Prebiotic efficacy and mechanism of inulin combined with inulin-degrading Lactobacillus paracasei I321 in competition with Salmonella

Inulin efficacy was proven for raising anti-Salmonella activity of the inulin-degrading Lactobacillus paracasei I321 (infant isolate) through the mechanisms of antibacterial secretion and competitive adhesion. Inulin significantly promoted competitive adhesion of L. paracasei I321 against many Gram-negative foodborne pathogenic bacteria. Salmonella Typhimurium SA2093 was completely suppressed under highly competitive niche of fecal microflora when inulin, L. paracasei I321, and their synbiotic combination were applied. Inulin supplementation obviously alleviated nutrient limitation in the mimicked proximal colon leading to complete destruction of Salmonella. This was achieved through the manipulation of fecal bifidobacteria which subsequently altered antibacterial metabolites. Acetate was the major metabolite correlating to high number of fecal bifidobacteria in the presence of inulin, whereas lactate became dominant when L. paracasei I321 was coupled. This inulin-degrading strain was able to persist and dominate in the competitive environment of fecal microflora and functioned synergistically with inulin to completely destroy Salmonella.