Inhibition of Brevibacterium linens by Probiotics from Dairy Products

Brevibacterium linens is an important species in dairy products rendering a specific taste and aroma to numerous smear ripened and blue veined cheeses due to proteolysis. However, the presence of the species in South African blue veined cheeses is undesirable and consumers demand the product void of the species. Accordingly, numerous methods including microbial inhibition using fungi and bacterial probiotic cultures with possible inhibitory effects were applied in an attempt to inhibit the species. None of the fungi, however, proved to be successful, whereas Lactobacillus rhamnosus and Bifidobacterium lactis, two typical probiotic species applied in dairy products, showed inhibitory effects against B. linens when tested using the spot-on-lawn assay

Development of Yeast Populations during Processing and Ripening of Blue Veined Cheese

Varieties of blue veined cheese were analyzed regularly during different stages of manufacturing and ripening to determine the origin of contaminating the yeasts present in them, their population diversity and development until the end of the storage. Yeast diversity and development in the inner and outer core of the cheeses during ripening were also compared. Air samples revealed few if any yeasts whereas the samples in contact with the equipment and the surroundings revealed high number of yeasts, implicating it as the possible main source of post-pasteurization contamination, as very few yeasts were isolated from the milk and cheese making process itself. Samples from the inner and outer core of the maturing cheeses had typical survival curves. The number of yeasts on the outer core was about a 100-fold more than of those in the inner core. The most abundant yeasts isolated from the environment and ripening cheeses were identified as Debaryomyces hansenii, Saccharomyces cerevisiae, Torulaspora delbrueckii, Trichosporon beigelii, Candida versatilis and Cryptococcus albidus, while the yeasts Candida zeylanoides and Dekkera anomala were additionally isolated from the environment. Yeasts were present in high number, making their occurrence in blue-veined cheeses meaningful

Ohmic Heating for the dairy industry: a potential technology to develop probiotic dairy foods in association with modifications of whey protein structure

The use of whey in dairy probiotics is a topic of great interest to the scientific community and the food industries. However, few studies address the effect of ohmic heating (OH) on cell metabolism and growth parameters of probiotic microorganisms. Despite of this, OH under sub-lethal conditions presents promising results regarding the enhancement of growth rate and bacteriocin activity, leading to considerable improvements in the fermentation process. Thus, this review highlights the main findings and advances on the effect of OH on probiotic metabolism, while addressing the modification of whey protein structure as potential carrier of probiotic entities, aiming at stimulating interest and encouraging the development of functional products using OH.This work was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and by BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 — Programa Operacional Regional do Norte. Pedro Santos is recipient of a fellowship supported by a doctoral advanced training (call NORTE-69-2015-15), funded by the European Social Fund under the scope of Norte2020 — Programa Operacional Regional do Norte. Ricardo Pereira is recipient of a fellowship supported by FCT (SFRH/BPD/81887/2011).info:eu-repo/semantics/publishedVersio

Fluorescence in situ hybridization method using a peptide nucleic acid probe for identification of Lactobacillus spp. in milk samples

Lactobacillus species constitute one of the dominant and beneficial bacteria in our body and are used in developed countries as a microbial adjuvant. Identification of these probiotic bacteria is traditionally performed by culture-based techniques. However, such methods are very time-consuming and can give inaccurate results, especially when Lactobacillus is present in mixed bacterial complex communities. Our study aimed to accurately identify Lactobacillus spp. using a novel Peptide Nucleic Acid (PNA) Fluorescence In Situ Hibridization (FISH) probe. The probe (Lac663) was tested on 36 strains belonging to different Lactobacillus species and on 20 strains of other bacterial species. The sensitivity and specificity of the method were 100% (95% confidence interval (CI), 88.0 to 100.0%) and 95.0% (95% CI, 73.1 to 99.7%), respectively. Additionally, we tested the applicability of the method on milk samples added with Lactobacillus strains at probiotic range concentrations and others taxonomically related bacteria, as well as pathogenic bacteria. The Lac663 probe bound exclusively to Lactobacillus strains and the described PNA-FISH method was capable of directly quantifying Lactobacillus spp. in concentrations at which these potential probiotic bacteria are considered to have an effective benefit on human health.This work was supported by European Union funds (FEDER/COMPETE) and by national funds (FCT) under the project with reference FCOMP-01-0124-FEDER-008991 (PTDC/BIA-MIC/098228/2008. Antonio Machado acknowledges the FCT individual fellowship-SFRH/BD/62375/2009. However, it is important to refer that FCT did not have any role in the design of the experiments or manuscript writing

Longitudinal and contemporaneous manganese exposure in apartheid-era South Africa: Implications for the past and future

