RESUMO
The effect of naturally occurring phenolic compounds on Aspergillus carbonarius growth and ochratoxin A (OTA) production was studied. Caffeic acid and the flavonoids, rutin and quercetin, were added to Czapek Yeast Extract agar at concentrations ranging between 50 and 500 mg/l. All phenolic compounds had a significant influence on growth rate and lag phase of A. carbonarius at 250 mg/l. The growth was completely inhibited with 500 mg/l. In comparison with the control, a significant decrease in OTA production was observed with all phenolic compounds. In general, effect on growth was less evident than effect on toxin production. An inhibitory effect on growth and OTA production, as concentration was increased was observed in all cases. The response of A. carbonarius to the flavonoids, rutin and quercetin, was similar. The inhibitory effect of these natural phenolic compounds on fungal growth and OTA production could be an alternative to the use of chemical fungicides.
RESUMO
Apples possess many beneficial properties for the human health related with their high content in phenolic compounds. The antimicrobial effect of these compounds from the skin of two apple varieties, Royal Gala and Granny Smith, against human pathogens was examined. The phenolic compounds were extracted with the following solvents: A, acetone: water: acetic acid; B, ethyl acetate: methanol: water and C, ethanol: water. Total phenolic, flavonoid and non-flavonoid contents were analyzed in the extracts. The antimicrobial effect was determined using the agar diffusion method. The highest inhibitory effect of both apple varieties corresponded to extract A, which contained a high phenolic content. The Granny Smith extracts with higher phenolic content presented a superior antimicrobial effect against the selected microorganisms: Escherichia coli, Escherichia coli ATCC 25922, Escherichia coli ATCC 35218, Staphylococcus aureus ATCC 25923, Staphylococcus aureus ATCC 29213, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 29212 and Listeria monocytogenes. The most sensitive microorganisms were Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853and Staphylococcus aureus ATCC 29213, whereas the most resistant strains were Escherichia coli ATCC 35218 and Escherichia coli. The results obtained demonstrate a direct relationship between the phenolic content of the extracts and the antimicrobial effect.
RESUMO
The genes implicated in the catabolism of the amino acid arginine by Lactobacillus hilgardii X(1)B were investigated to assess the potential for formation of ethyl carbamate precursors in wine. L. hilgardii X(1)B can use arginine via the arginine deiminase pathway. The complete nucleotide sequence of the arc genes involved in this pathway has been determined. They are clustered in an operon-like structure in the order arcABC. No evidence was found for the presence of a homologue of the arcD gene, coding for the arginine/ornithine antiporter. The arc genes have been expressed in Escherichia coli resulting in arginine deiminase (ArcA), ornithine carbamoyltransfera (ArcB) and carbamate kinase (ArcC) activities. The results indicate the need for caution in the selection of lactic acid bacteria for conducting malolactic fermentation in wine since arginine degradation could result in high amounts of ethyl carbamate.
Assuntos
Hidrolases/genética , Lactobacillus/genética , DNA Bacteriano/química , DNA Bacteriano/genética , Eletroforese em Gel de Poliacrilamida , Escherichia coli/genética , Regulação Enzimológica da Expressão Gênica , Ordem dos Genes , Genes Bacterianos/genética , Hidrolases/metabolismo , Lactobacillus/enzimologia , Dados de Sequência Molecular , Família Multigênica/genética , Ornitina Carbamoiltransferase/genética , Ornitina Carbamoiltransferase/metabolismo , Fosfotransferases (Aceptor do Grupo Carboxila)/genética , Fosfotransferases (Aceptor do Grupo Carboxila)/metabolismo , Análise de Sequência de DNARESUMO
From peruvian fermented beverages such as Chicha de Jora, there have been isolated several strains of lactc bacteria. After exploring ten strains we only got isolated Lactobacillus plantarum 1A as a producer of an antimicrobial substance that is neither an organic acid nor oxigenated water. Sach inhibitory substance was active against three strains Lactobacllus plantarum 2A, Lactobacillus vitulinus 6-13 and Lactobacillus buchneri 10. This inhibitory effect of Lactobacillus plantarum 1A, could e importand for the coontrol of undesirable microbial flora during the process of the elaboration of the Chicha de Jora and it could be used as a preservant in food industry.
A partir de bebida fermentada del Perú, como la chicha de Jora, se han aislado varias cepas de bacterias lácticas. DE 10 cepas exploradas, sólo Lactobacillus plantarum 1A produjo una sustancia antimicrobiana que no es ácido orgánico ni agua oxigenada. Dicha sustancia inhibidora fue activa contra 3 cepas. Lactobacillus vitulinus 6-13 y Lactobacillus buchneri 10. Este efeto inhibitorio de Lactobacills pantarunm 1A podría ser importante para el control de la flora microbiana indeseable durante el proceso de la elaboración de la Chicha de Jora y ser utilizada como preservante en la industria alimentaria.
