Development of an immunochemical method to detect Lactobacillus kefir

GRACIELA L. GARROTE; MARÍA A. SERRADELL; ANALÍA G. ABRAHAM; MARÍA C. AÑÓN; CARLOS A. FOSSATI; GRACIELA L. DE ANTONI

FOOD AND AGRICULTURAL IMMUNOLOGY

Taylor & Francis

Lugar: London; 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. Yhe 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 dot-blot. By indirect ELISA, specific antiserum against L. kefir showed reactivity against pure cultures of both L. kefir and L. parakefir, but did not react wtih L. brevis cells. Competitive ELISA allowed quantification of L. kefir at concentrations ranging from 5x 10^5 to 10^8 bacteria/ ml, but neither L. parakefir nor L. brevis pure cultures produced inhibition. Through this approach it was possible to detect 10^8 L. kefir/ml, in samplesof milk fermented for 48 h at 20°C 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.