Oral administration of kefiran induces changes in the balance of immune cells in a murine model

Lactic acid bacteria-derived exopolysaccharide: Formation, immunomodulatory ability, health effects, and structure-function relationship

Exopolysaccharides (EPSs) synthesized by lactic acid bacteria (LAB) have implications for host health and act as food ingredients. Due to the variability of LAB-EPS (lactic acid bacteria-derived exopolysaccharide) gene clusters, especially the glycosyltransferase genes that determine monosaccharide composition, the structure of EPS is very rich. EPSs are synthesized by LAB through the extracellular synthesis pathway and the Wzx/Wzy-dependent pathway. LAB-EPS has a strong immunomodulatory ability. The EPSs produced by different genera of LAB, especially Lactobacillus, Leuconostoc, and Streptococcus, have different immunomodulatory abilities because of their specific structures. LAB-EPS possesses other health effects, including antitumor, antioxidant, intestinal barrier repair, antimicrobial, antiviral, and cholesterol-lowering activities. The bioactivities of LAB-EPS are tightly related to their structures such us monosaccharide composition, glycosidic bonds, and molecular weight (MW). For the excellent physicochemical property, LAB-EPS acts as product improvers in dairy, bakery food, and meat in terms of stability, emulsification, thickening, and gelling. We systematically summarize the detailed process of EPS from synthesis to application, with emphasis on physiological mechanisms of EPS, and specific structure-function relationship, which provides theoretical support for the potential commercial value in the pharmaceutical, chemical, food, and cosmetic industries.

Effects of kefir fermented milk beverage on sodium dextran sulfate (DSS)-induced colitis in rats

Background and aim

The etiopathogenesis of inflammatory bowel disease (IBD) is associated with different factors such as genetic, infectious, immunological, and environmental, including modification of the gut microbiota. IBD's conventional pharmacological therapeutic approaches have become a challenge due to side effects, complications from prolonged use, and higher costs. Kefir fermented milk beverage is a functional food that has demonstrated multiple beneficial effects including anti-inflammatory and antioxidant activity. Alternative therapeutic strategies have been used for IBD as more natural products with low-cost and easy acquisition. The aim of this study is to evaluate the anti-inflammatory effects of kefir fermented milk beverage on sodium dextran sulfate (DSS)-induced colitis in rats.

Methods

We used 4 groups to perform this study: baseline control (BC), kefir control (KC), 5% untreated DSS-induced colitis (DSS), and 5% DSS-induced colitis treated with kefir (DSSK). The animals received fermented kefir milk beverage ad libitum for six days and the disease activity index was recorded daily. Colon samples were processed for Transmission Electron Microscopy and histopathological evaluation. We analyzed short fatty chain acids through the fecal sample using gas chromatography.

Results

Kefir supplementation was able to reduce the clinical activity index and inflammatory process evidenced by decreased neutrophil accumulation, decreased reticulum edema, and increased autophagosomes. Also, showed a trend to increase the levels of acetate and propionate.

Conclusions

Our results suggest that kefir fermented milk beverage may have an anti-inflammatory effect minimizing the intestinal damage of DSS-induced colitis.

Kefir microbiota and metabolites stimulate intestinal mucosal immunity and its early development

Kefir consists of a large number of probiotics, which can regulate or shape the balance of intestinal microbiota, and enhance the host's immune response. Kefir microbiota can shape the mucosal immunity of the body through SCFAs, EPS, polypeptides, lactic acid, and other metabolites and microbial antigens themselves, and this shaping may have time windows and specific pathways. Kefir can regulate antibody SIgA and IL-10 levels to maintain intestinal homeostasis, and its secreted SIgA can shape the stable microbiota system by wrapping and binding different classes of microorganisms. The incidence of intestinal inflammation is closely linked to the development and maturation of intestinal mucosal immunity. Based on summarizing the existing research results on Kefir, its metabolites, and immune system development, this paper proposes to use Kefir, traditional fermented food with natural immune-enhancing components and stable functional microbiota, as an intervention method. Early intervention in the immune system may seize the critical window period of mucosal immunity and stimulate the development and maturation of intestinal mucosal immunity in time.

