Enhancement of intestinal hydrolysis of lactose by microbial beta-galactosidase (EC 3.2.1.23) of kefir

Metagenomic and Functional Characterization of Two Chilean Kefir Beverages Reveals a Dairy Beverage Containing Active Enzymes, Short-Chain Fatty Acids, Microbial β-Amyloids, and Bio-Film Inhibitors

Kefir beverage is a probiotic food associated with health benefits, containing probiotic microorganisms and biomolecules produced during fermentation. The microbial composition of these beverages varies among countries, geographical regions, and the substrates, therefore, the characterization of kefir beverages is of great relevance in understanding their potential health-promoting and biotechnological applications. Therefore, this study presents the metagenomic and functional characterization of two Chilean kefir beverages, K02 and K03, through shotgun and amplicon-based metagenomic, microbiological, chemical, and biochemical studies. Results show that both beverages’ microbiota were mainly formed by Bacteria (>98%), while Eukarya represented less than 2%. Regarding Bacteria, the most abundant genera were Acetobacter (93.43% in K02 and 80.99% in K03) and Lactobacillus (5.72% in K02 and 16.75% in K03), while Kazachstania was the most abundant genus from Eukarya (42.55% and 36.08% in K02 and K03). Metagenomic analyses revealed metabolic pathways for lactose and casein assimilation, biosynthesis of health-promoting biomolecules, and clusters for antibiotic resistance, quorum sensing communication, and biofilm formation. Enzymatic activities, microbial β-amyloids, and short-chain fatty acids (acetic acid and propionic acid) were also detected in these beverages. Likewise, both kefir beverages inhibited biofilm formation of the opportunistic pathogen Pseudomonas aeruginosa.

Characterization of Kefir Produced in Household Conditions: Physicochemical and Nutritional Profile, and Storage Stability

Kefir, a traditional fermented food, has numerous health benefits due to its unique chemical composition, which is reflected in its excellent nutritional value. Physicochemical and microbial composition of kefir obtained from fermented milk are influenced by the type of the milk, grain to milk ratio, time and temperature of fermentation, and storage conditions. It is crucial that kefir characteristics are maintained during storage since continuous metabolic activities of residual kefir microbiota may occur. This study aimed to examine the nutritional profile of kefir produced in traditional in use conditions by fermentation of ultra-high temperature pasteurized (UHT) semi-skimmed cow milk using argentinean kefir grains and compare the stability and nutritional compliance of freshly made and refrigerated kefir. Results indicate that kefir produced under home use conditions maintains the expected characteristics with respect to the physicochemical parameters and composition, both after fermentation and after refrigerated storage. This work further contributes to the characterization of this food product that is so widely consumed around the world by focusing on kefir that was produced in a typical household setting.

Draft Genome Sequences of Lactobacillus plantarum Strain K03D08 and Acetobacter syzygii Strain K03D05, Isolated from a Kefir Beverage Collected in Chile

Kefir is an ancestral food produced using microbial consortia whose composition varies depending on the geographical origin and the substrate used for fermentation. This dairy beverage is considered a probiotic food, and its consumption has been associated with several health benefits. This report describes the isolation of bacterial strains from Chilean kefir.

Kefir is an ancestral food produced using microbial consortia whose composition varies depending on the geographical origin and the substrate used for fermentation. This dairy beverage is considered a probiotic food, and its consumption has been associated with several health benefits. This report describes the isolation of bacterial strains from Chilean kefir.

Kefir: a multifaceted fermented dairy product

Kefir is a fermented dairy beverage produced by the actions of the microflora encased in the "kefir grain" on the carbohydrates in the milk. Containing many bacterial species already known for their probiotic properties, it has long been popular in Eastern Europe for its purported health benefits, where it is routinely administered to patients in hospitals and recommended for infants and the infirm. It is beginning to gain a foothold in the USA as a healthy probiotic beverage, mostly as an artisanal beverage, home fermented from shared grains, but also recently as a commercial product commanding shelf space in retail establishments. This is similar to the status of yogurts in the 1970s when yogurt was the new healthy product. Scientific studies into these reported benefits are being conducted into these health benefits, many with promising results, though not all of the studies have been conclusive. Our review provides an overview of kefir's structure, microbial profile, production, and probiotic properties. Our review also discusses alternative uses of kefir, kefir grains, and kefiran (the soluble polysaccharide produced by the organisms in kefir grains). Their utility in wound therapy, food additives, leavening agents, and other non-beverage uses is being studied with promising results.

