Thermo-kinetic studies of in vitro digestion and colonic fermentation of inulin/Lactobacillus rhamnosus GG co-encapsulated composite beads

In this study, Lactobacillus rhamnosus GG (L.GG) and inulin were successfully co-encapsulated into alginate/pectin composite aerogel beads using high efficiency vibration technology with freeze-drying. The addition of inulin did not substantially affect the morphology or particle size of microcapsules but improved the survival number of L.GG during encapsulation process, storage and in vitro digestion. Isothermal microcalorimetry was used for the first time to investigate the thermos-kinetics properties of these encapsulated L.GG during in vitro gastrointestinal digestion and colon fermentation, revealing that the co-encapsulation with inulin increased the growth rate of L.GG in the logarithmic growth phase, without change the total heat production. The number of probiotic microcapsules surviving after 60 days of storage was still more than 8 Log CFU/g. Inulin co-encapsulation also significantly improved the storage and heat stability of L.GG, with the highest viability of 8 Log CFU/g after 60-day storage, 5.58 Log CFU/g after heating at 63 °C for 30 min, and 7.85 Log CFU/g at 72 °C for 3 min, respectively. These microcapsules also altered the composition and diversity of mice gut microbiota, increasing the relative abundance of Lactobacillus and decreasing that of Bacteroides. This study introduces a novel colon-targeted probiotic-delivery system and a method to understand the control-release thermodynamics of the encapsulated probiotics in simulated gastrointestinal digestion and colonic fermentation.