The Effects of Kefir and Kefir Components on Immune and Metabolic Physiology in Pre-Clinical Studies: A Narrative Review

Kefir, a fermented beverage made from kefir grains, has gained immense popularity around the world due to its potential health-promoting properties. Kefir beverages are both marketed commercially and brewed privately by individuals. Both milk and sugar solutions can be used as substrates with various additives included based on consumer preference. Fermentation occurs via microorganisms including lactic acid bacteria, acetic acid bacteria, and yeasts, which are naturally present in kefir grains. Health-promoting effects of kefir are thought to occur through immune, gastrointestinal, and metabolic regulation. Both clinical trials and mechanistic studies in cell culture and animal models have explored these effects. Studies in vitro and in animals have shown the ability of kefir and kefir components to antagonize pathogens, reduce proinflammatory cytokine production, contribute to cytotoxicity of tumor cell lines and reduce tumor burden, and improve serum glycemic and lipid profiles. However, some data from clinical trials are conflicting, and the precise mechanisms by which kefir promotes well-being are not completely defined. This review summarizes the current body of evidence in both cell culture and animal models that provide insight into the mechanisms by which kefir beverages may protect consumers from enteric infections and improve immune and metabolic health. We believe that readers will gain knowledge helpful for both developing more targeted mechanistic studies and selecting informative outcomes when designing clinical studies.

Lactobacillus kefiranofaciens: From Isolation and Taxonomy to Probiotic Properties and Applications

One of the main lactic acid bacterial species found in the kefir grain ecosystem worldwide is Lactobacillus kefiranofaciens, exhibiting strong auto-aggregation capacity and, therefore, being involved in the mechanism of grain formation. Its occurrence and dominance in kefir grains of various types of milk and geographical origins have been verified by culture-dependent and independent approaches using multiple growth media and regions of the 16S rRNA gene, respectively, highlighting the importance of their combination for its taxonomic identification. L. kefiranofaciens comprises two subspecies, namely kefiranofaciens and kefirgranum, but only the first one is responsible for the production of kefiran, the water-soluble polysaccharide, which is a basic component of the kefir grain and famous for its technological as well as health-promoting properties. L. kefiranofaciens, although very demanding concerning its growth conditions, can be involved in mechanisms affecting intestinal health, immunomodulation, control of blood lipid levels, hypertension, antimicrobial action, and protection against diabetes and tumors. These valuable bio-functional properties place it among the most exquisite candidates for probiotic use as a starter culture in the production of health-beneficial dairy foods, such as the kefir beverage.

Preventive oral kefir supplementation protects mice from ovariectomy-induced exacerbated allergic airway inflammation

Asthma is an inflammatory lung disease that affects more women than men in adulthood. Clinical evidence shows that hormonal fluctuation during the menstrual cycle and menopause are related to increased asthma severity in women. Considering that life expectancy has increased and that most women now undergo menopause, strategies to prevent the worsening of asthma symptoms are particularly important. A recent study from our group showed that re-exposure of ovariectomised allergic mice to antigen (ovalbumin) leads to an exacerbation of lung inflammation that is similar to clinical conditions. However, little is known about the role of probiotics in the prevention of asthma exacerbations during the menstrual cycle or menopause. Thus, our objective was to evaluate the effects of supplementation with kefir, a popular fermented dairy beverage, as a preventive strategy for modulating allergic disease. The results show that the preventive kefir administration decreases the influx of inflammatory cells in the airways and exacerbates the production of mucus and the interleukin 13 cytokine. Additionally, kefir changes macrophage polarisation by decreasing the number of M2 macrophages, as shown by RT-PCR assay. Thus, kefir is a functional food that potentially prevents allergic airway inflammation exacerbations in ovariectomised mice.