Distal Mucosal Site Stimulation by Kefir and Duration of the Immune Response

Kefir is a fermented milk (drink) produced by the action of lactic acid bacteria, yeasts and acetic acid bacteria. We recently reported a comparative study on the effect of kefir containing viable or non-viable bacteria by studying their modulatory activity on the intestinal immune response. A functional dose was established in a murine model and the pattern of regulatory and pro-inflammatory cytokines induced was also studied. The existence of a common mucosal immune system implies that the immune cells stimulated in one mucosal tissue can spread and relocate through various mucosal sites. The aim of this work was to determine the effect of an oral administration of kefir on the duration of the intestinal mucosa immune response and the modulatory activity in distal mucosal sites, specifically in the peritoneal and pulmonary macrophages and in the bronchial tissue. BALB/c mice were fed with kefir or pasteurized kefir at doses previously determined as functional for intestinal mucosa immunomodulation. Kefir feeding was stopped and the number of IgA, IgG, IL-4, IL-6, IL-10, IIFNγ and TNFα producing cells was determined in the lamina propria of small intestine immediately, and after 2 and 7 days of kefir withdrawal. IgA producing cells were also measured in the bronchial tissue of lungs immediately and 2 and 7 days after kefir withdrawal. Phagocytic activity of peritoneal and pulmonary macrophages was also determined. The oral administration of kefir or pasteurized kefir increased the number of IgA+ cells not only in the gut lamina propria, but also in the bronchial tissue, supporting the concept of local antibody secretion after remote-site stimulation in the intestinal tract. Both peritoneal and pulmonary macrophages were activated by kefir or pasteurized kefir feeding. Peritoneal macrophages were stimulated faster than pulmonary macrophages (for kefir). The enhanced phagocytic activity achieved by kefir or pasteurized kefir lasted longer for the peritoneal than for the pulmonary macrophages. Due to the increased bronchial IgA and phagocytic activity of pulmonary macrophages after kefir feeding observed in this study, the oral administration of kefir could act as a natural adjuvant for enhancing the specific immune response against respiratory pathogens. The parameters studied returned to control values within a week of cessation of kefir administration. This would suggest that there is a low risk of overstimulating the gut mucosal immune system during periodic consumption of kefir.

The Antimetastatic and Antiangiogenesis Effects of Kefir Water on Murine Breast Cancer Cells

Background. Kefir is a unique cultured product that contains beneficial probiotics. Kefir culture from other parts of the world exhibits numerous beneficial qualities such as anti-inflammatory, immunomodulation, and anticancer effects. Nevertheless, kefir cultures from different parts of the world exert different effects because of variation in culture conditions and media. Breast cancer is the leading cancer in women, and metastasis is the major cause of death associated with breast cancer. The antimetastatic and antiangiogenic effects of kefir water made from kefir grains cultured in Malaysia were studied in 4T1 breast cancer cells. Methods. 4T1 cancer cells were treated with kefir water in vitro to assess its antimigration and anti-invasion effects. BALB/c mice were injected with 4T1 cancer cells and treated orally with kefir water for 28 days. Results. Kefir water was cytotoxic toward 4T1 cells at IC₅₀ (half-maximal inhibitory concentration) of 12.5 and 8.33 mg/mL for 48 and 72 hours, respectively. A significant reduction in tumor size and weight (0.9132 ± 0.219 g) and a substantial increase in helper T cells (5-fold) and cytotoxic T cells (7-fold) were observed in the kefir water–treated group. Proinflammatory and proangiogenic markers were significantly reduced in the kefir water–treated group. Conclusions. Kefir water inhibited tumor proliferation in vitro and in vivo mainly through cancer cell apoptosis, immunomodulation by stimulating T helper cells and cytotoxic T cells, and anti-inflammatory, antimetastatic, and antiangiogenesis effects. This study brought out the potential of the probiotic beverage kefir water in cancer treatment.

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.

Review: functional properties of kefir

Kefir is a unique cultured dairy product due to combined lactic acid and alcoholic fermentation of lactose in milk. Kefir is produced by microbial activity of "kefir grains" which have a relatively stable and specific balance of lactic acid bacteria and yeast. Due to the claimed health benefits of kefir which include reduction of lactose intolerance symptoms, stimulation of the immune system, lowering cholesterol, and antimutagenic and anticarcinogenic properties, kefir has become an important functional dairy food and consequently, research on kefir has increased in the past decade. In the following review, recent studies on the functional properties of kefir are reviewed.

