Even if from long time the main source of probiotic bacteria has been considered the gastrointestinal tract (GIT), recently many studies investigated the potentialities of lactic acid bacteria (LAB) isolated from foodstuffs. The selection of beneficial LAB strains in the field of the dairy foods has been widely investigated, whereas the identification of new probiotic strains from fermented vegetables is just at the beginning. To this regard the table olives could be considered as a suitable source of probiotics in relation to their autochthonous microbiota, in which the most representative LAB is the Lactobacillus (L.) plantarum, a species that has well documented beneficial effects on the human GIT. With the purpose to isolate new potential probiotic LAB, 17 strains belonging to three different species (L. plantarum, L. pentosus and Leuconostoc mesenteroides) were isolated from table olives fermentations. All strains could survive in simulated GIT conditions and were further studied in vitro using human H4 intestinal epithelial cells as a gut model. Strains were checked for cytotoxicity as well as adhesion capability, both in 2D and 3D model of the gut. Furthermore, 3D model with cells growing on microporous membranes was used to investigate the direct interaction between bacteria and epithelial cells. Through the measurement of the transepithelial electrical resistance (TEER) we could follow the variation of the epithelial barrier function induced by the bacterial presence. Finally, the potential inhibition of Listeria (L.) monocytogenes adhesion and invasion were analyzed. All experiments were performed in triplicates and data obtained were subjected to ANOVA and Duncan???s test as post hoc statistical analysis. All strains confirmed not to be toxic for the H4 human cells. Concerning the adhesion capability, two strains (O1T90E, O2T60C) showed in the 3D gut model an attachment ratio significantly higher than the L. rhamnosus GG (P<0,05). Two strains (S1T10A and S11T3E) enhanced the integrity of the polarized epithelium. Moreover, the L. plantarum S11T3E, together with L. plantarum S2T10D and L. pentosus S3T60C showed the ability to inhibit the L. monocytogenes invasion in 2D epithelial model (P<0,05). The L. pentosus strain was also able to reduce the pathogen adhesion (P<0,05). However, the three strains did not confirm in a significant way (P>0,05) the reduction of pathogen invasion when tested in 3D model, despite the S11T3E decreased the number of recovered Listeria by more than 50%. In conclusion, L. plantarum strain S11T3E could be considered as a promising probiotic LAB, because it was able to enhance epithelial integrity and reduce L. monocytogenes invasion in the in vitro gut model.
Lactic acid bacteria from table olives fermentations: isolation of potential probiotic
BOTTA, CRISTIAN;COCOLIN, Luca Simone
2013-01-01
Abstract
Even if from long time the main source of probiotic bacteria has been considered the gastrointestinal tract (GIT), recently many studies investigated the potentialities of lactic acid bacteria (LAB) isolated from foodstuffs. The selection of beneficial LAB strains in the field of the dairy foods has been widely investigated, whereas the identification of new probiotic strains from fermented vegetables is just at the beginning. To this regard the table olives could be considered as a suitable source of probiotics in relation to their autochthonous microbiota, in which the most representative LAB is the Lactobacillus (L.) plantarum, a species that has well documented beneficial effects on the human GIT. With the purpose to isolate new potential probiotic LAB, 17 strains belonging to three different species (L. plantarum, L. pentosus and Leuconostoc mesenteroides) were isolated from table olives fermentations. All strains could survive in simulated GIT conditions and were further studied in vitro using human H4 intestinal epithelial cells as a gut model. Strains were checked for cytotoxicity as well as adhesion capability, both in 2D and 3D model of the gut. Furthermore, 3D model with cells growing on microporous membranes was used to investigate the direct interaction between bacteria and epithelial cells. Through the measurement of the transepithelial electrical resistance (TEER) we could follow the variation of the epithelial barrier function induced by the bacterial presence. Finally, the potential inhibition of Listeria (L.) monocytogenes adhesion and invasion were analyzed. All experiments were performed in triplicates and data obtained were subjected to ANOVA and Duncan???s test as post hoc statistical analysis. All strains confirmed not to be toxic for the H4 human cells. Concerning the adhesion capability, two strains (O1T90E, O2T60C) showed in the 3D gut model an attachment ratio significantly higher than the L. rhamnosus GG (P<0,05). Two strains (S1T10A and S11T3E) enhanced the integrity of the polarized epithelium. Moreover, the L. plantarum S11T3E, together with L. plantarum S2T10D and L. pentosus S3T60C showed the ability to inhibit the L. monocytogenes invasion in 2D epithelial model (P<0,05). The L. pentosus strain was also able to reduce the pathogen adhesion (P<0,05). However, the three strains did not confirm in a significant way (P>0,05) the reduction of pathogen invasion when tested in 3D model, despite the S11T3E decreased the number of recovered Listeria by more than 50%. In conclusion, L. plantarum strain S11T3E could be considered as a promising probiotic LAB, because it was able to enhance epithelial integrity and reduce L. monocytogenes invasion in the in vitro gut model.File | Dimensione | Formato | |
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