Structural characterization and immunomodulatory effects of Bifidobacterium bifidum biofilms enriched with extracellular polysaccharides and surface proteins

Probiotics enhance numerous physiological functions in humans. However, their oral administration has certain limitation owing to associated digestive challenges, such as reduced viability and colonization. Recently, probiotics in a biofilm state have been shown to exhibit significantly improved functional efficacy. In this study, we analyzed the characteristics of biofilms formed by Bifidobacterium bifidum FL-276.1 and FL-228.1 (FL-276.1 and FL-228.1), with a focus on comparing the functional efficacy differences between the planktonic and biofilm states. FL-228.1 exhibited stronger biofilm-forming capabilities than did FL-276.1. Compared to the FL-276.1 biofilm, the FL-228.1 biofilm exhibited a greater amount of extracellular substances, a higher proportion of surface proteins, greater thickness, and a denser structure. These characteristics positively correlate with enhanced digestive resistance and adhesion but not with improved immunomodulation. Both probiotic strains demonstrated significantly improved digestive resistance, enhanced adhesion capacity, and strengthened immunomodulatory functions in biofilms. Thus, biofilm-state probiotics demonstrate enhanced functionality and hold potential for development as next-generation probiotics.