Commercial Fermented Milk Products Research Articles

Influence of gut microbiome composition on effect variations of anti-cholesterol treatment among individual mice

This study investigated if the variation in the effect of anti-cholesterol (AC) treatment on individual mice are related to gut microbiome composition. The bile salt hydrolase (BSH) activity of 23 commercial fermented milk products was examined to select a fermented milk product for AC treatment. Mice were fed to different diets for 6 weeks: high-fat (660 % of total calories from fat; D1), high-dietary fibre (20 % cellulose; D2), and low-fat (17.2 % of total calories from fat; D3) diets to change their gut microbiomes. Subsequently, faecal microbiome was transplanted (FMT) into mice treated with high cholesterol diet contained 2 % cholesterol, followed by AC or non-AC (sterile tap water, STW) treatments. Control groups with normal (NC) and high-cholesterol diets (PC) were prepared for both AC and STW treatment. All experimental groups were subjected to serum and liver cholesterol, cholesterol metabolism-related (CMR) gene expression, and intestinal microbiome analyses. D3-FMT mice showed the most significant enhancements in cholesterol ratio and decreased hepatic cholesterol levels with AC treatment. Moreover, upregulation of the Cyp7a1 gene expression was observed in this group. Furthermore, the intestinal microbiome analysis indicated higher abundances of BSH-producing Eubacterium, Bifidobacterium, and Parabacteroides in the D3-FMT + AC group compare to others, potentially contributing to increased bile acid synthesis.

Development of fermented milk using food-grade recombinant Lactococcus lactis NZ3900

Fermented milk has been associated with the improvement of human health for decades. Food-grade Lactococcus lactis NZ3900 is a potential host for producing and delivering various biologics, including oral vaccines, hence it could enhance the functionality of fermented milk as a starter culture. A cultured fermented milk product was developed in this study using the food-grade recombinant L. lactis NZ3900 harboring plasmid pNZ8149. Response surface methodology was used to optimize the inoculum concentration (5–15% v/v), fermentation temperature (23–37 °C), and fermentation time (18–30 h) to enhance the viability, acidification activity, viscosity, and minimize syneresis of the L. lactis NZ3900-fermented milk using response surface methodology. The optimal inoculum concentration and fermentation conditions for L. lactis NZ3900-fermented milk are 12.5% (v/v) inoculum, 28 °C fermentation temperature, and 30 h of fermentation time, resulting in higher viability (9.64 log10 CFU/mL), acidification activity (pH 4.42, 0.78% titratable acidity), viscosity (11,096.9 mPa·s), and comparable syneresis (63.62%) against commercial fermented milk products. This shows that food-grade L. lactis NZ3900 can be used as a starter culture, and NZ3900-fermented milk could be used as a functional drink for oral vaccine delivery.

Viable Cell Counts and Identification of Species Used for Commercial Fermented Milk Products

Viable Cell Counts and Identification of Species Used for Commercial Fermented Milk Products

Modified PMA-qPCR Method for Rapid Quantification of Viable Lactobacillus spp. in Fermented Dairy Products

Quantification of viable lactic acid bacteria is an important quality index of fermented dairy products, but the current detection method, which is plate counting, is time-consuming. This study describes a modified PMA-qPCR assay that allows the detection and enumeration of total viable Lactobacillus spp. in commercial fermented milk products. Here, a new pair of genus-specific primers and minor groove binder probes was designed based on the 16S rRNA gene sequences of 24 reference strains, 13 of which were from different Lactobacillus species commonly used in commercial fermented dairy products. Subsequently, compared with the heat killing method, the 20-cycle homogenization method was chosen for initial PMA-qPCR optimization. Standard curves were prepared, and the efficiency obtained was 97% (R2 = 0.992), demonstrating that this PMA-qPCR method was feasible and effective. Additionally, the viable Lactobacillus spp. detection range was 103–109 CFU/mL, which meets the detection requirements in fermented dairy products. Furthermore, total number of viable Lactobacillus spp. in six different commercial fermented dairy products was estimated by three individual methods (plate count in MRS agar, qPCR, and PMA-qPCR). Comparison of results obtained by PMA-qPCR and plate counts was similar, and both decreased accordingly, showing a good correlation with the decline of strain vitality, 30 days after the expiration date. The PMA-qPCR procedure established in this paper allows the quantification of viable Lactobacillus spp. in approximately 3 h, greatly improving detection efficiency, and has broad application prospects in the testing of fermented dairy products.

