Cereals and Fruits as Effective Delivery Vehicles of Lacticaseibacillus rhamnosus through Gastrointestinal Transit

The viability of probiotic cells during their transit through the degradative conditions of the gastrointestinal tract is considered an essential prerequisite for their effectiveness. To enhance the survival of probiotics, cell immobilization has been proposed as a promising strategy, creating a protective microenvironment. In the present study, the viability of immobilized Lacticaseibacillus rhamnosus OLXAL-1 cells on cereals and fruits was investigated in comparison to free cells, applying both an in vitro static digestion and an in vivo mouse model. During the in vitro digestion, the survival rates of all immobilized L. rhamnosus OLXAL-1 cultures were higher compared to free cells, with the highest survival rate recorded in oat flakes (84.76%). In a subsequent step, following the administration of both immobilized and free cells to BALB/c mice, a significant increase in lactobacilli populations was observed in the mice feces compared to baseline. Notably, the group receiving the immobilized cells exhibited significantly higher lactobacilli counts compared to the group fed with free cells (8.02 log CFU/g and 7.64 log CFU/g, respectively). Finally, the presence of L. rhamnosus cells at levels > 6 log CFU/g was verified in the mice feces in both groups through multiplex PCR analysis.