Bifidobacteria In Fermented Milk Research Articles

Effects of milk components and food additives on survival of three bifidobacteria strains in fermented milk under simulated gastrointestinal tract conditions.

BackgroundIn the dairy industry, probiotic strains of Bifidobacterium are introduced into the composition of traditional starter cultures intended for the production of fermented foods, or sometimes are the sole microflora responsible for the fermentation process. In order to be able to reach the intestines alive and fulfil their beneficial role, probiotic strains must be able to withstand the acidity of the gastric juices and bile present in the duodenum.ObjectiveThe paper reports effects of selected fermented milk components on the viability of three strains of bifidobacteria in fermented milk during subsequent incubation under conditions representing model digestive juices.DesignThe viability of the bifidobacterial cells was examined after a 3-h incubation of fermented milk under simulated gastric juice conditions and then after 5-h incubation under simulated duodenum juice conditions. The Bifidobacterium strains tested differed in their sensitivity to the simulated conditions of the gastrointestinal juices.ResultsBifidobacterial cell viability in simulated intestinal juices was dependent on the strain used in our experiments, and product components acted protectively towards bifidobacterial cells and its dose.ConclusionsBifidobacterial cells introduced into the human gastrointestinal tract as food ingredients have a good chance of survival during intestinal transit and to reach the large intestine thanks to the protective properties of the food components and depending on the strain and composition of the food.

Development of a selective culture medium for bifidobacteria, Raffinose-Propionate Lithium Mupirocin (RP-MUP) and assessment of its usage with Petrifilm™ Aerobic Count plates

This study aimed to develop a selective culture media to enumerate bifidobacteria in fermented milk and to assess this medium when used with Petrifilm™ AC plates. For this purpose, Bifidobacterium spp., Lactobacillus spp. and Streptococcus thermophilus strains were tested to verify their fermentation patterns for different carbohydrates. All bifidobacteria strains were able to use raffinose. Based on these characteristic, a selective culture medium was proposed (Raffinose-Propionate Lithium Mupirocin, RP-MUP), used with Petrifilm™ AC plates, and was used to enumerate bifidobacteria in fermented milk. RP-MUP performance was assessed by comparing the results with this medium to reference protocols and culture media for bifidobacteria enumeration. RP-MUP, whether used or not with Petrifilm™ AC, presented similar performance to TOS-MUP (ISO 29981), with no significant differences between the mean bifidobacteria counts (p < 0.05) and with high correlation indices (r = 0.99, p < 0.05). As an advantage, reliable results were obtained after just 48 h of incubation when RP-MUP was used with Petrifilm™ AC, instead of the 72 h described in the ISO 29981 protocol.

Improved viability of bifidobacteria in fermented milk by cocultivation with Lactococcus lactis subspecies lactis

The poor survival of probiotic bacteria in commercial yogurts may limit their potential to exert health benefits in humans. The objective was to improve the survival of bifidobacteria in fermented milk. Cocultivation with some strains of Lactococcus lactis ssp. lactis improved the survival of bifidobacteria in fermented milk during refrigerated storage. Studies on one strain, Lc. lactis ssp. lactis MCC866, showed that the concentrations of dissolved oxygen were kept lower in the cocultivated fermented milk during storage compared with monocultured Bifidobacterium longum BB536 or samples cocultured with another noneffective Lc. lactis ssp. lactis strain. Degradation of genomic DNA was suppressed in the cocultivating system with Lc. lactis ssp. lactis MCC866. Several genes that participated in protection from active oxygen species (e.g., genes coding for alkyl hydroperoxide reductase and Fe2+ transport system) were expressed at higher levels during refrigerated storage in Lc. lactis ssp. lactis MCC 866 compared with another noneffective Lc. lactis ssp. lactis strain. Concentration of free iron ion was also lower in supernatants of fermented milk cocultivated with B. longum BB536 and Lc. lactis ssp. lactis MCC866. These results suggest that Lc. lactis ssp. lactis MCC 866 is potentially superior in reducing oxygen damage and consequently improves the survival of bifidobacteria in the cocultivating system. This cocultivation system is of industrial interest for producing fermented milk containing viable bifidobacteria with long shelf life.

Use of Tuf Gene‐Based Primers for the PCR Detection of Probiotic Bifidobacterium Species and Enumeration of Bifidobacteria in Fermented Milk by Cultural and Quantitative Real‐Time PCR Methods

Due to the increasing use of bifidobacteria in probiotic products, it is essential to establish a rapid method for the qualitative and quantitative assay of the bifidobacteria in commercial products. In this study, partial sequences of the tuf gene for 18 Bifidobacterium strains belonging to 14 species were determined. Alignment of these sequences showed that the similarities among these Bifidobacterium species were 82.24% to 99.72%. Based on these tuf gene sequences, 6 primer sets were designed for the polymerase chain reaction (PCR) assay of B. animalis subsp. animalis, B. animalis subsp. lactis, B. bifidum, B. breve, B. longum subsp. infantis, B. longum subsp. longum, and the genus of Bifidobacterium, respectively. These Bifidobacterium species are common probiotic species present in dairy and probiotic products. When each target Bifidobacterium spp. was assayed with the designed primers, PCR product with expected size was generated. In addition, for each target species, more than 70 bacterial strains other than the target species, including strains of other Bifidobacterium species, strains of Lactobacillus spp., Enterococcus spp., and other bacterial species, all generated negative results. PCR assay with primers specific to B. animalis subsp. lactis and B. longum subsp. longum confirmed the presence of these Bifidobacterium species in commercial yogurt products. In addition, for each product, enumeration of the bifidobacteria cells by culture method with BIM-25 agar and the quantitative real-time PCR showed similar cell counts. Such results indicated that within 15-d storage (4 °C) after manufacture, all the bifidobacteria cells originally present in yogurt products were viable and culturable during the storage.

