Biological activity of the non-microbial fraction of kefir: antagonism against intestinal pathogens.

IRAPORDA C.; ABATEMARCO JÚNIOR M.; NEUMANN E.; , CANTINI NUNES A.; NICOLI J.; ABRAHAM A G; GARROTE G L; IRAPORDA C.; ABATEMARCO JÚNIOR M.; NEUMANN E.; , CANTINI NUNES A.; NICOLI J.; ABRAHAM A G; GARROTE G L

Journal of Dairy Research

CAMBRIDGE UNIV PRESS

Lugar: Cambridge; Año: 2017 vol. 84 p. 339 - 345

0022-0299

Kefir is a fermented milk obtained by the activity of kefir grains which are composed by lactic and acetic acid bacteria, and yeasts. Many beneficial health effects have been associated with kefir consumption such as stimulation of the immune system and inhibition of pathogenic microorganism. Biological activity of kefir may be attributed to the presence of a complex microbiota as well as the microbial metabolites that are released during fermentation. The aim of this work was to characterize the non-microbial fraction of kefir and to study its antagonism against Escherichia coli, Salmonella spp. and Bacillus cereus. During milk fermentation there was a production of organic acids, mainly lactic and acetic acid, with a consequent decrease in pH and lactose content. The non-microbial fraction of kefir added to nutrient broth at concentrations above 75% v/v induced a complete inhibition of pathogens growth that could be was ascribed to the presence of undissociated lactic acid. In vitro assays using intestinal epithelial cell model indicates that pre-incubation of cells with non-microbial fraction of kefir did not modify the association/invasion of Salmonella whereas pre-incubation of Salmonella with this fraction in a condition that do not affect their viability significantly decreased the pathogen´s ability to invade epithelial cells. Lactate exerted a protective effect against Salmonella in a mice model demonstrating the relevance of metabolites present in the non-microbial fraction of kefir produced during milk fermentation.