Identificação molecular de bactérias ácido láticas isoladas de leite cru e queijo, e pesquisa de genes de bacteriocinas

• Ano de defesa: 2011
• Autor(a) principal: Moraes, Paula Mendonça
• Orientador(a): Nero, Luís Augusto
• Banca de defesa: Franco, Bernadette Dora Gombossy de Melo , Silva Júnior, Abelardo
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Mestrado em Medicina Veterinária
• Departamento: Biotecnologia, diagnóstico e controle de doenças; Epidemiologia e controle de qualidade de prod. de
• País: BR
• Palavras-chave em Português: Bacteriocinas; Atividade antagonista; Bactérias ácido láticas
• Palavras-chave em Inglês: Bacteriocin; Antagonist activity; Lactic acid bacteria
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA::INSPECAO DE PRODUTOS DE ORIGEM ANIMAL
• Link de acesso: http://locus.ufv.br/handle/123456789/5053

Considering the importance of the lactic acid bacteria (LAB) as biopreservatives, and their inhibitory potencial against pathogens and spoilage microrganisms, the aim of this study was identify using molecular methodologies LAB isolates obtained from raw milk and soft cheese, and to conduct a detailed study about the presence of bacteriocin codifying genes. There were utilized 101 LAB isolates previously characterized as antagonist against Listeria monocytogenes. All LAB were submitted to 16S rDNA sequencing. Considering identified genera, specific bacteriocin codifying genes were analised. Based on their antimicrobial activity and presence of nisin genes, 10 Lactococcus spp. isolates were selected and submitted to nisin codifying gene sequencing and translation, for further comparison of predicted proteins. Enterococcus spp. were submitted to phenotipic evaluation of pathogenicity factors. Considering the 16S rDNA sequencing, the most frequent genera obtained were Enterococcus, Lactococcus e Lactobacillus. Most of the analysed isolates (80%) presented at least one bacteriocin codifying gene, being the lantibiothics the most frequent, followed by nisin and enterocin P. Concerning the translated sequences of nisin codifying gene, two variations were observed: substitution of histidine for asparagine (position 27) in two cultures, typical of nisin Z variation, and the substitution of an histidine for threonine (position 31) in three cultures, a nisin variation not described until now. Concerning the Enterococcus spp. pathogenicity factors, only incomplete haemolysis in horse blood agar and gelatinase production were observed in 23 e 11 isolates, respectively. In conclusion, the evaluated cultures presented great potential to be used as biopreservatives in food, specially the genera Lactococcus wich carry the nisin variants codifying genes not described yet in the literature.