Potensi Beberapa Susu Fermentasi Komersial Sebagai Antifungi Candida albicans

Candida albicans cause opportunistic infection of the oral cavity. Probiotic has health benefits, produces organic acids as anti-C. albicans. The aim of this research was to determine the antifungal activity of commercial fermented milk products against Candida and viability of bacteria in commercial fermented milk products. The antifungal activity was determined using well diffusion method. Viability of lactic acid bacteria was done by plate count method. The results show that commercial fermented milk productshas an activity of anti-C.albicans were shown by irradical zone formed around well containing fermented dairy products. Viability of lactic acid bacteria 107-1010 CFU/mL.

Novel method based on chromogenic media for discrimination and selective enumeration of lactic acid bacteria in fermented milk products

Microbial analyses of fermented milk products require selective methods to discriminate between close species simultaneously present in high amounts. A culture-based method combining novel chromogenic agar media and appropriate incubation conditions was developed to enumerate lactic acid bacteria (LAB) strains in fermented milk. M1 agar, containing two chromogenic substrates, allowed selective enumeration of Lactobacillus rhamnosus, two strains of Lactobacillus paracasei subsp. paracasei and Streptococcus salivarius subsp. thermophilus based on differential β-galactosidase and β-glucosidase activities. Depending on the presence of some or all of the above strains, M1 agar was supplemented with l-rhamnose or vancomycin and incubations were carried out at 37 °C or 44 °C to increase selectivity. A second agar medium, M2, containing one chromogenic substrates was used to selectively enumerate β-galactosidase producing Lactobacillus delbrueckii subsp. bulgaricus at 47 °C. By contrast with the usual culture media, the chromogenic method allowed unambiguous enumeration of each species, including discrimination between the two L. paracasei, up to 109 CFU/g of fermented milk. In addition, the relevance of the method was approved by enumerating reference ATCC strains in pure cultures and fermented milk product. The method could also be used for enumerations on non-Danone commercial fermented milk products containing strains different from those used in this study, showing versatility of the method. To our knowledge, this is the first description of a chromogenic culture method applied to selective enumeration of LAB.

The effects of probiotics and prebiotics on the fatty acid profile and conjugated linoleic acid content of fermented cow milk

The ability of probiotic bacteria (Lactobacillus acidophilus La5 and Bifidobacterium animalis Bb12), to produce conjugated linoleic acid (CLA) in association with Streptococcus thermophilus and Lb. bulgaricus during milk fermentation has been evaluated in this study. Pasteurized cow milk and infant formula were used. Infant formula was selected for its high linoleic acid content, for being a source of CLA and for its prebiotic compounds, e.g. galacto-oligosaccharides. The microorganisms were not able to increase the CLA content of the fermented products under the given experimental conditions. No statistically significant differences (p > 0.05) occurred between the CLA content in milk and the fermented samples. The CLA contents of 10 commercial fermented milk products were determined. The highest CLA content was observed in fermented milk containing only Str. thermophilus and Lb. bulgaricus.

Survival of Mycobacterium avium ssp. paratuberculosis in yoghurt and in commercial fermented milk products containing probiotic cultures

To assess the survival of Mycobacterium avium ssp. paratuberculosis (MAP) in yoghurt and commercial fermented milk products containing probiotic strains. Whole and skimmed UHT milk artificially inoculated with MAP were used to manufacture yoghurt, using two different yoghurt starter cultures. Five commercial fermented milk products were inoculated with MAP. Two different MAP strains were studied. The survival of MAP in all products was monitored by culture over a 6-week storage period at 6°C. In yoghurt, MAP counts did not change appreciably during the storage period. Fat content and type of yoghurt starter culture had no consistent effect on the survival of MAP. In the fermented milk products, survival patterns varied but resulted in a 1·5 to ≥3·8 log reduction for the Niebüll strain and a 1·2-2·2 log reduction for the NIZO strain after 6 weeks, depending on the probiotic starters present in the product. MAP easily survived in yoghurt but MAP numbers decreased in fermented milk products containing probiotic cultures. The results contribute to the lack of knowledge on the behaviour of MAP in yoghurt and fermented milk products containing probiotic cultures. This knowledge is valuable in the context of the risk of MAP transmission to humans via yoghurt and the possible contribution of probiotic fermented milk products to the elimination of MAP.

