| Two lactobacilli strains,isolated from a traditional Chinese cheese product called as Naigeda collected from Xinjiang region of China,were identified as Lactobacillus pentosus Ind1 and Lactobacillus pentosus Ind3 based on their morphological,physiological-biochemical properties as well as 16s DNA sequence data.The objectives of this present study were to test the ability of 2 L.pentosus strains to resist artificial gastrointestinal stresses,and to evaluate their adhesion to the intestinal epithelium.Firstly,Lactobacillus pentosus strains Ind1 and Ind3,after grown in the gastric juice of pH 2.5, intestinal juice of pH 6.8 and 0.50%concentration of bile salt at 37℃for 4h,showed strong resistances to harmful gastrointestinal environments,with a viability of 85%.Secondly,the adhesion ability of 2 L.pentosus strains depended greatly on their cell counts and incubation time.In vitro,a cell concentration of 1×10~8cfu/mL for 2h-incubation was proved to improve significantly the adhesion of the two strains to Caco-2 cell lines.The commercial probiotic strains like L. acidophilus NCFM and L.plantarum LP115 showed a very nice adhesion to intestinal epithelium,but the adhesion index from L.pentosus Ind3 was higher than 800(calculated in live cells adhered per 100 intestinal epithelium).The adhesion index was 934.2±41.35 for strain LP115,873.0±44.86 for strain NCFM and 830.5±19.46 for strain Ind3.However,strain Ind1 had a poor adhesiveness,and its live cells adhered per 100 epithelial cells were only 431.0±28.16.Moreover,pH in media,temperature and the growth phase of 2 lactobacilli strains had an influence on the adhesive effect.If pH in media was controlled between 4 and 5,the cells of stationary phase from 2 L.pentosus strains incubated at 37℃had the most adhesion index.Use of Heat to kill cells did not destroy the adhesion ability of 2 L. pentosus strains to epithelial cells. The functions of metabolites and surface protein components from L.pentosus Ind1 and Ind3 in their adhesion were carried out.The exhausted supernatants treated with trypsin or heated boiling water for 10 minutes proved that the adhesion of L.pentosus Ind1 and Ind3 to Caco-2 cell lines decreased significantly.It was speculated that a heat-sensitive protein produced and excreted to media by L. pentosus might be responsible for its adhesion loss because presence of trypsin or protease K in media significantly lowered the adhesive ability of the 2 strains.No obvious loss in adhesion capacity of the strains treated with 5mol/L LiCl occurred,showing that the bacterial S-layer protein might not involve in the adhesion of L.pentosus strains Ind1 and Ind3.Thirdly,a 5×10~9cfu/mL of L.pentosus Ind1 and Ind3 as well as L.acidophilus NCFM and L.plantarum LP115 was orally administrated to mice used as animal models.Compared with skimmed-milk used as the control group,the counts of beneficial microorganisms like bifidobacteria and lactobacilli from the intestinal microflora in mice were significantly promoted.After oral-administration of the live cells of L.pentosus Ind1 and Ind3 for 10 days,rat's feces had more lactobacilli and bifidobacteria and less Enterobacter and Clostridium perfringens,although had no change in Enterococcus counts.The counts of the intestinal microflora seemed to have an unbalance between the beneficial and harmful bacteria only after the tested rats stopped the oral-administration of 2 L.pentosus strains for 16-days.It was clear that the oral-consumption of L.pentosus Ind1 and Ind3 should be very promising as probiotics in modulating the intestinal microflora of the host for long days.
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