| Probiotics are live microorganisms, which when administered in adequate amounts confer a health benefit in the host. As probiotics, characteristics commonly presumed to be essential, such as alleviation of lactose intolerance, regulation of immunity, the ability to improve the balance of the intestinal microbiota and to lower blood cholesterol levels. According to WHO working group report on drafting guidelines for the evaluation of probiotics in food, the experiments of probiotic properties included:(1) Resistance to gastric acidity,(2) Bile acid resistance,(3) Adherence to mucus and/or human epithelial cells and cell lines,(4) Antimicrobial activity against potentially pathogenic bacteria,(5) Ability to reduce pathogen adhesion to surfaces,(6) Bile salt hydrolase activity,(7) Resistance to spermicides(applicable to probiotics for vaginal use).Lactobacillus plantarum KLDS1.0391 and Lactobacillus plantarum KLDS1.0706 were isolated from ‘‘Jiaoke”, a traditional, naturally fermented cream from Inner Mongolia in China. The former is a bacteriocin-producing strain which can produce bacteriocin MG, and the later is a non-bacteriocin-producing strain. The aim of the study was to evaluate the the tolereance to the harsh environment of the digestive tract and then evaluate their in vitro probiotic properties and the safety of the strains, finally was to reveal the relationship between the ability of tolerance to harsh environment, in vitro probiotic properties and the bacteriocins.The antibiotic activity research results show that, the obvious inhibition zone was observed in the plate which contained the cell-free supernatants(CFSs) of Lactobacillus plantarum1.0391 and Lactobacillus plantarum KLDS1.0706 respectively. The same result were founded in the plate contained tenfold concentrated CFSs of Lactobacillus plantarum KLDS1.0391 which pretreated to remove the component of H2O2 and organic acid. The above results illustrated that the two Lactobacillus plantarum strains produced some antibacterial substances(like organic acid and H2O2 etc) after the fermentation so that could inhibit the growth of pathogens. While the pro-prosessing CFSs of Lactobacillus plantarum KLDS1.0391 had the sme result certified that Lactobacillus plantarum KLDS1.0391 is a bacteriocin-producing strain, and Lactobacillus plantarum KLDS1.0706 is a non- bacteriocin-producing strain.Both of lactobacilli strains showed bad performance to p H 2. However, both of the tested strains showed good tolerance to p H 3, at which the viable counts exceeded 109 CFU/ml after incubation for 3 h. Lactobacillus plantarum KLDS1.0391 possessed better tolerance at p H 2 than Lactobacillus plantarum KLDS1.0706(P<0.05), but it possessed slight lower tolerance than the reference strain LGG. Lactobacillus plantarum KLDS1.0391 and Lactobacillus plantarum KLDS1.0706 showed a good capability to grow in different concentration of bile salt. The viable counts for lactobacilli strains were above 108 CFU/ml, while Lactobacillus plantarum KLDS1.0391 showed better risistence wich was similar to the result of the tolerance to artificial gastric juice and artificial pancreatic juices. However, compaired with LGG, Lactobacillus plantarum KLDS1.0391 showed the similar or the better performance, but Lactobacillus plantarum KLDS1.0706 were not.Surface properties and adhesion abilities. Lactobacillus plantarum KLDS1.0391 possessed better performance in surface properties(including surface hydrophobicity, auto-aggregation assay and co-aggregation assay) compared with Lactobacillus plantarum KLDS1.076, but there was no significant differences(P>0.05). But LGG performed the strongest surface properties among the three strains. In the adhesion assay, the adhesion ability followed the order: LGG >Lactobacillus plantarum KLDS1.0391 > Lactobacillus plantarum KLDS1.0706. While in the assay of inhibition adhesion, both of the Lactobacillus plantarum strains showed better performance to LGG, and Lactobacillus plantarum showed the best effect.BSH activity and cholesterol removal capability. BSH activity was followed the order: Lactobacillus plantarum KLDS1.0706>LGG>Lactobacillus plantarum KLDS1.0391,while the cholesterol removal capability was followed the order: Lactobacillus plantarum KLDS1.0391>Lactobacillus plantarum KLDS1.0706 > LGG. There was no relationship between the two properties.In the preliminary evaluation of immunological activity, Lactobacillus plantarum KLDS1.0706 exhibited more effective than that of Lactobacillus plantarum KLDS1.0391(no matter active lactobacillus and the heat-killed ones). Compared with the commercial strain LGG, Lactobacillus plantarum KLDS1.0391 showed lower effective, but there were no significant differences between each other. The result showed that both Lactobacillus plantarum KLDS1.0391 and Lactobacillus plantarum KLDS1.0706 showed the potencial in immunomodulatory in vitro.In the hemolytic activity, there was no hemolysis ring appearing on the Columbia plate. It demonstrated that Lactobacillus plantarum KLDS1.0391 and Lactobacillus plantarum KLDS1.0706 were non-hemolytic strains; in antibiotic resistance assay, we found that the two Lactobacillus plantarum strains only had resistance to vancomycin and streptomycin which had the same resistance with LGG. In addition, Lactobacillus plantarum KLDS1.0706 also had resistance to gentamicin. Through the evaluation of the above two aspects, we prove that there was no security problems with Lactobacillus plantarum KLDS1.0391 and Lactobacillus plantarum KLDS1.0706.In summary, Lactobacillus plantarum KLDS1.0391 had better performance in the tolerance to harsh environment, surface properties, adhesion ability and cholesterol removal capability than Lactobacillus plantarum KLDS1.0706. While Lactobacillus plantarum KLDS1.0706 showed better performances in BSH activity and immunological activity than Lactobacillus plantarum KLDS1.0391. Compaired with LGG, both of the Lactobacillus plantarum strains showed the same or more prominent performance except the tolerance to harsh environment and surface properties. So Lactobacillus plantarum KLDS1.0391 and Lactobacillus plantarum KLDS1.0706 had the potential of being as probiotics. |
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