Comparison of Bifidobacteria Selective Media for the Detection of Bifidobacteria in Korean Commercial Fermented Milk Products

This study was carried out to compare the efficacy and selectivity of TOS and BS media for enumeration of bifidobacteria in commercial fermented milk products. First, bifidobacteria was isolated from 20 fermented milk products, and all isolated bifidobacteria were identified by genomic technology as Bifidobacterium lactis. The two media significantly differed from each other with regard to the recovery of B. lactis, that is, the recovery of this organism was as much as 6 logs lower on BS medium than on TOS. When the concentration of BS solution (mixture of paromomycin sulfate, neomycin, sodium propionate, and lithium chloride) used in BS medium was reduced to 50% (BS50), a relatively high percentage recovery of bifidobacteria from pure cultures was achieved. Susceptibility tests to antibiotics and tests for selective agents for the isolated bifidobacteria and lactic acid bacteria were conducted. The BS solution inhibited some lactic acid bacteria and Bifidobacterium species, while mupirocin (MU) suppressed the growth of all tested lactic acid bacteria but not Bifidobacterium. As compared with BS50 medium, TOS with or without MU showed good bifidobacteria recovery and readily distinguishable colonies; in particular, TOS supplemented with MU had a high selectivity for bifidobacteria. In conclusion, all results suggested that TOS medium with or without MU was found to be suitable for selective enumeration of bifidobacteria from mixed cultures in fermented milk, and better in that capacity than BS medium.

Development and Use of tuf Gene–Based Primers for the Multiplex PCR Detection of Lactobacillus acidophilus, Lactobacillus casei Group, Lactobacillus delbrueckii, and Bifidobacterium longum in Commercial Dairy Products

PCR primers specific for the detection of Lactobacillus acidophilus, Lactobacillus casei group, Lactobacillus delbrueckii, and Bifidobacterium longum were designed based on the elongation factor Tu gene (tuf). The specificity of these four primer sets were confirmed by PCR with 88 bacterial strains of Lactobacillus, Enterococcus, Bifidobacterium, and other bacterial species. Results indicated that these primer sets generated predicted PCR products of 397, 230, 202, and 161 bp for L. acidophilus, L. delbrueckii, L. casei group, and B. longum, respectively. Bacterial species other than the target organisms tested did not generate false-positive results. When these four primer sets were combined for the simultaneous detection of the lactic acid bacteria (LAB) in fermented milk products including yogurt, the LAB species listed on the labels of these products could be identified without the preenrichment step. The identification limit for each LAB strain with this multiplex PCR method was N × 103 CFU/ml in milk samples. The results of our multiplex PCR method were confirmed by PCR assay using primers based on the 16S rDNA or the 16S–23S intergenic spacer region and by biochemical tests using the API 50 CHL kit. When this multiplex PCR method was used with the determination of counts of total viable LAB and bifidobacteria, the quality of commercial fermented milk products could be assured.

Molecular quantification of lactic acid bacteria in fermented milk products using real-time quantitative PCR

Real-time quantitative PCR assays were developed for the absolute quantification of lactic acid bacteria (LAB) ( Streptococcus thermophilus, Lactobacillus delbrueckii, L. casei, L. paracasei, L. rhamnosus, L. acidophilus and L. johnsonii) in fermented milk products. The results of molecular quantification and classic bacterial enumeration did not differ significantly with respect to S. thermophilus and the species of the L. casei group which were detected in the six commercial fermented products tested, thus showing that DNA extraction was efficient and that genomic DNA solutions were free of PCR inhibitors. For L. delbrueckii, the results of bacterial enumeration were generally lower by a factor 10 to 100 than those of PCR quantification, suggesting a loss of viability during storage of the dairy products at 1–8 °C for most of the strains in this species. Real-time quantitative assays enabled identification of the species of lactic acid bacterial strains initially present in commercial fermented milk products and their accurate quantification with a detection threshold of 10 3 cells per ml of product.

Populations of Lactobacillus acidophilus, Bifidobacterium spp., and Lactobacillus casei in Commercial Fermented Milk Products

Populations of Lactobacillus acidophilus, Bifidobacterium spp., and Lactobacillus casei in Commercial Fermented Milk Products