Valorization of spent black tea polyphenols as a functional coating for probiotic protection and colitis alleviation.

Excessive reactive oxygen species (ROS) play a central role in the development of inflammatory bowel disease (IBD). A promising therapeutic strategy involves delivering probiotics alongside polyphenolic antioxidants, which can protect the probiotics while scavenging ROS. Although biomass is a versatile source of polyphenols, abundant agro-industrial waste remains largely untapped, despite its food-grade safety, anti-inflammatory properties, and sustainability. In this study, we focused on spent black tea (SBT), a widely available food processing byproduct, as a rich source of polyphenols. We developed a simple and environmentally friendly method to coordinate polyphenols extracted from SBT using hot water with ferric ions, creating a self-assembled metal-polyphenol network on the surface of Escherichia coli Nissle 1917 (ECN), resulting in the formation of ECN@SBT-Fe. This biomass-derived coating provided ECN with enhanced ROS scavenging abilities, improved survival under simulated gastrointestinal stress, and extended intestinal retention. In a mouse model of DSS-induced colitis, oral administration of ECN@SBT-Fe significantly reduced inflammation, restored epithelial barrier integrity, decreased oxidative stress, and effectively modulated gut microbiota by increasing diversity and promoting beneficial commensal bacteria. This research demonstrates a biomass-derived coating that serves as both a protective shield and a therapeutic agent, presenting a simple and sustainable encapsulation strategy for IBD treatment.