Abstract: In this study, we developed a metal-phenolic supramolecular nanocoating on the surface of Corynebacterium glutamicum (CG) via the self-assembly of tannic acid (TA) or isochlorogenic acid (ICGA) with the assistance of FeCl3 solution. As a result, two nanoencapsulated bacteria were obtained, namely FeIIITA@CG and FeIIIICGA@CG, and their therapeutic effects on ulcerative colitis (UC) in mice were investigated. We found that the ICGA nanocoating enhanced the survival rate of CG in simulated gastrointestinal fluids by 24- and 6-fold compared with free CG and the TA nanocoating, respectively. At 24 hours after oral administration of FeIIIICGA@CG to UC mice, the survival rate of CG was 4.3 times higher than that of FeIIITA@CG. In terms of intestinal barrier repair, CG, FeIIITA@CG, and FeIIIICGA@CG significantly increased the fluorescence intensity of tight junction proteins (ZO-1 and occludin) and effectively suppressed the production of the pro-inflammatory cytokine interleukins-6 by 59.52%, 72.38% and 78.4%, respectively. Furthermore, FeIIITA@CG and FeIIIICGA@CG increased the release of the anti-inflammatory cytokine interferon-β by 35.44% and 31.81%, respectively. Besides, CG, FeIIITA@CG, and FeIIIICGA@CG reduced malondialdehyde (MDA) levels by 29.42%, 36.01% and 37.34%, respectively. Notably, FeIIIICGA@CG increased the abundance of beneficial bacteria (e.g., Lactobacillus and Ligilactobacillus) and suppressed harmful bacteria (e.g., Bacteroides and Escherichia-Shigella), thereby attenuating UC. The ICGA-based nanocoating, with excellent physicochemical properties, can serve as a delivery system, providing a new idea for expanding the application of microbiome-based therapies for the treatment of inflammatory bowel diseases.

Key words: ulcerative colitis; Corynebacterium glutamicum; tannic acid; isochlorogenic acid; nanocoating