Oxidative stress adaptation of probiotic bacteria

Oxidative stress adaptation was studied to increase the tolerance of probiotic bacteria to the dissolved oxygen in yoghurt. Several strains of Lactobacillus acidophilus and Bifidobacterium spp. were passaged in increasingconcentrations of dissolved oxygen (0, 62, 150 and 210 ppm) in yoghurt. Although all strains recorded a decrease in cell counts with increasing oxygen concentration, some cells demonstrated viability even after passage in 210 ppm of dissolved oxygen in yoghurt, indicating that the cells had adapted to oxygen. This was confirmed by the absence of any viability losses when these cells were incubated for 35 days in yoghurt containing 210 ppm of dissolved oxygen. The protocol reported in this study therefore offers a practical method to adapt probiotic strains to withstand high levels of oxygen in yoghurts.