Survival of cheese bacteria in a gastrointestinal tract simulator

The microbial population of 90-day-old semi-hard cheeses from two dairies was studied before and after transit through a gastrointestinal tract simulator (GITS). In total, 8 species of lactic acid bacteria (22 different genotypes) were identified from one cheese (average survival 4.9 ± 3.6%), and 9 species (13 genotypes) from the second cheese (2.9 ± 2.3%). Survival of different species in the GITS varied significantly. The most abundant non-starter species, Lactobacillus casei/paracasei, showed the highest survival (up to 24%), while survival of the most resistant starter species, Lactococcus lactis subsp. lactis, remained below 3% in all experiments. Addition of the digestive enzymes pepsin and pancreatin into the GITS decreased bacterial diversity and survival significantly. The study showed that the GITS is an efficient tool for the isolation of acid-, bile- and digestive-enzyme-tolerant, potentially probiotic, strains from complex food ecosystems like cheese.