| Summary: | 碩士 === 國立臺灣大學 === 動物科學技術學研究所 === 101 === Microbial viability is an important factor to exert health benefits, especially in host’s lower digestive tract. However, most of microorganisms cannot stand the adverse conditions like industrial heating processes and the digestive juice. Hence the purpose of the study was to develop heat-tolerant probiotic microcapsules to improve the survival of probiotics under heat treatment and the passage through the simulated gastrointestinal fluid (SGIF). The functionality of encapsulated probiotics was also evaluated.
Gellan gum, sodium alginate and skim milk powder were incorporated as coating materials to encapsulate Lactobacillus kefiranofaciens M1 (M1) and Lb. mali APS1 (APS1) separately. The optimal proportion of gellan gum, sodium alginate and skim milk powder in microcapsules was determined by preliminary thermal-tolerant test. The bacterial counts in freeze-dried microcapsules stored at 4 oC were determined at different storage periods and heat treatments, followed by treatment of the SGIF. The initial bacteria counts of M1 and APS1 were 8.3 and 10.3 log CFU/g. The bacteria counts of M1 and APS1 after 8 weeks storage were 6.6 and 9.7 log CFU/g. After heat treatment, the bacteria numbers dropped to 5.8 and 9.2 log CFU/g. The viability of encapsulated M1 and APS1 were above 5.0 log CFU/g and 7.0 log CFU/g in SGIF test. On the contrary, the two free strains cannot detect viable bacteria counts after 8 weeks among these tests.
Since both M1and APS1 demonstrated an anti-colitis effect in our previous study, we further investigated the anti-colitis effect of encapsulated these two strains in vivo and in vitro. Both heated encapsulated M1 and APS1 could significantly ameliorate the symptoms of DSS-induced colitis, including bleeding score, weight losing and colon length shortening, when compared with non-encapsulated groups in vivo. It is worth to notice that the distribution of lactobacilli and coliform in cecum was no difference among all experimental groups. We further studied the possible mechanism involved in the anti-colitis effect in vitro. The results indicated that both encapsulated strains could significantly increase the transepithelial electrical resistance (TEER) in Caco2 monolayer when compared with the blank group. However, the elevation of TEER value and CCL20 production was not found in the heated encapsulated strains.
These findings revealed that encapsulated strains with heat-stable coating materials could elevate the viability during storage, heat resistance and simulated gastrointestinal conditions. Furthermore, the heat encapsulated strains demonstrated an anti-colitis effect in vivo. The heat-tolerant microcapsule might provide a high potential to apply the probiotics in warm drinks in the near future.
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