Intrinsic and inducible resistance to hydrogen peroxide in Bifidobacterium species

Interest in, and use of, bifidobacteria as a probiotic delivered in functional foods has increased dramatically in recent years. As a result of their anaerobic nature, oxidative stress can pose a major challenge to maintaining viability of bifidobacteria during functional food storage. To better understand the oxidative stress response in two industrially important bifidobacteria species, we examined the response of three strains of B. longum and three strains of B. animalis subsp. lactis to hydrogen peroxide (H₂O₂). Each strain was exposed to a range of H₂O₂ concentrations (0-10 mM) to evaluate and compare intrinsic resistance to H₂O₂. Next, strains were tested for the presence of an inducible oxidative stress response by exposure to a sublethal H₂O₂ concentration for 20 or 60 min followed by challenge at a lethal H₂O₂ concentration. Results showed B. longum subsp. infantis ATCC 15697 had the highest level of intrinsic H₂O₂ resistance of all strains tested and B. animalis subsp. lactis BL-04 had the highest resistance among B. lactis strains. Inducible H₂O₂ resistance was detected in four strains, B. longum NCC2705, B. longum D2957, B. lactis RH-1, and B. lactis BL-04. Other strains showed either no difference or increased sensitivity to H₂O₂ after induction treatments. These data indicate that intrinsic and inducible resistance to hydrogen peroxide is strain specific in B. longum and B. lactis and suggest that for some strains, sublethal H₂O₂ treatments might help increase cell resistance to oxidative damage during production and storage of probiotic-containing foods.