delbrueckii DSM 20074 L. delbrueckii subsp.lactis DSM 20076 L. delbrueckii subsp.bulgaricus MB 453 L. salivarius subsp.salicinius ATCC 11742 L. salivarius subsp.salivarius ATCC 11741 L. gasseri MB 335 L. helveticus S 36.2; S40.8 L. plantarum ATCC 8014; NCDO 1193; MB 456 Assessment of the antagonistic activity The antagonistic activity of the selected Lactobacillus strains against the isolated coliforms was assayed by using both agar plates and liquid co-cultures of both strains. – Antimicrobial activity on agar plates

In this assay both Lactobacillus spp. cells and Lactobacillus neutralized selleck chemicals cell-free supernatants (NCS) were employed. Each Lactobacillus strain was grown in MRS broth for 48 h at 37°C in 5% CO2 atmosphere and then centrifuged at 15000 g at 4°C for 15 minutes. pH of the cultures was neutralized to pH 7 with 1N NaOH and cells were separated through filtration (via a 0.2 μm pore size filter). Lactobacillus cells were washed twice with saline

and suspended in saline at concentrations ranging from 104 to 106 CFU/ml. Lactobacillus cells were washed twice with saline and suspended in saline at concentrations of 104 , 105 and 106 CFU/ml. All the cell suspensions were assayed to optimize the most suitable cell concentration; the cell concentration of 106 CFU/ml was then used to perform the CUDC-907 research buy comparative assay of the inhibitory activity of the two Lactobacillus strains against coliforms. The paper-disk assay of Kirby-Bauer [23] was used with some modifications as follows. 50 μl of coliform liquid culture in LB broth containing from 103 to 106 CFU/ml, in the majority of cases between 105 and 106, was streaked on a Mac Conkey and LB agar plate; subsequently two sterile paper blank disks (diameter 6 mm) were placed on the agar plate and imbibed one with 50 μl of washed Lactobacillus cells and the other with 50 μl of the corresponding NCS. After incubation for 18 h at 37°C, the diameters of the inhibition zones were evaluated. The experiments were made in triplicate. – Antimicrobial activity in liquid co-cultures The capability of Lactobacillus DSM 20074 of interfering with

the growth of coliforms was evaluated by co-incubating both strains. The Lactobacillus strains and the coliform strains new were grown on MRS broth and LB broth, respectively. The co-culture experiments was performed in a modified LB medium (i.e. LB additioned with 3% w/v yeast extract) capable of sustaining the growth of both microorganisms. The medium was inoculated with 105 CFU/ml of both the Lactobacillus and the coliform strains and Evofosfamide chemical structure incubated at 37°C in microaerophylic conditions. Controls were prepared by inoculating the same medium either with the Lactobacillus strain or with the coliform one; in addition coliforms were co-cultured with a Lactobacillus strain with no inhibition activity (L. casei MB50, Table 2).