A review of nondairy kefir products: their characteristics and potential human health benefits

Functional foods are foods that, in addition to having nutrients, contain in their composition ingredients that act specifically on body functions associated with the control and reduction of the risk of developing some diseases. In this sense, kefir, a group of microorganisms in symbiosis, mainly yeasts and lactic acid bacteria, stands out. The trend of ingesting kefir has been focused on the development of products that serve specific consumers, such as those who are lactose-intolerant, vegans and vegetarians, and consumers in general who seek to combine the consumption of functional products with the improvement of their health and lifestyle. This overview provides an insight into kefir, presenting the technological process to produce a nondairy beverage and evidence of the benefits of its use to reduce the risk of disease. We also discuss regulatory aspects of products fermented using kefir. Until now, the use of kefir (isolated microorganism, kefiran, or fermented product) has demonstrated the potential to promote an increase in the number of bifidobacteria in the colon and an increase in the glycemic control while reducing the blood cholesterol and balancing the intestinal microbiota, which helps in reducing constipation and diarrhea, improving intestinal permeability, and stimulating and balancing the immune system. However, the literature still has gaps that need to be clarified, such as the consumption dose of kefir or its products to cause some health benefit.

Kefiran ameliorates malfunctions in primary and functional immune cells caused by lipopolysaccharides

Kefiran is a water-soluble polysaccharide well recognized as a bioactive ingredient to enhance nutritional and health-promoting features. Also, some therapeutic properties have made this macromolecule an active ingredient in ointments and oral anti-inflammatory drugs. However, the details of the molecular and cellular aspects of these effects have not been addressed. In this study, lipopolysaccharides (LPS)-induced monocytes, lymphocytes, and monocyte-derived dendritic cells (MDDCs) as representative cells for both innate and adaptive immunity were treated with kefiran for 2 h. Kefiran had an anti-inflammatory effect on monocytes to reduce pro-inflammatory cytokines, interleukin 1 β (IL-1β) & tumor necrosis factor α (TNF-α), as well as nuclear factor kappa b (NF-kb). However, it did not affect lymphocytes. Overexpression of Toll-like receptor 4 (TLR4) in LPS-induced cells was not reduced after kefiran treatment. Kefiran balanced MDDCs secretion of pro/anti-inflammatory cytokines by reducing and enhancing the expression of IL-1β and interleukin 10 (IL-10), respectively. Also, kefiran decreased the number of apoptotic immature MDDCs and promoted dose-dependent phagocytosis capacity of MDDCs. According to the results of the current study, it may be concluded that the immunomodulatory effects of kefiran are due to antagonist against innate immune receptors especially TLR4. The results of this study can be used as a guide to developing kefiran-based non-aggressive anti-inflammatory drugs. Furthermore, understanding the immunobiological effects of kefiran on monocytes and lymphocytes was another outcome of this study.

Kefir peptides alleviate high-fat diet-induced atherosclerosis by attenuating macrophage accumulation and oxidative stress in ApoE knockout mice

In the past decade, the high morbidity and mortality of atherosclerotic disease have been prevalent worldwide. High-fat food consumption has been suggested to be an overarching factor for atherosclerosis incidence. This study aims to investigate the effects of kefir peptides on high-fat diet (HFD)-induced atherosclerosis in apolipoprotein E knockout (ApoE^−/−) mice. 7-week old male ApoE^−/− and normal C57BL/6 mice were randomly divided into five groups (n = 8). Atherosclerotic lesion development in ApoE^−/− mice was established after fed the HFD for 12 weeks compared to standard chow diet (SCD)-fed C57BL/6 and ApoE^−/− control groups. Kefir peptides oral administration significantly improved atherosclerotic lesion development by protecting against endothelial dysfunction, decreasing oxidative stress, reducing aortic lipid deposition, attenuating macrophage accumulation, and suppressing the inflammatory immune response compared with the HFD/ApoE^−/− mock group. Moreover, the high dose of kefir peptides substantially inhibited aortic fibrosis and restored the fibrosis in the aorta root close to that observed in the C57BL/6 normal control group. Our findings show, for the first time, anti-atherosclerotic progression via kefir peptides consumption in HFD-fed ApoE^−/− mice. The profitable effects of kefir peptides provide new perspectives for its use as an anti-atherosclerotic agent in the preventive medicine.

Prospects of kefiran as a food-derived biopolymer for agri-food and biomedical applications

There is a huge demand for food-derived polysaccharides in the field of materials research due to the increasing concerns posed by synthetic biopolymers.

