Genomic and functional characterization of Limosilactobacillus fermentum DX2034 identifies a probiotic candidate with TLR2-associated anti-adipogenic activity

Limosilactobacillus fermentum is a promising probiotic species with reported benefits for gastrointestinal health and host metabolism. In this study, a novel L. fermentum strain, DX2034, isolated from the feces of a healthy Korean infant, was characterized through phenotypic and genomic analyses, and its anti-adipogenic activity was evaluated in differentiated 3T3-L1 adipocytes. DX2034 exhibited high tolerance to simulated gastric and bile conditions and showed stronger adhesion to Caco-2 cells than the reference strain L. fermentum CECT5716. The strain showed no hemolytic activity and was susceptible to most tested antibiotics. Whole-genome sequencing revealed a single circular chromosome of 2 160 171 bp with no acquired antibiotic resistance genes, virulence-associated factors, or concerning secondary metabolite biosynthetic gene clusters. Comparative genomic analysis identified genomic regions showing low similarity to reference strains, including a putative glycosyltransferase-associated locus, and genes associated with stress adaptation, gastrointestinal persistence, surface modification, and quorum sensing. Heat-killed DX2034 significantly reduced lipid accumulation, intracellular triglyceride content, and expression of adipogenesis-related genes, including C/EBPα, PPARγ, FABP4, LPL, and FASN. These effects were attenuated by the TLR2 inhibitor C29, suggesting involvement of TLR2-associated signaling. Collectively, DX2034 exhibits favorable probiotic-associated characteristics, genomic safety, and TLR2-associated anti-adipogenic activity, supporting its potential as a functional probiotic or postbiotic candidate.