18.71+/-0.19 g/l) were achieved when 15 g/ l of glucose was employed as the carbon source.