Enhancing the Functional and Health Properties of Blueberry Juice via Probiotic Fermentation

In recent years, the food market has witnessed the emergence of several new plant-based fermented foods, driven by a global resurgence of interest in fermented dairy alternatives and their purported health benefits. Within this context, fermented blueberries can hold a special place: often hailed as a "superfood," blueberries are rich in health-promoting phytochemicals, including vitamins, antioxidants, and other beneficial plant compounds, whose potential could be further enhanced through fermentation. The present study aims at characterizing the functional profile of blueberry juice fermented by Leuconostoc mesenteroides LM2, isolated from blueberries, and Lactiplantibacillus plantarum LP, an industrial probiotic strain. Blueberry juice was fermented using the two strains, individually and in combination. Fermentation kinetics, microbial viability, and metabolic activity of the fermented blueberry juice were assessed via microcalorimetry and selective plating. Chemical composition, antioxidant capacity, and phenolic content were also analyzed using HPLC and spectrophotometric assays. In addition, cytotoxicity, barrier integrity, and oxidative stress were evaluated on CaCo-2 cells. Finally, an ex vivo human distal colon model and downstream 16S rRNA metabarcoding were used to assess the ability of the fermented blueberry juice to modulate the gut microbiota. Fermentation of the blueberry juice with L. mesenteroides LM2 and Lpb. plantarum LP impacted juice acidity, sugar content, and organic acid profiles, with the LM2:LP 10:1 ratio yielding the highest acetic acid concentration and lowest pH. The antioxidant capacity of the fermented juice varied by strain and assay, with LM2 enhancing 2,2-diphenyl-1-picrylhydrazyl (DPPH) DPPH activity and LP increasing Ferric Reducing Antioxidant Capacity (FRAP) values. The fermented juice maintained probiotic viability during storage and showed no cytotoxicity on CaCo-2 cells. It preserved epithelial barrier integrity and reduced oxidative stress. Ex vivo colon model experiments fermentation revealed that the fermented blueberry juice elicited a reduction in the ed levels of Clostridium perfringens and Escherichia spp., indicating microbiota modulation. These findings suggest that probiotic-fermented blueberry juice represents a promising candidate as a functional food product. However, its health benefits require further substantiation through well-designed, targeted clinical trials. This research contributes to the growing body of evidence supporting the potential of fruit-based fermented beverages as vehicles for delivering health-promoting compounds, particularly in the context of an increasingly health-conscious consumer landscape.