CONICET | Buscador de Institutos y Recursos Humanos

The lactic acid bacteria (LB) are subject to constant scientific studies in the field of biotechnology.The use of LB as probiotic cultures has grown significantly in last years. The incorporation of the probiotic cultures more adapted to the new technological processes is a requirement for their use in the modern food industry. While the fermented foods containing probiotics LB are generally associated with milk based products that require cold chain for storage, the need to expand the use of probiotic strains in foods not requiring refrigeration for storage is a valuable contribution for the industry. The objective of this work was to develop new strategies of conservation at room temperature of probiotic strains previously selected (Lactobacillus (L.) casei CRL 731 and L. reuteri CRL 1098). In this context, the formulation of an economic culture media for the development of probiotic strains; the evaluation of different lyophilization substrates and the study of storage conditions without using cold chain considering time/temperature and cell viability variables were carried out. Biomass production was carried out with two defined experimental media (M1 and M2 for L. reuteri CRL 1098 and L. casei CRL 731, respectively) under controlled conditions (temperature and pH constants). Lyophilization process was standardized evaluating different substrates:powdered skim milk (10 and 20%) and two type of soy flour‐based beverage (A and B) to 10%; in all cases, the monosodium glutamate 5% (w/v) was used as lyoprotector. For conservation studies, lyophilized microorganisms were packed in bi‐laminated polyester metallic containers with polyethylene, vacuum sealed and stored at 22 ± 2ºC during 5 months. Cell viability was determined by cell plate count using specific culture medium for each strain. The best results in terms of low cost biomass recovering were obtained with the medium containing glucose as a carbon source, manganese sulfate as essential salt and yeast extract, trypticase and meat peptone as nitrogen source. With respect to the studies of different lyophilization supports, 20% and 10% skim milk powder and soy beverage B (flavored soy meal) showed the best results. L. reuteri CRL 1098 retained viability during more than 2 months, yielding 107 CFU/g after 42 days of storage when milk at 20% was used as lyophilization support and 106 CFU/g during 56 days when the support used was soy beverage B. L. casei CRL 731 remained viable at room temperature for only 14 days at the assayed storage conditions. The minimum cell concentration required of probiotic microorganism to exert a beneficial effect in the host ranges from 106 to107 CFU/g. In consequence the results obtained in this study are promising as they would allow expanding the use of probiotic strains in products that not require cold chain for marketing constituting an interesting technological application for the food industry.