16S Metagenomic Microbial Composition Analysis of Kefir Grain using MEGAN and BaseSpace

Kefir is a unique cultured product traditionally made from the fermentation of milk with kefir grains. Metagenomics analysis of kefir grain is essential to understand the composition of microbial populations in the kefir grain. Many microbial populations have been reported in kefir grains from different parts of the world. Although the kefir from Malaysian kefir grain is regularly consumed locally, no report has been made on the kefir grain microbial profile. The present study used kefir grain obtained locally and the microbial composition in the kefir grain was determined using Next Generation Sequencing (NGS). The taxonomic results analysis obtained when using BaseSpace (Illumina) and MEGAN were compared. The software agreed that Lactobacillus genus dominated the samples and the predominant species was L. kefiranofaciens (81.45–91.93%) while L. kefiri (2.01–2.47%) was the second in abundance. The results suggested that Malaysian kefir grain contained the same top two predominant species using both software methods and the microbial composition between both software did not vary significantly.     

Application of culture-dependent and culture-independent methods for the identification of Lactobacillus kefiranofaciens in microbial consortia present in kefir grains

The biological and technological characteristics of kefiran as well as its importance in grain integrity led us to analyze the microbial kefir grain consortium with focus on Lactobacillus kefiranofaciens. The presence of L. kefiranofaciens in the nine kefir grains studied was demonstrated by denaturing gradient gel electrophoresis. By culture dependent methods applying a methodology focused on the search of this species, 22 isolates with typical morphology were obtained and identified applying a combination of SDS-PAGE of whole cell proteins, (GTG)₅-PCR and sequence analysis of the housekeeping gene encoding the α-subunit of bacterial phenylalanyl-tRNA synthase (pheS). This polyphasic approach allowed the reliable identification of 11 L. kefiranofaciens, 5 Lactobacillus paracasei, 4 Lactobacillus kefiri and 2 Lactobacillus parakefiri isolates. Isolated L. kefiranofaciens strains produced polysaccharide in strain-dependent concentrations and EPS produced by them also differed in the degree of polymerization. The isolation and accurate identification of L. kefiranofaciens is relevant taking into account the important role of this microorganism in the grain ecosystem as well as its potential application as starter in food fermentations.     

Cell wall structure of selected yeast species as a factor of magnesium binding ability

This study was undertaken to determine the magnesium ion biosorption ability of the C. utilis and S. cerevisiae yeast species during cultivation in model media supplemented with magnesium. The mannoprotein and β-glucan content in the investigated yeast cell wall were analyzed because of the essential function of yeast cell wall structural components in metal ion binding. At the same time, an observation of yeast cells with the use of a transmission electron microscopy (TEM) was performed. The S. cerevisiae No. 1 yeast demonstrated the largest magnesium cation biosorption capacity. The magnesium content in biomass of S. cerevisiae No. 1 was about 16 mg Mg²⁺/g of dry substance after living cell incubation in MgSO₄ solution and about 18 mg Mg²⁺/g of dry substance after pasteurized biomass incubation in YPD medium supplemented with magnesium ions. The tested yeast strains differed in mannoprotein and β-glucan content in the cell wall. The cell wall of S. cerevisiae 102, coming from YPD + Mg²⁺ medium, contained the greatest amount of glycoproteins (approx. 66 % adjusted to a total sugar basis). The cell wall of C. utilis ATTC 9950 yeast incubated under the same conditions was composed mainly of β-glucans (approx. 78 %) with prevailing β-(1,6)-glucans in this glucose polymer fraction (approx. 53 %). In S. cerevisiae No. 1 and C. utilis yeasts, higher degrees of magnesium ion binding were observed in the presence of higher β-glucan content in the cell wall structure, whereas in S. cerevisiae, 102 cells the magnesium ion adsorption was determined mainly on the grounds of mannoprotein presence. The process of yeast cell pasteurization increased the magnesium ion binding ability in the tested fungi strains as a result of cell wall structure loosening.     