Manganese is a potent environmental toxin, with significant effects on human health. Manganese exposure is of particular concern in South Africa where in the last decade, lead in gasoline has been replaced by methylcyclopentadienyl manganese tricarbonyl (MMT). We investigated recent historical levels of manganese exposure in urban Gauteng, South Africa prior to the introduction of MMT in order to generate heretofore non-existent longitudinal public health data on manganese exposure in urban South Africans. Cortical bone manganese concentration was measured by inductively coupled plasma mass spectrometer in 211 deceased adults with skeletal material from a fully identified archived tissue collection at the University of Pretoria, South Africa. All tissues came from individuals who lived and died in urban Gauteng (Transvaal), between 1958 and 1998. Median Mn concentration within the sampled tissues was 0.3μgg, which is within reported range for bone manganese concentration in non-occupationally exposed populations and significantly below that reported in individuals environmentally exposed to MMT. No significant differences were seen in bone Mn between men and women or in individuals of different ethnicity, which further suggests environmental, as opposed to occupational exposure. There were no significant temporal or geographic differences in bone Mn. The results suggest that Mn exposure was low and uniformly distributed across the whole population prior to the introduction of MMT as a gasoline additive. In addition, should manganese exposure follow the same patterns as vehicle-emitted lead, a clear pattern of exposure will emerge with individuals in the urban core facing the greatest manganese exposure

Edible films and coatings as carriers of living microorganisms: a new strategy towards biopreservation and healthier foods

Edible films and coatings have been extensively studied in recent years due to their unique properties and advantages over more traditional conservation techniques. Edible films and coatings improve shelf life and food quality, by providing a protective barrier against physical and mechanical damage, and by creating a controlled atmosphere and acting as a semipermeable barrier for gases, vapor, and water. Edible films and coatings are produced using naturally derived materials, such as polysaccharides, proteins, and lipids, or a mixture of these materials. These films and coatings also offer the possibility of incorporating different functional ingredients such as nutraceuticals, antioxidants, antimicrobials, flavoring, and coloring agents. Films and coatings are also able to incorporate living microorganisms. In the last decade, several works reported the incorporation of bacteria to confer probiotic or antimicrobial properties to these films and coatings. The incorporation of probiotic bacteria in films and coatings allows them to reach the consumers gut in adequate amounts to confer health benefits to the host, thus creating an added value to the food product. Also, other microorganisms, either bacteria or yeast, can be incorporated into edible films in a biocontrol approach to extend the shelf life of food products. The incorporation of yeasts in films and coatings has been suggested primarily for the control of the postharvest disease. This work provides a comprehensive review of the use of edible films and coatings for the incorporation of living microorganisms, aiming at the biopreservation and probiotic ability of food products.Ana Guimaraes received support through grant SFRH/BD/ 103245/2014 from the Portuguese Foundation for Science and Technology (FCT). Luís Abrunhosa was supported by grant UMINHO/BPD/51/2015 from project UID/BIO/04469/2013 financed by FCT/MEC (OE). This study was supported by FCT under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684), and of BioTecNorte operation (NORTE-01-0145-FEDER000004) funded by European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. Vectors used in Figure were designed by Freepik.info:eu-repo/semantics/publishedVersio

The Effect of Incubation Temperature on the Survival and Growth of Yeasts in Sethemi, South African Naturally Fermented Milk

The effect of temperature on the growth of yeasts during the production of Sethemi, South African naturally fermented milk (NFM), was studied by incubating raw milk and milk inoculated with selected yeast strains at 7, 15, 25 and 37 °C. The different temperatures were selected to represent the average ambient temperatures around Bloemfontein, South Africa, during winter, spring, summer, and in the human body, respectively. The yeast strains used had previously been isolated from Sethemi and identified as Kluyveromyces marxianus, Saccharomyces cerevisiae, Candida albicans and Debaryomyces hansenii. The yeast strains were inoculated into raw milk separately and also as a mixture of the four strains. The yeast counts, lactic acid bacteria counts and pH were monitored over a period of 20 days. It was observed that although all the yeast strains grew in the milk at all temperatures, the fastest growth was at 37 °C but there was a prolonged lag phase at 7 and 15 °C. The highest yeast counts of 8.30 log (CFU/mL) were obtained at 25 °C in the milk inoculated with K. marxianus. At all temperatures, the initial yeast count in the control was significantly (p<0.05) lower than the counts in the inoculated milk. Lactic acid bacteria also grew to high numbers both with added yeast and in the control. The highest LAB counts of about 11.59 log (CFU/mL) were obtained in the presence of S. cerevisiae after about 4 days of incubation at 25 °C. The addition of different yeast strains did not affect significantly the growth of LAB at all temperatures. After 3 days, the LAB counts decreased rapidly at 37 °C, while from day 2 to day 5 the LAB numbers remained stable at 25 °C. There was a rapid decrease in pH at higher temperatures than at 7 or 15 °C, corresponding to the LAB growth. A temperature of 25 °C was found to be ideal for producing fermented milk with high LAB counts, low pH and a visually acceptable coagulum