CONICET | Buscador de Institutos y Recursos Humanos

Probiotic additives in animals feed are a new alternative to replace antibiotics as growth factors. The design of a new probiotic product to be used in newborn calves was the main objective of our group. After the selection of the bacterial strains based on their beneficial properties, some technological preservation methods were evaluated, being freeze-drying one of the most frequently used processes for the survival and storage of microorganisms for a market product. Nevertheless, the method involves critical injuries to bacteria that could affect their viability. The aim of this work was to freeze dry six different strains of lactobacilli (with beneficial characteristics) with different cryoprotectants (skimmed milk, milk whey and lactose), to evaluate their survival to the process and their viability during six months of storage. The microorganisms were evaluated both individually and in mixtures, based in their beneficial properties. Milk-lyophilized product was added with,minerals, vitamins and inulin to advance in the design of the final product. Lactobacillus johnsonii CRL1693, L. murinus CRL1695, L. mucosae CRL1696, L. salivarius CRL1702, L. amylovorus CRL1697 and Enterococcus faecium CRL1703 were freeze dried with the different lyoprotectors and later stored at 4ºC for six months. Before and after the process, the number of viable cells was determined in selective media based on the microbial sensitivity to antibiotics. The efficiency of the process was calculated for all the combinations assayed. Results showed that the resistance of each strain to the freeze drying process depended on the intrinsic characteristics of each particular strain, the conditions of the process and the cryoprotector employed. E. faecium CRL1703 was the most resistant strain to the freeze drying process and conservation, whilst L. mucosae CRL1696 and L. amylovorus CRL1697 were more resistant to lyophilization than the other assayed lactobacilli. L. johnsonii CRL1693 and L. amylovorus CRL1697 were highly affected during storage. No viable cells were recovered from L. johnsonii CRL1693 at the end of the assay. Among the cryoprotectors, skimmed milk was the most efficient, not only during the process, but also during storage for most of microorganisms. The addition of lactose did not surpass the protection of milk and similar results were obtained with milk whey. The survival of freeze-dried mixed strains was lower in all the experiments. The viability was also affected during storage: only the combination of L. salivarius CRL1702 and L. mucosae CRL1696 with 10% inulinsurvived after six months of storage. The results obtained showed that milk would be the optimal cryoprotective agent for lactobacillus lyophilization, which must be individually freezedried and later combined for the development of a probiotic product for calves