Interactive Effects of Temperature, Initial pH, Sodium Chloride, and Sodium Pyrophosphate on the Growth Kinetics of Clostridium perfringens†

1996 ◽  
Vol 59 (9) ◽  
pp. 963-968 ◽  
Author(s):  
VIJAY K. JUNEJA ◽  
BENNE S. MARMER ◽  
JOHN G. PHILLIPS ◽  
SAMUEL A. PALUMBO
Keyword(s):  
Sodium Chloride ◽  
Growth Kinetics ◽  
Generation Time ◽  
Interactive Effects ◽  
Sodium Pyrophosphate ◽  
Lag Phase ◽  
Phase Duration ◽  
Initial Ph ◽  
Effects Of Temperature ◽  
Kinetics Of

The interactive effects of temperature (12 to 42°C), initial pH (5.5 to 7), sodium chloride (0 to 3%) and sodium pyrophosphate concentrations (0 to 0.3%) on the growth in Trypticase-peptone-glucose-yeast extract broth of a three-strain mixture of Clostridium perfringens vegetative cells were determined. The number of viable C. perfringens cells was determined at appropriate intervals by plating on tryptose-sulfite-cycloserine agar. Growth data were analyzed by the Gompertz equation; the gompertz B and M parameters were then used to calculate lag-phase duration, exponential growth rate, generation time, and maximum population-density values. The data indicated that the growth kinetics of C. perfringens were dependent on the interaction of the four variables, particularly in regard to exponential growth rates and lag-phase durations. Cubic models based on the natural logarithm transformation of lag-phase duration and generation time were evaluated and appeared to adequately fit the data. The data suggest that sodium pyrophosphate can have significant bacteriostatic activity against C. perfringens and may provide processed meats with a degree of protection against this microorganism, particularly if employed in conjunction with a combination of acidic pH, high salt concentrations, and adequate refrigeration.

Growth kinetics ofStaphylococcus aureuson Brie and Camembert cheeses

2014 ◽  
Vol 81 (2) ◽  
pp. 252-256 ◽  
Author(s):  
Heeyoung Lee ◽  
Kyungmi Kim ◽  
Soomin Lee ◽  
Minkyung Han ◽  
Yohan Yoon
Keyword(s):  
Growth Kinetics ◽  
Storage Temperature ◽  
Model Performance ◽  
Lag Phase ◽  
Square Root ◽  
Growth Data ◽  
Phase Duration ◽  
Mannitol Salt Agar ◽  
Staph Aureus ◽  
Kinetics Of

In this study, we developed mathematical models to describe the growth kinetics ofStaphylococcus aureuson natural cheeses. A five-strain mixture ofStaph. aureuswas inoculated onto 15 g of Brie and Camembert cheeses at 4 log CFU/g. The samples were then stored at 4, 10, 15, 25, and 30 °C for 2–60 d, with a different storage time being used for each temperature. Total bacterial andStaph. aureuscells were enumerated on tryptic soy agar and mannitol salt agar, respectively. The Baranyi model was fitted to the growth data ofStaph. aureusto calculate kinetic parameters such as the maximum growth rate in log CFU units (rmax; log CFU/g/h) and the lag phase duration (λ; h). The effects of temperature on the square root ofrmaxand on the natural logarithm of λ were modelled in the second stage (secondary model). Independent experimental data (observed data) were compared with prediction and the respective root mean square error compared with theRMSEof the fit on the original data, as a measure of model performance. The total growth of bacteria was observed at 10, 15, 25, and 30 °C on both cheeses. Thermaxvalues increased with storage temperature (P<0·05), but a significant effect of storage temperature on λ values was only observed between 4 and 15 °C (P<0·05). The square root model and linear equation were found to be appropriate for description of the effect of storage temperature on growth kinetics (R2=0·894–0·983). Our results indicate that the models developed in this study should be useful for describing the growth kinetics ofStaph. aureuson Brie and Camembert cheeses.

scholarly journals Quantitative Interaction Effects of Carbon Dioxide, Sodium Chloride, and Sodium Nitrite on Neurotoxin Gene Expression in Nonproteolytic Clostridium botulinum Type B

2004 ◽  
Vol 70 (5) ◽  
pp. 2928-2934 ◽  
Author(s):  
Maria Lövenklev ◽  
Ingrid Artin ◽  
Oskar Hagberg ◽  
Elisabeth Borch ◽  
Elisabet Holst ◽  
...  
Keyword(s):  
Gene Expression ◽  
Carbon Dioxide ◽  
Growth Rate ◽  
Sodium Chloride ◽  
Optical Density ◽  
Sodium Nitrite ◽  
Clostridium Botulinum ◽  
Lag Phase ◽  
Type B ◽  
Phase Duration