Fermented product of rice with Lactobacillus kefiranofaciens induces anti-aging effects and heat stress tolerance in nematodes via DAF-16

Rice kefiran is superior in functionality, has high concentration of mucilaginous polysaccharide, and low lipid content, compared to conventional kefiran. However, reports on its physiological functionality, especially studies on life expectancy and aging, in model organisms are rare. In this study, nematodes were used as model organisms that were fed rice kefiran, along with Escherichia coli OP50, as a result of which, the lifespan of nematodes was extended and age-related retardation of mobility was suppressed. It also increased the heat stress resistance in nematodes. Experiments using daf-16 deletion mutant revealed that rice kefiran functions via DAF-16. Thus, this study revealed the longevity, anti-aging and heat stress tolerance effects of rice kefiran in nematodes.

Effects of chocolate containing Leuconostoc mesenteroides strain NTM048 on immune function: a randomized, double-blind, placebo-controlled trial

Background

Previous reports showed that oral administration of Leuconostoc mesenteroides strain NTM048 increases IgA levels and CD4+ T cell population in feces and mice, respectively, as revealed by flow cytometric analysis of splenocytes. This study aimed to evaluate the effect of chocolate supplemented with L. mesenteroides strain NTM048 (> 1.00 × 10⁹ CFU/day, NTM048) on the immune parameters of healthy subjects, using a randomized, placebo-controlled, double-blinded study design.

Methods

Participants (mean age: 46.3 years) ingested 28 g of test food daily, at a time of their own choice, for 4 weeks. The immunological parameters of all participants were evaluated two times (pre- and post- ingestion). At the end of the study, various immunological parameters of the participants were measured and scoring of immunological vigor (SIV) was performed using a comprehensive algorithm.

Results

Ingestion of NTM048-supplemented chocolate significantly improved SIV in the NTM048 group (18.6 ± 1.6) compared to that in the placebo group (17.8 ± 2.0) after 4 weeks (p = 0.049). Several immunological parameters (CD8⁺T cells, CD8⁺CD28⁺ T cells, and memory T cells) were significantly elevated in the NTM048 group as compared to the placebo group (all p < 0.05). In addition, T cell proliferation index at post-ingestion significantly increased compared with that at pre-ingestion in the NTM048 (p = 0.017) and placebo groups (p = 0.037), although no differences were observed between the two groups.

Conclusion

Our results suggest that ingestion of chocolate supplemented with NTM048 is effective against the age-related decline in T cell-related immune functions.

Trial registration

UMIN Clinical Trials Registry UMIN000021989. Registered 19 April 2016, https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000025321

Antiobesity Effect of Exopolysaccharides Isolated from Kefir Grains

Physiological properties of water-soluble exopolysaccharides (EPS) and residues after EPS removal (Res) from the probiotic kefir were determined in high-fat (HF) diet-fed C57BL/6J mice. EPS solutions showed rheological properties and lower viscosity compared to those of β-glucan (BG). EPS significantly suppressed the adipogenesis of 3T3-L1 preadipocytes in a dose-dependent manner. Mice were fed HF diets containing 5% EPS, 5% BG, 8% Res, or 5% microcrystalline cellulose (control) for 4 weeks. Compared with the control, EPS supplementation significantly reduced HF diet-induced body weight gain, adipose tissue weight, and plasma very-low-density lipoprotein cholesterol concentration (P < 0.05). Res and BG significantly reduced body weight gain; however, reduction in adipose tissue weight was not statistically significant, suggesting that the antiobesity effect of EPS occurs due to viscosity and an additional factor. EPS supplementation significantly enhanced abundance of Akkermansia spp. in feces. These data indicate that EPS shows significant antiobesity effects possibly via intestinal microbiota alterations.

Kefir prevented excess fat accumulation in diet-induced obese mice

Excessive body fat accumulation can result in obesity, which is a serious health concern. Kefir, a probiotic, has recently shown possible health benefits in fighting obesity. This study investigated the inhibitory effects of 0.1 and 0.2% kefir powder on fat accumulation in adipose and liver tissues of high-fat diet (HFD)-induced obese mice. Kefir reduced body weight and epididymal fat pad weight and decreased adipocyte diameters in HFD-induced obese mice. This was supported by decreased expression of genes related to adipogenesis and lipogenesis as well as reduced proinflammatory marker levels in epididymal fat. Along with reduced hepatic triacylglycerol concentrations and serum alanine transaminase and aspartate transaminase activities, genes related to lipogenesis and fatty acid oxidation were downregulated and upregulated, respectively, in liver tissue. Kefir also decreased serum triacylglycerol, total cholesterol, and low-density lipoprotein–cholesterol concentrations. Overall, kefir has the potential to prevent obesity.

