| Summary: | 碩士 === 中國醫藥大學 === 營養學系 === 96 === Many species of lactic acid bacteria (LAB) like Lactobacillus reuteri can benefit the human health. The survival of the ingested LAB may be decreased when arriving at the lower digestive tract due to the gastric acid and bile salts existed in the gastrointestinal system. In this study, two immobilization materials–Ca-alginate and chitosan-Ca-alginate were used to encapsulate L. reuteri. Based on the characterictics of immobilization materials, the experimental groups were divided into two, i.e. Ca-alginate group (A group) and chitosan-Ca-alginate complex material group (CA group). The group of free L. reuteri cells without encapsulation was the control group and designated as the F group. The survival rate of L. reuteri after the treatment of simulated gastrointestinal conditions, as well as that of the released cells of the entrapped L. reuteri in the simulated colon fluid were investigated. The adherence rate, antagonistic activity and safety property of the released bacteria using Caco-2 cell as the in vitro test model were determined, and β-galactosidase activity manifesting the effect of simulated gastrointestinal conditions on the bacterial cell membrane was also analyzed. Results showed that immobilization increased survival rate of L. reuteri after the treatment of simulated gastrointestinal conditions with the CA group had a better protective effect (p < 0.05). Analysis for β-galactosidase activity revealed that the injury of L. reuteri cell membrane raised with the increased bile salt concentration at the same pH values, and the injury of the encapsulated LAB cell membrane caused by acid and bile salt was less than the free LAB. Adhesive rates of the released L. reuteri showing the adhesiveness ability expressed in descending order, were CA group (0.524%) > A group (0.360%) > F group (0.275%) – i.e. the bacteria released from gel beads had higher adherence trait. All of the three groups of L. reuteri treated with simulated gastrointestinal conditions retained the antagonistic ability against Listeria monocytogenes with the released LAB from both immobilization materials exhibiting higher inhibition ability than free LAB. The result of invasion test indicated that the released LAB cells were safe in vitro. This research suggestes that immobilization not only can enhance the survival of L. reuteri treated with simulated gastrointestinal conditions, decrease the injury of cell membrane, but also retains the probiotic characteristics of adhesiveness and antagonistic activity.
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