Abstract
Probiotics, particularly lactic acid bacteria (LAB) like Lactobacillus rhamnosus, are recognized for their health-promoting properties and ability to prevent gastrointestinal disorders. This study focused on isolating and evaluating the probiotic potential of Lactobacillus rhamnosus GG (ATCC 53103), isolated from fermented milk. The bacterium was tested for survival in harsh gastrointestinal conditions, bile salt tolerance, sugar fermentation, and morphological physiological characterization. The isolate exhibited robust growth under a pH range of 4.5–7.5, with no growth at extremely acidic or alkaline conditions. It demonstrated significant (p<0.05) bile salt tolerance, maintaining viability across concentrations of sodium deoxycholate, sodium taurocholate, and cholic acid, particularly favoring conjugated bile salts. Gastric and intestinal fluid tolerance tests revealed a high survival rate (70–90%), indicating its potential to endure gastrointestinal transit. The sugar fermentation profile classified L. rhamnosus as heterofermentative, with carbon dioxide production observed alongside lactic acid. The isolate showed no catalase activity, confirming its anaerobic nature. Morphological and cultural analyses revealed colonies as Gram-positive rods and cocci with smooth, creamy characteristics. The findings confirm the probiotic potential of L. rhamnosus GG, highlighting its ability to survive under gastrointestinal and bile conditions. This study supports the application of L. rhamnosus GG in functional foods and supplements, emphasizing its role in gut health and its adaptability to diverse gastrointestinal challenges. These results provide a foundation for further exploration of L. rhamnosus in therapeutic and dietary applications, addressing safety and efficacy for human consumption.