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Biopolymer microgels were designed to encapsulate and protect probiotics during storage and passage through the upper human gastrointestinal tract (GIT), but then release them in the colon. An anaerobic probiotic strain (Bifidobacterium pseudocatenulatum G7; BPG7) was encapsulated within calcium alginate microgels. In some cases, either colloidal antacid (CaCO 3) or colloidal antacid and nanoemulsion (nE) lipid droplets were co-encapsulated with the probiotics. These additives were used to control the porosity and/or internal pH of the microgels. Initially, the viability of free and encapsulated probiotics was evaluated when they were stored at 4 °C for 28 days. The free probiotics rapidly degraded during storage. Encapsulation greatly improved the stability of the probiotics, with the effectiveness depending on the formulation: antacid-microgels > control microgels > antacid-nE-microgels. These effects were mainly attributed to the ability of the colloidal CaCO 3 particles to inhibit molecular diffusion processes. The ability of the microgels to protect the probiotics under simulated gastrointestinal tract (GIT) conditions was then assessed. The free probiotics were completely inactivated when exposed to gastric and small intestine conditions. In contrast, the antacid- and antacid-nE-microgels were highly effective at improving the viability of the probiotics during passage through the upper GIT. Moreover, these microgels were fermented under simulated colonic conditions, thereby releasing the probiotics. These results suggest that antacid-loaded calcium alginate microgels can be used for the encapsulation, protection, and colonic delivery of probiotics. Nevertheless, further studies are required using in vivo models. Image 1 • Antacid alginate-microgels greatly improved the stability of the probiotics during storage. • The antacid agent/antacid and nanoemulsion improved the viability of the probiotics during digestion. • The alginate microgels was fermented to release probiotics under simulated colonic conditions. [ABSTRACT FROM AUTHOR]