Controllable engineered probiotic microspheres for treating ulcerative colitis: A cascade enzyme‐catalyzed strategy to restore intestinal redox homeostasis

Oral administration of probiotics is a promising approach for the prevention and treatment of ulcerative colitis. However, the therapeutic efficacy is limited by low bioactivity under harsh gastrointestinal conditions, especially under excessive intestinal reactive oxygen species (ROS) activity. Herein, a dual strategy combining genetic engineering with physical encapsulation was proposed to enhance the stress tolerance of probiotics. To endow Saccharomyces boulardii with robust antioxidant properties, a mutant strain capable of simultaneously overexpressing the SOD1 and CTT1 antioxidant genes was constructed. To eliminate intestinal ROS in situ, a signal peptide was co‐introduced to facilitate the extracellular secretion of cascade enzymes. To improve the safety and controllability of the engineered probiotics, an auxotrophic strain was constructed that could only survive and grow when exogenous arginine was supplied. The engineered S. boulardii was then encapsulated in sodium alginate microspheres using droplet rotation technology. This physical barrier protected the probiotics from gastric acid damage and enabled their targeted release in the intestines. H&E and immunohistochemical staining revealed that the probiotic microspheres reduced intestinal inflammation and restored redox homeostasis by clearing ROS. The 16S rRNA sequencing analysis revealed an increase in beneficial microbes and recovery of microbial diversity following treatment, confirming the remission of ulcerative colitis. This strategy provides new insights for the treatment of gastrointestinal disorders.