Lactobacillus paracasei isolated from kefir: probiotic and technologycal properties

ZAVALA, LUCÍA; CARASI PAULA; GOLOWCZYC M.; SERRADELL MARÍA DE LOS ANGELES; ABRAHAM A.

Tucumán

Simposio; IV Simposio Internacional de Bacterias Lácticas (SIBAL); 2013

Cerela - CONICET

Kefir is a probiotic beverage obtained through fermentation of milk with ?kefir grains?. Kefir grains are constituted by a natural selection of highly competitive microorganisms (lactic acid bacteria, acetic acid and yeast), capable of stimulating each other and also able to prevent the development of other potentially pathogenic microorganisms. Lactobacillus paracasei is one of the species recently isolated from kefir grains that produce acid gels with interesting rheological properties. In order to evaluate the potentiality of L. paracasei as probiotic starter some factors involved in the selection criteria for a potentially successful probiotic were studied: resistance to artificial gastric and intestinal juices, the adhesion capacity to the intestinal mucosa, and the interaction of the strains with epithelial cells and Salmonella. In addition, spray drying studies were performed in a small-scale Büchi Mini Spray Dryer B-191, outlet temperature 70-72°C, inlet temperature 180°C. L. paracasei strains CIDCA 8339, 83120, 83121, 83123, 83124 were used. Viability of bacterial suspensions- incubated sequentially in solutions simulating gastric (pepsin, pH 2, 90 minutes) and intestinal (pancreatin and bovine bile salts, pH 8, 180 minutes) compartments- was assessed. According to these results, different strains were selected and adhesion assays to mucin and epithelial cells were performed after simulation of gastrointestinal tract´s passage. L. paracasei CIDCA 8339 was the most resistant strain to simulated gastric and intestinal fluids meanwhile L. paracasei CIDCA 83121 and CIDCA 83124 were very sensitive to this treatment, decreasing counting at least 4 logs. For all the bacterial strains under study, the critical step was the incubation in simulated gastric juice. Regarding adhesion properties, L. paracasei strains adhered 1.5x105 - 1.7x106 CFU/ml to mucin and 3.0x105 - 5.0x106 CFU/ml to Caco-2/TC-7 cells. Gastrointestinal tract´s passage simulation significantly increased adhesion to mucin of L. paracasei CIDCA 8339, 83123, 83124. However, adhesion capacity to Caco-2/TC7 cells was increased only for L. paracasei CIDCA 83123 and 83124. On the other hand, L. paracasei CIDCA 8339, 83123, 83124 were able to reduce the invasion rate of Salmonella to Caco-2/TC-7 cells. These 3 strains resisted well to the drying process while maintaining a larger number of viable microorganisms (108 CFU/g starting initially 109 CFU/g). During storage at 4°C the 3 strains maintained the number of viable microorganisms above 1x106 CFU/g to 90 days of storage while they lost their viability at 40 days when were stored at room temperature. Considering the properties evaluated it can be conclude that L paracasei strains studied are promising strains for the development of new foods with defined functionality.