The probiotic properties of two selected lactobacilli strains were assessed. L. salivarius and L. plantarum displayed higher hydrophobicity (48% and 54%, resp.) and coaggregation ability with four pathogens (from 7.9% to 57.5%). L. salivarius and L. plantarum had good inhibitory effects on S. aureus (38.2% and 49.5%, resp.) attachment to Caco-2 cells. Live lactobacilli strains and their conditioned media effectively inhibited IL-8 production (<14.6 pg/mL) in TNF-α-induced Caco-2 cells. Antibiotic-treated and the sonicated lactobacilli also maintained inhibitory effects (IL-8 production from 5.0 to 36.3 pg/mL); however, the heat-treated lactobacilli lost their inhibitory effects (IL-8 production from 130.2 to 161.0 pg/mL). These results suggest that both the structural components and the soluble cellular content of lactobacilli have anti-inflammatory effects. We also found that pretreatment of Caco-2 cells with lactobacilli inhibited S. typhimurium-induced IL-8 production (<27.3 pg/mL). However, lactobacilli did not inhibit IL-8 production in Caco-2 cells pretreated with S. typhimurium. These results suggest that the tested lactobacilli strains are appropriate for preventing inflammatory diseases caused by enteric pathogens but not for therapy. In short, L. salivarius and L. plantarum are potential candidates for the development of microbial ecological agents and functional foods.
Objective. Lactic acid bacteria (LAB) were isolated from fermented foods, such as glutinous rice dough, corn noodle, chili sauce, potherb mustard pickles, and stinky tofu, in northeast China. LAB strains with antimicrobial activities were screened, and seven of these Lactobacillus strains were identified as L. plantarum, L. pentosus, and L. paracasei through 16S rRNA gene analysis. After the supernatant of LAB was treated with proteinase K, pepsin, and papain, their antibacterial effect almost disappeared. Most strains with antibacterial activities were highly resistant to heat (65°C–121°C), acidity (pH 2–6), and alcohol. The antimicrobial effect of most strains treated with the Tween-80 surfactant was significantly reduced, and the antibacterial property of T4 was even lost. Ammonium sulfate precipitation, PCR, and nanoLC-ESI-MS/MS results confirmed that T8 produced antibacterial substances belonging to a protein family, and its zone of inhibition against pathogens significantly increased (>13 mm). In bacterial growth inhibition experiments, the colony count of Staphylococcus aureus was up to 1015 CFU/mL in the 3⁎de Man, Rogosa, and Sharpe (MRS) group, and this value was more than that in the 3⁎S6 supernatant group (1012 CFU/mL) and the control group (1010 CFU/mL) at 12 h. This study provided a basis for the selection of antimicrobial peptides and the development and utilization of LAB.
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