Characterization of homofermentative lactobacilli isolated from kefir grains: potential use as probiotic

Abstract

Considering that several health promoting properties are associated with kefir consumption and a reliable probiotic product requires a complete identification of the bacterial species, the present work evaluates several proved markers of probiotic potential of eleven isolates of homofermentative lactobacilli isolated from kefir grains and molecular identification and genotypic diversity. Using restriction analysis of amplified ribosomal DNA (ARDRA) and analysis of the 16S–23S rRNA internal spacer region we confirmed that all homofermentative lactobacilli belong to the speciesLactobacillus plantarum. RAPD-PCR analysis allowed the discrimination of lactobacilli in five clusters. All isolates exhibited high resistance to bile salt. High survival after one hour of exposure to pH 2·5 was observed inLb. plantarumCIDCA 8313, 83210, 8327 and 8338. All isolates were hydrophilic and non autoaggregative. Isolate CIDCA 8337 showed the highest percentage of adhesion among strains. All tested lactobacilli had strong inhibitory power againstSalmonella typhimuriumandEscherichia coli. Seven out of eleven isolates showed inhibition againstSal. entericaand five isolates were effective againstSal. gallinarum. Only CIDCA 8323 and CIDCA 8327 were able to inhibitSal. sonnei. We did not find any correlation between the five clusters based on RAPD-PCR and the probiotic properties, suggesting that these isolates have unique characteristics.