Characterising the functional potential of fermented blueberry juice and its impact on the gut microbiota in an ex vivo colon model

Blueberries, widely recognized as a “superfood,” are rich in bioactive compounds whose functionality may be further enhanced through fermentation. This study investigated the nutritional and functional potential of blueberry juice fermented with Leuconostoc mesenteroides VUCC R-037 (or LM2), a native isolate, and Lactiplantibacillus plantarum DSM 25710 (or LP09), an industrial probiotic strain. Fermentation kinetics, microbial viability, and metabolic activity were monitored by microcalorimetry and selective plating, while compositional and functional changes in the fermented blueberry juice (FBJ) (such as total phenolics, antioxidant capability, putative cytotoxicity) were assessed through HPLC, chemical assays (FRAP), and in vitro cellular models (MTT and cytochrome c assay). Strain-specific contributions shaped the final product with LM2 promoting stronger acidification and acetic acid production, while LP09, favoured lactic acid accumulation and increased ferric reducing antioxidant capacity. Additionally, LM2 enhanced radical scavenging activity with co-cultures revealing complementary effects. FBJ supported probiotic viability, showed no cytotoxicity in CaCo-2 intestinal epithelial cells, preserved epithelial barrier integrity, and mitigated oxidative stress. Assays for impact of the FBJ on the gut microbiota was carried out in the micro-Matrix™ ex vivo distal colon model, where it selectively reduced Clostridium perfringens and Escherichia spp., suggesting a role in beneficial gut microbiota modulation. Overall, fermentation with native and probiotic lactic acid bacteria improved the biochemical, functional, and cytoprotective profile of blueberry juice, highlighting its promise as a novel functional beverage. While further clinical validation is forthcoming, these results strengthen the case for fruit-based fermented products as innovative vehicles to deliver both health-promoting microbes and bioactive compounds to consumers.