Abstract In the present study, probiotic sour milk was produced by freeze-dried Lactobacillus casei ATCC 393 cells, free or immobilized on wheat bran. Wheat bran was used with and without lignin removal. The aim was to evaluate the possibility to produce sour milk using immobilized probiotic biocatalysts that could be removed after the end of fermentation and be used in a next fermentation batch. The effect of the biocatalysts on product quality was also evaluated during 30 days of storage at 4 °C. The aroma profile, organic acids production, residual sugar content and culture viability were monitored during that period. The immobilized bacteria on wheat bran were better protected in the acidic environment of the sour milk fermentations, compared to free cells. The microbial populations (>7.5 log cfu g−1) were significantly higher in sour milks produced with the immobilized biocatalysts during the 30 day storage, while no growth of pathogenic microorganisms was observed. The microbiological, physicochemical, and sensory characteristics of the sour milks produced using the immobilized biocatalysts, indicated high commercialization potential of these products.