Antimicrobial Effect of Citric, Acetic, Lactic Acids and Sodium Nitrite against Escherichia Coli in Tryptic Soy Broth

Antimicrobial effect of organic acids against E. coli (EC1 and EC2) was studied in  tryptic soy broth (pH 5) adjusted to various concentrations 1, 2, 3, 4 or 6% of the citric,  acetic and lactic acid then incubated at 5, 20 and 37ºC during 96 hours. In the second study, the effect of sodium nitrite on the survival of E. coli cells was investigated at pHs (4.5 and 6).   ¶¶In the majority of the cases, the order of effectiveness of the organic acids was: citric >acetic > lactic¶.¶ At low temperature, 1 to 6% of lactic and acetic acid does not seem sufficient concentrations to influence cellular viability significantly. ¶ In contrast, addition of citric acid (3%) to TSB medium reduced E. coli from approximately 6.3 log CFU/ml to an undetectable number. Furthermore, antimicrobial effect of all organic acids increased with increasing the temperature of incubation. This study has confirmed that the lethal effect of sodium nitrite was much enhanced by low pH. Thus, the most bactericidal effect was obtained at pH = 4.5 and the concentrations NaNO2 (0.4 or 0.6). Key words: Escherichia coli, Antimicrobial effect, citric acid, acetic acid, lactic acid, sodium nitrite

Évolution de la teneur glucidique et protéique dans les tubercules de topinambour (Helianthus tuberosus L.)

Cette note concerne l'étude de la production de matière sèche, de glucides totaux et de protéine pendant les différents stades du développement des tubercules de topinambour. (Helianthus tuberosus L.). La matière sèche varie de 17 à 20% matière frafche, les glucides totaux de 8,85 à 14,5% matière frafche dont 75% de fructose (6,71 à 12,3% matière frafche) et les proMines de 9,20 à 12,85% du poids sec. La production moyenne de glucides totaux à l'hectare se situe en année normale à 6,5 Tlha (5,9-7,2); les tubercules perdent une fraction de leur glucides en hiver. Les sous-produits d'extraction des glucides contiennent des résidus sucrés et des acides aminés et constituent un aliment dont la valeur nutritive n'est pas négligeable en période hivernale.Carbohydrates and proteins evolution in the Jerusalem artichoke (HelianthUil tubero.UII L.) tubersThis note concerns a study of production of dry matter, total carbohydrate and protein at aIl stages of development of the tubers of the Jerusalem Artichoke (Helianthus tuberosus L.). Dry matter ranges from 17 to 20% fresh matter, overall carbohydrates from 8,85 to 14,5% fresh matter, of wich 75% is fructose (6,71 à 12,3% matière frafche) and protein from 9,20 to 12,85% dry matter. The average overall carbohydrate production per hectare amounts to 6,5 Tlha (5,9-7,2) in a normal year; the tubers lose a fraction oftheir carbohydrates in winter. The byproduct from extraction of carbohydrates contain residual carbohydrates and amino-acids and orovide a food of significant nutrition al value for the win ter season

Activité antifongique in vitro du phoséthyl-Al sur quelques souches de Verticillium albo-atrum Reinke & Berthold

La fongitoxicité du phosphonate, métabolite actif du phoséthyl-Al est modulée par la composition des milieux de culture. Sur le Cristomalt (milieu naturel) la toxicité du phosphonate vis-à-vis du Verticillium albo-atrum Reinke & Berthold. fonne à microsclérotes. est beaucoup plus grande que sur le Ribeiro (milieu synthétique). L'addition du phosphate au milieu de culture abaisse l'efficacité du phosphonate. Ce sont toujours les souches de Verticillium pathogènes sur la tomate, qui sont les plus sensibles au phoséthyl-Al.In vitro antifungal activity of fosetyl-Al on several strains of Verticillium albo-alrum Reinloe & BertholdToxicity of phosphonate, the active breakdown product of the fosethyl-Al, is modulated by culture media composition. On the Cristomalt ( natural medium), phosphonate toxicity against Verticillium albo-atrum Reinke & Berthold,-microsclerotial fonn, is higher than in synthetic media (Ribeiro). Phosphate is the main constituent of culture medium which modifies phosphonate fungitoxicity. Strains ofVerticillium, pathogenicon tomato, are al ways more sensitive" to fosethyl-Al

Regional microbial signatures positively correlate with differential wine phenotypes: evidence for a microbial aspect to terroir

Many crops display differential geographic phenotypes and sensorial signatures, encapsulated by the concept of terroir. The drivers behind these differences remain elusive, and the potential contribution of microbes has been ignored until recently. Significant genetic differentiation between microbial communities and populations from different geographic locations has been demonstrated, but crucially it has not been shown whether this correlates with differential agricultural phenotypes or not. Using wine as a model system, we utilize the regionally genetically differentiated population of Saccharomyces cerevisiae in New Zealand and objectively demonstrate that these populations differentially affect wine phenotype, which is driven by a complex mix of chemicals. These findings reveal the importance of microbial populations for the regional identity of wine, and potentially extend to other important agricultural commodities. Moreover, this suggests that long-term implementation of methods maintaining differential biodiversity may have tangible economic imperatives as well as being desirable in terms of employing agricultural practices that increase responsible environmental stewardship