Lactic acid bacteria (LAB) are one of the most widely used groups of microorganisms in functional foods and fermentation systems. Known for their well-established safety status (Generally recognized as safe (GRAS)), probiotic mechanisms, and metabolic versatility, LAB have been extensively utilized to modulate gut microbiota, enhance mucosal immunity, and synthesize essential nutrients such as vitamins. These properties have positioned LAB as important microbial agents for nutritional interventions and chronic disease management [[1], [2], [3]]. Additionally, their metabolites, including exopolysaccharides (EPSs), surface adhesion proteins, and short-chain fatty acids (SCFAs)—act synergistically to support gut microbial balance and strengthen epithelial barrier function [4,5].

However, LAB are highly sensitive to external stressors. Environmental factors such as thermal treatment, pH fluctuations, and digestive fluids during food processing or gastrointestinal transit can lead to bacterial inactivation, significantly compromising their biological functionality [6,7]. Consequently, improving LAB viability, stability, and targeted delivery within food products and the human body has become a vital challenge in the development of functional foods.

Traditional strategies have primarily used food-grade inert materials—such as proteins, polysaccharides, and lipids—to encapsulate LAB. These materials create protective structures, including microcapsules, gels, or emulsions, which enhance gastrointestinal resistance and facilitate controlled release [[7], [8], [9]]. While these "unidirectional protection" systems have improved LAB viability and intestinal transit to some extent, emerging studies indicate that LAB should not be seen merely as vulnerable components in need of protection. Instead, their intrinsic structural features, interfacial functionality, and metabolic activity position them promising active carriers for co-delivering functional ingredients—such as polyphenols, vitamins, and fatty acids—thereby enabling the construction of microbe-bioactive compound composite delivery systems [[10], [11], [12]]. This shift provides a new scientific perspective for designing next-generation food delivery systems.

LAB's distinctive features, including cell wall architecture, multifunctional surface groups, EPSs secretion capacity, and membrane permeability regulation, allow for their application in various delivery strategies, including surface adsorption, intracellular loading, co-encapsulation, and engineered microbial carriers [[13], [14], [15], [16]]. These active delivery systems, characterized by integrated "structure-function-responsiveness," go beyond the limitations of conventional encapsulation by providing protection, targeting, and biological synergy simultaneously.

Moreover, the rapid growth of functional foods, dietary supplements, and medical nutrition products has increased the demand for delivery systems that can transport structurally complex, unstable, and poorly bioavailable compounds, such as bioactive peptides and trace minerals. Given their diverse physicochemical properties and dynamic behavior in the body, these substances require delivery systems with improved structural compatibility, stimuli-responsiveness, and physiological adaptability [[17], [18], [19]]. Thus, designing food-grade delivery systems centered on LAB for efficient loading and targeted release has become a major focus of research and application.

This review systematically explores the dual roles of LAB in food delivery systems—acting both as passive encapsulation targets and active delivery agents. It examines the interfacial interaction mechanisms between LAB and representative food-grade materials, including proteins, polysaccharides, and lipids. The structural advantages and regulation strategies are examined across four representative delivery systems: surface adsorption, intracellular loading, co-encapsulation, and engineered microbial carriers. Furthermore, through practical examples involving hydrocolloid-rich food systems such as yogurt, plant-based beverages, and gels, the review summarizes the structural stabilization, synergistic release behavior, and nutritional enhancement potential of LAB-based systems. Finally, it identifies critical challenges related to material compatibility, structural responsiveness, mechanistic understanding, and industrial scalability, while proposing future research directions to support the development of edible, intelligent, and functionally synergistic LAB-based delivery systems in future food systems.