Modelling the effects of pH, storage temperature and redox potential (Eh) on the survival of bifidobacteria in fermented milk

SummaryThe effects of storage temperature, pH and Eh on the survival of Bifidobacterium longum and Bifidobacterium animalis ssp. lactis were modelled in a 3 × 4 × 3 factorial design using three storage temperatures (4, 8, 12 °C), four pH (4.0, 4.25, 4.5, 4.75) and three Eh (0, 200, 400 mV) values. Bifidobacterium animalis ssp. lactis showed significantly better survival than B. longum (P &lt; 0.0001) in fermented milk under normal environmental conditions. Bifidobacterium longum was more susceptible to acidity and survival was log‐linear at low pH values whereas at higher pH pronounced shouldering and tailing effects were apparent. Both individual environmental conditions (T, pH, Eh) and interactions between Eh and pH affected survival and death was always more rapid in B. longum. Bifidobacterium animalis ssp. lactis generally showed a simple log‐linear reduction over time. Temperature, pH and Eh could be manipulated to enhance survival but Eh reduction appears to be the best way to enhance survival without adversely affecting other properties.

Simultaneous detection and enumeration of viable lactic acid bacteria and bifidobacteria in fermented milk by using propidium monoazide and real-time PCR

This study describes a procedure that allows specific detection and enumeration of viable bacteria in four species of lactic acid bacteria ( Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus casei subsp. casei and Lactobacillus acidophilus) and of Bifidobacterium lactis, mixed in fermented milk products. The procedure is based on the combined use of propidium monoazide (PMA), able to distinguish between viable and irreversibly damaged cells, with species-specific quantitative real-time PCR (RTi-PCR). Loss of viability of the species in a fermented milk through storage at 4 °C was similarly ( P < 0.05) detected by PMA–RTi-PCR and selective plate counts. Furthermore, comparison of results obtained by both methods showed a Pearson linear correlation of 0.995. The enumeration of viable bacteria by PMA–RTi-PCR could be performed in 3 h, whereas enumeration by selective plate counts required three days. The procedure developed is a fast method for the identification, enumeration and discrimination of viability of lactic acid bacteria and bifidobacteria mixed in fermented milk products.

Développement d'un milieu sélectif pour le dénombrement des bifidobactéries dans les laits fermentés

Development of a selective culture medium for the enumeration of bifidobacteria in fermented milks. The use of selective culture media is necessary to demonstrate the presence of bifidobacteria in European fermented milks, since Lactobacillus (L.) acidophilus, L. delbrueckii ssp. bulgaricus and Streptococcus (S.) thermophilus usually dominate the flora in these products. But a fully selective medium suppressing these microorganisms does not exist as yet. Therefore, the selec- tivity and productivity of three media were tested qualitatively and quantitatively: DIC (pH 6.8) and BEE (pH 5.0) were based on TPY and Columbia agar with dicloxacillin and propionic acid respec- tively, as inhibitory agents. A new combination, DP (pH 6.8), was created on the base of Columbia agar with both propionic acid and dicloxacillin as additives. The elective medium BIO, which is based on RCM agar supplemented with lactose and human erythrocyte concentrate was used as con- trol medium. The samples tested were either single strains of Bifidobacterium spp., L. acidophilus, L. delbrueckii ssp. bulgaricus and S. thermophilusor mixte cultures in form of starter cultures or fer- mented milks. DIC allowed a good growth of bifidobacteria as well as L. acidophilus. On BEE bifi- dobacteria as well as L. delbrueckii ssp. bulgaricus grew irregularly. DP allowed a quantitatively suf- ficient growth of bifidobacteria and prevented the growth of accompanying L. acidophilus, L. delbrueckii ssp. bulgaricus and S. thermophilusstrains. Therefore, DP is advantageous over DIC and BEE and can be recommended for the selective isolation of bifidobacteria from starter cultures and from different fermented milks products in Europe. bifidobacteria / selective medium / fermented milk / lactic acid bacteria

Effect of yogurt cultures on the survival of bifidobacteria in fermented milks

Three species of Bifidobacterium, Bif bifidum, Bif longum and Bif adolescentis were grown in reconstituted skim milk (12% total solids) either individually or in combination with one of three commercial yogurt cultures. Total colony counts were recorded for the bifidobacteria over a growth period of 24 hours and, for samples with the fermentation halted at pH 4.6, during storage at 5°C for up to 21 days. The results indicated that, while co‐inoculation with the yogurt organisms tended to suppress the growth of the bifidobacteria, subsequent storage in the presence of the yogurt cultures did not lead to any significant decline in numbers.

Selective Agar Medium for Counting Viable Cells of Bifidobacteria in Fermented Milk

Selective Agar Medium for Counting Viable Cells of Bifidobacteria in Fermented Milk