scholarly journals Inhibitory Effects of Arginine on the Aggregation of Bovine Insulin

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Michael M. Varughese ◽  
Jay Newman
Keyword(s):  
Bovine Insulin ◽  
Insulin Concentration ◽  
Lag Phase ◽  
Aggregation Kinetics ◽  
Initial Growth ◽  
Inhibitory Effects ◽  
Phase Duration ◽  
Quench Temperature ◽  
Increasing Temperature ◽  
Kinetics Of

Static and dynamic light scattering were used to investigate the effects of L-arginine, commonly used to inhibit protein aggregation, on the initial aggregation kinetics of solutions of bovine insulin in 20% acetic acid and 0.1 M NaCl as a model system for amyloidosis. Measurements were made as a function of insulin concentration (0.5–2.0 mM), quench temperature (60–85°C), and arginine concentration (10–500 mM). Aggregation kinetics under all conditions had a lag phase, whose duration decreased with increasing temperature and with increasing insulin concentration but which increased by up to a factor of 8 with increasing added arginine. Further, the initial growth rate after the lag phase also slowed by up to a factor of about 20 in the presence of increasing concentrations of arginine. From the temperature dependence of the lag phase duration, we find that the nucleation activation energy doubles from to  kcal/mol in the presence of 500 mM arginine.

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.

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.

A Predictive Model for the Growth of Listeria monocytogenes in Commercial Blue Crab (Callinectes sapidus)

2017 ◽  
Vol 80 (11) ◽  
pp. 1872-1876
Author(s):  
Salina Parveen ◽  
Channel White ◽  
Mark L. Tamplin
Keyword(s):  
Listeria Monocytogenes ◽  
Blue Crab ◽  
Callinectes Sapidus ◽  
Lag Phase ◽  
Published Data ◽  
Predictive Tool ◽  
Phase Duration ◽  
Primary Model ◽  
Increasing Temperature ◽  
Crab Meat

ABSTRACT During the processing and handling of commercial blue crab (Callinectes sapidus), Listeria monocytogenes can potentially contaminate cooked meat and grow to hazardous levels. To manage this risk, predictive models are useful tools for designing and implementing preventive controls; however, no model specific for blue crab meat has been published or evaluated. In this study, a cocktail of L. monocytogenes strains was added to pasteurized blue crab meat, which was incubated at storage temperatures from 0 to 35°C. At selected time intervals, L. monocytogenes was enumerated by direct plating onto modified Oxford agar. A primary model was fitted to kinetic data to estimate the lag-phase duration (LPD) and growth rate (GR). Listeria monocytogenes replicated from 0 to 35°C, with GR ranging from 0.004 to 0.518 log CFU/h. Overall, the LPD decreased with increasing temperature, displaying a maximum value of 187 h at 0°C; however, this trend was not consistent. The LPD was not detected at 10°C, and it occurred inconsistently from trial to trial. A secondary GR model (R2 = 0.9892) for pasteurized crab meat was compared with the L. monocytogenes GR in fresh crab meat, demonstrating bias and accuracy factors of 0.98 and 1.36, respectively. The model estimates varied from other published data and models, especially at temperatures ≥5°C, supporting the need for a specific predictive tool for temperature deviations.

scholarly journals Behavior of Bacillus anthracis Strains Sterne and Ames K0610 in Sterile Raw Ground Beef

2007 ◽  
Vol 74 (4) ◽  
pp. 1111-1116 ◽  
Author(s):  
Mark L. Tamplin ◽  
Robert Phillips ◽  
Tod A. Stewart ◽  
John B. Luchansky ◽  
Lynda C. Kelley
Keyword(s):  
Growth Rate ◽  
Bacillus Anthracis ◽  
Elevated Temperatures ◽  
Stationary Phases ◽  
Ground Beef ◽  
Growth Patterns ◽  
Lag Phase ◽  
Phase Duration ◽  
Increasing Temperature ◽  
Storage Temperatures