Effects of Lactobacillus kefiranofaciens M1 isolated from kefir grains on enterohemorrhagic Escherichia coli infection using mouse and intestinal cell models

A potential probiotic strain, Lactobacillus kefiranofaciens M1, was previously isolated from kefir grains, which are used to manufacture the traditional fermented drink kefir. The aim of this study was to investigate the effects of Lb. kefiranofaciens M1 on enterohemorrhagic Escherichia coli (EHEC) infection, using mice and intestinal cell models. BALB/c mice were daily administrated with either phosphate buffered saline or Lb. kefiranofaciens M1 at 2 × 10⁸ cfu/mouse per day intragastrically for 7 d. Intragastric challenges with EHEC (2 × 10⁹ cfu/mouse) were conducted on d 0, 4, and 7 after treatment. Administration of Lb. kefiranofaciens M1 was able to prevent EHEC infection-induced symptoms, intestinal damage, renal damage, bacterial translocation, and Shiga toxin penetration. Furthermore, the mucosal EHEC-specific IgA responses were increased after Lb. kefiranofaciens M1 administration in the EHEC-infected mouse system. Additionally, in vitro, Lb. kefiranofaciens M1 was shown to have a protective effect on Caco-2 intestinal epithelial cells and Caco-2 intestinal epithelial cell monolayers; the bacteria limited EHEC-induced cell death and reduced the loss of epithelial integrity. These findings support the potential of Lb. kefiranofaciens M1 treatment as an approach to preventing EHEC infection and its effects.     

Analysis of the microflora in Tibetan kefir grains using denaturing gradient gel electrophoresis

The microflora of Tibetan kefir grains was investigated by culture- independent methods. Denaturing gradient gel electrophoresis (DGGE) of partially amplified 16S rRNA for bacteria and 26S rRNA for yeasts, followed by sequencing of the most intense bands, showed that the dominant microorganisms were Pseudomonas sp., Leuconostoc mesenteroides, Lactobacillus helveticus, Lactobacillus kefiranofaciens, Lactococcus lactis, Lactobacillus kefiri, Lactobacillus casei, Kazachstania unispora, Kluyveromyces marxianus, Saccharomyces cerevisiae, and Kazachstania exigua. The bacterial communities between three kinds of Tibetan kefir grains showed 78–84% similarity, and yeasts 80–92%. The microflora is held together in the matrix of fibrillar material composed largely of a water-insoluble polysaccharide.     

Development of rapid and highly specific TaqMan probe-based real-time PCR assay for the identification and enumeration of Lactobacillus kefiri in kefir milk

Lactobacillus kefiri is one of the key functional lactic acid bacteria in kefir milk. We designed a novel real-time PCR primer/probe set, LK_508 targeting the recA gene, for the rapid identification and enumeration of L. kefiri. In inclusivity and exclusivity test using standard strains and kefir isolates, only the 9 tested L. kefiri strains were positive, with the remaining 38 closely related microorganisms testing negative, thus indicating 100% sensitivity and specificity of the assay. The population of L. kefiri was 3.77, 4.30, 4.79, and 5.63 log cfu mL⁻¹ of kefir milk fermented at 25 °C with 5% grain-milk ratio for 12, 24, 36, and 48 h, respectively. The newly developed qPCR assay could be applied to investigate the quantitative relationship of kefir microbiota in fermentation process.     

Comparison of antioxidant capacity of cow and ewe milk kefirs

This research aimed to evaluate the effects of using either grain or commercial starter culture on the antioxidative capacity of cow and ewe milk kefirs. The antioxidant capacity of kefir samples during fermentation and 21 d of storage was assessed by using 3 assays: 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical cation decolorization; 2,2-diphenyl-1-picrylhydrazyl (DPPH^?) radical scavenging activity assay; and Fe⁺³-reducing power (ferric reducing antioxidant power assay, FRAP). Vitamin E and β-carotene contents were also quantified. All kefir samples exhibited varying values for DPPH, ABTS, and FRAP assays depending on the starter culture and milk type. Vitamin E and β-carotene contents were similar in all kefir samples during storage. The results of this study suggest that milk type (cow or ewe) and culture type (kefir grains or commercial starter) were the significant parameters for the antioxidative activity of kefir.     

