Elahe Khademi, Fahimeh Nemati, Tohid Piri‐Gharaghie
BACKGROUND AND OBJECTIVE: Saccharomyces boulardii is a probiotic yeast with promising effects on poultry gut health and immunity, yet its application is limited by sensitivity to heat, pH and storage conditions. This study aimed to develop and evaluate an alginate-based microencapsulation system to improve the in vitro stability, storage viability and antimicrobial performance of S. boulardii for poultry feed applications. METHODS: A probiotic strain of S. boulardii was isolated, characterised and cultured under optimised fermentation conditions. The yeast was encapsulated using sodium alginate and cryoprotectants via extrusion, followed by freeze-drying. Microcapsules were characterised using FESEM, DLS, zeta potential and FTIR. Probiotic traits, including acid and bile salt tolerance, NaCl resistance, antibiotic susceptibility and antagonistic activity against common pathogens, were assessed. Encapsulation efficiency, viability before/after processing and shelf-life at 4°C and 25°C over 90 days were also evaluated. RESULTS: The microencapsulation efficiency was 73.27% ± 0.39%, with stable spherical capsules averaging 2-5 µm in size. The encapsulated yeast showed enhanced acid and bile salt tolerance, no sensitivity to tested antibiotics, and significantly greater antimicrobial activity compared to free yeast. Viability declined by ∼11% following freeze-drying. During storage, encapsulated yeast retained higher viability than free yeast, particularly at 25°C. FTIR confirmed successful molecular interaction between alginate and probiotic components. CONCLUSION: Alginate-based microencapsulation significantly enhanced the physicochemical stability, probiotic functionality and shelf-life of S. boulardii under simulated poultry feed processing and storage conditions. This technology offers a practical, scalable solution for delivering viable probiotics in poultry nutrition, supporting antibiotic-free production strategies.