Oral administration of live probiotics such as Lactobacillus and Bifidobacterium spp. possess numerous beneficial effects. However, delivering viable probiotics to the host intestine has been a challenge due to poor survival of these bacteria during the gastric transit. An improved oral delivery system (modified alginate microcapsules) was developed in this study for targeted release of viable probiotics to the host intestine. Effect of various encapsulation parameters such as capsule size, alginate concentration, calcium chloride concentration, gelling/hardening time of microcapsules, addition of prebiotics and polymer coating, were individually investigated for improving the stability of microcapsules under simulated gastrointestinal (GI) conditions. Ability of microcapsules in protecting the viability of encapsulated bacteria improved significantly (p<0.05) in improving the stability of microcapsules. Optimisation of encapsulation parameters significantly improved the viability of encapsulated probiotics under simulated GI conditions. Furthermore, co-encapsulation of probiotics with complementary prebiotics (such as Hi-Maize starch) and chitosan coating provided additional protection to the encapsulated bacteria under simulated GI conditions. Release profile of chitosan-coated alginate-starch (CCAS) encapsulated bacteria was investigated in the GI tracts of different animal models. Addition of CCAS encapsulated bacteria to porcine GI contents (ex vivo) resulted in complete release of microencapsulated bacteria in the ileal contents within 8 h, while there was no significant release (p>0.05) of encapsulated bacteria in the gastric contents even after 24 h of incubation. In another experiment, CCAS microcapsules containing Lactobacillus casei Shirota (LCS) was orally administered to mice and the release profile of encapsulated bacteria was monitored throughout the murine GI tract for 24 h. Partial release of microencapsulated LCS was observed in duodenal and jejunal regions, while no significant (p>0.05) release of microencapsulated bacteria was observed in the stomach during the 24 h monitoring period. However, a significant release (nearly complete release) of microencapsulated bacteria was observed in ileal and colon of murine GI tract after 24 h. Elevated counts of LCS in ileum and colon indicated the most favorable site for the release of CCAS encapsulated bacteria. Further studies investigated the immunomodulatory activity of microencapsulated probiotic bacteria in a murine model. Lactobacillus casei Shirota was orally administered to mice either as microencapsulated or as free bacteria (non encapsulated) for two weeks. On day 14, the splenocytes from different experimental groups were harvested and assessed for ConA induced cytokine levels. A significant increase (p>0.05) in IFN-γ levels was observed in the activated splenocytes of groups treated with microencapsulated and free (non-encapsulated) LCS, compared to the control group (no LCS treatment). However, there was no significant difference (p<0.05) in the IFN-γ concentration between the groups treated with microencapsulated and free (non-encapsulated) LCS. No significant difference (p<0.05) in the IL-10 concentration was observed in the activated splenocytes of groups treated with microencapsulated and free (non-encapsulated) LCS. Finally, the stability of microencapsulated probiotics in different dairy products was investigated. CCAS microcapsules significantly protected the viability of probiotic bacteria in set and stirred yoghurts over 6-week refrigerated storage conditions compared to free (non-encapsulated) probiotics. Overall, chitosan-coated alginate-starch microcapsules developed in this study effectively protected the viability of probiotics from adverse gastric conditions and released the bacteria in the host intestine without detrimentally affecting its immunomodulatory properties. / Doctor of Philosophy
| Identifer | oai:union.ndltd.org:ADTP/234752 |
| Date | January 2005 |
| Creators | Iyer, Chandra, University of Western Sydney, College of Health and Science, Centre for Plant and Food Science |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
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