Engineered Phytoene-Producing Saccharomyces cerevisiae Alleviates Cyclophosphamide-Induced Intestinal Barrier Dysfunction and Gut Dysbiosis.

Intestinal mucosal barrier dysfunction is a critical driver of various gastrointestinal disorders, typically manifesting as physicochemical barrier disruption, immune dysregulation, and microbial dysbiosis. Harnessing the potent antioxidant properties and high intestinal bioavailability of phytoene, alongside the suitability of Saccharomyces cerevisiae as a food-grade expression host, we evaluated the efficacy of engineered phytoene-producing S. cerevisiae (PSc) in attenuating cyclophosphamide (CP)-induced jejunal mucosal damage in mice. Single-dose oral retention assays revealed that PSc preserved viability during gastric transit and transiently colonized the intestine for over 24 h. Dietary supplementation with PSc effectively mitigated CP-induced jejunal injury and reversed the pathological atrophy in lymphoid organs, specifically the spleen and thymus. Mechanistically, PSc restored the mucus barrier by augmenting goblet cell counts and MUC2 expression, reinforced epithelial integrity by upregulating tight junction proteins, and fortified the immunological barrier by modulating the secretion of sIgA and cytokines (e.g., IL-1β, IL-6, TNF-α, and TGF-β3). Furthermore, PSc remodeled both gut bacterial and fungal communities, enriching beneficial taxa such as Muribaculaceae, Lachnospiraceae, and Kazachstania while suppressing pathogenic microbes, thereby restoring microbial homeostasis and facilitating mucosal repair. In conclusion, this study demonstrates that PSc ameliorated CP-induced intestinal injury by restoring multi-layered barrier functions, establishing a robust rationale for its development as a novel probiotic and functional food supplement for managing chemotherapy-induced intestinal complications.