Diversity of lactic acid bacteria isolated from Brazilian water buffalo mozzarella cheese.

The water buffalo mozzarella cheese is a typical Italian cheese which has been introduced in the thriving Brazilian market in the last 10 y, with good acceptance by its consumers. Lactic acid bacteria (LAB) play an important role in the technological and sensory quality of mozzarella cheese. In this study, the aim was to evaluate the diversity of the autochthones viable LAB isolated from water buffalo mozzarella cheese under storage. Samples were collected in 3 independent trials in a dairy industry located in the southeast region of Brazil, on the 28th day of storage, at 4 ºC. The LAB were characterized by Gram staining, catalase test, capacity to assimilate citrate, and production of CO2 from glucose. The diversity of LAB was evaluated by RAPD-PCR (randomly amplified polymorphic DNA-polymerase chain reaction), 16S rRNA gene sequencing, and by Vitek 2 system. Twenty LAB strains were isolated and clustered into 12 different clusters, and identified as Streptococcus thermophilus, Enterococcus faecium, Enterococcus durans, Leuconostoc mesenteroides subsp. mesenteroides, Lactobacillus fermentum, Lactobacillus casei, Lactobacillus delbrueckii subsp. bulgaricus, and Lactobacillus helveticus. Enterococcus species were dominant and citrate-positive. Only the strains of L. mesenteroides subsp. mesenteroides and L. fermentum produced CO2 from glucose and were citrate-positive, while L. casei was only citrate positive. This is the first report which elucidates the LAB diversity involved in Brazilian water buffalo mozzarella cheese. Furthermore, the results show that despite the absence of natural whey cultures as starters in production, the LAB species identified are the ones typically found in mozzarella cheese.

Petit suisse from black soybean: bioactive compounds and antioxidant properties during development process.

This study aimed to evaluate the antioxidant properties, bioactive compounds and other physico-chemical parameters from black soybean and its derivatives over 30 days under refrigeration at 4 °C and develop a probiotic petit suisse produced from black soybean. The soymilk showed the highest levels of isoflavones (109 mg/100 g), total phenolics (600 mg/100 g) and total anthocyanins (388 mg/100 g) with the highest response in the tests with DPPH• and ABTS+• on a dry basis. There was a significant increase (p ≤ 0.05) in antioxidant activity during storage due to the hydrolysis of isoflavone glycosides to aglycones in soymilk sample, having a strong linear correlation between the concentration of isoflavone aglycones and the antioxidant activity for ABTS+• (R = 0.9437, 0.9624 and 0.9992) and DPPH• (R = 0.9865, 0.9978 and 0.9911), respectively, for soymilk, quark and petit suisse. The conversion of isoflavone was influenced directly by the characteristics of each sample, inhibiting or promoting the action of the enzyme. The petit suisse developed is an alternative for consumers, providing isoflavones and anthocyanins, possessing probiotic average counts (108 CFU g⁻¹) during storage.

Production of natural folates by lactic acid bacteria starter cultures isolated from artisanal Argentinean yogurts.

Folate is a B-group vitamin that cannot be synthesized by humans and must be obtained exogenously. Although some species of lactic acid bacteria (LAB) can produce folates, little is known about the production of this vitamin by yogurt starter cultures. Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus strains were isolated from artisanal Argentinean yogurts and were grown in folate-free culture medium (FACM) and nonfat milk after which intracellular and extracellular folate production were evaluated. From the initial 92 isolated LAB strains, 4 L. delbrueckii subsp. bulgaricus and 32 S. thermophilus were able to grow in the absence of folate. Lactobacillus delbrueckii subsp. bulgaricus CRL 863 and S. thermophilus CRL 415 and CRL 803 produced the highest extracellular folate levels (from 22.3 to 135 µg/L) in FACM. In nonfat milk, these strains were able to increase the initial folate concentrations by almost 190%. This is the first report where native strains of L. delbrueckii subsp. bulgaricus were shown to produce natural folate. The LAB strains identified in this study could be used in developing novel fermented products bio-enriched in natural folates that could in turn be used as an alternative to fortification with the controversial synthetic chemical folic acid.

Growth and exopolysaccharide production by Streptococcus thermophilus ST1 in skim milk

To analyze the exopolysaccharide (EPS) production by Streptococcus thermophilus ST1, cultures were cultivated in 10 percent (w/v) reconstituted skim milk under different growth conditions including various temperatures and pHs of growth medium, supplementation of the medium with various carbon sources (glucose, lactose, sucrose, galactose and fructose) and nitrogen source (whey protein concentrate, or WPC). The results showed that most EPS production by strain ST1 was obtained at a temperature (42°C) and pH (6.5) optimal for its growth. Supplementation of the skim milk medium with either carbohydrates or WPC increased both growth and polymer formation by different extents, with sucrose being most effective among the carbon sources tested. Under the optimal cultural conditions, i.e. pH 6.5, 42°C with 2 percent (w/v) sucrose and 0.5 percent (w/v) WPC, 135.80 mg l-1 of EPS was produced by strain ST1. The monosaccharide composition of the EPS was determined to be glucose and galactose (2:1), and the molecular mass of the EPS was 3.97 × 10(6) Da. The aqueous solution of the EPS at 1 percent (w/v) showed relatively high viscosity, indicating the potential of this EPS-producing S. thermophilus strain for applications in the improvement of physical properties of fermented milk products.

Effect of freeze drying process on some properties of Streptococcus thermophilus isolated from dairy products

The present investigation represents the effect of freeze drying on some properties as acid and bile tolerance of Streptococcus thermophilus MTCC 1938 culture isolated from dairy products. The cell paste obtained from milk based medium was freeze dried with a pressure of 50-100 mtorr for 24h at -40ºC. Acid and bile tolerance test exhibited 3.8-4.9 and 3.2-3.8 log counts reduction after freeze drying respectively.

