Structural and functional roles of lactic acid bacteria in food delivery systems: A dual perspective of passive encapsulation and active carriers.

As the demand for functional foods and precision nutrition continues to rise, there is an urgent need for advanced delivery systems that improve the stability, bioavailability, and targeted release of sensitive bioactive compounds. Lactic acid bacteria (LAB), commonly found in fermented foods, have taken on a dual role-as both passive encapsulation targets and active delivery carriers-forming a conceptual basis for the development of next-generation food delivery systems. This review examines the interactions between LAB and various food-grade encapsulation materials including proteins (such as whey protein, casein, zein), polysaccharides (like alginate, chitosan), and lipids (such as liposomes, W/O/W emulsions), highlighting roles of electrostatic interactions, hydrogen bonding, hydrophobic interaction, covalent cross-linking, and interfacial self-assembly. Moreover, four emerging LAB-based delivery systems are classified: (i) surface adsorption via non-covalent interactions, (ii) intracellular loading driven by membrane transport or biosynthesis, (iii) co-encapsulation in hydrogels and emulsions, as well as (iv) engineered LAB capable of in situ synthesis and targeted release. The review also summarizes practical applications in hydrocolloid-rich food systems, such as yogurt, plant-based gels, and functional beverages. These applications highlight LAB's contribution to enhancing structural stability, controlled release, and nutritional functionality. Finally, key challenges are discussed, including the limited compatibility between encapsulating materials and food matrices, insufficient understanding of the interactions between exopolysaccharides and interfaces, and the need for in vivo validation. Based on these insights, future directions are proposed to guide the rational design of next-generation LAB-based delivery systems for precision nutrition and functional food innovation.