For all stress tolerance assays, serial dilutions of the samples were prepared immediately after stress exposure and these serial dilutions were immediately plated on MRS agar. Plates were incubated at 30°C for 2 days for CFU enumeration according to the technique described by Sieuwerts et al. (46). Oxidative stress tolerance was determined upon suspending the L. plantarum cells in PBS containing 40 mM hydrogen peroxide, a concentration which is lethal to L. plantarum WCFS1 (52). Cells were collected every 5 min for 60 min for CFU enumeration.