Abstract
The aim of this work is to study the expression of stress genes and those involved in pediocin and nisin production in Pediococcus acidilactici UL5 and Lactococcus lactis ATCC11454 under simulated gastrointestinal (GI) physiological conditions. The two strains were fed to a dynamic GI model (TIM-1). Samples were taken from different compartments and analysed for strain survival as well as for the expression of pediocin PA-1 operon, nisin A production gene and stress genes using RT-qPCR. Ileal-delivered efflux showed a survival rate of 17 and 0·0007% for Ped.acidilactici and La.lactis, respectively. Pediocin operon genes from stressed cells were generally expressed at least at the same level as for unstressed cells. However, pedA is up-regulated in the effluent at 120 and 180min. Nisin A genes were always up-regulated with particularly in the stomach after 70min compared with control. Bacteriocin production of Ped.acidilactici UL5 and Lc.lactis ATCC 11454 are not affected by upper GI simulated conditions and thus could be considered as relevant probiotic candidates. This study demonstrates the capacity of lactic acid bacteria to survive and express their bacteriocins genes under simulated GI conditions.
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