Lactococcus lactis SpOx spontaneous mutants: a family of oxidative stress resistant dairy strains

ROCHAT TATIANA,; GRATADOUX JEAN,; CORTIER GERARD,; COQUERAN BERARD,; MARIA ELENA FÁTIMA NADER; GRUSS ALEXANDRA,; LANGELLA PHILIPPE,

APPLIED AND ENVIRONMENTAL MICROBIOLOGY

American Society of Microbiology

Lugar: Washington; Año: 2005 vol. 71 p. 2782 - 2788

0099-2240

Numerous industrial bacteria generate hydrogen peroxide (H2O2), which may inhibit growth of other bacteria in mixed ecosystems. We isolated oxidative stress resistant Lactococcus lactis strains using a natural selection method, and two conditions were imposed to assure applicability to industrial settings: i) the use of milk-adapted strains on dairy culture medium; and ii) the isolation of Spontaneous Oxidative stress resistant (SpOx) mutants instead of genetically manipulated strains. Three SpOx mutants of a milk-adapted derivative of L. lactis strain MG1363 were selected in the presence of H2O2 and displayed greater H2O2 resistance during both exponential and stationary growth phases. One of them, SpOx3 has a better behaviour in different oxidative stress situations: i) 200- and 40-fold higher long-term survival upon aeration in LM17 and milk, respectively; and ii) the ability to grow in the presence of H2O2-producing Lactobacillus delbrueckii subsp. delbrueckii strains. Furthermore, we concluded that H2O2 resistance did not affect the transit kinetics of the SpOx3 mutant in the digestive tract of a human flora associated mouse model. Our results suggest that SpOx mutants may be of particular interest for improving reproducibility of dairy fermentation processes and could give rise to the development of new products.