Caracterização fenotípica e genotípica de bactérias do ácido acético isoladas de alimentos
Ficheiros
Data
2014-11-11
Título da revista
ISSN da revista
Título do Volume
Editora
Resumo
As bactérias do ácido acético (BAA) são responsáveis pela produção de vários
subprodutos muito utilizados na indústria alimentar. Podem atuar como agentes de
transformação no caso do vinagre e como agentes de contaminação no caso do vinho.
Neste trabalho, a resistência das bactérias acéticas a vários fatores de stress que
ocorrem durante a produção industrial de vinagre, foi avaliada. Para tal, foram utilizadas
70 isolados provenientes de uvas sãs e podres, mostos, vinhos, sãos e alterados, e
vinagres caseiros. A capacidade de resistência a diferentes condições de etanol, ácido
acético, SO2 e pH e o efeito cruzado da temperatura foi avaliada por crescimento em
meio de cultura sólidos. Foi observada uma grande variabilidade na resistência às
diferentes condições testadas, sendo que a temperatura de incubação foi diretamente
correlacionada com o aumento da sua sensibilidade.
Foi observado que apenas um número reduzido destas bactérias demonstram
capacidade para produzir aminas biogénicas nomeadamente a histamina (3%), e a
putrescina (5%). Por outro lado, as bactérias acéticas estudadas revelaram um perfil de
multiresistência a vários antibióticos o que sugere que estudos posteriores deverão ser
conduzidos de forma a avaliar o seu impacto em termos de segurança alimentar.
Com o objetivo de proceder à identificação dos isolados foram incluídas neste
trabalho sete estirpes de referência, pertencentes à Colecção Espanhola de Culturas Tipo
(CECT). A utilização da técnica de PCR fingerprinting com os primers M13, ERIC e
(GTG)5 não permitiu obter a identificação credível dos isolados em estudo. Pela análise
das sequências parciais do rDNA 16S foi possivel a identificação de 17 estirpes
selecionadas aleatoriamente o que permitiu inferir a identificação de outros isolados.
Assim, um grupo de estirpes identificados como Acetobacter pasteurianus foi
caracterizado genotípicamente, tendo-se verificado uma grande variabilidade, também traduzida nos parâmetros fenotípicos avaliados.
Acetic acid bacteria (AAB) are responsible for the production of some interesting products, very useful for a variety of industries including food industry. They can have a positive role as transformation agents in vinegar production, but their growth is undesirable in the the wine industry being responsible for wine spoilage. In this work, the resistance of the acetic bacteria to some stress factors that they may encounter during production of vinegar, was evaluated. For such purpose, 70 acetic bacteria strains isolated from healthy and rotten grapes, grape-juices, wines, either spoiled or not, and vinegars, were used. The resistance of the isolates to different conditions of ethanol, acetic acid, SO2 and pH and the cross-effect of temperature was evaluated by its growth in solid culture media. A great variability in the resistance to the different tested conditions was observed, being temperature of incubation directly correlated with the increase of its sensitivity. Only a reduced number of these bacteria demonstrated capacity to produce biogenic amines, like histamine (3%) and putrescine (5%). On the other hand, acetic bacteria displayed an antibiotic multiresistance profile suggesting that further studies should be performed to assess its impact on food safety and public health. In order to identify the natural isolates used, seven reference strains belonging to the Spanish Type Culture Colection (CECT) were included in this work. PCR fingerprinting technique using M13, ERIC e (GTG)5 primers did not allow a reliable identification of the strains. Yet, 17 randomly selected strains were identified by analysis of the partial sequences of 16S rDNA which allowed us to infer the identification of some other isolates through the analysis of similarity of genotypic profiles obtained. The genotypic dissimilarity observed within the group of strains identified as Acetobacter pasteurianus was correlated with its divergence phenotypic profiles.
Acetic acid bacteria (AAB) are responsible for the production of some interesting products, very useful for a variety of industries including food industry. They can have a positive role as transformation agents in vinegar production, but their growth is undesirable in the the wine industry being responsible for wine spoilage. In this work, the resistance of the acetic bacteria to some stress factors that they may encounter during production of vinegar, was evaluated. For such purpose, 70 acetic bacteria strains isolated from healthy and rotten grapes, grape-juices, wines, either spoiled or not, and vinegars, were used. The resistance of the isolates to different conditions of ethanol, acetic acid, SO2 and pH and the cross-effect of temperature was evaluated by its growth in solid culture media. A great variability in the resistance to the different tested conditions was observed, being temperature of incubation directly correlated with the increase of its sensitivity. Only a reduced number of these bacteria demonstrated capacity to produce biogenic amines, like histamine (3%) and putrescine (5%). On the other hand, acetic bacteria displayed an antibiotic multiresistance profile suggesting that further studies should be performed to assess its impact on food safety and public health. In order to identify the natural isolates used, seven reference strains belonging to the Spanish Type Culture Colection (CECT) were included in this work. PCR fingerprinting technique using M13, ERIC e (GTG)5 primers did not allow a reliable identification of the strains. Yet, 17 randomly selected strains were identified by analysis of the partial sequences of 16S rDNA which allowed us to infer the identification of some other isolates through the analysis of similarity of genotypic profiles obtained. The genotypic dissimilarity observed within the group of strains identified as Acetobacter pasteurianus was correlated with its divergence phenotypic profiles.
Descrição
Dissertação de Mestrado em Biotecnologia e Qualidade Alimentar
Palavras-chave
Bactérias , Ácido acético , Antibióticos , DNA , Tolerâncias/resistências , Fingerprinting , 16 rDNA