Tea-Residue-Derived Klebsiella pneumoniae CGMCC 31459: Genomic Insights and Antioxidant Activity of Its Exopolysaccharides

Exopolysaccharides (EPSs) are important extracellular metabolites secreted by microorganisms. <i>Klebsiella pneumoniae</i> is an opportunistic pathogen widely distributed in the environment, host mucosal and intestinal surfaces, and EPS from <i>Klebsiella pneumoniae</i> are of significant interest. Conventional studies have mainly focused on hypervirulent strains, whereas comprehensive investigations of non-hypervirulent strains and their EPS functionalities remain limited. This study employed ST678-type <i>Klebsiella pneumoniae</i> CGMCC 31459 as the model to investigate genomic characteristics, EPS structural features, and biological activities. Its genome comprises one chromosome and four plasmids, functionally enriched in carbohydrate metabolism genes, including abundant glycoside hydrolases and glycosyltransferases essential for EPS biosynthesis. Virulence and antimicrobial resistance assessments confirmed the absence of typical hypervirulence loci, indicating genetic stability with low pathogenic and resistance potential. EPS-KP is a weakly acidic, branched heteropolysaccharide composed of glucose, galactose, mannose, and glucuronic acid. EPS-KP exhibited significant antioxidant and anti-aging activities, with a 77.47% (5 mg/mL) superoxide anion scavenging rate and a 30.9% (200 μg/mL) lifespan extension in <i>Caenorhabditis elegans</i>, accompanied by enhanced SOD/CAT enzyme activity and reduced lipofuscin accumulation. This integrated genomic and biochemical analysis provides new insights into the safe, non-hypervirulent <i>Klebsiella pneumoniae</i> strain and its functional EPS, highlighting its potential for biotechnological applications.