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

PASTERIS, S.E.; GUIDOLI, M.; OTERO M. C.; BÜHLER, M.I.; NADER MACÍAS M. E.

Tucumán. Argentina.

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

CERELA-CONICET

Red leg syndrome (RLS) is an infectious disease that affects Rana catesbeiana hatcheries, causing important economics losses. Preventive measures generally involve the use of chemotherapeutic agents. The treatments with antibiotics can alter the meat quality and induce bacterial resistance. Probiotics are widely used either in endothermic and poikilothermic animals and considered an alternative way to control infectious diseases and also the sanitary quality of the water in hatcheries. In previous investigations it has been proved that commercial probiotics increase the weight of juvenile frogs without any effect over animal’s health. Since the beneficial strains to be included in a probiotic product for use in a defined ecological niche and host should be isolated from the same area where it will be applied, our group isolated a group of lactic acid bacteria (LAB) from animals and hatcheries environmental. Their characterization allowed us to select Lactococcus lactis CRL 1584 as a potential probiotic candidate. Taking into account that industrial production, commercialization and distribution as well as the probiotic administration requires an appropriate conservation method to maintain the cell viability and beneficial properties, the aim of this work was to evaluate the effect of different cryoprotective media on L. lactis CRL 1584. Keeping in mind that the probiotic could be administered together with balanced feed, we also studied the growth and antimicrobial activity of the LAB strain when inoculated in both single and mixed cultures together with C. freundii, a RLS associated pathogen. Thus, L. lactis CRL 1584 resuspended into different low cost cryoprotective media was lyophilized. 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. The viability in dried cultures decreased only in 2 log units after 3 months storage at 4º C in both media, while when lyophilized into water the LAB strain lost its viability during the first month. Moreover, L. lactis CRL 1584 maintained the ability to produce the antimicrobial compounds (lactic acid, H2O2, and lactococcin) during 4 months after lyophilisation. To determine if dried cultures of LAB strain were able to keep its viability and inhibit the growth of the pathogenic microorganism, 1x1011 CFU/mL of LAB and 1x101 CFU/mL of C. freundii were inoculated in a basal culture medium prepared with balance feed for frog nutrition. Cultures were incubated at 30ºC for 72 h (simulating the pre-fermentation of the food before supplying to animals) and samples were taken at 0, 4, 8, 12, 24, 48 and 72 h. L. lactis CRL 1584 and C. freundii viabilities increased in 2 and 9,5 log units at 24 h, respectively. However, LAB viability remained constant while C. freundii diminished to 7,5 log units at 72 h. These results indicate that L. lactis is not only resistant to the lyophilisation process but also is able to grow, maintain its viability and retain its ability to produce antimicrobial metabolites in balanced feed, making this media a feasible strategy to apply the proposed probiotic product in raniculture.