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N. Leticia Ramírez-Chavarín, (1), M. Lourdes Pérez-Chabela, (1), J. Mariano García-Garibay (1),Carmen Wacher-Rodarte (2), Carlos Alberto Eslava-Campos (3) y José Molina-López (3).
(1) Departamento de Biotecnología. Universidad Autónoma Metropolitana Iztapalapa. Av. San Rafael Atlixco 186,Iztapalapa, C.P. 09340. Ciudad de México, Distrito Federal. E-mail:
(2) Alimentos y Biotecnología. Universidad Autónoma Nacional de México. Av. Universidad 3000, Copilco, Ciudad Universitaria, C.P. 04510. Ciudad de México, Distrito Federal. Delegación Coyoacán. E-mail:
(3) Investigación Básica. Universidad Autónoma Nacional de México. Av.Universidad 3000, Copilco, Ciudad Universitaria, C.P. 04510. Ciudad de México, Distrito Federal. Delegación Coyoacán. E.mail: y
Key words: lactic acid bacteria, thermotolerant, probiotics

Introduction. Probiotics are microorganisms introduced orally in the gastrointestinal tract and able to contribute positively to the activity of intestinalmicroflora and, therefore, to the host health (1). The criteria to consider microorganisms as probiotic include the survival of the transit and at low pH through gastrointestinal tract, bile a tolerant, the adhesion to intestinal ephitelial cells and colonization, and no pathogenicity (2). Pennacchia et al. (2004) isolated and identified 25 strains of Lactobacillus plantarum traditional fermented drysausages, which were able to resist low pH and grow under conditions of simulated intestinal environment, ensuring their value as probiotics. Arihara et al. (1998) found that strains of Lactobacillus gasseri JCM1131 can be applied in fermented meat to improve the safety of these products due to their probiotic potential. Bacteria were isolated native bacteria in meat products, so they extend theshelf life of products such as bioprotective cultures and give health beneficial as probiotic cultures and finally not to increase the economic value of the product. As the Mexican population consumes a large amount of cooked meats is necessary to give added value to these products, so thermotolerant lactic acid bacteria were evaluated for use as probiotics, increasing the security value of thesefoods.
Methodology. Ten identified lactic acid bacteria thermotolerance (LAB-T) isolated from cooked meat products such as five strains of Pediococcus pentosaceus, two strains of Lactobacillus plantarum, two strains of Enterococcus faecium and one strains of Aerococcus viridans were tested as possible probiotics evaluating their tolerance to acid pH with values of 0.5 a 5 for 1 a 4 h of incubationat 35°C (5). Tolerance to simulated gastric juice were inoculated strains of LAB-T were incubated at 35°C for 90 min (6). Tolerance to bile, the strains LAB-T were inoculated MRS broth supplemented with 0.1 a 2.0% bile extract porcine were incubated for 7 h (7). Coaggregation test was performed with Salmonella parera IV O11:Z4Z23 and E. coli O139:H26 strains indicated (8). Autoaggregation test,were inoculated strains of LAB-T were inoculated phosphate-buffered solution (PBS, 0.1%) were incubated at 35°C for 2 and 24 h (9). The adherence assays was performed with Hep-2 epithelial cells (10).
Results and Discussions. Tolerance to low pH and bile salts is of great importance in the survival and growth of bacteria in the gastrointestinal tract and are also considered a prerequisite forprobiotic bacteria (11). In Table 1 shows that the 10 strains LAB-T showed good growth in an incubation period of 4 had pH values 4 and 5, this is because the optimum pH of the lactic bacteria is approximately 4.5 to 6.5 (12). In other pH values did not have good growth for 1, 2 and 4 h of incubation. However, it has been reported that some lactic acid bacteria can survive and grow in the presence...
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