Milk kefir: nutritional, microbiological and health benefits

Kefir is fermented milk produced from grains that comprise a specific and complex mixture of bacteria and yeasts that live in a symbiotic association. The nutritional composition of kefir varies according to the milk composition, the microbiological composition of the grains used, the time/temperature of fermentation and storage conditions. Kefir originates from the Caucasus and Tibet. Recently, kefir has raised interest in the scientific community due to its numerous beneficial effects on health. Currently, several scientific studies have supported the health benefits of kefir, as reported historically as a probiotic drink with great potential in health promotion, as well as being a safe and inexpensive food, easily produced at home. Regular consumption of kefir has been associated with improved digestion and tolerance to lactose, antibacterial effect, hypocholesterolaemic effect, control of plasma glucose, anti-hypertensive effect, anti-inflammatory effect, antioxidant activity, anti-carcinogenic activity, anti-allergenic activity and healing effects. A large proportion of the studies that support these findings were conducted in vitro or in animal models. However, there is a need for systematic clinical trials to better understand the effects of regular use of kefir as part of a diet, and for their effect on preventing diseases. Thus, the present review focuses on the nutritional and microbiological composition of kefir and presents relevant findings associated with the beneficial effects of kefir on human and animal health.

Oral administration of kefiran exerts a bifidogenic effect on BALB/c mice intestinal microbiota

The activity of kefiran, the exopolysaccharide present in kefir grains, was evaluated on intestinal bacterial populations in BALB/c mice. Animals were orally administered with kefiran and Eubacteria, lactobacilli and bifidobacteria populations were monitored in faeces of mice at days 0, 2, 7, 14 and 21. Profiles obtained by Denaturing Gradient Gel Electrophoresis (DGGE) with primers for Eubacteria were compared by principal component analysis and clearly defined clusters, correlating with the time of kefiran consumption, were obtained. Furthermore, profile analysis of PCR products amplified with specific oligonucleotides for bifidobacteria showed an increment in the number of DGGE bands in the groups administered with kefiran. Fluorescent In Situ Hybridisation (FISH) with specific probes for bifidobacteria showed an increment of this population in faeces, in accordance to DGGE results. The bifidobacteria population was also studied on distal colon content after 0, 2 and 7 days of kefiran administration. Analysis of PCR products by DGGE with Eubacteria primers showed an increment in the number and intensity of bands with high GC content of mice administered with kefiran. Sequencing of DGGE bands confirmed that bifidobacteria were one of the bacterial populations modified by kefiran administration. DGGE profiles of PCR amplicons obtained by using Bifidobacterium or Lactobacillus specific primers confirmed that kefiran administration enhances bifidobacteria, however no changes were observed in Lactobacillus populations. The results of the analysis of bifidobacteria populations assessed on different sampling sites in a murine model support the use of this exopolysaccharide as a bifidogenic functional ingredient.

Intestinal immunomodulating activity and structural characterization of a new polysaccharide from stems of Dendrobium officinale

A newly branched Dendrobium officinale polysaccharide (DOP-W3-b) with a high intestinal immunomodulating activity and a relatively low molecular weight was obtained through a bioactivity-guided sequential isolation procedure.

Propriedades antimicrobianas do kefir

RESUMO: Os leites fermentados têm sido amplamente consumidos desde a Antiguidade e, atualmente, comercializados em todo o mundo. Kefir é um leite fermentado, ácido, levemente alcoólico, produzido artesanalmente a partir da fermentação do leite pelos grãos de kefir, os quais contêm uma população estável de micro-organismos. O processo fermentativo gera uma série de compostos que conferem sabor e aroma característicos ao kefir, além de substâncias bioativas, responsáveis por propriedades nutracêuticas. A utilização de micro-organismos com propriedades antimicrobianas como conservantes naturais é uma alternativa que tem como vantagem a inibição do desenvolvimento de bactérias deteriorantes e patogênicas sem o uso de substâncias químicas indesejáveis. O interesse em tais espécies aumentou nos últimos anos, viabilizando o uso desses micro-organismos probióticos como conservantes e inibidores naturais em vários produtos de origem animal, como leites, carnes e derivados. O objetivo deste trabalho foi apresentar uma revisão da literatura sobre as propriedades antimicrobianas atribuídas ao kefir.

