Evaluation of the retention process of bile acids by cell surface of inactivated Lacticaseibacillus rhamnosus GG using spray drying under in vitro digestion simulation

This work aimed to evaluate bile acid retention by the cell surface of Lacticaseibacillus rhamnosus GG inactivated using spray drying using an in vitro methodology. The impact of the inactivation method on the morphological aspect of the postbiotic was analyzed by a combined approach between flow cytometry and transmission electron microscopy. The method for determining bile acid retention is based on the harmonized INFOGEST in vitro digestion, centrifugation and dialysis, followed by the quantification of primary and secondary bile acids by ultra-performance liquid chromatography. This process resulted in a dehydrated dairy product with a<inf>w</inf> of 0.23, in which the initial cells were reduced by 73.3% and the extent of damage caused by the action of heat on the cellular morphology occurred in the membrane and cell wall. Furthermore, inactivation by spray drying modified the cell morphology of L. rhamnosus GG, but this change was not sufficient to retain bile acids on the cell surface in the centrifugation method and in the initial 8 h of the dialysis process (p > 0.05). Further studies are needed to understand the impact of other cell inactivation methods on the hydrophobic interaction between the cell surface and bile acids using in vitro dynamic systems.