Validation of a model describing the effects of temperature and water activity on the growth of psychrotrophic pseudomonads

Health benefits of dietary phytochemicals have been suggested in recent years. Among 1000s of different compounds, Betalains, which occur in vegetables of the Cariophyllalae order (cactus pear fruits and red beet), have been considered because of reducing power and potential to affect redox-modulated cellular processes. The antioxidant power of Betalains is strictly due to the dissociation rate of the acid moieties present in all the molecules of this family of phytochemicals. Experimentally, only the pK avalues of betanin were determined. Recently, it was evidenced it was evidenced as the acid dissociation, at different environmental pHs, affects on its electron-donating capacity, and further on its free radical scavenging power. The identical correlation was studied on another Betalains family compound, Betalamic Acid. Experimental evidences showed that the free radical scavenging capacity of this compound drastically decreases at pH [ 5, but pK a values were experimentally not measured. With the aim to justify the Betalamic Acid behavior as free radical scavenger, in this paper we tried to predict in silico the pK a values by means different approaches. Starting from the known experimental pK a s of acid compounds, both phytochemicals and small organic, two empirical approaches and quantum-mechanical calculation were compared to give reliable prediction of the pK a s of Betalamic Acid.Results by means these computational approaches are consistent with the experimental evidences. As shown herein, in silico, the totally dissociated species, at the experimental pH [ 5 in solution, is predominant, exploiting the higher electron-donating capability (HOMO energy). Therefore, the computational estimated pK a values of Betalamic Acid resulted very reliable.

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“…lower) than 1 indicates that the model predicts, on average, pK a values higher (resp. lower) than experimental ones [39,40].…”

Section: Indices Of Performances Of Modelsmentioning

confidence: 55%

“…The bias factor (B f ) and the accuracy factor (A f ) are two indices of performance that allow to compare the goodness-of-fit of challenging models [39,40].…”

Section: Indices Of Performances Of Modelsmentioning

confidence: 99%

Theoretical Determination of the pK a Values of Betalamic Acid Related to the Free Radical Scavenger Capacity: Comparison Between Empirical and Quantum Chemical Methods

Tutone

Lauria

Almerico

2015

Interdiscip Sci Comput Life Sci

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“…The validation was based on eight independent fermentations performed under a free pH course which were not included in the construction of the model, namely: 20°C, pH 0 Validation parameters mean square error (MSE), correlation coefficient (r 2 ), bias factor, and accuracy factor were calculated as described elsewhere (21,25). Briefly, the MSE is a measure of variability remaining, mainly due to systematic errors and biological variability.…”

Section: Methodsmentioning

confidence: 99%

“…The parameter k inact was a function of temperature and pH only, the kinetic coefficients K 0 , k 1 , and k 2 needed to calculate k inact (see equation 21) were estimated at 4 ϫ 10 Ϫ7 liters (g of CDM)…”

Section: Estimation Of Model Parameters (I) Modeling Of Cell Growthmentioning

confidence: 99%

A Combined Model To Predict the Functionality of the Bacteriocin-Producing Lactobacillus sakei Strain CTC 494

Leroy

Vuyst

2003

Appl Environ Microbiol

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The use of bacteriocin-producing lactic acid bacteria for improved food fermentation processes seems promising. However, lack of fundamental knowledge about the functionality of bacteriocin-producing strains under food fermentation conditions hampers their industrial use. Predictive microbiology or a mathematical estimation of microbial behavior in food ecosystems may help to overcome this problem. In this study, a combined model was developed that was able to estimate, from a given initial situation of temperature, pH, and nutrient availability, the growth and self-inhibition dynamics of a bacteriocin-producing Lactobacillus sakei CTC 494 culture in (modified) MRS broth. Moreover, the drop in pH induced by lactic acid production and the bacteriocin activity toward Listeria as an indicator organism were modeled. Self-inhibition was due to the depletion of nutrients as well as to the production of lactic acid. Lactic acid production resulted in a pH drop, an accumulation of toxic undissociated lactic acid molecules, and a shift in the dissociation degree of the growth-inhibiting buffer components. The model was validated experimentally.Predictive microbiology is frequently applied in the area of food microbiology to develop and apply mathematical models to simulate the responses of undesirable microorganisms to specified environmental variables (8,10,18,22,24). In the meat industry, for example, several of these models have been successfully developed in the area of risk assessment and microbial shelf-life studies, focusing on the outgrowth, toxin production, or inactivation of harmful microorganisms (1,19).Recently, there has also been interest in the modeling of beneficial microorganisms deliberately added to food to produce a desired effect. For instance, modeling of the functionality of bacteriocin-producing lactic acid bacteria seems promising for the prediction of bacteriocin bioactivity in foods (12). Bacteriocins are, in general, small peptides or proteins with an antibacterial mode of action towards strains that are closely related to the producer organism, often encompassing spoilage bacteria and food-borne pathogens (6). Bacteriocin-producing strains may be applied as starter cultures or cocultures in the food fermentation industry to obtain more competitive strains and to reduce the risk of the outgrowth of such undesirable bacteria (5). However, some doubt about their industrial application as novel functional starter cultures remains. Strains that display bacteriocin activity under laboratory conditions do not necessarily perform well once they are applied in the food under fermentation conditions (20). Modeling may help to clarify how specific conditions that prevail in the food environment during fermentation influence the performance of bacteriocin-producing starters (16).As an example, Lactobacillus sakei CTC 494 is of particular interest as a functional bacteriocin-producing starter for sausage fermentation (2, 11). In previous studies, the effects of constant temperature and pH (13), the prese...

