Enhancing Stress Tolerance of Probiotics: Mechanisms, Strategies, and Translational Challenges

Probiotics provide multiple health benefits and are widely used in food, pharmaceutical, and agricultural applications. However, their viability and efficacy are severely compromised during production, storage, and application due to environmental stresses, including heat, dehydration, oxidation, acids, and bile salts, with mortality rates reaching up to 90% during industrial processing. Probiotic stress tolerance is a complex, multilayered physiological process involving cell membrane integrity, protein stability, stress-responsive signaling pathways, nucleic acid protection, osmoprotectant accumulation, and metabolic reprogramming. This review systematically summarizes the molecular mechanisms underlying probiotic stress tolerance and critically evaluates current enhancement strategies, including strain screening, adaptive evolution, genetic engineering, and encapsulation technologies. Furthermore, emerging approaches, such as CRISPR-based genome editing, synthetic biology, and nanomaterial-assisted delivery, are highlighted as promising solutions to overcome translational bottlenecks. At the same time, challenges related to regulatory approval and large-scale manufacturing remain to be addressed.