Probiotics provide benefits for gut health, immune modulation, and skin and mental health. However, their use is limited by concerns regarding antibiotic resistance, poor intestinal colonization, strain-specific effects, and inter-individual variability. In contrast, postbiotics, including culture broth, are inactivated by heat or pressure yet retain immunomodulatory, anti-inflammatory, intestinal barrier–protective, and antioxidant activities through cell wall components, proteins, and metabolites. They contribute to the alleviation of intestinal inflammation and restoration of gut microbial balance. Postbiotics can serve as alternatives to live probiotics in animal feed by improving productivity, suppressing pathogens, and also reducing stress. Their applications are currently expanding to areas such as anticancer activity, metabolic disease management, gut–brain axis modulation, and oral health. Although postbiotics offer superior safety and stability, challenges still remain, including an insufficient mechanistic understanding, lack of standardized production, and limited large-scale clinical evidence. With further strain-specific mechanistic studies and regulatory establishment, postbiotics have a strong potential as functional ingredients in regard to food and feed applications.

Abstract
Introduction
Probiotic Efficacy Limitations
    Immunomodulatory function
    Improvement of skin health
    Metabolic function regulation
Concept and Classification of InactivatedProbiotics
Physiological Effects of Postbiotics
    Immunomodulatory and anti-inflammatory effects
    Improve intestinal health and microbiota composition
    Promote skin health
    Incorporation into feed
    Emerging applications: anticancer effects, metabolicdisorders, the gut–brain axis, and oral health
    Effects summary
Regulatory Considerations for Postbiotics
    Ingredient approval and safety assessment
    Health and functional claims
    Quality control standards
    Practical applications of postbiotics
Conclusion
ORCID
Conflict of interests
Acknowledgements
Data availability
Authorship contribution statement
Ethics approval
References

• Seok-cheol Cho(Department of Food Science & Engineering, Seowon University, Cheongju 28674, Korea) Corresponding author