Physiological Characteristics of Lactobacillus casei Strains and Their Alleviation Effects against Inflammatory Bowel Disease

100,000 people.India and China have the highest incidences of IBD, at 9.31 and 3.64 per 100,000 people, respectively [3].Probiotics are receiving attention as a potential treatment for IBD, and strains including Bacillus licheniformisLactobacillus reuteri [9] and many others have been shown to restore body weight, regulate the gut microbiome and restore intestinal barrier integrity in mouse models.This indicates the potential of probiotics to significantly Lactobacillus casei, one of the most widely used probiotics, has been reported to alleviate multiple diseases.However, the effects of this species on intestinal diseases are strain-specific.Here, we aimed to screen L. casei strains with inflammatory bowel disease (IBD)-alleviating effects based on in vitro physiological characteristics.Therefore, the physiological characteristics of 29 L. casei strains were determined, including gastrointestinal transit tolerance, oligosaccharide fermentation, HT-29 cell adhesion, generation time, exopolysaccharide production, acetic acid production, and conjugated linoleic acid synthesis.The effects of five candidate strains on mice with induced colitis were also evaluated.The results showed that among all tested L. casei strains, only Lactobacillus casei M2S01 effectively relieved colitis.This strain recovered body weight, restored disease activity index score, and promoted anti-inflammatory cytokine expression.Gut microbiota sequencing showed that L. casei M2S01 restored a healthy gut microbiome composition.The western blotting showed that the alleviating effects of L. casei M2S01 on IBD were related to the inhibition of the NF-κB pathway.A good gastrointestinal tolerance ability may be one of the prerequisites for the IBDalleviating effects of L. casei.Our results verified the efficacy of L. casei in alleviating IBD and lay the foundation for the rapid screening of L. casei strain with IBD-alleviating effects.