TECHNOLOGICAL EVALUATION OF Lactococcus lactis CRL 1584, A POTENTIAL PROBIOTIC FOR RANICULTURE

PASTERIS, S.E.; GUIDOLI, M.G.; OTERO, M.C.; BUHLER, M.I.; NADER-MACÍAS, M. E.

Tucumán. Argentina

Simposio; III INTERNATIONAL SYMPOSIUM ON LACTIC ACID BACTERIA. II ARGENTINEAN LAB NET MEETING; 2009

Red leg syndrome (RLS) is an infectious disease that affects Rana catesbeiana hatcheries, causing main economics losses. Preventive methods involve the use of chemotherapeutic agents. The treatments with antibiotics can alter the meat quality and also induce bacterial resistance. Probiotics are widely used either in endothermic and poikilothermic animals and are considered to be an alternative technique to control infectious diseases. Also, some commercial probiotics of unknown origin increase the weight of frogs. In previous works, the isolation of a group of lactic acid bacteria (LAB) from animals and hatcheries environment was performed, based on the host and niche specificity demonstrated for the members of the indigenous microbiota. Their characterization allowed us to select Lactococcus lactis CRL 1584 as a potential probiotic candidate. As the industrial production of a probiotic product, its commercialization and distribution require an appropriate conservation of microorganisms, either in their viability and beneficial properties maintenance, one of the aim of this work was to evaluate the effect of different cryoprotective media on the lyophilization of L. lactis CRL 1584. As probiotic microorganisms can be administered together with the balanced feed, the second aim was to evaluate the functional properties of LAB strain in the conditions of food administration in hatcheries. L. lactis CRL 1584 cells were cultivated during exponential phase, concentrated and resuspended into different low cost cryoprotective media. Viability was measured before and after lyophilization and during storage at 4°C. Later, to determine the potential application in food, dried cultures of LAB strain were inoculated in a basal culture medium prepared with hydrated balanced feed for frog nutrition in order to evaluate the ability of the potencial probiotic to grow, maintain its viability and antimicrobial activity. The culture media were incubated at 30ºC for 72 h in order to simulate the food prefermetations before supplying to animals. The results showed that the best drying media were: a) 10% whey protein concentrate added with 5% sucrose, and b) 10% skim milk added with 5% sucrose. When suspended in medium (a) the viability remained constant after lyophilisation and decreased only 2 log units after 3 months storage, while in medium (b) diminished 1 log unit after liophilization and 1 log unit after 3 months storage, while in water, the viable cells decreased 7 log units and to 0 after the 1st month of storage. Moreover, L. lactis CRL 1584 maintained the capability to produce the antimicrobial compounds during 4 months after lyophilization. When inoculated in food media, the LAB strain increased its viability in 2 log units that remains constant until 72 h. In these conditions LAB strain was able to inhibit the growth of Citrobacter freundii, a red-leg associated pathogen. These results indicate that L. lactis CRL 1584 maintain its viability and antimicrobial activity after lyophilization during 4 months and that balanced feed could be an adequate vehicle for LAB administration. Also the results allow indicate that frogs food is a suitable medium for C. freundii growth, being essential to avoid contamination during its formulation and storage.