The effects of postexercise consumption of a kefir beverage on performance and recovery during intensive endurance training

This study was designed to determine whether kefir accentuates the positive health benefits assessed by measures in fitness, body composition, or both, as a measure of cardiovascular disease risk as well as the biomarker C-reactive protein (CRP). Sixty-seven adult males and females aged 18 to 24 yr were assigned to 1 of 4 groups: (1) endurance training + control beverage, (2) endurance training +kefir beverage,(3) active control + control beverage, or (4) active control + kefir beverage. The exercise groups completed 15 wk of structured endurancetraining while the active control groups maintained their usual exercise routine. Additionally, each group was assigned to either a kefir or a calorie/macronutrient matched placebo beverage that was consumed twice per week. No significant interactions were found among groups with respect to outcome variables with the exception of serum CRP. The endurance training was effective in improving 1.5-mile (2.41 km) times and kefir supplementation may have been a factor in attenuating the increase in CRP that was observed over the course of the intervention period. This preliminary study suggests that kefir may be involved in improving the risk profile for cardiovascular disease as defined by CRP.

Bioprocess development for kefiran production by Lactobacillus kefiranofaciens in semi industrial scale bioreactor

Lactobacillus kefiranofaciens is non-pathogenic gram positive bacteria isolated from kefir grains and able to produce extracellular exopolysaccharides named kefiran. This polysaccharide contains approximately equal amounts of glucose and galactose. Kefiran has wide applications in pharmaceutical industries. Therefore, an approach has been extensively studied to increase kefiran production for pharmaceutical application in industrial scale. The present work aims to maximize kefiran production through the optimization of medium composition and production in semi industrial scale bioreactor. The composition of the optimal medium for kefiran production contained sucrose, yeast extract and K₂HPO₄ at 20.0, 6.0, 0.25 g L⁻¹, respectively. The optimized medium significantly increased both cell growth and kefiran production by about 170.56% and 58.02%, respectively, in comparison with the unoptimized medium. Furthermore, the kinetics of cell growth and kefiran production in batch culture of L. kefiranofaciens was investigated under un-controlled pH conditions in 16-L scale bioreactor. The maximal cell mass in bioreactor culture reached 2.76 g L⁻¹ concomitant with kefiran production of 1.91 g L⁻¹.

Selection of lactic acid bacteria from Brazilian kefir grains for potential use as starter or probiotic cultures

Brazilian kefir is a homemade fermented beverage that is obtained by incubating milk or a brown sugar solution with kefir grains that contribute their different microbiological compositions. It is highly important to isolate and characterize microorganisms from Brazilian kefir grains to obtain starter cultures for the industrial production of a standardized commercial kefir. Thus, the present study aimed to isolate lactic acid bacteria from eight kefir grains that were propagated in milk or sugar solutions from five different locations in Brazil and to select Lactobacillus isolates based on desirable in vitro probiotic properties. One hundred eight isolates from both substrates were identified by amplified ribosomal DNA restriction analysis and/or 16S rRNA gene sequencing and were determined to belong to the following 11 species from the genera: Lactococcus, Leuconostoc, Lactobacillus (L.), and Oenococcus. Leuconostoc mesenteroides, Lactobacillus kefiri, and Lactobacillus kefiranofaciens were isolated only from milk grains, whereas Lactobacillus perolens, Lactobacillus parafarraginis, Lactobacillus diolivorans, and Oenococcus oeni were isolated exclusively from sugar water grains. When the microbial compositions of four kefir grains were evaluated with culture-independent analyses, L. kefiranofaciens was observed to predominant in milk grains, whereas Lactobacillus hilgardii was most abundant in sugar water kefir. Unfortunately, L. hilgardii was not isolated from any grain, although this bacteria was detected with a culture-independent methodology. Fifty-two isolated Lactobacilli were tested for gastric juice and bile salt tolerance, antagonism against pathogens, antimicrobial resistance, and surface hydrophobicity. Three Lactobacillus strains (L. kefiranofaciens 8U, L. diolivorans 1Z, and Lactobacillus casei 17U) could be classified as potential probiotics. In conclusion, several lactic acid bacteria that could be used in combination with yeasts as starter cultures for both milk kefir and sugar water kefir were characterized, and the functional properties of several of the lactobacilli isolated from the kefir grains were suggestive of their possible use as probiotics in both kefir and other dairy products.

