Search results for "PORES"
showing 10 items of 155 documents
Empirical model building based on Weibull distribution to describe the joint effect of pH and temperature on the thermal resistance of Bacillus cereu…
2002
Abstract A mathematical model based on Weibull parameters was built to describe the joint effect of temperature and pH on thermal inactivation of Bacillus cereus spores (strain INRA TZ415). The effect of these factors on Weibull model parameters ( β , 1/ α ) was also studied. Heat inactivation tests were carried out in acidified carrot broth as vegetable substrate, following a full factorial design at four levels for temperature (80, 85, 90 and 95 °C) and pH (6.2, 5.8, 5.2 and 4.7). The Weibull distribution model provided good individual fits for the different combinations of temperature–pH tested, with discrepancy factors, D f , coming close to 25% for most cases. The temperature and pH di…
Inactivation of conidia of Penicillium chrysogenum, P. digitatum and P. italicum by ethanol solutions and vapours
2008
A fractional factorial design, 2(5-1) experiments, was used for assessing the influence of 5 factors: water activity, aw [0.7, 0.9], temperature, T ( degrees C) [10, 30], mode of application, A [liquid, vapour], ethanol concentration, E (% w/w) [5, 10] and time, t (d) [1, 4] on the inactivation of spores of Penicillium chrysogenum, P. digitatum and P. italicum. Survival was determined by germination at optimal conditions within 3d. The experimental response was log (N 0/Nt), where N 0 and Nt (spore ml(-1)) the concentrations of viable spores at t=0 and t respectively. By a decreasing order of sensitivity to ethanol, moulds were ranked as followed: P. digitatum, P. italicum and P. chrysogenu…
Modeling the effect of ethanol vapor on the germination time of Penicillium chrysogenum.
2005
The influence of ethanol vapor on germination of Penicillium chrysogenum was determined on yeast nitrogen base plus glucose agar medium at 25 degrees C. Ethanol vapors were generated by 0 to 6% (wt/wt) ethanol solutions at the bottom of hermetically closed petri dishes. The logistic equation was used to describe the data as the percentage of germination versus time and to estimate the germination time. The effect of ethanol concentration on germination time was described by a new reparameterized equation, resulting in an estimated limiting ethanol concentration of 4.3%. Up to 3% ethanol, all spores germinated, and the germination time increased with increasing ethanol concentration. At 3.5 …
A redox-sensitive nanofluidic diode based on nicotinamide-modified asymmetric nanopores
2017
[EN] We demonstrate a redox-sensitive nanofluidic diode whose ion rectification is modulated by the oxidation and reduction of chemical moieties incorporated on its surface. To achieve this goal, we have first synthesized the chemical compounds 1-(4-aminobutyl)-3-carbamoylpyridin-1-ium (Nic-BuNH2) and 3-carbamoyl-1-(2,4-dinitrophenyl)pyridinium (Nic-DNP). Then, the surface of track-etched single asymmetric nanopores is decorated with the redox-sensitive Nic-BuNH2 and Nic-DNP molecules using carbodiimide coupling chemistry and Zincke reaction, respectively. The success of the modification reactions is monitored through the changes in the current¿voltage (I¿V) curves prior to and after pore f…
Use of the Weibull model to describe inactivation of dry harvested conidia of different Penicillium species by ethanol vapours
2010
Aims: This study aimed at modelling the effect of ethanol vapours, in the range 0·7–7·5 kPa, on the inactivation of dry-harvested conidia of Penicillium chrysogenum, Penicillium digitatum and Penicillium italicum. Methods and Results: Survival curves were modelled by a Weibull model: log (N/N0) = −1/2·303 (t/α)β. The shape parameter β was different from one in all cases, indicating that the classical first-order kinetics approach is the exception rather than the rule. Survival curves exhibited upward concavity (β < 1) with the notable exception of P. chrysogenum at ethanol vapour pressures 0·7 and 1·5 kPa. The scale parameter α (h) varied greatly depending on the ethanol vapour pressure a…
Preparation of fungal conidia impacts their susceptibility to inactivation by ethanol vapours.
2009
Abstract A common protocol employed for the preparation of conidia employs flooding a fungal colony grown on semi-solid media under optimum conditions with an aqueous solution. In contrast, conidia produced in a natural environment are usually not hydrated when disseminated in air and can be produced under water stress. In order to simulate the latter conditions, cultures were grown at different water activities and conidia were dry-harvested on the lid by turning the dishes upside-down then gently tapping the bottom of the box. This study aimed at assessing the effect of the preparation of fungal conidia on their inactivation by ethanol vapours. Firstly ethanol vapours (either 0.30 or 0.45…
Significance of the physiological state of fungal spores.
2008
In predictive mycology, most of the studies have been concerned with the influence of some environmental factors on fungal growth and production of mycotoxins, at steady-state. However, fluctuating conditions, interactions between organisms, and the physiological state of the organisms may also exert a profound influence on fungal responses in food and in the environment. In the laboratory, fungal spores are widely used as a biological material. They are produced under optimal conditions then, partially re-hydrated for obtaining standardized spore suspensions. In real conditions, spores are produced under suboptimal conditions and can be submitted to various stresses prior to their germinat…
Prediction of conidial germination of Penicillium chrysogenum as influenced by temperature, water activity and pH.
2001
M. SAUTOUR, A. ROUGET, P. DANTIGNY, C. DIVIES AND M. BENSOUSSAN. 2001 Aims: Conidial germination of Penicillium chrysogenum was carried out under operating conditions compatible with a pastries manufacturing process. Methods and Results: A range, limited by two experimental values, was defined for each environmental factor tested: temperature (15 or 25°C), water activity (0·75 or 0·85) and pH (3·5 or 5·5). A closed device was made, which maintained an equilibrium between water activity of the culture medium and atmospheric relative humidity during 25 days, to follow spore germination. The combined effects of temperature, water activity and pH on spore germination were studied by applying fa…
Impact of water activity of diverse media on spore germination of Aspergillus and Penicillium species
2010
International audience; The effects of water activity (aw) of diverse media i/ culture medium for sporogenesis, aw sp ii/ liquid spore suspension medium, aw su and iii/ medium for germination, aw ge, on the germination time tG of Aspergillus carbonarius, Aspergillus flavus, Penicillium chrysogenum and Penicillium expansum were assessed according to a screening matrix at 0.95 and 0.99 aw. It was shown that i/ reduced tGs were obtained at 0.95 aw sp except for P. expansum ii/ a significant effect of aw su on tG was demonstrated for A. carbonarius, P. chrysogenum and P. expansum iii/ the most important factor for controlling the germination time was the medium for germination except for A. car…
Indicateurs pour l'évaluation de l'impact de produits phytosanitaires sur la composante microbienne de la qualité biologique des sols
2011
National audience