Effect of the Food Matrix on the Survival to the Gastrointestinal Transit of <i>Lacticaseibacillus rhamnosus</i> CRL1505: A Randomized, Controlled, Crossover Study

Probiotic survival is crucial for their beneficial effect, but only a few studies have assessed the impact of delivery format on probiotic viability after passage through the gastrointestinal tract.Our study aimed to investigate the survival of Lacticaseibacillus rhamnosus (L. rhamnosus) CRL1505 through the gastrointestinal transit in healthy volunteers after a daily consumption of at least 1 billion CFUs per day administered as freeze-dried cells or incorporated into oat- and milk-fermented drinks. The probiotic's survival was evaluated by combining culture-based and molecular techniques. Our findings revealed that L. rhamnosus CRL1505 survival was significantly higher when the probiotic was administered as an oat- and as a milk-fermented drink. The study highlighted the persistence of CRL1505 in a subset of volunteers 1 week after the last administration. The metataxonomic analysis of fecal samples did not reveal significant changes in microbiota diversity among treatment groups, as expected after probiotic administration in healthy subjects.The survival of CRL1505 through the human gastrointestinal tract was demonstrated with and without the protection of food matrices, highlighting the strain's remarkable ability to withstand harsh conditions. Our findings emphasize the importance of food matrix selection for improving probiotic viability and its potential efficacy in functional foods.