[Identification, quantification and antimicrobial susceptibility pattern of probiotic bacteria added to common use food products in Costa Rica]. / Identificación, cuantificación y determinación del perfil de sensibilidad a antibióticos de bacterias prebióticas adicionadas a productos de consumo frecuente en Costa Rica.

In the last years, due to the high demand of food products supplemented with probiotics and the multiple nutritional and therapeutic benefits associated with them, research on these microorganisms has advanced considerably, including their selection and characterization. As a general recommendation, several entities as World Health Organization (WHO) and United Nations Organization for Agriculture and Food recommend that the specification of the alive species contained and their number shall appear in the label of the product. In the present study, six different commercially available products, supplemented with probiotics were analyzed, in order to evaluate the concentration of microorganisms through the shelf life of the product, identify the strains isolated and determine the antibiotic susceptibility pattern of these. Results demonstrated that the strains isolated kept acceptable concentrations during the 28 days of storage. Nevertheless, the identification of these strains variated from the one reported on the label on several of the products tested. This can be due to the commercial method used for the identifications, which is based in the carbohydrate fermentation pattern and not in genotypic trials. The antimicrobials' susceptibility patterns found show that further research shall be performed in order to establish the intrinsic or acquired nature of the resistance determinants, and if these are codified by transferable elements among bacteria.

Effect of infant formula with probiotics on intestinal microbiota.

Weaning during infancy refers to the initiation of complementary food to breast milk. During weaning, there are significant changes on the gastrointestinal microbiota. Deleterious alterations of the gastrointestinal microbiota can result in pathological processes while measures that stimulate its development and stability, like the use of probiotics, are beneficial. The mechanisms by which probiotics achieve their effects have not been clearly established. Present work compares the microbial composition of feces from infants that were weaned to regular family food, formula with probiotics (B. Lactis BL y S. Thermophilus) or formula without probiotics. Accordingly, analysis of rDNA of microbial fecal samples by molecular techniques was used. Formula with or without probiotics was well tolerated and safe for all participating children. Probiotics present in formula were viable and susceptible to culture. There was not difference on physical growth or development among all participants. The microbiota of children supplemented with formula with- or without probiotics was different than that observed in children supplemented with regular food. It was not possible to determine enrichment of B. Lactis BL and S. Thermophilus in the feces of children that consumed the probiotics. Present work contributes to the understanding of probiotics effects in human health.

Sensitivity of capsular-producing Streptococcus thermophilus strains to bacteriophage adsorption.

AIMS: To determine whether the presence and type of exopolysaccharides (EPS), slime-EPS or capsular, and the structural characteristics of the polymers produced by Streptococcus thermophilus strains could interfere with or be involved in phage adsorption. METHODS AND RESULTS: Phage-host interactions between eight EPS-producing Strep. thermophilus strains (CRL419, 638, 804, 810, 815, 817, 821, 1190) and five streptococcus specific phages (phiYsca, phi3, phi5, phi6, phi8) isolated from Argentinean faulty fermentation failed yoghurts were evaluated. No relationship was found between the EPS chemical composition and the phage sensitivity/resistance phenotype. In general, the capsular-producing strains were more sensitive to phage attacks than the noncapsular-producing strains. Streptococcus thermophilus CRL1190 (capsular-producing) was the only strain sensitive to all bacteriophages and showed the highest efficiency of plating. Phage adsorption to a capsular-negative, EPS low-producing mutant of strain CRL1190 was reduced, especially for phiYcsa and phi8. CONCLUSIONS: The presence of capsular polysaccharide surrounding the cells of Strep. thermophilus strains could play a role in the adsorption of specific phages to the cells. SIGNIFICANCE AND IMPACT OF THE STUDY: Capsular-producing Strep. thermophilus strains should be evaluated for their bacteriophage sensitivity if they are included in starter cultures for the fermented food industry.

Identification and characterization of starter lactic acid bacteria and probiotics from Columbian dairy products.

AIMS: Considering the significant rise in the probiotic market in Columbia, and given the lack of reports concerning the microbial population and strain performance in products from different producers, this study aims at determining the number of viable starter bacteria and probiotics in bio-yoghurts available at the Columbian market, identifying the species and analysing the performance of the isolated strains in bile acid resistance, antagonistic activity against pathogens, and adherence capacity to human intestinal epithelial cells. METHODS AND RESULTS: Seven bio-yoghurts were analysed for the bacterial species present. Species identification was carried out using 16S rRNA gene targeted PCR. The cultured bacteria were tested for bile acid resistance, adherence to a human intestinal epithelial cell line, and antagonism against the pathogen Salmonella enterica serovar Typhimurium. A total of 17 different strains were identified. Based on plate counting, all bio-yoghurts have at least total viable cells of approximately 10(7) CFU ml(-1). Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus were the most frequently isolated bacteria. Viable Bifidobacterium was only recovered from one product. However, after PCR analysis, DNA of this genus was confirmed in five out of seven products. Major differences were found for S. typhimurium antagonism. The adherence capacity to Caco-2 cells was observed in 10 of the isolated strains. In general, low survival to simulated gastric juice was observed. CONCLUSIONS: Some of the isolated strains have probiotic potential, although not all of them were present in the advised amount to exert beneficial health effects. However, the full correct scientific name of the isolated bacteria and their viable counts were not included on the product label. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report describing the identification and functionality of starter bacteria and probiotics present in dairy products on the Columbian market.