Introduction

IBD is a gastrointestinal condition resulting from the complex interaction of genetic, gut microbiota, and environmental factors, encompassing Crohn's disease and UC (Caruso et al. 2020; Danne et al. 2023; Verstockt et al. 2023). Currently, it is estimated that approximately 5 million individuals worldwide suffer from UC, and the incidence rate continues to rise, posing a significant burden on global healthcare systems (Ungaro et al. 2017). UC is characterized by high incidence, incurability, and recurrence, manifesting as symptoms such as diarrhea, rectal bleeding, fecal incontinence, and abdominal cramping (Gros and Kaplan 2023). Although the pathogenesis of UC remains incompletely understood, intestinal microbial dysbiosis and barrier impairment have been identified as critical factors promoting UC development (Luo et al. 2023). Microbial dysbiosis leads to the loss of beneficial microbial flora, the increase of pathogenic bacteria and harmful metabolites, and the activation of mucosal immunity, resulting in chronic inflammation (Gilliland et al. 2023; Mills et al. 2022). Conversely, this process stimulates the overgrowth of harmful bacteria and their continuous invasion of the intestinal mucosal and epithelial barriers, triggering intestinal barrier dysfunction (Yue et al. 2024). This impairment accelerates the transfer of luminal antigens and pathogens to the intestinal wall, stimulating the release of proinflammatory cytokines from immune cells in the lamina propria, further exacerbating the inflammatory response (de Souza and Fiocchi 2015).

UC is an incurable, recurrent inflammatory bowel disease with diverse clinical treatment regimens, which can be categorized into chemical drugs, biological agents, small‐molecule targeted medicines, surgical resection and adjuvant nutritional interventions (Argyriou et al. 2026). First‐line conventional drugs include 5‐aminosalicylic acid, glucocorticoids and immunosuppressants: 5‐ASA agents relieve mild UC via local mucosal anti‐oxidation, while glucocorticoids rapidly control acute moderate–severe flares, yet long‐term administration causes severe systemic side effects; immunosuppressants are only suitable for hormone‐dependent patients with risks of myelotoxicity and liver damage (Raine et al. 2021). For refractory moderate–severe UC, anti‐TNF‐α and anti‐IL‐12/IL‐23 monoclonal antibodies as well as oral JAK inhibitors are applied as second‐line targeted therapies, but their high cost, infection risk and drug resistance greatly restrict long‐term application. Total colectomy is reserved for patients with life‐threatening complications, which permanently impairs intestinal physiological function and lowers life quality. Given the limitations of pharmaceutical therapies, natural dietary and probiotic interventions have attracted extensive attention as safe auxiliary strategies for UC prevention and remission maintenance (Verstockt et al. 2023).

RB, a dense source of nutrients and phytochemicals, is rich in various beneficial components such as dietary fiber, polysaccharides, proteins, polyphenols, and vitamins (Pengkumsri et al. 2017). However, its high‐value utilization in humans is limited, with most RB being used as animal feed or fertilizer (Goodyear et al. 2015). This significant waste of RB greatly reduces the added value of agricultural products, necessitating further processing to enhance its utilization. Previous reports indicate that active substances present in RB possess anti‐colitis potential (Pengkumsri et al. 2017; Tanideh et al. 2020). The dietary fiber in RB regulates intestinal ecological balance and serves as a nutrient for specific microbial populations to produce SCFAs (Koh et al. 2016). SCFAs are the primary energy source for intestinal epithelial cells, promoting their proliferation and enhancing intestinal barrier function. Additionally, SCFAs have been shown to promote the maturation and differentiation of colonic regulatory T cells, limiting inflammation driven by innate immune cells (Wu et al. 2023).

RB also contains feruloyl oligosaccharides (FOs), which possess both feruloyl and hydrophilic oligosaccharide groups, conferring dual activity similar to ferulic acid and oligosaccharides. This dual activity enables FOs to exert antioxidant, antibacterial, and immunomodulatory effects (Deng et al. 2022; Yue et al. 2024). However, due to the crosslinking of ester bonds in FOs, they are difficult to utilize in the stomach and small intestine. Instead, they are degraded by enzymes released by the gut microbiota in the large intestine, releasing ferulic acid and oligosaccharides, which then exert their physiological effects (Vitaglione et al. 2008).

Single probiotic supplementation can partially regulate gut microbiota but fails to efficiently release phenolic active substances from grain by‐products. In this study, we innovatively combined RB with feruloyl esterase‐high‐yielding Lactobacillus johnsonii 23. The strain‐produced feruloyl esterase hydrolyzes feruloyl oligosaccharides in RB to liberate free ferulic acid and oligosaccharides in the colon. The composite intervention synergistically alleviates DSS‐induced colitis via enhancing intestinal antioxidant capacity, balancing pro−/anti‐inflammatory cytokines, restoring cecal short‐chain fatty acid pools, and repairing damaged colon mucosal barrier. Compared with conventional chemical drugs, this compound dietary supplement is low‐cost, biocompatible, and free of obvious toxic side effects, offering a promising novel adjuvant strategy for UC prevention and auxiliary treatment to compensate for the drawbacks of existing clinical therapeutic options.