Kefir induces cell-cycle arrest and apoptosis in HTLV-1-negative malignant T-lymphocytes

BACKGROUND

Adult lymphoblastic leukemia (ALL) is a malignancy that occurs in white blood cells. The overall cure rate in children is 85%, whereas it is only 40% in adults. Kefir is an important probiotic that contains many bioactive ingredients, which give it unique health benefits. It has been shown to control several cellular types of cancer.

PURPOSE

The present study investigates the effect of a cell-free fraction of kefir on CEM and Jurkat cells, which are human T-lymphotropic virus type I (HTLV-1)-negative malignant T-lymphocytes.

METHODS

Cells were incubated with different kefir concentrations. The cytotoxicity of the compound was evaluated by determining the percentage viability of cells. The effect of all the noncytotoxic concentrations of kefir on the proliferation of CEM and Jurkat cells was then assessed. The levels of transforming growth factor-alpha (TGF-α), transforming growth factor- beta1 (TGF-β1), matrix metalloproteinase-2 (MMP-2), and MMP-9 mRNA upon kefir treatment were then analyzed using reverse transcriptase polymerase chain reaction (RT-PCR). Finally, the growth inhibitory effects of kefir on cell-cycle progression/apoptosis were assessed by Cell Death Detection (ELISA) and flow cytometry.

RESULTS

The maximum cytotoxicity recorded after 48-hours treatment with 80 μg/μL kefir was only 42% and 39% in CEM and Jurkat cells, respectively. The percent reduction in proliferation was very significant, and was dose-, and time-dependent. In both cell lines, kefir exhibited its antiproliferative effect by downregulating TGF-α and upregulating TGF-β1 mRNA expression. Upon kefir treatment, a marked increase in cell-cycle distribution was noted in the preG(1) phase of CEM and Jurkat cells, indicating the proapoptotic effect of kefir, which was further confirmed by Cell Death Detection ELISA. However, kefir did not affect the mRNA expression of metalloproteinases needed for the invasion of leukemic cell lines.

CONCLUSION

In conclusion, kefir is effective in inhibiting proliferation and inducing apoptosis of HTLV-1-negative malignant T-lymphocytes. Therefore, further in vivo investigation is highly recommended.

Inhibitory activity of cheese whey fermented with kefir grains

We investigated the chemical and microbiological compositions of three types of whey to be used for kefir fermentation as well as the inhibitory capacity of their subsequent fermentation products against 100 Salmonella sp. and 100 Escherichia coli pathogenic isolates. All the wheys after fermentation with 10% (wt/vol) kefir grains showed inhibition against all 200 isolates. The content of lactic acid bacteria in fermented whey ranged from 1.04 × 10(7) to 1.17 × 10(7) CFU/ml and the level of yeasts from 2.05 × 10(6) to 4.23 × 10(6) CFU/ml. The main changes in the chemical composition during fermentation were a decrease in lactose content by 41 to 48% along with a corresponding lactic acid production to a final level of 0.84 to 1.20% of the total reaction products. The MIC was a 30% dilution of the fermentation products for most of the isolates, while the MBC varied between 40 and 70%, depending on the isolate. The pathogenic isolates Salmonella enterica serovar Enteritidis 2713 and E. coli 2710 in the fermented whey lost their viability after 2 to 7 h of incubation. When pathogens were deliberately inoculated into whey before fermentation, the CFU were reduced by 2 log cycles for E. coli and 4 log cycles for Salmonella sp. after 24 h of incubation. The inhibition was mainly related to lactic acid production. This work demonstrated the possibility of using kefir grains to ferment an industrial by-product in order to obtain a natural acidic preparation with strong bacterial inhibitory properties that also contains potentially probiotic microorganisms.

The antiproliferative effect of kefir cell-free fraction on HuT-102 malignant T lymphocytes

Kefir is produced by adding kefir grains (a mass of proteins, polysaccharides, bacteria, and yeast) to pasteurized milk; it has been shown to control several cellular types of cancer, such as Sarcoma 180 in mice, Lewis lung carcinoma, and human mammary cancer. Human T-cell lymphotropic virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia, which is a fatal disease with no effective treatment. The current study aims at investigating the effect of a cell-free fraction of kefir on HuT-102 cells, which are HTLV-1-positive malignant T-lymphocytes. Cells were incubated with different kefir concentrations: the cytotoxicity of the compound was evaluated by determining the percentage viability of cells. The effect of all the noncytotoxic concentrations of kefir cell-free fraction on the proliferation of HuT-102 cells was then assessed. The levels of transforming growth factor (TGF)-alpha mRNA upon kefir treatment were then analyzed using reverse transcriptase polymerase chain reaction. Finally, the growth inhibitory effects of kefir on cell cycle progression and/or apoptosis were assessed by flow cytometry. The maximum cytotoxicity recorded at 80 microg/microL for 48 hours was only 43%. The percent reduction in proliferation was very significant, dose and time dependent, and reached 98% upon 60-microg/microL treatment for 24 hours. Kefir cell-free fraction caused the downregulation of TGF-alpha, which is a cytokine that induces the proliferation and replication of cells. Finally, a marked increase in cell cycle distribution was noted in the pre-G1 phase. In conclusion, kefir is effective in inhibiting proliferation and inducing apoptosis of HTLV-1-positive malignant T-lymphocytes. Therefore, further in vivo investigation is highly recommended.