ABSTRACT The behavior of Bacillus anthracis Sterne spores in sterile raw ground beef was measured at storage temperatures of 2 to 70°C, encompassing both bacterial growth and death. B. anthracis Sterne was weakly inactivated (−0.003 to −0.014 log10 CFU/h) at storage temperatures of 2 to 16°C and at temperatures greater than and equal to 45°C. Growth was observed from 17 to 44°C. At these intermediate temperatures, B. anthracis Sterne displayed growth patterns with lag, growth, and stationary phases. The lag phase duration decreased with increasing temperature and ranged from approximately 3 to 53 h. The growth rate increased with increasing temperature from 0.011 to 0.496 log10 CFU/h. Maximum population densities (MPDs) ranged from 5.9 to 7.9 log10 CFU/g. In addition, the fate of B. anthracis Ames K0610 was measured at 10, 15, 25, 30, 35, 40, and 70°C to compare its behavior with that of Sterne. There were no significant differences between the Ames and Sterne strains for both growth rate and lag time. However, the Ames strain displayed an MPD that was 1.0 to 1.6 times higher than that of the Sterne strain at 30, 35, and 40°C. Ames K0610 spores were rapidly inactivated at temperatures greater than or equal to 45°C. The inability of B. anthracis to grow between 2 and 16°C, a relatively low growth rate, and inactivation at elevated temperatures would likely reduce the risk for recommended ground-beef handling and preparation procedures.

Growth Variation Among Species and Strains of Listeria in Culture Broth

1994 ◽  
Vol 57 (9) ◽  
pp. 765-769 ◽  
Author(s):  
WERNER B. BARBOSA ◽  
LAURA CABEDO ◽  
HEIDI J. WEDERQUIST ◽  
JOHN N. SOFOS ◽  
GLENN R. SCHMIDT
Keyword(s):  
Growth Parameters ◽  
Phosphate Buffer Solution ◽  
Growth Curves ◽  
Culture Broth ◽  
Lag Phase ◽  
Gompertz Function ◽  
Buffer Solution ◽  
Phase Duration ◽  
Growth Variation ◽  
Increasing Temperature

Culture suspensions of 45 species and strains of Listeria were prepared in tryptic soy broth with 0.6% yeast extract (TSBYE) for 24 h at 37°C, and were then diluted with phosphate buffer solution and standardized to 0.10 ± 0.01 absorbance at 600 nm. Spectrophotometer tubes containing 5 ml of TSBYE (pH 7.2) were inoculated with 0.1 ml of the standardized cultures and incubated at 4, 10 or 37°C. Absorbance readings were taken during storage. Growth curves were fitted using the Gompertz function, and growth parameters were calculated. There were major differences in lag phase duration (LPD), generation time (GT) and exponential growth rate (EGR) among species and strains of Listeria tested. Values for LPD and GT decreased (P <0.05) with increasing temperature of incubation, while EGR and maximum population density (MPD) values increased. Lag phase duration and GT values at a given temperature were lower for Listeria monocytogenes compared to other Listeria spp. At 4°C, LPDs for L. monocytogenes strains ranged from 69.8 to 270.8 h. Of the L. monocytogenes cultures tested, strain Scott A had the longest average (209.8 ± 0.1) h LPD at 4°C. At l0°C, LPDs ranged from 36.5 to 68.9 h, with Scott A being again one of the strains with the longest average LPD (62.8 ± 0.7 h). At 37°C, LPDs ranged from 4.4 to 11.1 h. Variation was also observed in GT and EGR, especially at 4°C. Although there were major variations in growth parameters due to strain and temperature, no significant (P >0.05) trends were observed in average values among different serotypes of L. monocytogenes tested.

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.

