Survival of Lactobacillus acidophilus LA5® in probiotic formulations under simulated intake and static digestion conditions

Objective: The aim was to evaluate the effect of liquid foods on viability of three commercial preparations containing Lactobacillus acidophilus LA5® during simulated static gastrointestinal digestion. Methods: Three probiotic formulations (single-strain lyophilized granules - Brand 1, single-strain lyophilized capsules - Brand 2, and a multi-strain fermented yogurt - Brand 3) were subjected to a simulated gastrointestinal digestion according to the INFOGEST consensus protocol using apple juice and a yogurt drink as cell carriers. Fresh viable cells inoculated in model foods as well as the formulations resuspended in phosphate buffer solution were included as controls. The survival of Lactobacillus acidophilus LA5® was assessed at the start of digestion, following the gastric phase and after the intestinal phase. Results: After the gastric phase, the cell viability of Lactobacillus acidophilus LA5® was reduced by 2-7 log cfu mL-1 in apple juice, and by 4-6 log cfu mL-1 in the yogurt drink, depending on the probiotic formulation. After the intestinal phase, only fresh cells survived at levels of 4–5 log CFU/mL in both food models and in the phosphate buffer solution. L. acidophilus LA5® remained viable at about 3 log cfu mL-1 at the end of digestion process of the multi-strain fermented yogurt. Conclusions: Model foods showed moderate protective effect on LA5® strain survival during the simulated digestion. Metabolic active cells, included in these foods from broth culture or as a multi-strain yogurt, showed better ability to survive after the intestinal phase compared to lyophilized formulations.