ABSTRACT The effects of carbon dioxide, sodium chloride, and sodium nitrite on type B botulinum neurotoxin (BoNT/B) gene (cntB) expression in nonproteolytic Clostridium botulinum were investigated in a tryptone-peptone-yeast extract (TPY) medium. Various concentrations of these selected food preservatives were studied by using a complete factorial design in order to quantitatively study interaction effects, as well as main effects, on the following responses: lag phase duration (LPD), growth rate, relative cntB expression, and extracellular BoNT/B production. Multiple linear regression was used to set up six statistical models to quantify and predict these responses. All combinations of NaCl and NaNO2 in the growth medium resulted in a prolonged lag phase duration and in a reduction in the specific growth rate. In contrast, the relative BoNT/B gene expression was unchanged, as determined by the cntB-specific quantitative reverse transcription-PCR method. This was confirmed when we measured the extracellular BoNT/B concentration by an enzyme-linked immunosorbent assay. CO2 was found to have a major effect on gene expression when the cntB mRNA levels were monitored in the mid-exponential, late exponential, and late stationary growth phases. The expression of cntB relative to the expression of the 16S rRNA gene was stimulated by an elevated CO2 concentration; the cntB mRNA level was fivefold greater in a 70% CO2 atmosphere than in a 10% CO2 atmosphere. These findings were also confirmed when we analyzed the extracellular BoNT/B concentration; we found that the concentrations were 27 ng · ml−1 · unit of optical density−1 in the 10% CO2 atmosphere and 126 ng · ml−1 · unit of optical density−1 in the 70% CO2 atmosphere.

Validation and Analysis of Modeled Predictions of Growth of Bacillus cereus Spores in Boiled Rice

2000 ◽  
Vol 63 (2) ◽  
pp. 268-272 ◽  
Author(s):  
DANA M. McELROY ◽  
LEE-ANN JAYKUS ◽  
PEGGY M. FOEGEDING
Keyword(s):  
Growth Rate ◽  
Bacillus Cereus ◽  
Exponential Growth ◽  
Generation Time ◽  
Time Lag ◽  
Lag Phase ◽  
Exponential Growth Rate ◽  
Phase Duration ◽  
Margin Of Safety ◽  
Fail Safe

The growth of psychrotrophic Bacillus cereus 404 from spores in boiled rice was examined experimentally at 15, 20, and 30°C. Using the Gompertz function, observed growth was modeled, and these kinetic values were compared with kinetic values for the growth of mesophilic vegetative cells as predicted by the U.S. Department of Agriculture's Pathogen Modeling Program, version 5.1. An analysis of variance indicated no statistically significant difference between observed and predicted values. A graphical comparison of kinetic values demonstrated that modeled predictions were “fail safe” for generation time and exponential growth rate at all temperatures. The model also was fail safe for lag-phase duration at 20 and 30°C but not at l5°C. Bias factors of 0.55, 0.82, and 1.82 for generation time, lag-phase duration, and exponential growth rate, respectively, indicated that the model generally was fail safe and hence provided a margin of safety in its growth predictions. Accuracy factors of 1.82, 1.60, and 1.82 for generation time, lag-phase duration, and exponential growth rate, respectively, quantitatively demonstrated the degree of difference between predicted and observed values. Although the Pathogen Modeling Program produced reasonably accurate predictions of the growth of psychrotrophic B. cereus from spores in boiled rice, the margin of safety provided by the model may be more conservative than desired for some applications. It is recommended that if microbial growth modeling is to be applied to any food safety or processing situation, it is best to validate the model before use. Once experimental data are gathered, graphical and quantitative methods of analysis can be useful tools for evaluating specific trends in model prediction and identifying important deviations between predicted and observed data.

scholarly journals Substantiation of the sell-by date of food products

2020 ◽  
Vol 52 (1) ◽  
pp. 59-63
Author(s):  
S.M. Kuzminskiy ◽  
T.V. Adamchuk ◽  
О.М. Holinko ◽  
N.P. Levytska
Keyword(s):  
Food Products ◽  
Storage Conditions ◽  
Lag Phase ◽  
Contamination Level ◽  
Second Phase ◽  
Phase Duration ◽  
Normative Documents ◽  
Culture Development ◽  
Storage Distribution ◽  
Kinetics Of

Objective of the Work. The overview of current methodical approaches for experimental substantiation of the sell-by date of food products. Methods and Materials. Data analysis of scientific literature and normative documents on methods of substantiation of the sell-by date of food products. Results and Discussion. Sell-by date is a period since product’s manufacture, during which it maintains its safety and quality (including nutritional value) within reasonably foreseeable conditions of storage, distribution and consumption. In the case of new products (recipes) introduction it is necessary to review the sell-by date, and its extending as the need arises. The main aspects of microbiological substantiation of the sell-by date of food products are considered. The identification of microbial hazard for particular product is the first phase of the work. The second phase of the work is to determine the kinetic parameters of precise microorganism’s accumulation to maximum permitted level within regulated and aggravated conditions of product’s storage. Conclusions. In the process of microbiological substantiation of the sell-by date of food products it should be taken into consideration the presence of leading pathogen and causative microorganisms of microbial spoilage, the initial contamination level, the lag phase duration of germ culture development, variations between strains, the kinetics of microorganisms’ accumulation within the product in real and aggravated storage conditions, the indetermination connected with biological nature of microorganisms and their inhomogeneous allocation within the product, the limitation for shortcut research methods (if applicable). The decision rule should be based on the consumer’s risk concept. Key Words: food products, sell-by date, substantiation, microbiological indicators.