Gelling ability of kefiran in the presence of sucrose and fructose and physicochemical characterization of the resulting cryogels

In this work, the influence of sucrose and fructose on the gel-forming capacity of kefiran was investigated as well as the physicochemical characteristics of the resulting gels. The addition of sugar to gel-forming solutions did not alter the pseudoplastic flow properties of kefiran solutions and after one freeze-thaw cycle translucent gels with high water-holding capability were obtained. A highly porous matrix was revealed by microscopy whose pore size varied with sugar concentration. Sucrose and fructose had different effects on the rheological characteristics of sugar-kefiran gels. An increment in the strength of the gels with progressive concentrations of sucrose was evidenced by an increase in the elastic modulus (G'), indicating that sucrose reinforces the binding interactions between the polymer molecules (p ≤ 0.05). A drastic reduction in elastic modulus occurred, however, when 50.0 % w/w sucrose was added to kefiran gels, resulting in less elasticity. In contrast, when fructose was added to kefiran gels, elastic modulus decreased slightly with progressive sugar concentrations up to 10 %, thereafter increasing up to 50 % (p ≤ 0.05). Supplementation with up to 30 % sugar contributed to water retention and increased the viscous modulus. The relative increment in the elastic and viscous moduli elevated the loss tangent (tanδ) depending on the type and concentration of sugar. Sugars (sucrose, fructose) present in the matrix of the polysaccharide networks modified water-polymer and polymer-polymer interactions and consequently changed the gels' physicochemical characteristics, thus allowing the possibility of selecting the appropriate formulation through tailor-made kefiran cryogels.

Murine model of Bacillus cereus gastrointestinal infection

Bacillus cereus is a spore-forming micro-organism responsible for foodborne illness. In this study, we focus on the host response following intragastric challenge with a pathogenic B. cereus strain (B10502) isolated from a foodborne outbreak. C57BL/6J female mice were infected by gavage with strain B10502. Controls were administered with PBS. Infection leads to significant modification in relevant immune cells in the spleen, Peyer's patches (PP) and mesenteric lymph nodes (MLN). These findings correlated with an increase in the size of PP as compared with uninfected controls. Histological studies showed that B. cereus infection increased the ratio of intestinal goblet cells and induces mononuclear cell infiltrates in spleen at 5 days post-infection. Evaluation of cytokine mRNA expression demonstrated a significant increase in IFN-γ in MLN after 2 days of infection. The present work demonstrates that infection of mice with vegetative B. cereus is self-limited. Our findings determined relevant cell populations that were involved in the control of the pathogen through modification of the ratio and/or activation.

Microbiological, technological and therapeutic properties of kefir: a natural probiotic beverage

Kefir is a fermented milk beverage produced by the action of bacteria and yeasts that exist in symbiotic association in kefir grains. The artisanal production of the kefir is based on the tradition of the peoples of Caucasus, which has spread to other parts of the world, from the late 19^th century, and nowadays integrates its nutritional and therapeutic indications to the everyday food choices of several populations. The large number of microorganisms present in kefir and their microbial interactions, the possible bioactive compounds resulting of microbial metabolism, and the benefits associated with the use this beverage confers kefir the status of a natural probiotic, designated as the 21^th century yoghurt. Several studies have shown that kefir and its constituents have antimicrobial, antitumor, anticarcinogenic and immunomodulatory activity and also improve lactose digestion, among others. This review includes data on the technological aspects, the main beneficial effects on human health of kefir and its microbiological composition. Generally, kefir grains contain a relatively stable and specific microbiota enclosed in a matrix of polysaccharides and proteins. Microbial interactions in kefir are complex due to the composition of kefir grains, which seems to differ among different studies, although some predominant Lactobacillus species are always present. Besides, the specific populations of individual grains seem to contribute to the particular sensory characteristics present in fermented beverages. This review also includes new electron microscopy data on the distribution of microorganisms within different Brazilian kefir grains, which showed a relative change in its distribution according to grain origin.

