Partial characterization of nine bacteriocins produced by lactic acid bacteria isolated from cold-smoked salmon with activity against listeria monocytogenes

Nine LAB bacteriocin-producers, isolated from vacuum-packaged cold-smoked salmon (CSS), were phenotypically and genotypically identified as Lactobacillus curvatus, Lactobacillus delbrueckii, Lactobacillus fermentum, Enterococcus faecium, and Pediococcus acidilactici. Their bacteriocins were partially characterized. The antimicrobial spectrum was determined against Listeria monocytogenes, E. faecalis, E. faecium, and Staphylococcus aureus. The molecular size of bacteriocins ranged from 2.8 to 4.5 kDa. They were inactivated by treatment with proteolytic enzymes but not by lipolytic or glycolytic enzymes. Maximal activity against L. monocytogenes ranged between 800 and 10000 AU/mL at pH 6.5. Most of the bacteriocins maintained full activity in a pH range of 2.0 to 8.0 but were partially or completely inactivated at pH 10.0. After heating at 60°C and 100°C, only two bacteriocins from Lb. curvatus strains partially lost activity. All bacteriocins showed a narrow spectrum of activity and a high anti-listerial activity, which is characteristic of the class IIa bacteriocins. Isolated bacteriocinproducing LAB could be used successfully in the bio-preservation of CSS and development of new potential bio-preservatives for CSS active against L. monocytogenes

Optimization of growth and bacteriocin production by Lactobacillus sakei subsp. sakei 2a

<p><italic>Lactobacillus sakei</italic> subsp. <italic>sakei</italic> 2a is a bacteriocinogenic lactic acid bacterium isolated from Brazilian pork sausage, capable of inhibiting the growth of microbial pathogens, mainly <italic>Listeria monocytogenes</italic>. In order to optimize bacteriocin production for industrial applications, this study evaluated the effect of supplementation of MRS broth with glucose, Tween 20, Tween 80, sodium citrate, potassium chloride and cysteine, and effect of the initial pH and temperature of incubation of the medium on production of bacteriocins by <italic>L. sakei</italic> 2a. Adding glucose and Tween 20 to the medium, an initial pH of 5.0 or 5.5, and incubation temperatures of 25 °C or 30 °C resulted to the highest bacteriocin yields. Thus, a 2⁴ factorial design with the four variables was performed, and statistical analysis showed that it was an adequate model (<italic>R</italic>² = 0.8296). In the studied range, the four parameters significantly influenced bacteriocin production, with the maximum yield produced at an initial pH between 5.5 and 7.0, a temperature between 25 and 30 °C and supplementation of the MRS broth with glucose from 3.25 to 6.0 g L⁻¹ and Tween 20 from 0.575 to 1.15% (v/v). Response Surface Methodology analysis indicated that the highest bacteriocin production (12800 AU mL⁻¹) occurred in the MRS broth supplemented with 5.5 g L⁻¹ glucose and 1.05% Tween 20 at an initial pH of 6.28 and an incubation temperature of 25 °C. The amount of bacteriocin produced in commercial MRS broths under the same conditions was only 5600AU mL⁻¹.</p

Phenotypic and genetic heterogeneity of lactic acid bacteria isolated from “Alheira”, a traditional fermented sausage produced in Portugal

The aim of this study was to evaluate the phenotypic and genetic heterogeneity of lactic acid bacteria (LAB) isolated from ‘‘alheira”, a fermented sausage produced in Portugal. LAB were identified to genus and species level by phenotypic characteristics, using genus or speciesspecific primers and sequencing of the gene encoding 16S rRNA. Two-hundred and eighty-three isolates were grouped into 14 species. Lactobacillus plantarum was isolated from all sausages and Enterococcus faecalis from most of the samples. Low numbers of Lactobacillus paraplantarum, Lactobacillus brevis, Lactobacillus rhamnosus, Lactobacillus sakei, Lactobacillus zeae, Lactobacillus paracasei, Leuconostoc mesenteroides, Pediococcus pentosaceus, Pediococcus acidilactici, Weissella cibaria, Weissella viridescens and Enterococcus faecium were recorded. The genetic heterogeneity of L. plantarum and E. faecalis strains were determined by numerical analysis of DNA banding patterns obtained by RAPD–PCR. Strains of L. plantarum and E. faecalis were different from different producers. This study forms the basis from which starter cultures could be selected for production of ‘‘Alheira”.info:eu-repo/semantics/acceptedVersio

Evaluation of the bioavailability and intestinal effects of milk fermented by folate producing lactic acid bacteria in a depletion/repletion mice model

