Evaluation of lactobacilli resistance to freeze drying

MALDONADO NC; SILVA DE RUIZ C; NADER-MACÍAS ME

Rosario

Congreso; VII Congreso argentino de microbiología General. SAMIGE del Bicentenario; 2011

SAMIGE

Probiotic additives in animals feed are a new alternative in replacing of antibiotics as growth factors. The design of a new probiotic product to be use in newborn calves is the main objective of our group. After the selection of the strains by theirs beneficial properties, technologic properties were evaluated. Freeze drying is one of the most frequently process for the conservation of microorganisms. Nevertheless, the method involves critical injures to the bacteria that could affect its viability. The aim of this work was to freeze dry six lactobacilli (previously selected) with different cryoprotectants (skim milk, milk whey and lactose), evaluate the survival of the strains to the process and the viability during six month of storage. The microorganisms were studied separately and in mixtures combining its beneficial properties. Once the mixes were lyophilized in milk, were added with minerals, vitamins and inulin to improve the beneficial characteristics of the product. Lactobacillus johnsonii CRL1693, L. murinus CRL1695, L. mucosae CRL1696, L. salivarius CRL1702, L. amylovorus CRL1697 y Enterococcus faecium CRL1703 were freeze dried with different protected substances and conserved at 4ºC during six month. After the process, the viable cell counts were evaluated in selective media according to theirs sensibility profiles against antibiotics. The efficient of the process was calculated for all the combination assayed. The results show that resistance of strains to the freeze drying process depend on intrinsic characteristics of the bacteria and also the conditions of the process as the cryoprotectant employed. Enterococcus faecium CRL1703 strain was the less affected to the freeze drying process and conservation. However, L. mucosae CRL1696 and L. amylovorus CRL1697 strains were more resistant to lyophilization than the other lactobacilli strains. Lactobacillus johnsonii CRL1693 and L. amylovorus CRL1697 were deeply affected during storage and no viable cell counts were recovered from Lactobacillus johnsonii CRL1693 at the end of the assay. Among the protectors, the milk was the most protective substance, not only in the process, but also during storage for the majority of the microorganisms. The addition of lactose did not increase the protective capability of milk, similar results were observed with milk whey. The survival of the strains to the process in mixtures decreases in all cases and became more sensible to the process than separately. The viability was also affected during conservation, only the mixture of L. salivarius CRL1702 and L. mucosae CRL1696 with inulin 10% resisted six month of storage. As a result, we can conclude that milk is the most convened cryoprotectant to be use for the lyophilization and it is suggests preparing the mixtures once the strains were lyophilized.