Enhancing gastrointestinal survival of probiotics using calcium alginate-based liquid-core beads: A strategy for modulating the gut microbiota in children

• Modified MRS broth markedly improves PLCB storage stability. • Ruptured or intact PLCB has higher gastrointestinal tolerance than free probiotics • PLCB outperforms free probiotics in modulating pediatric gut microbiota. • B. animalis BLa80 tolerates gastric digestion better than L. rhamnosus LRa05. • L. rhamnosus LRa05 dominates during co-fermentation with B. animalis BLa80. The children's gut is highly sensitive and developmentally immature, making it susceptible to various disorders, which may be mitigated through probiotic supplementation. To enhance probiotic delivery to the children’s intestinal tract, we engineered probiotic liquid-core beads (PLCBs) to encapsulate Lactobacillus rhamnosus LRa05 and Bifidobacterium animalis BLa80 based on the calcium alginate reverse spherification. Optimization of preparation parameters (2% CaCl₂, 0.9% HA, 356 kDa high-G sodium alginate) significantly mitigated bead swelling during re-culturing and storage while improving bursting strength and gastrointestinal tolerance. Storage stability was further enhanced using modified MRS broth (retaining essential nutrients only). Simulated gastrointestinal digestion demonstrated that the ruptured or intact PLCB provided significantly superior protection to the probiotics compared to free probiotics, with BLa80 exhibiting higher gastric acid tolerance than LRa05. Ruptured PLCBs more effectively modulated the gut microbiota in children than free probiotics by increasing beneficial genera (e.g., Faecalibacterium ) and reducing potential pathogens (e.g., Streptococcus ). During co-fermentation, LRa05 dominated as the primary strain, demonstrating stronger acid production and microbiota-modulating effects than BLa80. This study offers a theoretical foundation and technical underpinning for developing probiotic delivery systems targeting children.