CONICET | Buscador de Institutos y Recursos Humanos

Lactobacilli are widely applied as probiotic microorganisms to restore the ecological balance of different animal or human tracts, and to produce a physiological effect in the host. They contribute to the reestablishment of the indigenous vaginal microflora preventing the adhesion or the growth of uropathogenic microorganisms, or stimulating the immune system. To design a probiotic product to restore and maintain the indigenous vaginal flora, both functional and technological properties of the potentially probiotic strains must be well determined. Maximum survival of probiotic microorganisms during the industrial processes of biomass production and storage is of vital importance. The objective of the present study was to determine the effects of lyoprotectors on the survival of four potentially probiotic vaginal lactobacilli during the freeze-drying process and their subsequent storage in presence of prebiotic or pharmaceutical substances. Lactobacillus spp. CRL 1263, Lactobacillus spp. CRL 1251, Lactobacillus spp. CRL 1294 and L. salivarius CRL 1328 were subcultured under optimal growth conditions at 37°C three times, and the last culture harvested in stationary phase. The cell pellets were washed twice with distilled water, and re-suspended in each one of the following protective medium: 10% whey protein concentrate (WPC) or 6% reconstituted skim milk added with 12% lactose (RSM/lactose). Bacterial suspensions were freeze-dried, the lyophilized powders were combined with inulin, ascorbic acid or asiatic centella extract, the resulting mixtures were placed into gelatin capsules and stored at 7°C. Viable counts of vaginal lactobacilli were determined before and after freeze-drying, and at different times throughout 60 days of storage, by employing the plate dilution method. The degree of survival was expressed in log CFU/g (colony forming units per g of freeze-dried powder). For most of the microorganisms, losses of viability during freeze-drying were not significant in presence of the two lyoprotectors evaluated, except for L. salivarius CRL 1328 (2 log down in RSM/lactose). Viability of microorganisms during storage was affected at different extents depending on lyoprotectors, storage time and substances added to the freeze-dried powders. As a general result, maximum survival up to 60 days was observed with WPC and RSM/lactose, supplemented with either inulin or asiatic centella for all the strains. The results of this work indicate that both lyoprotectors tested were effective in protecting the microorganism during the freeze-drying process and subsequent storage. Among the substances added after lyophlization process, only ascorbic acid not favored the survival of the cells during storage in gelatin capsules. These findings help in the design of a pharmaceutical product containing probiotic microorganisms for the prevention of urogenital infections, which is the final objective of our research group.