Development Of Lactobacillus Delbrueckii Composite Microcapsules

The purpose of this item is to improve the ability of probiotics (using Lactobacillus delbrueckii typical strain) to tolerate the extreme environment of digestive tract through microencapsulation, and thus planting more live bacteria into middle or lower part of small intestine to embody their probootic effects. The study used Soy Protein Isolate (SPI) and High Methoxyl Pectin (HMP) as compound wall materials to encapsulating L.delbrueckii and protected the L.delbrueckii against loss when passing upper digestive tract there by more L.delbrueckii could be released in small intestine.The main process and the results are as follows:(1) The optimal technological parameters for preparing SPI-HMP compound microcapsule are as follows:the concentration of SPI solution is 9%(w/v); the concentration of HMP solution is 1 mg/mL; the volume ratio of SPI solution and HMP solution is 7:1 (v/v); the volume ratio of SPI-HMP compound solution and bacteria suspension liquid isl:1 (v/v).(2) Simulated human digestive tract test:After passing through simulation digestive tract, naked bacteria density decreases from over 109 CFU/mL to 104CFU/mL, descendind by 5log units. While the bacterial density in SPI-HMP compound microcapsule decreased from over 109 CFU/mL to 108 CFU/mL after simulated digestive tract test, descending by 11og units. The release profile of L.delbrueckii from SPI-HMP compound microcapsules can keep the L.delbrueckii at high orders of magnitude, which can compensate for the number of lost probiotics in digestive tract, thus playing probiotic function.(3) The structure of compound microcapsule was characterized by SEM, FTIR, TG, DSC, CD, Zeta potential and size distribution analysis. Through the SEM observation, the surface of SPI-HMP compound microcapsule is smooth, full with embedding bacteria, the surface of SPI-HMP compound microcapsule sticks large amount of bacterica. Combined with the size distribution analysis, we can conclude that the size of SPI-HMP compound microcapsule were small than that of SPI microcapsules. Structural analysis indicates that during microcapsulating process, the SPI secondary structure has changed.The SPI-HMP compound microcapsules loading L.delbrueckii were prepared by single coacervation. The preparation parameters were optimized using embedding rate and release profile as indexes. The optimized compound microcapsules were characterized structurally and the formation of SPI and HMP compound were study preliminary.