Fig. 3.

Cross-protections conferred to P. freudenreichii are medium-dependent. P. freudenreichii CIRM-BIA 129 was cultivated until the beginning of the stationary phase in YEL-type media (A, C, E, G) and dairy-type media (B, D, F, H), with and without NaCl. Cultures were then subjected to heat (A and B, 60 °C for 10 min), oxidative (C and D, 1.25 mM H₂O₂ for 1 h), acid challenges (E and F, pH = 2 for 1 h), or bile salts (G and H, 1 g L⁻¹ for 1 h) challenges, as described in the “Materials and methods” section. P. freudenreichii viability was determined by CFU counting in treated and control samples. Results are expressed as a percentage of survival. Error bars represent the standard deviation for triplicate experiments. Significant differences are reported with different letters above the columns (p > 0.05). YEL: yeast extract lactate. L: lactose. MU: milk ultrafiltrate. SW: sweet whey