This study aimed to evaluate the bioavailability and effects on the intestinal mucosa of a bioenriched fermented milk (BFM) prepared with folate-producing lactic acid bacteria, using a depletion/repletion BALB/c mice model. Five Streptococcus thermophilus strains were combined with Lactobacillus plantarum 16cv and the combination that resulted in the best folate production was used for preparation of BFM. The folate content in BFM, prepared under controlled conditions (pH 6.0, 42 °C, 70 rpm, 24 h), was 321.1 ± 14.1 ng/mL. Results for mice fed with BFM were compared to those fed with other diets. The BFM group presented an increase in hemoglobin, hematocrit and red blood cells, and the villi height/crypt depth ratio was similar to that of animals receiving milk supplemented with commercial folic acid. The strains were sensitive to most tested antibiotics and lacked virulence genes, indicating that consumption of BFM may be a promising alternative to increase intake of folate.Fil: Cucick, Ana Clara C.. Universidade de Sao Paulo; BrasilFil: Gianni de Carvalho, Katia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; ArgentinaFil: Todorov, Svetoslav D.. Universidade de Sao Paulo; BrasilFil: de Moreno, Maria Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Leblanc, Jean Guy Joseph. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Centro de Referencia para Lactobacilos; ArgentinaFil: Franco, Bernadette D. G. M.. Universidade de Sao Paulo; Brasi

Procjena probiotičkih svojstava bakterije Enterococcus mundtii, njezino preživljavanje u bozi i proizvodnja bakteriocina in situ

Boza is a low-pH and low-alcohol cereal-based beverage produced in the Balkan Peninsula. Barley was cooked and prepared according to a traditional recipe and inoculated with Enterococcus mundtii ST4V (a potential probiotic and bacteriocin-producing strain), commercially produced boza, Saccharomyces cerevisiae, and a combination of strain E. mundtii ST4V and Saccharomyces cerevisiae. Fermentation was carried out at 37 °C for 3 h. The organoleptic properties of fermented products were evaluated by a qualified taste panel. No significant differences in rheological properties were observed, suggesting that E. mundtii ST4V had no effect on the quality of the final product. Microbial cell numbers remained relatively unchanged during one week of storage. The preservative properties of bacteriocin ST4V were evaluated by contaminating boza with Lactobacillus sakei DSM 20017. Changes in microbial populations were monitored by using classical microbiological methods, PCR with species-specific primers and denaturing gradient gel electrophoresis (DGGE). Adsorption of bacteriocin ST4V to target cells is pH-dependent, with the highest adsorption (88 %) recorded at pH=8.0 and pH=10.0. Maximum adsorption of bacteriocin ST4V (75 %) to Enterococcus faecalis and Listeria innocua was recorded at 25 to 37 °C. Growth of E. mundtii ST4V was inhibited only by a few antibiotics and anti-inflammatory medicaments, suggesting that the strain may be used as a probiotic by individuals receiving medical treatment.Boza je napitak od žitarica, male pH-vrijednosti i neznatnog udjela alkohola, koji se priprema na Balkanu. U istraživanju je upotrijebljena boza pripremljena kuhanjem ječma prema tradicionalnom receptu, inokulirana bakterijskim sojem Enterococcus mundtii ST4V (koji proizvodi bakteriocin i ima probiotička svojstva), bozom proizvedenom na komercijalan način, kvascem Saccharomyces cerevisiae i kombinacijom bakterijskog soja i kvasca. Tim stručnjaka ispitao je organoleptička svojstva proizvoda dobivenih nakon 3 sata fermentacije pri 37 ºC. Nije utvrđena značajna razlika u reološkim svojstvima dobivenih proizvoda, što upućuje na zaključak da inokulacija sojem E. mundtii ST4V nije utjecala na kakvoću proizvoda. Čak ni nakon tjedan dana skladištenja nije se promijenio broj stanica mikroorganizama u proizvodima. Da bi se procijenio zaštitni učinak bakteriocina ST4V, ispitana je boza inokulirana sojem Lactobacillus sakei DSM 20017, pa je mikrobna populacija praćena klasičnim mikrobiološkim metodama, reakcijom polimeraze (PCR) sa specifičnim početnicama i elektroforezom u gradijentu denaturirajućega gela (DGGE). Adsorpcija bakteriocina ST4V na ciljane stanice ovisi o pH-vrijednosti, s najvećom adsorpcijom (88 %) zabilježenom pri pH=8 i pH=10. Maksimalna adsorpcija bakteriocina (75 %) na stanice Enterococcus faecalis i Listeria innocua zabilježena je u rasponu temperature od 25 do 37 ºC. Rast bakterije E. mundtii ST4V inhibirali su samo neki antibiotici i protuupalni lijekovi, što upućuje na to da taj soj ima probiotički učinak i na pacijente koji primaju određenu terapiju

Bacteriocins: exploring alternatives to antibiotics in mastitis treatment

Mastitis is considered to be the most costly disease affecting the dairy industry. Management strategies involve the extensive use of antibiotics to treat and prevent this disease. Prophylactic dosages of antibiotics used in mastitis control programmes could select for strains with resistance to antibiotics. In addition, a strong drive towards reducing antibiotic residues in animal food products has lead to research in finding alternative antimicrobial agents. In this review we have focus on the pathogenesis of the mastitis in dairy cows, existing antibiotic treatments and possible alternative for application of bacteriocins from lactic acid bacteria in the treatment and prevention of this disease