RESUMO
The aim of this research was to evaluate the suitability of uracil as an hygienic quality index of tomato products. Whereas uridine was naturally present throughout tomato fruits' ripening, uracil appeared only after microbial contamination. In tomato pulp inoculated with nine different microbial strains, all five lactic acid bacteria (LAB) studied released relevant quantities of uracil (150-1040 mg/kg of dm), with a correlated partial or total decrease of uridine. Uracil production by yeasts and molds was very low or nonexistent; the starting uridine concentration (approximately 960 mg/kg of dm) remained constant or increased. Uracil thermostability was also verified. Twenty-six samples of tomato paste (30 degrees Brix) were collected from bag-in-drums produced in an industrial processing plant, some with evident swelling symptoms. All of the samples with high microbial count presented uracil. Uracil was also present in samples with microbial contamination under the detection limit and Howard mold count below legislation limits, implying the reprocessing, at least partial, of altered tomato product. The results indicate that uracil presence in tomato products is an index of LAB contamination that has occurred before heat treatment.
Assuntos
Microbiologia de Alimentos , Lactobacillus , Leuconostoc , Pediococcus , Solanum lycopersicum/microbiologia , Uracila/análise , Estabilidade de Medicamentos , Temperatura Alta , Uridina/análiseRESUMO
The paper provides a simple protocol that uses the polymerase chain reaction to amplify a specific portion of the 16S gene, allowing the recognition of Pseudomonas fluorescens from other group I Pseudomonas. The amplified DNA patterns of 16S rRNA and ITS1, from the restriction fragment length polymorphisms VspI, HaeIII and TaqI digestion, produced band patterns that distinguished the biotypes of Ps. fluorescens. In addition to distinguishing the biotypes C and 3 we used a phenotypical method for levan production.
Assuntos
Técnicas de Tipagem Bacteriana/métodos , Reação em Cadeia da Polimerase/métodos , Pseudomonas fluorescens/classificação , Pseudomonas fluorescens/isolamento & purificação , Impressões Digitais de DNA , DNA Bacteriano/isolamento & purificação , DNA Bacteriano/metabolismo , DNA Espaçador Ribossômico/genética , Desoxirribonucleases de Sítio Específico do Tipo II/metabolismo , Frutanos/biossíntese , Genótipo , Polimorfismo de Fragmento de Restrição , Pseudomonas fluorescens/genética , RNA Bacteriano/genética , RNA Ribossômico 16S/genéticaRESUMO
Sixty-four strains of Enterococcus spp. of different origin were identified using traditional phenotypic, biochemical and cultural tests, together with molecular tests. API 20 STREP tests identified the species at a preliminary level, only one strain remaining unidentified. Strains belonging to the genus Enterococcus were tested with genus-specific primers, while species-level identification was carried out with the 16S-23S rDNA intergenic region (ITS) and species-specific primers for E. faecium and E. faecalis. Those strains found to be negative with the species-specific primers were subjected to 16S rDNA partial sequencing.
Assuntos
Técnicas de Tipagem Bacteriana , Queijo/microbiologia , Enterococcus/classificação , Enterococcus/metabolismo , Fezes/microbiologia , Animais , Bovinos , Primers do DNA , DNA Ribossômico/análise , DNA Espaçador Ribossômico/análise , Enterococcus/genética , Genótipo , Humanos , Dados de Sequência Molecular , Fenótipo , RNA Ribossômico 16S/genética , RNA Ribossômico 23S/genética , Análise de Sequência de DNA , Especificidade da EspécieRESUMO
Twenty-five yeast strains isolated from sourdough samples for Panettone, Pandoro and Cornetto brioche manufactured by eight different bakeries in northern Italy were characterised. Classification was performed by the simplified identification method (SIM), Kurtzman and Fell's identification protocol, the API system from bioMérieux (France) and the MicroLog system from Biolog (USA). Genetic diversity was investigated by randomly amplified polymorphic DNA fingerprinting and mitochondrial-DNA restriction enzyme analysis. Sequences of the internal transcribed spacers between 18S and 26S rDNA genes were analysed. Candida humilis was the predominant species (56% of isolates), whereas the remaining strains (44%) were related to the Saccharomyces cerevisiae sensu stricto group. Identification systems based on phenotypic analysis proved to be unreliable to identify yeasts from sourdough. Either RAPD-PCR or mtDNA restriction analysis showed to be suitable for the identification of species, but could not be used to differentiate among the isolates at the strain level. Sequencing of the ITS region permitted a consistent classification of the sourdough yeasts.
Assuntos
Pão/microbiologia , Candida/classificação , Saccharomyces cerevisiae/classificação , Candida/genética , Candida/crescimento & desenvolvimento , Contagem de Colônia Microbiana , DNA Fúngico/análise , DNA Mitocondrial/análise , DNA Ribossômico/análise , Variação Genética , Itália , Dados de Sequência Molecular , Técnicas de Tipagem Micológica , RNA Ribossômico/genética , RNA Ribossômico 18S/genética , Técnica de Amplificação ao Acaso de DNA Polimórfico/métodos , Mapeamento por Restrição , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crescimento & desenvolvimento , Análise de Sequência de DNARESUMO
Phenotypic and genotypic characterizations of Lactobacillus maltaromicus strains DSM 20342(T) and DSM 20344 provided evidence for the reclassification of this species in the genus Carnobacterium. Moreover, phenotypic and genotypic comparisons made between L. maltaromicus and Carnobacterium piscicola highlighted that these two species should be considered synonyms. For these reasons, the species Carnobacterium maltaromaticum comb. nov. (type strain DSM 20342(T) = ATCC 27865(T) = CCUG 30142(T) = CIP 103135(T) = JCM 1154(T) = LMG 6903(T) = NRRL B-14852(T)) is proposed to accommodate L. maltaromicus and C. piscicola.