Modelling the effects of temperature and osmotic shifts on the growth kinetics of Bacillus weihenstephanensis in broth and food products

2012 ◽  
Vol 158 (1) ◽  
pp. 36-41 ◽  
Author(s):  
V. Antolinos ◽  
M. Muñoz-Cuevas ◽  
M. Ros-Chumillas ◽  
P.M. Periago ◽  
P.S. Fernández ◽  
...  
Keyword(s):  
Growth Kinetics ◽  
Food Products ◽  
Bacillus Weihenstephanensis ◽  
Effects Of Temperature ◽  
Kinetics Of

scholarly journals Chemical Forms of Selenium in the Metal-Resistant Bacterium Ralstonia metallidurans CH34 Exposed to Selenite and Selenate

2005 ◽  
Vol 71 (5) ◽  
pp. 2331-2337 ◽  
Author(s):  
Géraldine Sarret ◽  
Laure Avoscan ◽  
Marie Carrière ◽  
Richard Collins ◽  
Nicolas Geoffroy ◽  
...  
Keyword(s):  
Transformation Product ◽  
Lag Phase ◽  
Elemental Selenium ◽  
Experimental Conditions ◽  
Phase Duration ◽  
Contact Exposure ◽  
Ralstonia Metallidurans ◽  
A Minor ◽  
X Ray Absorption ◽  
Kinetics Of

ABSTRACT Ralstonia metallidurans CH34, a soil bacterium resistant to a variety of metals, is known to reduce selenite to intracellular granules of elemental selenium (Se0). We have studied the kinetics of selenite (SeIV) and selenate (SeVI) accumulation and used X-ray absorption spectroscopy to identify the accumulated form of selenate, as well as possible chemical intermediates during the transformation of these two oxyanions. When introduced during the lag phase, the presence of selenite increased the duration of this phase, as previously observed. Selenite introduction was followed by a period of slow uptake, during which the bacteria contained Se0 and alkyl selenide in equivalent proportions. This suggests that two reactions with similar kinetics take place: an assimilatory pathway leading to alkyl selenide and a slow detoxification pathway leading to Se0. Subsequently, selenite uptake strongly increased (up to 340 mg Se per g of proteins) and Se0 was the predominant transformation product, suggesting an activation of selenite transport and reduction systems after several hours of contact. Exposure to selenate did not induce an increase in the lag phase duration, and the bacteria accumulated approximately 25-fold less Se than when exposed to selenite. SeIV was detected as a transient species in the first 12 h after selenate introduction, Se0 also occurred as a minor species, and the major accumulated form was alkyl selenide. Thus, in the present experimental conditions, selenate mostly follows an assimilatory pathway and the reduction pathway is not activated upon selenate exposure. These results show that R. metallidurans CH34 may be suitable for the remediation of selenite-, but not selenate-, contaminated environments.

scholarly journals AUTORADIOGRAPHIC STUDIES ON THE IMMUNE RESPONSE

1962 ◽  
Vol 115 (1) ◽  
pp. 209-230 ◽  
Author(s):  
G. J. V. Nossal ◽  
O. Mäkelä
Keyword(s):  
Immune Response ◽  
Growth Kinetics ◽  
Generation Time ◽  
Doubling Time ◽  
Plasma Cells ◽  
Single Pulse ◽  
Tracer Injection ◽  
Autoradiographic Labeling ◽  
Kinetics Of ◽  
Stimulation Of

The origin and growth kinetics of plasma cells have been investigated using autoradiographic labeling techniques. Rats immunized once with Salmonella flagella were given a single pulse of H3-thymidine 4 or 40 weeks later. 2 hours after the tracer injection, they received a secondary antigenic stimulus. When animals were sacrificed immediately only certain cells from the resting primarily immunized lymph nodes, notably large and medium lymphocytes, were labeled. Subsequent to secondary stimulation, animals were killed at intervals; nearly all the plasma cells formed within the next 5 to 6 days were labeled. They must thus have been the progeny of cells already capable of synthesizing DNA in resting nodes, most probably of large lymphocytes. Plasmacytopoiesis began with little or no lag following secondary immunization, and the number of labeled plasma cells rose exponentially between the 2nd and 4th day, with a doubling time of about 12 hours. Studies of mean grain counts of primitive cells also suggested that the generation time of plasmablasts was 12 hours or less. The hypothesis was proposed that immunological memory depended on the persistence, following primary stimulation, of a continuously dividing stem line of primitive lymphocytes, reactive at all times to further antigenic stimulation.

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