Effects of milk protein variants on the protein composition of bovine milk

The effects of β-lactoglobulin (β-LG), β-casein (β-CN), and κ-CN variants and β-κ-CN haplotypes on the relative concentrations of the major milk proteins α-lactalbumin (α-LA), β-LG, α_S1-CN, α_S2-CN, β-CN, and κ-CN and milk production traits were estimated in the milk of 1,912 Dutch Holstein-Friesian cows. We show that in the Dutch Holstein-Friesian population, the allele frequencies have changed in the past 16 years. In addition, genetic variants and casein haplotypes have a major impact on the protein composition of milk and explain a considerable part of the genetic variation in milk protein composition. The β-LG genotype was associated with the relative concentrations of β-LG (A » B) and of α-LA, α_S1-CN, α_S2-CN, β-CN, and κ-CN (B > A) but not with any milk production trait. The β-CN genotype was associated with the relative concentrations of β-CN and α_S2-CN (A² > A¹) and of α_S1-CN and κ-CN (A¹ > A²) and with protein yield (A² > A¹). The κ-CN genotype was associated with the relative concentrations of κ-CN (B > E > A), α_S2-CN (B > A), α-LA, and α_S1-CN (A > B) and with protein percentage (B > A). Comparing the effects of casein haplotypes with the effects of single casein variants can provide better insight into what really underlies the effect of a variant on protein composition. We conclude that selection for both the β-LG genotype B and the β-κ-CN haplotype A²B will result in cows that produce milk that is more suitable for cheese production.     

Microbiological and chemical properties of kefir manufactured by entrapped microorganisms isolated from kefir grains

In this study, various yeasts (Kluyveromyces marxianus, Saccharomyces turicensis, Pichia fermentans) and lactic acid bacteria (Lactobacillus kefiranofaciens, Lactobacillus kefiri, Leuconostoc mesenteroides) were entrapped in 2 different microspheres using an entrapment ratio for the strains that was based on the distribution ratio of these organisms in kefir grains. The purpose of this study was to develop a new technique to produce kefir using immobilized starter cultures isolated from kefir grains. An increase in cell counts with fermentation cycles was observed for both the lactic acid bacteria (LAB) and yeasts, whereas the cell counts of kefir grains were very stable during cultivation. Scanning electron microscopy showed that the short-chain lactobacilli and lactococci occupied the surface of the LAB microspheres, whereas the long-chain lactobacilli were inside the microspheres. When the yeasts were analyzed, cells at a high density were entrapped in cracks on the surface and within the microspheres, where they were surrounded by the short-chain lactobacilli. The distribution of the LAB and yeast species in kefir produced from grains and microspheres showed that there was no significant difference between the kefirs produced by the 2 methods; moreover, Leu. mesenteroides and K. marxianus were the predominating microflora in both types of kefir. There was no significant difference in the ethanol and exopolysaccharide contents between the 2 kefirs, although the acidity was different.     

Chemical composition of the cell wall of probiotic and brewer’s yeast in response to cultivation medium with glycerol as a carbon source

The structure of cell wall of yeasts (genus Saccharomyces) is one of the factors that determine their health-promoting properties connected to the presence of β-glucans and mannoprotein. The aim of the study was to determine the influence of glycerol as a carbon source on structural polymers of cell wall (β-glucan and mannoprotein) of probiotic yeasts Saccharomyces cerevisiae var. boulardii and brewer’s yeasts S. cerevisiae R9. Significant increase of the percentage of polysaccharide content in the cell wall dry weight of S. cerevisiae R9 brewer’s yeasts was noted (in the range of 10–20 %) after cultivation in medium containing glycerol at a concentration of 2–5 % and pH 4.0. The highest content of carbohydrates in probiotic yeasts’ cell wall (58 %) was observed after cultivation in medium containing 3 % of glycerol and pH 5.0. The cell wall of probiotic yeasts was characterized by higher content of mannoprotein comparing with cell wall preparation of brewer’s yeasts S. cerevisiae R9 composed mainly of β-glucans. After cultivation in mediums with 2 and 3 % of glycerol, the cell of brewer’s yeasts contained the highest amount of β(1,3/1,6)-glucan in dry weight of the cell wall (about 36 %). Glycerol at a concentration of 3 and 5 % also intensified mannoprotein biosynthesis in cell wall of S. cerevisiae R9, approximating their content to those noted in the cells of probiotic yeasts (about 29 % (w/w) of dry weight of the cell wall) after cultivation in a medium of pH 5.0 containing 3 % of glycerol.     

Modulation of the intestinal microbiota of dogs by kefir as a functional dairy product

