STRESS RESPONSES OF PROBIOTIC LACTOBACILLI

摘要

Before a probiotic bacterium can even reach the site of interaction in the human intestine, it must survive a battery of environmental stresses - from those encountered during food processing to the natural blockades that lie along the gastrointestinal tract. Food associated stresses include the extremes in temperatures encountered during drying processes, as well as oxidative, osmotic and food matrix stresses. The gastrointestinal tract is naturally designed to impede the passage of pathogenic microorganisms with deleterious lows in pH encountered in the stomach to the detergent-like properties of bile in the duodenum. Indeed, we have used a variety of approaches for enhancing probiotic robustness which vary from pre-stress treatments and encapsulation to the generation of strains which over-express GroESL or the exopolysaccharide β-glucan. The resulting strains have exhibited improved performance under a number of environmental stresses. For example, heterologous expression of P-glucan improved the heat tolerance of the probiotic strain 60-fold, its acid-tolerance 20-fold, and its ability to survive in simulated gastric juice by 15-fold. Understanding the intricacies behind bacterial survival in hostile environments is an essential element to probiotic science. Exploiting this knowledge should lead to the development of next-generation probiotics and potentially further the applications of these highly-beneficial microorganisms.