The article reviews the role of bile salt hydrolase (BSH) activity in probiotics, highlighting its potential benefits and concerns. Probiotics are defined as live microorganisms that provide health benefits to the host beyond basic nutrition. They are known to alleviate various gastrointestinal disorders and have a positive impact on intestinal flora. The selection of probiotic strains often includes criteria such as tolerance to physiological stresses like low pH and bile. BSH activity, which hydrolyzes bile salts, is a key criterion for strain selection. However, its presence in probiotics has both advantages and potential drawbacks. **Advantages of BSH Activity:** 1. **Nutritional Role:** BSH activity can liberate amino acids from bile salts, which can serve as carbon, nitrogen, and energy sources for the bacteria. 2. **Membrane Characteristics:** BSHs may facilitate the incorporation of cholesterol or bile into bacterial membranes, enhancing membrane strength and resistance to damage from host defenses. 3. **Bile Detoxification:** BSHs help detoxify glycoconjugated bile salts, which are more toxic at low pH, thereby improving bile tolerance and survival in the gastrointestinal tract. 4. **Gastrointestinal Persistence:** BSH activity may enhance the survival and persistence of probiotic strains within the gut by protecting them from the harsh conditions of the stomach and small intestine. **Concerns and Potential Drawbacks:** 1. **Unconjugated Bile Salts:** Large amounts of unconjugated bile salts produced by BSH activity can have adverse effects on the host, such as impaired lipid digestion and absorption, and may contribute to the formation of gallstones. 2. **Host Health Impacts:** While probiotics can lower cholesterol levels, the excessive production of unconjugated bile salts could counteract this benefit. **Future Directions:** 1. **Research Focus:** Future studies should focus on understanding the precise role of BSH enzymes in gastrointestinal bacteria, including the fate of their products and the impact on membrane properties. 2. **Application Potential:** Understanding BSH activity could guide the selection and design of probiotic strains, potentially leading to more robust and effective probiotics. Techniques like microencapsulation and strain selection could address safety concerns and enhance the therapeutic benefits of probiotics. In conclusion, while BSH activity can provide significant benefits to probiotic strains, it also poses potential risks. Further research is needed to optimize the use of probiotics in therapeutic applications.The article reviews the role of bile salt hydrolase (BSH) activity in probiotics, highlighting its potential benefits and concerns. Probiotics are defined as live microorganisms that provide health benefits to the host beyond basic nutrition. They are known to alleviate various gastrointestinal disorders and have a positive impact on intestinal flora. The selection of probiotic strains often includes criteria such as tolerance to physiological stresses like low pH and bile. BSH activity, which hydrolyzes bile salts, is a key criterion for strain selection. However, its presence in probiotics has both advantages and potential drawbacks. **Advantages of BSH Activity:** 1. **Nutritional Role:** BSH activity can liberate amino acids from bile salts, which can serve as carbon, nitrogen, and energy sources for the bacteria. 2. **Membrane Characteristics:** BSHs may facilitate the incorporation of cholesterol or bile into bacterial membranes, enhancing membrane strength and resistance to damage from host defenses. 3. **Bile Detoxification:** BSHs help detoxify glycoconjugated bile salts, which are more toxic at low pH, thereby improving bile tolerance and survival in the gastrointestinal tract. 4. **Gastrointestinal Persistence:** BSH activity may enhance the survival and persistence of probiotic strains within the gut by protecting them from the harsh conditions of the stomach and small intestine. **Concerns and Potential Drawbacks:** 1. **Unconjugated Bile Salts:** Large amounts of unconjugated bile salts produced by BSH activity can have adverse effects on the host, such as impaired lipid digestion and absorption, and may contribute to the formation of gallstones. 2. **Host Health Impacts:** While probiotics can lower cholesterol levels, the excessive production of unconjugated bile salts could counteract this benefit. **Future Directions:** 1. **Research Focus:** Future studies should focus on understanding the precise role of BSH enzymes in gastrointestinal bacteria, including the fate of their products and the impact on membrane properties. 2. **Application Potential:** Understanding BSH activity could guide the selection and design of probiotic strains, potentially leading to more robust and effective probiotics. Techniques like microencapsulation and strain selection could address safety concerns and enhance the therapeutic benefits of probiotics. In conclusion, while BSH activity can provide significant benefits to probiotic strains, it also poses potential risks. Further research is needed to optimize the use of probiotics in therapeutic applications.