Kefir is a traditional dairy product with multiple probiotic characteristics derived from its associated microorganisms, including more than 50 species of lactic acid bacteria and yeast. For centuries, many people have produced kefir for human consumption; its consumption and potential role as a probiotic supplement in companion animals have never been tested. The present study explored the potential application of kefir as a probiotic supplement for dogs. Kefir was orally administered to healthy adult dogs (n = 6) for 2 wk. On d 0 and 14 (before and after kefir consumption, respectively), gut microbiota was analyzed comprehensively using quantitative PCR and 16S rDNA amplicon-based community analysis using fresh fecal samples. The 16S rDNA amplicon-based community analysis showed that the relative abundance of the phylum Fusobacteria was significantly decreased after kefir consumption. Furthermore, the relative abundance of the families Prevotellaceae, Selenomonadaceae, and Sutterellaceae increased significantly, whereas that of the families Clostridiaceae, Fusobacteriaceae, and Ruminococcaceae decreased significantly. The quantitative PCR assay showed that kefir consumption significantly increased the population of lactic acid bacteria and the lactic acid bacteria:Enterobacteriaceae ratio and significantly decreased the Firmicutes:Bacteroidetes ratio. In summary, 2-wk kefir administration successfully modified the gut microbiota without causing any clinically evident adverse effects. Therefore, kefir could be further developed as a novel probiotic food supplement for dogs to improve the quality of life of dogs.     

Effects of kefir supernatant and lactic acid bacteria isolated from kefir grain on cytokine production by macrophage

The objective of this study was to investigate the in vitro immuno-modulating capacity and mechanisms of lactic acid bacteria (LAB) isolated from kefir grains and their individual supernatants by cytokine profiles through a toll-like receptor pathway. Results demonstrated that kefir supernatants, obtained from kefir fermented more than 24 h, induced the production of pro-inflammatory cytokines in RAW 264.7 cells. Among four LAB isolated from kefir grains and their supernatants, Lactobacillus kefiranofaciens M1 and its supernatant had strong potential to induce in vitro production of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-12 in RAW 264.7 cells and murine peritoneal macrophages. Moreover, blocking toll-like receptor (TLR)-2 using anti-TLR-2 mAb and TLR-2^?/? mice showed a significant inhibition (p < 0.05) of IL-6 and TNF-α production. These findings indicated that kefir influenced the secretion of pro-inflammatory cytokines TNF-α and IL-6 through TLR-2, which would potentially have beneficial effects on promotion of cell-mediated immune responses against tumors and also against intracellular pathogenic infections. The putative immunomodulin in the kefir supernatant was also characterized and may be a protein with a molecular mass larger than 30 kDa.     

Proteomic analysis of the temporal expression of bovine milk proteins during coliform mastitis and label-free relative quantification

The discovery of biomarkers in milk indicative of local inflammation or disease in the bovine mammary gland has been hindered by the extreme biological complexity of milk, the dynamic range of proteins in the matrix that renders the identification of low-abundance proteins difficult, and the challenges associated with quantifying changes during disease in the abundance of proteins for which no antibody exists. The objectives of the current study were to characterize the temporal expression of milk proteins following Escherichia coli challenge and to evaluate change in relative abundance of identified proteins using a liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) label-free semiquantitative approach. Liquid chromatography-MS/MS conducted on whey from milk samples collected just before infusion with E. coli and at 12, 18, 24, 36, 48, and 60 h following infection resulted in the identification of the high- to medium-abundance proteins α_S1-, α_S2- β-, and κ-caseins and the whey proteins serum albumin, β-lactoglobulin, and α-lactalbumin. Additionally, a select number of lower abundance markers of inflammation were also identified, including lactoferrin, transferrin, apolipoprotein AI, fibrinogen, glycosylation-dependent cell adhesion molecule-1, peptidoglycan recognition receptor protein, and cyclic dodecapeptide-1. Normalized peptide counts for each protein identified were used to evaluate temporal changes in milk proteins following infection. For comparison with relative protein abundance determined using proteomic-based methods, changes in serum albumin, lactoferrin, and transferrin in milk during disease were also measured using ELISA. Label-free, proteomic-based quantification revealed relative changes in milk proteins that corresponded to expression profiles generated by ELISA. The results indicate that label-free LC-MS/MS methods are a viable means of tracking changes in relative protein abundance in milk during disease. Despite the identification of primarily abundant milk proteins, the results indicate that, with further refinement, LC-MS/MS could be used to evaluate temporal changes in proteins related to host response for which no antibody or ELISA currently exists.     

