Phages in Whey Derivatives: From Problem to Application in the Dairy Industry.

Fifteen samples of whey protein concentrate (WPC) were tested against 37 commercial strains to detect infective bacteriophages. Seventy-three diverse phages were isolated from 12 samples, characterized by using DNA restriction patterns and host range analyses. Sixty-two of them were classified as , two as , and nine as 5093, according to PCR multiplex assays.

Bacteriophages in dairy plants.

Bacteriophages represent the main microbiological threat for the manufacture of fermented foods. The dairy industry is the most affected by this problem, as phages are naturally present in raw milk, surfaces, vats, tanks, floors, and distributed by air displacements. Cheese whey may also contain high phage concentrations.

Inactivation of Dairy Bacteriophages by Thermal and Chemical Treatments.

This article provides information on the characteristics of diverse phages of lactic acid bacteria and highlights the incidence of their presence in different dairy fermentations. As it is known, thermal treatments on raw milk and use of sanitizers in the disinfection of surfaces and equipment are strategies usually applied in dairy to prevent bacteriophage infections. In this sense, this review mainly focuses on the existing data about the resistance against thermal treatments and sanitizers usually used in the dairy industry worldwide, and the differences found among bacteriophages of diverse genera are remarked upon.

Virulence of Leuconostoc phages: Influence of stress conditions associated to dairy processes on their host-phage interactions.

In this work, we assessed the impact of technological cell stress conditions, commonly present in industrial dairy processes, on the host strain-phage interactions in Leuconostoc. Adsorption and burst size of LDG (Leuconostoc pseudomesenteroides) and Ln-9 (Leuconostoc mesenteroides) phages were evaluated under the following conditions: i) MRS broth, 30 °C; ii) MRS broth at pH 5.5, 30 °C (acidic stress); iii) MRS broth added of NaCl at 4% w/v, 30 °C (osmotic stress) and iv) MRS broth, 10 °C (cold stress).

New semi-pilot-scale reactor to study the photocatalytic inactivation of phages contained in aerosol.

The aims of this work were to design and build a photocatalytic reactor (UV-A/TiO) to study the inactivation of phages contained in bioaerosols, which constitute the main dissemination via phages in industrial environments. The reactor is a close system with recirculation that consists of a stainless steel camera (cubic form, side of 60 cm) in which air containing the phage particles circulates and an acrylic compartment with six borosilicate plates covered with TiO. The reactor is externally illuminated by 20 UV-A lamps.

Phage adsorption and lytic propagation in Lactobacillus plantarum: could host cell starvation affect them?

Background: Bacteriophages constitute a great threat to the activity of lactic acid bacteria used in industrial processes. Several factors can influence the infection cycle of bacteriophages. That is the case of the physiological state of host cells, which could produce inhibition or delay of the phage infection process.

Bacteriophages and dairy fermentations.

This review highlights the main strategies available to control phage infection during large-scale milk fermentation by lactic acid bacteria. The topics that are emphasized include the factors influencing bacterial activities, the sources of phage contamination, the methods available to detect and quantify phages, as well as practical solutions to limit phage dispersion through an adapted factory design, the control of air flow, the use of adequate sanitizers, the restricted used of recycled products, and the selection and growth of bacterial cultures.

Characterization of two virulent phages of Lactobacillus plantarum.

We characterized two Lactobacillus plantarum virulent siphophages, ATCC 8014-B1 (B1) and ATCC 8014-B2 (B2), previously isolated from corn silage and anaerobic sewage sludge, respectively. Phage B2 infected two of the eight L. plantarum strains tested, while phage B1 infected three.

Thermal, chemical, and photocatalytic inactivation of Lactobacillus plantarum bacteriophages.

The effect of several biocides, thermal treatments, and photocatalysis on the viability of four Lactobacillus plantarum phages was investigated. Times to achieve 99% inactivation (T99) of phages at 63, 72, and 90 degrees C were evaluated in four suspension media: deMan Rogosa Sharpe broth, reconstituted skim milk, a commercial EM-glucose medium, and Tris magnesium gelatin buffer. The four phages studied were highly resistant to 63 degrees C (T99 > 45 min); however, counts < 10 PFU/ml were achieved by heating at 90 degrees C for 5 min.

Spontaneous Lactobacillus delbrueckii phage-resistant mutants with acquired bile tolerance.

Three commercial phage-sensitive strains of Lactobacillus delbrueckii (strains Ab(1), YSD V and Ib(3)) and four spontaneous phage-resistant mutants (strains A(7), A(17), V(2) and I(39)) isolated from them, all with a probiotic potential previously demonstrated were studied for their tolerance of bile salts (ox gall). Minimal Inhibitory Concentrations (MICs) ranged from 0.30% to 0.

Phage-resistant mutants of Lactobacillus delbrueckii may have functional properties that differ from those of parent strains.

Three commercial phage sensitive Lactobacillus delbrueckii strains (identified as Ab(1), YSD V and Ib(3)), and four spontaneous phage-resistant mutants isolated from them were tested for their capacity to activate the gut mucosal immune response in mice, as indicated by the numbers of IgA-producing cells. Random Amplified Polymorphic DNA (RAPD) analysis revealed a strong genetic homology between the sensitive strains and their respective derivatives. The phage-resistant mutants exhibited high levels of phage resistance, elevated stability of this phenotype and technological properties comparable to those of their respective parent strains.