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“…The bias factor (B f ) and the accuracy factor (A f ) are two indices of performance that enable to compare the goodness-of-fit of competing models [24,25].…”

Section: Indices Of Performance Of Modelsmentioning

confidence: 99%

Comparison of PredictedpK_aValues for Some Amino-Acids, Dipeptides and Tripeptides, Using COSMO-RS, ChemAxon and ACD/Labs Methods

Toure

Dussap

Lebert

2013

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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Re´sume´-Comparaison des valeurs de pK a de quelques acides amine´s, dipeptides et tripeptides, pre´-dites en utilisant les me´thodes COSMO-RS, ChemAxon et ACD/Labs -Les valeurs de constantes d'acidite´(pK a ) jouent un roˆle tre`s important, en particulier dans l'industrie alimentaire. Les proprie´te´s chimiques des mole´cules de´pendent significativement de leurs e´tats d'ionisation. La plupart des mole´cules sont capables de gagner et/ou perdre un proton dans les solutions aqueuses. Ce transfert de proton apparaıˆt la plupart du temps entre l'eau et un atome ionisable de la mole´-cule organique. La re´ponse de la mole´cule a`la protonation ou a`la de´protonation de´pend significativement du site concerne´par le transfert de proton. La distribution partielle des charges dans la mole´cule varie e´galement en fonction des sites actifs pour la protonation du couple acide/base. Par conse´quent on peut l'utiliser pour de´terminer le pK a d'une mole´cule. Dans un premier temps, nous avons utilise´la me´thode COSMO-RS, une combinaison du mode`le de solvatation die´lectrique (COSMO) et d'un traitement de thermodynamique statistique pour des solvants plus re´els (RS), pour pre´dire les constantes de dissociation de 50 mole´cules environ (des acides amine´s, des dipeptides et des tripeptides). Les re´sultats de pK a obtenus ont e´te´com-pare´s aux valeurs expe´rimentales, ainsi qu'aux valeurs de pK a pre´dites par deux autres me´thodes. Nous avons utilise´respectivement la me´thode ChemAxon, utilisant un programme base´sur le calcul des charges partielles des atomes d'une mole´cule, et la me´thode ACD/Labs qui permet de de´terminer des valeurs de pK a pour chaque centre de dissociation en conside´rant que le reste de la mole´cule est neutre, en utilisant une base de donne´es internes contenant des structures chimiques ainsi que leurs valeurs expe´rimentales de pK a . L'e´cart-type moyen des valeurs pre´dites vaut respectivement 0,596 pour la me´thode COSMO-RS, 0,445 pour la me´thode ChemAxon et 0,490 pour la me´thode ACD/Labs. Au vu de ces re´sultats, la me´thode COSMO-RS apparaıˆt comme une me´thode prometteuse pour pre´dire les valeurs de pK a de mole´cules d'inte´reˆt dans l'industrie alimentaire pour lesquelles peu de donne´es de pK a sont disponibles comme les peptides, d'autant plus que les me´thodes ACD/Labs et ChemAxon ont e´teṕ arame´tre´es en utilisant un grand nombre de donne´es expe´rimentales (incluant certaines des mole´cules e´tudie´es dans cet article) alors que la me´thode COSMO-RS a e´te´utilise´e d'un point de vue purement pre´dictif. L'objectif final de cette e´tude est d'utiliser ces valeurs de pK a dans un mode`le thermodynamique pre´dictif pour des produits d'inte´reˆt dans l'industrie alimentaire. Pour ce faire, les effets de

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Validation of a model describing the effects of temperature and water activity on the growth of psychrotrophic pseudomonads

Cited by 66 publications

References 21 publications

Theoretical Determination of the pK a Values of Betalamic Acid Related to the Free Radical Scavenger Capacity: Comparison Between Empirical and Quantum Chemical Methods

Theoretical Determination of the pK a Values of Betalamic Acid Related to the Free Radical Scavenger Capacity: Comparison Between Empirical and Quantum Chemical Methods

A Combined Model To Predict the Functionality of the Bacteriocin-Producing Lactobacillus sakei Strain CTC 494

Comparison of PredictedpK_aValues for Some Amino-Acids, Dipeptides and Tripeptides, Using COSMO-RS, ChemAxon and ACD/Labs Methods

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Validation of a model describing the effects of temperature and water activity on the growth of psychrotrophic pseudomonads

Cited by 66 publications

References 21 publications

Theoretical Determination of the pK a Values of Betalamic Acid Related to the Free Radical Scavenger Capacity: Comparison Between Empirical and Quantum Chemical Methods

Theoretical Determination of the pK a Values of Betalamic Acid Related to the Free Radical Scavenger Capacity: Comparison Between Empirical and Quantum Chemical Methods

A Combined Model To Predict the Functionality of the Bacteriocin-Producing Lactobacillus sakei Strain CTC 494

Comparison of PredictedpKaValues for Some Amino-Acids, Dipeptides and Tripeptides, Using COSMO-RS, ChemAxon and ACD/Labs Methods

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Comparison of PredictedpK_aValues for Some Amino-Acids, Dipeptides and Tripeptides, Using COSMO-RS, ChemAxon and ACD/Labs Methods