LACTOBACILLUS SURVIVAL TO OXIDATIVE STRESS: EFFECT OF MILK AND HONEY MATRICES

Prebiotics are substances that beneficially affect the host by selectively stimulating the growth and / or activity of one or a limited number of bacteria in the colon, the probiotic bacteria. Lactobacilli benefit in environments with low redox potential and the presence of antioxidant compounds is important in this context. Research has shown that honey and milk are matrices that can improve survival of probiotics during storage as well as their metabolism. The aim of this study was to evaluate the effect of honey and milk on the tolerance of Lactobacillus against reactive oxygen species (ROS) generated by hydrogen peroxide addition, as well as the effect of this oxidant on membrane lipid peroxidation using malondialdehyde determination (MDA). Viability assays were performed with and without the addition of hydrogen peroxide in three different matrices: 0.9% peptone saline, 5% honey solutions or 12% reconstituted skim milk. The dairy matrix provided protection for L. paracasei and L. rhamnosus but this protective effect was not observed in the survival of L. acidophillus. Honey solution did not maintain the viability of probiotic microorganisms exposed to hydrogen peroxide, on the contrary, it caused a significant reduction in the L. rhamnosus population (P <0.001). The lack of honey protective effect was possibly due to the presence of Fe2 + which reacts with hydrogen peroxide producing hydroxyl radicals. Lower lipid peroxidation was observed in L. acidophilus and L. rhamnosus, but this marker did not show relation to viability. t was concluded that: i) lactobacilli from the L. casei group were the ones that most benefited from the lactic environment; ii) probiotics have different mechanisms to avoid the toxic effects of reactive radicals caused by exogenous H2O2; iii) food matrices should be specifically selected for each probiotic species.