Microbial diversity and stability during primary cultivation and subcultivation processes of Tibetan kefir

In this study, we have investigated the microbial diversity and stability in the Tibetan kefir during the primary cultivation and subcultivation processes via a combination of culture‐independent and culture‐dependent methods. According to the culture‐independent methods, the profiles of PCR‐DGGE (polymerase chain reaction–denaturing gradient gel electrophoresis) indicated that nine microbial species were predominant at different cultivation stages; seventy four isolates of seven predominant species were obtained and identified via the culture‐dependent methods. PCR‐DGGE further confirmed that Lactobacillus kefiranofaciens, Lactobacillus kefiri, Lactobacillus paracasei, Streptococcus thermophilus, Kazachstania unispora and Saccharomyces cerevisiae were the most dominant species in the Tibetan kefir during the process of primary cultivation, among which Lb. kefiri, Lb. paracasei and K. unispora showed relative strong stability during both the processes of primary cultivation and subcultivation. These findings suggested that some isolates of the three species possessed the potentiality of being used in the development of direct vat set (DVS) starters for the production of Tibetan kefir and the related products.     

Cryogelation phenomena in mixed skim milk powder – barley β-glucan–polyol aqueous dispersions

The effects of polyols (fructose, glucose, sorbitol, sucrose and xylose) on cryostructurization of barley mixed-linkage (1 → 3), (1 → 4) β-d-glucans (β-glucans) in the presence of skim milk proteins were investigated; three β-glucan isolates differing in molecular size (apparent molecular weight of 210, 140 and 70 × 10³ Da) were used. Polyols were incorporated at 15% (w/w) concentration into aqueous β-glucan (3% w/w)–skim milk (12% w/w) dispersions and the mixed dispersions were subjected to 14 repeated freezing (−15 °C for 24 h) and thawing (5 °C for 24 h) cycles; all preparations gave compact, opaque gels. For the high molecular weight (210 × 10³) preparation, with exception of sorbitol, the addition of polyols to β-glucan-skim milk dispersions retarded the cryostructurization, as shown by phenomenological observations after each freezing–thawing cycle and resulted in weaker cryostructurates compared to those of control (polyol-free gels), as determined by small deformation mechanical measurements. Xylose and fructose showed a stronger inhibitory effect on structure formation compared to sucrose and glucose, whereas sorbitol appeared as a network promoting co-solute. However, the above effects of polyols were largely diminished with decreasing of the β-glucan molecular weight and seemed to be independent on the type of polyol for the 140 and 70 × 10³ β-glucan samples. Despite the fact that molecular weight of β-glucans can have an impact on the effect of individual polyol on thermostability of cryogels, generally it seems that the melting temperature (T_m) of β-glucan-skim milk cryostructurates, as determined by dynamic rheometry, followed the order sorbitol > sucrose > control, glucose > fructose > xylose. On the other hand, large deformation mechanical tests (compression mode) revealed an increase in firmness and a decrease in brittleness of β-glucan–skim milk cryogels with inclusion of polyols in the order of: sorbitol < sucrose, xylose < fructose, glucose.     

Determination of lactic microflora of kefir grains and kefir beverage by using culture-dependent and culture-independent methods

Abstract: In this study, we investigated the bacterial compositions of kefir grains and kefir beverages collected from different regions of Turkey by using culture‐independent and culture‐dependent methods. In the culture‐independent detection, 10 different species of bacteria were detected in total by using the polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) analysis of the 16S rRNA gene V3 region. Among these species, Lactobacillus kefiranofaciens was the most dominant one in the kefir grains, while Lactococcus lactis was found to be significantly prevalent in the kefir beverages. In the culture‐dependent detection, the primary differentiation and grouping of the isolates from kefir beverages and kefir grains were performed using repetitive sequence‐based PCR (rep‐PCR) fingerprinting, and the results were validated by 16S rDNA full‐length sequencing. According to the results of culture‐dependent methods, the most frequently isolated species were L. lactis, Leuconostoc mesenteroides, and Lactobacillus kefiri, respectively. Only 3 species, which are L. lactis, Lactobacillus acidophilus, and Streptococcus thermophilus, were detected with both culture‐dependent and culture‐independent methods. This study showed that the combination of both methods is necessary for a detailed and reliable investigation of microbial communities in kefir grains and kefir beverages. Practical Application: Due to their artisan‐ and region‐dependent microflora, kefir products can be a source of interesting lactic acid bacteria, either new taxa or strains with specific functional properties, which might be used for the development of new starter cultures and innovative food products. Therefore, an increasing demand exists for new strains that show desirable effects on the product characteristics Artisan dairy products are a candidate source of such microorganisms. For this reason, in this study, the bacterial compositions of kefir grains and kefir beverages obtained from different regions of Turkey were studied using culture‐dependent and culture‐independent molecular methods.     