Kefir improves lactose digestion and tolerance in adults with lactose maldigestion

OBJECTIVE

Kefir is a fermented milk beverage that contains different cultures than yogurt. The objective of this study was to determine whether kefir improves lactose digestion and tolerance in adults with lactose maldigestion.

DESIGN

Randomized block design.

SUBJECTS

Fifteen healthy, free-living adults with lactose maldigestion.

MAIN OUTCOME MEASURES

Breath hydrogen excretion and lactose intolerance symptoms were monitored hourly for 8 hours after each test meal.

INTERVENTION

Subjects were fed test meals consisting of 20 g lactose portions of milk (2% reduced fat), plain and raspberry flavored kefir, and plain and raspberry flavored yogurt, each following an overnight (12 hour) fast.

STATISTICAL ANALYSIS

Mixed model ANOVA was performed on raw or transformed data, followed by Tukey HSD post hoc tests (when appropriate). Significance was defined as P<.05.

RESULTS

The breath hydrogen area under the curve (AUC) for milk (224+/-39 ppm x h) was significantly greater than for the plain yogurt (76+/-14 ppm x h, P<.001), the plain kefir (87+/-37 ppm x h, P<.001), and the flavored yogurt (76+/-14 ppm x h, P=.005). The flavored kefir had an intermediate response (156+/-26 ppm x h). The yogurts and kefirs all similarly reduced the perceived severity of flatulence by 54% to 71% relative to milk. Abdominal pain and diarrhea symptoms were negligible among the five treatments.

APPLICATIONS/CONCLUSION

Because kefir improved lactose digestion and tolerance in this study, its use may be another potential strategy for overcoming lactose intolerance. Further studies of other types of kefir for improving lactose digestion are warranted.

Probiotics--compensation for lactase insufficiency

Yogurt and other conventional starter cultures and probiotic bacteria in fermented and unfermented milk products improve lactose digestion and eliminate symptoms of intolerance in lactose maldigesters. These beneficial effects are due to microbial beta-galactosidase in the (fermented) milk product, delayed gastrointestinal transit, positive effects on intestinal functions and colonic microflora, and reduced sensitivity to symptoms. Intact bacterial cell walls, which act as a mechanical protection of lactase during gastric transit, and the release of the enzyme into the small intestine are determinants of efficiency. There is a poor correlation between lactose maldigestion and intolerance; in some studies, low hydrogen exhalation without significant improvement of clinical symptoms was observed. Probiotic bacteria, which by definition target the colon, normally promote lactose digestion in the small intestine less efficiently than do yogurt cultures. They may, however, alleviate clinical symptoms brought about by undigested lactose or other reasons.

[Lactose intolerance and consumption of milk and milk products]

The disaccharide lactose is present as a natural component of foods only in milk and dairy products. In the gastrointestinal tract, lactose is hydrolysed by the enzyme beta-galactosidase (lactase) into glucose and galactose. These components are absorbed. With the exception of the caucasian race, the lactase activity decreases in most people at an age of 4 to 6 years. Lactose intake can cause symptoms of bloating, flatulence, abdominal pain, and diarrhea due to the lactose reaching the large intestine. This phenomenon is called lactose intolerance. It is generally recommended to those persons that they refrain from the consumption of milk and dairy products. However, most lactose intolerant people are able to digest small amounts of milk. They can also consume cheese that contains no (hard and semi-hard) or only small amounts of lactose (present in only 10% of soft cheeses). These products are very important sources of calcium. Compared to milk, the lactose content of yogurt is usually lower by about one third. Studies during the last 10 years have shown that in spite of its lactose content yogurt is very well tolerated by lactose intolerant persons. This advantage is ascribed to the presence of living lactic acid bacteria in fermented dairy products which survive passage through the stomach and also to the lactase present in these products.