Oral delivery of engineered Lactococcus lactis microcapsules expressing antioxidant enzymes for inflammatory bowel disease: Mechanisms of intestinal barrier repair and microbiota modulation

Inflammatory bowel disease (IBD) is characterized by elevated levels of reactive oxygen species (ROS) and pro-inflammatory cytokines, alongside disrupted gut microbiota. Therefore, eliminating ROS in the inflammatory site by antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD) represents a promising therapeutic strategy for IBD. To this end, we genetically engineered Lactococcus lactis to construct an antioxidant probiotic strain, LL-SC, by integrating a fusion gene (SC) encoding SOD and CAT. To further enhance gastrointestinal survival, LL-SC was encapsulated with a composite nanomaterial of mucosal-adhesive chitosan and sodium alginate to produce LL-SC-C 2 A 2 with antioxidant enzyme expression capability and a nano-protective coating. Compared to uncoated LL-SC, LL-SC-C 2 A 2 exhibited significantly improved gastric acid tolerance with 1.4-fold increases. Protective effects of LL-SC-C 2 A 2 were confirmed across cellular and animal models, including H 2 O 2 -stimulated Caco-2 cells and a DSS-induced murine colitis model. This was achieved through ROS scavenging, pro-inflammatory cytokine reduction, intestinal barrier reinforcement, and restoration of gut microbiota homeostasis. Overall, food-grade LL-SC-C 2 A 2 represents a novel approach to probiotic modification, providing a new strategy and experimental evidence supporting further development for IBD therapy.