Diversidade molecular da microbiota lática bacteriocinogênica de leite de cabra e caracterização de seu potencial bioconservador para a produção de queijo Minas

• Ano de defesa: 2014
• Autor(a) principal: Perin, Luana Martins
• Orientador(a): Nero, Luís Augusto
• Banca de defesa: Carvalho, Antônio Fernandes de , Todorov, Svetoslav Dimitrov , Bogsan, Cristina Stewart , Martins, Elaine Cristina Pereira de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Viçosa
• Programa de Pós-Graduação: Doutorado 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; Leite de cabra; Queijo Minas
• Palavras-chave em Inglês: Bacteriocins; Goat milk; Minas cheese
• Área do conhecimento CNPq: CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA::INSPECAO DE PRODUTOS DE ORIGEM ANIMAL
• Link de acesso: http://locus.ufv.br/handle/123456789/1483

The raw goat milk is an important source of new bacteriocinogenic lactic acid bacteria (LAB) strains. The constant demand of consumers for foods without chemical additives justifies the study of alternatives for biopreservation. This study aimed to isolate and identify bacteriocinogenic LAB strains present in the autochthonous microbiota of raw goat milk, characterize their bacteriocins, virulence potential and evaluate its bioconservative potential in Minas cheese manufactured with raw goat milk. As an additional preservative aspect, biogenic amines (BA) present in the produced cheeses were quantified. LAB were isolated from raw goat milk using selective media and subjected to evaluation of their bacteriocinogenic potential from molecular and phenotypic tests using Listeria monocytogenes ATCC 7644 as target. Nisin positive strains were submitted to gene sequencing in order to identify possible variations in amino acid composition of the peptide codified. Strains characterized as bacteriocinogenic were identified by 16S rRNA with additional pheS sequencing to identify Enterecoccus species. These strains were grouped according to their genetic similarity by rep-PCR and some isolates were selected and submitted to further phenotypic and molecular tests for identification of their virulence potential. Lactococcus lactis subsp. lactis GLc05 was selected based on its interesting bacteriocinogenic potential and absence of virulence factors for producing Minas cheese manufactureted with raw goat milk. The cheeses microbiota with (A) and without (B) addition of GLc05 was analyzed using culture-dependent (selective media) and - independent (rep-PCR and DGGE) methods. The BA quantification in the Minas cheeses was performed by HPLC. Bacteriocinogenic strains were identified as Lactococcus spp. (24) and Enterococcus spp. (33). Among them, 9 Lactococcus lactis were identified as producing a new variant of nisin with broad antimicrobial activity spectrum. Characterization of virulence potential showed the presence of genes related to pathogenicity and their expression in some isolates identified as Lactococcus spp. Moreover, some isolates identified as Enterococcus spp. usually considered opportunistic pathogens, did not presented these genes. Analysis of the cheeses A and B using culture-dependent and -independent methods showed that L. lactis subsp. lactis GLc05 was able to control the coagulase-positive cocci population and was capable to cause changes in the microbiota composition in Minas cheese manufactured with raw goat milk. High concentrations of BA were found in the cheeses, revealing the importance of ensuring the sanitary quality of the milk used. However BA concentrations were significantly lower in cheeses A. The results indicate that L. lactis subsp. lactis GLc05 can be used for the production of cheeses manufactured with raw milk as it is capable of controlling pathogenic microorganisms populations and also the concentrations of BA.