Administration of kefir-fermented milk protects mice against Giardia intestinalis infection

Giardiasis, caused by the protozoan Giardia intestinalis, is one of the most common intestinal diseases worldwide and constitutes an important problem for the public health systems of various countries. Kefir is a probiotic drink obtained by fermenting milk with 'kefir grains', which consist mainly of bacteria and yeasts that coexist in a complex symbiotic association. In this work, we studied the ability of kefir to protect mice from G. intestinalis infection, and characterized the host immune response to this probiotic in the context of the intestinal infection. Six- to 8-week-old C75BL/6 mice were separated into four groups: controls, kefir mice (receiving 1 : 100 dilution of kefir in drinking water for 14 days), Giardia mice (infected orally with 4×10(7) trophozoites of G. intestinalis at day 7) and Giardia-kefir mice (kefir-treated G. intestinalis-infected mice), and killed at 2 or 7 days post-infection. Kefir administration was able to significantly reduce the intensity of Giardia infection at 7 days post-infection. An increase in the percentage of CD4(+) T cells at 2 days post-infection was observed in the Peyer's patches (PP) of mice belonging to the Giardia group compared with the control and kefir groups, while the percentage of CD4(+) T cells in PP in the Giardia-kefir group was similar to that of controls. At 2 days post-infection, a reduction in the percentage of B220-positive major histocompatibility complex class II medium cells in PP was observed in infected mice compared with the other groups. At 7 days post-infection, Giardia-infected mice showed a reduction in RcFcε-positive cells compared with the control group, suggesting a downregulation of the inflammatory response. However, the percentages of RcFcε-positive cells did not differ from controls in the kefir and Giardia-kefir groups. An increase in IgA-positive cells was observed in the lamina propria of the kefir group compared with controls at 2 days post-infection. Interestingly, the diminished number of IgA-positive cells registered in the Giardia group at 7 days post-infection was restored by kefir feeding, although the increase in IgA-positive cells was no longer observed in the kefir group at that time. No significant differences in CXCL10 expression were registered between groups, in concordance with the absence of inflammation in small-intestinal tissue. Interestingly, a slight reduction in CCL20 expression was observed in the Giardia group, suggesting that G. intestinalis might downregulate its expression as a way of evading the inflammatory immune response. On the other hand, a trend towards an increase in TNF-α expression was observed in the kefir group, while the Giardia-kefir group showed a significant increase in TNF-α expression. Moreover, kefir-receiving mice (kefir and Giardia-kefir groups) showed an increase in the expression of IFN-γ, the most relevant Th1 cytokine, at 2 days post-infection. Our results demonstrate that feeding mice with kefir reduces G. intestinalis infection and promotes the activation of different mechanisms of humoral and cellular immunity that are downregulated by parasitic infection, thus contributing to protection.

Assessment of the probiotic potential of a dairy product fermented by Propionibacterium freudenreichii in piglets

Dairy propionibacteria, including Propionibacterium freudenreichii , display promising probiotic properties, including immunomodulation. These properties are highly strain-dependent and rarely studied in a fermented dairy product. We screened 10 strains, grown in a newly developed fermented milk ultrafiltrate, for immunomodulatory properties in vitro. The most anti-inflammatory strain, P. freudenreichii BIA129, was further tested on piglets. P. freudenreichii -fermented product improved food intake and growth of piglets. Colonic mucosa explants of treated pigs secreted less interleukin 8 (-25%, P < 0.05) and tumor necrosis factor α (-20%, P < 0.05), either in basal conditions or after a lipopolysaccharide challenge. By contrast, the gut structure, barrier function (measured ex vivo in Ussing chambers), microbial diversity (assessed by 16S rRNA pyrosequencing), and colonic short-chain fatty acid content were unchanged, assuming maintenance of normal intestinal physiology. In conclusion, this work confirms in vivo probiotic properties of dairy propionibacteria-fermented products, which are promising for the prevention or healing of inflammatory bowel diseases.