Functional Fractionation of Platelets: Aggregation Kinetics and Glycoprotein Labeling of Differing Platelet Populations

1982 ◽  
Vol 48 (02) ◽  
pp. 211-216 ◽  
Author(s):  
V M Haver ◽  
A R L Gear
Keyword(s):  
Galactose Oxidase ◽  
Aggregation Kinetics ◽  
Maximal Rate ◽  
Membrane Glycoproteins ◽  
Whole Cells ◽  
Reversible Aggregation ◽  
Significant Difference ◽  
Small Doses ◽  
Major Loss ◽  
Kinetics Of

SummaryPlatelet heterogeneity has been studied with a technique called functional fractionation which employs gentle centrifugation to yield subpopulations (“reactive” and “less-reactive” platelets) after exposure to small doses of aggregating agent. Aggregation kinetics of the different platelet populations were investigated by quenched-flow aggregometry. The large, “reactive” platelets were more sensitive to ADP (Ka = 1.74 μM) than the smaller “less-reactive” platelets (Ka = 4.08 μM). However, their maximal rate of aggregation (Vmax, % of platelets aggregating per sec) of 23.3 was significantly lower than the “less-reactive” platelets (Vmax = 34.7). The “reactive” platelets had a 2.2 fold higher level of cyclic AMP.Platelet glycoproteins were labeled using the neuraminidase-galactose oxidase – [H3]-NaBH4 technique. When platelets were labeled after reversible aggregation, the “reactive” platelets showed a two-fold decrease in labeling efficiency (versus control platelets). However, examination of whole cells or membrane preparations from reversibly aggregated platelets revealed no significant difference in Coomassie or PAS (Schiff) staining.These results suggest that the large, “reactive” platelets are more sensitive to ADP but are not hyperaggregable in a kinetic sense. Reversible aggregation may cause a re-orientation of membrane glycoproteins that is apparently not characterized by a major loss of glycoprotein material.

scholarly journals Reciprocal hemizygosity analysis reveals that the Saccharomyces cerevisiae CGI121 gene affects lag time duration in synthetic grape must

2021 ◽  
Author(s):  
Runze Li ◽  
Rebecca C Deed
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Low Temperatures ◽  
Lag Time ◽  
Lag Phase ◽  
Phenotypic Traits ◽  
Time Duration ◽  
Phase Duration ◽  
Grape Must ◽  
The Impact ◽  
Reciprocal Hemizygosity Analysis

Abstract It is standard practice to ferment white wines at low temperatures (10-18 °C). However, low temperatures increase fermentation duration and risk of problem ferments, leading to significant costs. The lag duration at fermentation initiation is heavily impacted by temperature; therefore, identification of Saccharomyces cerevisiae genes influencing fermentation kinetics is of interest for winemaking. We selected 28 S. cerevisiae BY4743 single deletants, from a prior list of open reading frames (ORFs) mapped to quantitative trait loci (QTLs) on chromosomes VII and XIII, influencing the duration of fermentative lag time. Five BY4743 deletants, Δapt1, Δcgi121, Δclb6, Δrps17a, and Δvma21, differed significantly in their fermentative lag duration compared to BY4743 in synthetic grape must (SGM) at 15 °C, over 72 h. Fermentation at 12.5 °C for 528 h confirmed the longer lag times of BY4743 Δcgi121, Δrps17a, and Δvma21. These three candidate ORFs were deleted in S. cerevisiae RM11-1a and S288C to perform single reciprocal hemizygosity analysis (RHA). RHA hybrids and single deletants of RM11-1a and S288C were fermented at 12.5 °C in SGM and lag time measurements confirmed that the S288C allele of CGI121 on chromosome XIII, encoding a component of the EKC/KEOPS complex, increased fermentative lag phase duration. Nucleotide sequences of RM11-1a and S288C CGI121 alleles differed by only one synonymous nucleotide, suggesting that intron splicing, codon bias, or positional effects might be responsible for the impact on lag phase duration. This research demonstrates a new role of CGI121 and highlights the applicability of QTL analysis for investigating complex phenotypic traits in yeast.

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