In vitro evaluation of potential antimicrobial synbiotics using Lactobacillus kefiri isolated from kefir grains

A strain of Lactobacillus kefiri, isolated from kefir grains and identified by DNA sequencing, was examined for properties associated with probiotic bacteria. The strain was fully resistant to bile at 0.4% (w/v), but showed only moderate resistance to acid. It grew well on media supplemented with prebiotic compounds (two fructooligosaccharides, galactooligosaccharide (GOS) and lactulose) and significant inactivation of Listeria monocytogenes was observed when GOS was added to the co-culture medium, whereas Escherichia coli was not significantly affected. The data suggested that acidification was not the sole cause of the inactivation, as similar decreases in pH with other prebiotics did not result in comparable inactivation of L. monocytogenes. Lb. kefiri isolated from kefir grains in the present work shows potential as a probiotic, which is a first step towards the development of a functional product. The present data indicate that it would be most effective in a synbiotic combination with GOS.