Functional Evaluation of Fermented Pomegranate Juice in Vitro and in Vivo and Its Impact on the Gut Microbiota

To evaluate the functional properties of the Limosilactobacillus fermentum FUA033 in fermenting pomegranate juice (FPJ), in vitro and in vivo experiments were conducted to comprehensively assess its functional potential. UPLC-MS profiling showed an increase in catechin-type compounds and a decrease in astringent phenolics. FPJ significantly prolonged the lifespan of Caenorhabditis elegans without inducing avoidance behavior. In mice, FPJ supplementation increased grip strength from 109 ± 3.35 gf to 123.7 ± 2.66 gf, improved endurance performance, enhanced glycogen storage, and increased overall antioxidant capacity. Moreover, 16S rRNA sequencing showed that FPJ reduced the firmicutes/bacteroidetes ratio and enriched beneficial genera. Correlation analysis linked these microbial changes to stronger antioxidant defenses, enhanced energy metabolism, and lower levels of fatigue-related biomarkers, suggesting a gut microbiota-mediated mechanism. Overall, pomegranate juice fermented by L. fermentum FUA033 is a promising functional beverage that may support metabolic health through the combined effects of bioactive compound enrichment and gut microbiota modulation.