scholarly journals Quantifying the Significance of Phage Attack on Starter Cultures: a Mechanistic Model for Population Dynamics of Phage and Their Hosts Isolated from Fermenting Sauerkraut

2006 ◽  
Vol 72 (6) ◽  
pp. 3908-3915 ◽  
Author(s):  
P. Mudgal ◽  
F. Breidt ◽  
S. R. Lubkin ◽  
K. P. Sandeep
Keyword(s):  
Leuconostoc Mesenteroides ◽  
Model Simulation ◽  
Mechanistic Model ◽  
Resistant Cell ◽  
Starter Cultures ◽  
Multiplicity Of Infection ◽  
Model Simulations ◽  
Host Interaction ◽  
Waste Salt ◽  
Kinetics Of

ABSTRACT We investigated the possibility of using starter cultures in sauerkraut fermentation and thereby reducing the quantity of salt used in the process. This, in turn, would reduce the amount of waste salt that would enter in our water resources. Phage, naturally present in sauerkraut fermentation, could potentially affect the starter cultures introduced. Thus, a mechanistic mathematical model was developed to quantify the growth kinetics of the phage and starter cultures. The model was validated by independent experiments with two Leuconostoc mesenteroides strains isolated from sauerkraut and their corresponding phage. Model simulations and experimental evidence showed the presence of phage-resistant cell populations in starter cultures which replaced phage-sensitive cells, even when the initial phage density (P 0) and multiplicity of infection (MOI) were low (P 0 < 1 � 103 PFU/ml; MOI < 10−4) in the MRS media. Based on the results of model simulation and parameter optimization, it was suggested that the kinetic parameters of phage-host interaction, especially the adsorption rate, vary with the initial phage and host densities and with time. The model was validated in MRS broth. Therefore, the effects of heterogeneity and other environmental factors, such as temperature and pH, should be considered to make the model applicable to commercial fermentations.

scholarly journals Dynamic modelling of the killing mechanism of action by virus-infected yeasts

2019 ◽  
Vol 16 (152) ◽  
pp. 20190064
Author(s):  
Sean Sheppard ◽  
Duygu Dikicioglu
Keyword(s):  
Large Scale ◽  
Mechanistic Model ◽  
Dynamic Modelling ◽  
Starter Cultures ◽  
Apoptotic Pathway ◽  
Toxic Activity ◽  
Killer Activity ◽  
Killer Yeasts ◽  
Death Kinetics ◽  
Kinetics Of

Killer yeasts are microorganisms, which can produce and secrete proteinaceous toxins, a characteristic gained via infection by a virus. These toxins are able to kill sensitive cells of the same or a related species. From a biotechnological perspective, killer yeasts are beneficial due to their antifungal/antimicrobial activity, but also regarded as problematic for large-scale fermentation processes, whereby those yeasts would kill starter cultures species and lead to stuck fermentations. Here, we propose a mechanistic model of the toxin-binding kinetics pertaining to the killer population coupled with the toxin-induced death kinetics of the sensitive population to study toxic action. The dynamic model captured the transient toxic activity starting from the introduction of killer cells into the culture at the time of inoculation through to induced cell death. The kinetics of K1/K2 activity via its primary pathway of toxicity was 5.5 times faster than its activity at low concentration inducing the apoptotic pathway in sensitive cells. Conversely, we showed that the primary pathway for K28 was approximately three times slower than its equivalent apoptotic pathway, indicating the particular relevance of K28 in biotechnological applications where the toxin concentration is rarely above those limits to trigger the primary pathway of killer activity.

scholarly journals Understanding the killing mechanism of action by virus-infected yeasts

2018 ◽  
Author(s):  
Sean Sheppard ◽  
Duygu Dikicioglu
Keyword(s):  
Large Scale ◽  
Deterministic Model ◽  
Mechanistic Model ◽  
Starter Cultures ◽  
Apoptotic Pathway ◽  
Toxic Activity ◽  
Killer Activity ◽  
Killer Yeasts ◽  
Death Kinetics ◽  
Kinetics Of

AbstractKiller yeasts are microorganisms, which can produce and secrete proteinaceous toxins, a characteristic gainedviainfection by a virus. These toxins are able to kill sensitive cells of the same or a related species. From a biotechnological perspective, killer yeasts have been considered as beneficial due to their antifungal/antimicrobial activity, but also regarded as problematic for large-scale fermentation processes, whereby those yeasts would kill species off starter cultures and lead to stuck fermentations. Here, we propose a mechanistic model of the toxin-binding kinetics pertaining to the killer population coupled with the toxin-induced death kinetics of the sensitive population to study toxic actionin silico. Our deterministic model explains how killerSaccharomyces cerevisiaecells distress and consequently kill the sensitive members of the species, accounting for the K1, K2 and K28 toxin mode of action at high or low concentrations. The dynamic model captured the transient toxic activity starting from the introduction of killer cells into the culture at the time of inoculation through to induced cell death, and allowed us to gain novel insight on these mechanisms. The kinetics of K1/K2 activityviaits primary pathway of toxicity was 5.5 times faster than its activity at low concentration inducing the apoptotic pathway in sensitive cells. Conversely, we showed that the primary pathway for K28 was approximately 3 times slower than its equivalent apoptotic pathway, indicating the particular relevance of K28 in biotechnological applications where the toxin concentration is rarely above those limits to trigger the primary pathway of killer activity.

