Aims:  To investigate the adhesion of lactobacilli and their subsequent competitive exclusion ability against pathogens. Methods and Results:  Four species of putative probiotic lactobacilli were studied for their adhesion abilities. First, the adhesion to Caco‐2 cells was examined by light and electron microscopy. The four species were then labelled by [methyl‐3H] thymidine and their adhesion to porcine intestinal mucus was determined by radioactivity. The tested lactobacilli showed best adhesion on ileal mucus compared with duodenal and jujenal mucus. Oxidative compound pre‐treatment (NaIO3 and NaIO4) dramatically decreased the adhesion of the lactobacilli to mucus. Pre‐treating mucus with proteolytic enzymes (proteinase K and trypsin) resulted in the increase of adhesion in Lactobacillus serotype Reuteri I2021, but the results in the other species were variable. Lactobacillus serotype Fermentum I5007 showed greatest adhesion potential and exerted the best competitive exclusion against Salmonella and Escherichia. Conclusions:  Adhesion ability in lactobacilli is species‐specific. Lactobacilli with higher adhesion index have better competitive exclusion ability. Significance and Impact of the Study:  This study suggests that there is a positive correlation between adhesion and competitive exclusion ability of lactobacilli. Additionally, the in vitro adhesion assay is a feasible way to screen unknown lactobacilli, potentially for future industrial applications.

Five LAB strains were evaluated using the acid production ability test, morphological observation, Gram staining, physiological, biochemical and acid tolerance tests. All five strains (LP1, LP2, LP3, LC1 and LC2) grew at pH 4·0, and LP1 grew at 15°C. Strains LP1, LP2 and LP3 were identified as Lactobacillus plantarum, whereas LC1 and LC2 were classified as Lactobacillus casei by sequencing 16S rDNA. The five isolated strains and two commercial inoculants (PS and CL) were added to native grass and Leymus chinensis (Trin.) Tzvel. for ensiling. All five isolated strains decreased the pH and ammonia nitrogen content, increased the lactic acid content and LP1, LP2 and LP3 increased the acetic content and lactic/acetic acid ratio of L. chinensis silage significantly. The five isolated strains and two commercial inoculants decreased the butyric acid content of the native grass silage. LP2 treatment had lower butyric acid content and ammonia nitrogen content than the other treatments. The five isolated strains improved the quality of L. chinensis silage. The five isolated strains and the two commercial inoculants were not effective in improving the fermentation quality of the native grass silage, but LP2 performed better comparatively. Significance and impact of the study: Leymus chinensis is an important grass in China and Russia, being the primary grass of the short grassland 'steppe' regions of central Asia. However, it has been difficult to make high-quality silage of this species because of low concentration of water-soluble carbohydrates (WSC). Isolating and evaluating lactic acid bacteria strains will be helpful for improving the silage quality of this extensively grown species.