Barley β-glucan extracts as rich sources of polyphenols and antioxidants

Barley β-glucan is a functional ingredient implicated to lower glycemic response, plasma cholesterol and food intake. The objective of the present study was to analyse the polyphenol content and antioxidant activities of four different solvent extracts of three barley β-glucan samples – Glucagel, Barley Balance (BB) and barley fibre rich fraction (BFRF). The polyphenol content and antioxidant activities of the β-glucans were in the order BFRF > BB > Glucagel (P < 0.05). Of the four different solvents used (70% acetone, 70% methanol, 70% ethanol and acidified methanol), 70% acetone gave the highest phenolic content (P < 0.05). The free radical scavenging capacities of 200 mg of BB and BFRF in 70% acetone were very similar to 40 μg of standard gallic acid, ferulic acid, ascorbic acid and trolox. We discuss the possibility that health benefits associated with β-glucan samples might depend on their polyphenol and antioxidant contents that vary with method of preparation and purity.     

Short communication: Effect of kefir grains on proteolysis of major milk proteins

The effect of kefir grains on the proteolysis of major milk proteins in milk kefir and in a culture of kefir grains in pasteurized cheese whey was followed by reverse phase-HPLC analysis. The reduction of κ-, α-, and β-caseins (CN), α-lactalbumin (α-LA), and β-lactoglobulin (β-LG) contents during 48 and 90 h of incubation of pasteurized milk (100 mL) and respective cheese whey with kefir grains (6 and 12 g) at 20°C was monitored. Significant proteolysis of α-LA and κ-, α-, and β-caseins was observed. The effect of kefir amount (6 and 12 g/100 mL) was significant for α-LA and α- and β-CN. α-Lactalbumin and β-CN were more easily hydrolyzed than α-CN. No significant reduction was observed with respect to β-LG concentration for 6 and 12 g of kefir in 100 mL of milk over 48 h, indicating that no significant proteolysis was carried out. Similar results were observed when the experiment was conducted over 90 h. Regarding the cheese whey kefir samples, similar behavior was observed for the proteolysis of α-LA and β-LG: α-LA was hydrolyzed between 60 and 90% after 12 h (for 6 and 12 g of kefir) and no significant β-LG proteolysis occurred. The proteolytic activity of lactic acid bacteria and yeasts in kefir community was evaluated. Kefir milk prepared under normal conditions contained peptides from proteolysis of α-LA and κ-, α-, and β-caseins. Hydrolysis is dependent on the kefir:milk ratio and incubation time. β-Lactoglobulin is not hydrolyzed even when higher hydrolysis time is used. Kefir grains are not appropriate as adjunct cultures to increase β-LG digestibility in whey-based or whey-containing foods.     

Short communication: Conservation of Streptococcus uberis adhesion molecule and the sua gene in strains of Streptococcus uberis isolated from geographically diverse areas

The objective was to identify and sequence the sua gene (GenBank no. DQ232760; http://www.ncbi.nlm.nih.gov/genbank/) and detect Streptococcus uberis adhesion molecule (SUAM) expression by Western blot using serum from naturally S. uberis-infected cows in strains of S. uberis isolated in milk from cows with mastitis from geographically diverse areas of the world. All strains evaluated yielded a 4.4-kb sua-containing PCR fragment that was subsequently sequenced. Deduced SUAM AA sequences from those S. uberis strains evaluated shared >97% identity. The pepSUAM sequence located at the N terminus of SUAM was >99% identical among strains of S. uberis. Streptococcus uberis adhesion molecule expression was detected in all strains of S. uberis tested. These results suggest that sua is ubiquitous among strains of S. uberis isolated from diverse geographic locations and that SUAM is immunogenic.     

Effect of fermentation on content,molecule weight distribution and viscosity of β-glucans in oat sourdough

This study investigated the effect of fermentation on the physicochemical properties of β-glucans in oat sourdough. Sourdoughs were produced from oat using homo-fermentative lactic acid bacteria, Lactobacillus plantarum 22134. The contents of total β-glucan and soluble β-glucan, the molecular weight (MW) of β-glucan and the viscosity of the extracted β-glucans were determined at 0, 4, 8, 10 and 12 h of fermentation. The total β-glucan content decreased from 4.89% to 4.23% after 12 h of fermentation. The soluble β-glucan concentration increased from 1.89% to 2.18% and then decreased to 1.97% after 8 h of fermentation. The content of β-glucans with MW > 10⁵ decreased from 0 to 4 h of fermentation, followed by an increase and then a decrease after 8 h. The oat sourdough fermented for 8 h had high viscosity, which could be more beneficial for health and bread texture quality, especially for gluten-free breads.