# From Macromolecule to Microbe: Identification of Ligilactobacillus salivarius D3-8 as a Key Degrader of Ejiao and a Novel Therapeutic Probiotic for Ulcerative Colitis

## TL;DR

This study identifies a gut bacterium that breaks down a traditional Chinese medicine and helps treat ulcerative colitis.

## Contribution

Ligilactobacillus salivarius D3-8 is shown to degrade Ejiao and alleviate colitis through specific metabolic pathways.

## Key findings

- Ligilactobacillus salivarius D3-8 strongly degrades Ejiao, releasing 50 novel peptides.
- Administration of D3-8 reduces colitis in animal models and increases anti-inflammatory metabolites.
- D3-8 promotes the growth of beneficial bacteria like Dubosiella newyorkensis.

## Abstract

Background/Objectives: Ejiao, a macromolecular protein complex derived from donkey hide, is a traditional Chinese medicine with clinically demonstrated efficacy against ulcerative colitis (UC). Due to its large molecular size and poor absorbability, its therapeutic effects are presumed to depend on gut microbiota. We hypothesized that specific gut bacteria capable of degrading Ejiao might also mediate its biological functions. Methods: To test this hypothesis, a systematic investigation was conducted by integrating culturomics, proteomics, metabolomics, 16S rRNA gene amplicon high-throughput sequencing, and animal disease models. Results: A total of 134 human gut bacterial strains capable of utilizing Ejiao as a nutrient source were isolated. Among them, Ligilactobacillus salivarius D3-8 exhibited the strongest growth in Ejiao-based medium. Genomic analysis identified 63 protease/peptidase genes, and peptidomic profiling confirmed its degradation activity, which released 50 novel peptides. Notably, administration of L. salivarius D3-8 alone significantly alleviated dextran sodium sulfate (DSS)-induced colitis, concurrently increasing the abundance of beneficial bacterium Dubosiella newyorkensis and elevating the anti-inflammatory metabolite indole-3-carbinol via upregulated tryptophan metabolism. Conclusions: Our findings identify L. salivarius D3-8 as both a dedicated Ejiao-degrader and a protective probiotic against colitis. This work provides direct evidence that gut bacteria can utilize Ejiao and proposes a potential novel mechanistic framework in which the biological effects of Ejiao may be mediated through its interaction with specific, functionally potent degraders such as L. salivarius D3-8.