PRESERVATION AND PROBIOTIC PROPERTIES OF A FREEZE-DRIED MIXTURE OF MICROORGANISMS ISOLATED FROM KEFIR

BOLLA, P; SERRADELL, M; DE URRAZA, PATRICIO; DE ANTONI, G

San Miguel de Tucumán, Argentina

Simposio; III Simposio Internacional de Bacterias Lácticas; 2009

CERELA - CONICET

Kefir is a milk fermented product originated many centuries ago and has become popular in many European countries; its consumption has been associated to several health-promoting properties such as antimicrobial and immunological effects. Because kefir composition is very complex, is difficult to maintain a constant quality of fermented milk, and the useful life of the product is limited. Taking into account these issues, we have developed a microbial mixture composed by two yeast  (Kluyveromyces marxianus CIDCA 8154 and Saccharomyces cerevisiae CIDCA 8112) and three bacterial strains (Lactococcus lactis spp lactis CIDCA 8221, Lactobacillus plantarum CIDCA 83114 and Lactobacillus kefir CIDCA 8348) isolated from kefir that could be used as a diet supplement. The aim of this work was to analyze the effects of freeze-drying on the survival rates and probiotic properties of the microbial mixture. The microbial mixture was lyophilized for 24 h using sterile milk UHT or UHT added with trehalose or sucrose as cryoprotectants. Addition of sugars did not improve the survival rates of lactobacilli and S. cerevisieae. However, sucrose addition decreased the survival rate of K. marxianus. Storage of milk lyophilized samples at 4°C produced a reduction in survival rates of all microorganisms between 0,5 and 1 log up to 30 days. Co-incubation of equal volumes of 1e+8 Shigella sonnei with reconstituted microbial mixture in Casoy media at 37 °C produced a decrease of 4 logs in the number of viable Shigella after 24 hs. To test translocation of kefir isolated microorganisms in vivo, seven-week-old BALB/c females were fed daily ad libitum with freeze-dried microbial mixture suspended in sterile PBS (1/100 dilution) for 7 or 20 consecutive days. At the end of each feeding period, no translocation of microorganisms to liver or spleen was observed, since no colonies were detected on either of five agar media selected to this assay (VRBG Agar, 1.1.1, MRS, YGC, and Nutritive Agar. In conclusion, lyophilization in milk is a good procedure to preserve the viability and inhibitory capacity against Shigella of a mixture containing microorganisms isolated from kefir.