Development of an immunochemical method to detect Lactobacillus kefir

GARROTE, G.L., SERRADELL, M.A.; ABRAHAM, A.G.; AÑÓN, M.C.; FOSSATI, C.A.; DE ANTONI, G.L.

FOOD AND AGRICULTURAL IMMUNOLOGY

Año: 2005 vol. 16 p. 221 - 233

0954-0105

Kefir is a fermented milk elaborated with kefir grains. It constitutes an ecological system composed by a protein-polysaccharide matrix on which a complex microbiota is naturally immobilized. The objective of this work was to develop an antibody-based method in order to achieve a simple and rapid way to quantify Lactobacillus kefir in a complex environment. Rabbit antisera against isolated S-layer proteins from L. kefir and L. parakefir were obtained. Both antisera recognized the 21 strains of L. kefir and the three strains of L. parakefir analysed by dotblot. By indirect ELISA, specific antiserum against L. kefir S-layer showed reactivity against pure cultures of both L. kefir and L. parakefir, but did not react with L. brevis cells. Competitive ELISA allowed quantification of L. kefir at concentrations ranging from 5_/105 to 108 bacteria ml_1, but neither L. parakefir nor L. brevis pure cultures produced inhibition. Through this approach it was possible to detect 108 L. kefir ml_1, in samples of milk fermented for 48 h at 208C with different kefir grains. Competitive ELISA developed in our laboratory is a suitable method to detect and quantify L. kefir in milk and in consequence it could be applied to analyse the relationship between the composition of microflora and probiotic and technological characteristics of the products.