Research progress regarding physiological functions of probiotics and techniques to enhance their stress resistance: a review

Probiotics have received widespread attention for their unique physiological functions, such as promoting digestion and absorption of nutrients, modulating the immune system, and inhibiting pathogenic microorganisms. However, probiotics face severe challenges in terms of stability and viability in practical applications, such as environmental factors like acid, osmotic pressure, temperature, oxidation and bile salts, which make it difficult to maintain sufficient numbers of probiotics when they are delivered to their target location. Therefore, some technical protection is needed to improve the adhesion and viability of probiotics in the gastrointestinal tract and to minimize damage to probiotic products during processing, transportation and handling. We review the underlying mechanisms by which probiotics exert their physiological functions, as well as various strategies to enhance probiotic tolerance, especially traditional production methods and modification of genetic pathways. In addition, the application and challenges of tolerogenic probiotics in fermented foods and clinical medicine are discussed. Through in-depth analysis of the potential mechanisms of the physiological function of probiotics and strategies for tolerance enhancement, not only to provide theoretical support for the application of probiotics, but also to pave the way for the development of functional foods and innovative human disease treatment strategies.