Polymerization Kinetics of Wheat Gluten upon Thermosetting. A Mechanistic Model

2002 ◽  
Vol 50 (21) ◽  
pp. 5947-5954 ◽  
Author(s):  
Sandra Domenek ◽  
Marie-Hélène Morel ◽  
Joëlle Bonicel ◽  
Stéphane Guilbert
Keyword(s):  
Mechanistic Model ◽  
Wheat Gluten ◽  
Polymerization Kinetics ◽  
Kinetics Of

scholarly journals WRF Model Simulations of the Influence of the Athabasca Oil Sands Development on Convective Storms

2018 ◽  
Vol 22 (3) ◽  
pp. 1-25 ◽  
Author(s):  
Daniel Brown ◽  
Gerhard Reuter
Keyword(s):  
Land Surface ◽  
Oil Sands ◽  
Waste Heat ◽  
Model Simulation ◽  
Wrf Model ◽  
Initiation Time ◽  
Athabasca Oil Sands ◽  
Model Simulations ◽  
Surface Disturbance

Abstract The Athabasca oil sands development has created a land surface disturbance of almost 900 km2 in northeastern Alberta. Both through industrial processes and the removal of boreal forest vegetation, this surface disturbance impacts meteorology in the vicinity by releasing waste heat, raising the surface temperature, and lowering the surface humidity. To investigate the effects of the Athabasca oil sands development on thunderstorm intensity, initiation time, and duration, the Weather Research and Forecasting (WRF) Model was employed to simulate the effect of the surface disturbance on atmospheric conditions on 10 case study days. The results suggested the oil sands surface disturbance was not associated with substantial increases in thunderstorm intensity on any of the case study days. On two case study days, however, the WRF Model simulations differed substantially from the observed meteorological conditions and only approached the observations when the oil sands surface disturbance was included in the model simulation. Including the oil sands surface disturbance in the model simulations resulted in thunderstorm initiation about 2 h earlier and increased thunderstorm duration. Data from commercial aircraft showed that the 850–500-mb temperature difference was greater than 30°C (very unstable) only on these 2 days. Such cases are sufficiently rare that they are not expected to affect the overall thunderstorm climatology. Still, in these very unstable cases, the oil sands development appears to have a significant effect on thunderstorm initiation time and duration.

A mechanistic model for swelling kinetics of waxy maize starch suspension

2018 ◽  
Vol 222 ◽  
pp. 237-249 ◽  
Author(s):  
Gnana Prasuna Desam ◽  
Jinsha Li ◽  
Guibing Chen ◽  
Osvaldo Campanella ◽  
Ganesan Narsimhan
Keyword(s):  
Mechanistic Model ◽  
Swelling Kinetics ◽  
Maize Starch ◽  
Waxy Maize ◽  
Kinetics Of

Limitation of the Rate of Ribulosebisphosphate Carboxylase Activation by Carbamylation and Ribulosebisphosphate Carboxylase Activase Activity: Development and Tests of a Mechanistic Model

1996 ◽  
Vol 23 (2) ◽  
pp. 141 ◽  
Author(s):  
IE Woodrow ◽  
ME Kelly ◽  
KA Mott
Keyword(s):  
Mechanistic Model ◽  
Large Subunit ◽  
Intercellular Co2 Concentration ◽  
Rubisco Activase ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Bisphosphate Carboxylase ◽  
Ribulosebisphosphate Carboxylase ◽  
Kinetics Of ◽  
Rubisco Activation

A mechanistically-based model of light-mediated activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is developed. The model describes the kinetics of Rubisco activation following a relatively rapid increase in photon flux density (PPFD) from an initially low level. Underlying the model is the assumption that there are two slow processes that could potentially limit the rate of light-mediated Rubisco activation. These processes are the addition of the activator CO2 to the large subunit of Rubisco, which is accompanied by a conformational change in the enzyme (carbamylation), and activase-mediated removal of ribulose 1,5-bisphosphate from the inactive form of the enzyme. The contribution of these slow processes to the overall activation kinetics of Rubisco was resolved by measuring Rubisco activation in whole spinach leaves using non-steady-state CO2 exchange. It was found that when the change in PPFD was relatively small and a correspondingly small proportion of the Rubisco pool was activated, the kinetics of activation were highly sensitive to the intercellular CO2 concentration (ci). The apparent rate constant for activation under these conditions was found to be similar to that for the carbamylation of purified spinach Rubisco. When the change in PPFD and the proportion of Rubisco activated was relatively large, however, the kinetics of Rubisco activation were almost completely CO2 insensitive and were consistent with those of an enzyme-catalysed reaction. It is suggested that (1) CO2-insensitive activation reflects the operation of Rubisco activase and (2) the increasing CO2 sensitivity seen as the change in PPFD decreases reflects a transition to limitation by carbamylation.

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