scholarly journals Monod model is insufficient to explain biomass growth in nitrogen-limited yeast fermentation

2021 ◽  
Author(s):  
David Henriques ◽  
Eva Balsa-Canto
Keyword(s):  
Goodness Of Fit ◽  
Total Protein Content ◽  
Yeast Fermentation ◽  
Biomass Growth ◽  
Negative Consequences ◽  
Monod Model ◽  
Carbohydrate Accumulation ◽  
Biomass Formation ◽  
Fermentation Rate ◽  
Monod Equation

The yeast Saccharomyces cerevisiae is an essential microorganism in food biotechnology; particularly, in wine and beer making. During wine fermentation, yeasts transform sugars present in the grape juice into ethanol and carbon dioxide. The process occurs in batch conditions and is, for the most part, an anaerobic process. Previous studies linked limited-nitrogen conditions with problematic fermentations, with negative consequences for the performance of the process and the quality of the final product. It is, therefore, of the highest interest to anticipate such problems through mathematical models. Here we propose a model to explain fermentations under nitrogen-limited anaerobic conditions. We separated the biomass formation into two phases: growth and carbohydrate accumulation. Growth was modelled using the well-known Monod equation while carbohydrate accumulation was modelled by an empirical function, analogous to a proportional controller activated by the limitation of available nitrogen. We also proposed to formulate the fermentation rate as a function of the total protein content when relevant data are available. The final model was used to successfully explain experiments taken from the literature, performed under normal and nitrogen-limited conditions. Our results revealed that Monod model is insufficient to explain biomass formation kinetics in nitrogen-limited fermentations of S. cerevisiae . The goodness-of-fit of the herewith proposed model is superior to that of previously published models, offering the means to predict, and thus control fermentations. Importance: Problematic fermentations still occur in the winemaking industrial practise. Problems include sluggish rates of fermentation, which have been linked to insufficient levels of assimilable nitrogen. Data and relevant models can help anticipate poor fermentation performance. In this work, we proposed a model to predict biomass growth and fermentation rate under nitrogen-limited conditions and tested its performance with previously published experimental data. Our results show that the well-known Monod equation does not suffice to explain biomass formation.

scholarly journals Monod law is insufficient to explain biomass growth in nitrogen-limited yeast fermentation

2021 ◽  
Author(s):  
David Henriques ◽  
Eva Balsa-Canto
Keyword(s):  
Goodness Of Fit ◽  
Grape Juice ◽  
Total Protein Content ◽  
Yeast Fermentation ◽  
Biomass Growth ◽  
Negative Consequences ◽  
Carbohydrate Accumulation ◽  
Available Nitrogen ◽  
Biomass Formation ◽  
Fermentation Rate

ABSTRACTThe yeast Saccharomyces cerevisiae is an essential microorganism in food biotechnology; particularly, in wine and beer making. During wine fermentation, yeasts transform sugars present in the grape juice into ethanol and carbon dioxide. The process occurs in batch conditions and is, for the most part, an anaerobic process. Previous studies linked limited-nitrogen conditions with problematic fermentations, with negative consequences for the performance of the process and the quality of the final product. It is, therefore, of the highest interest to anticipate such problems through mathematical models. Here we propose a model to explain problematic fermentations under nitrogen-limited anaerobic conditions. We separated the biomass formation into two phases: growth and carbohydrate accumulation. Growth was modelled using the well-known Monod law while carbohydrate accumulation was modelled by an empirical function, analogous to a proportional controller activated by the limitation of available nitrogen. We also proposed to formulate the fermentation rate as a function of the total protein content when relevant data are available. The final model was used to successfully explain a series of experiments taken from the literature, performed under normal and nitrogen-limited conditions. Our results revealed that Monod law is insufficient to explain biomass formation kinetics in nitrogen-limited fermentations of S. cerevisiae. The goodness-of-fit of the herewith proposed model is superior to that of previously published models, offering the means to predict, and thus control, problematic fermentations.IMPORTANCEProblematic fermentations still occur in the winemaking industrial practise. Problems include sluggish rates of fermentation, which have been linked to insufficient levels of assimilable nitrogen. Data and relevant models can help anticipate poor fermentation performance. In this work, we proposed a model to predict biomass growth and fermentation rate under nitrogen-limited conditions and tested its performance with previously published experimental data. Our results show that the well-known Monod law does not suffice to explain biomass formation. A second term accounting for carbohydrate accumulation is required to predict successfully, and thus control, problematic fermentations.

scholarly journals Monod model is insufficient to explain biomass growth in nitrogen-limited yeast fermentation

2021 ◽  
Author(s):  
David Henriques ◽  
Eva Balsa-Canto
Keyword(s):  
Goodness Of Fit ◽  
Grape Juice ◽  
Total Protein Content ◽  
Yeast Fermentation ◽  
Negative Consequences ◽  
Monod Model ◽  
Carbohydrate Accumulation ◽  
Available Nitrogen ◽  
Biomass Formation ◽  
Monod Equation

The yeast Saccharomyces cerevisiae is an essential microorganism in food biotechnology; particularly, in wine and beer making. During wine fermentation, yeasts transform sugars present in the grape juice into ethanol and carbon dioxide. The process occurs in batch conditions and is, for the most part, an anaerobic process. Previous studies linked limited-nitrogen conditions with problematic fermentations, with negative consequences for the performance of the process and the quality of the final product. It is, therefore, of the highest interest to anticipate such problems through mathematical models. Here we propose a model to explain fermentations under nitrogen-limited anaerobic conditions. We separated the biomass formation into two phases: growth and carbohydrate accumulation. Growth was modelled using the well-known Monod equation while carbohydrate accumulation was modelled by an empirical function, analogous to a proportional controller activated by the limitation of available nitrogen. We also proposed to formulate the fermentation rate as a function of the total protein content when relevant data are available. The final model was used to successfully explain experiments taken from the literature, performed under normal and nitrogen-limited conditions. Our results revealed that Monod model is insufficient to explain biomass formation kinetics in nitrogen-limited fermentations of S. cerevisiae. The goodness-of-fit of the herewith proposed model is superior to that of previously published models, offering the means to predict, and thus control fermentations.

scholarly journals Statistical Modeling of Determinants of Anemia Prevalence among Children Aged 6–59 Months in Nigeria: A Cross-Sectional Study

Anemia ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Ropo Ebenezer Ogunsakin ◽  
Bayowa Teniola Babalola ◽  
Oludare Akinyemi
Keyword(s):  
Public Health ◽  
Logistic Regression ◽  
Regression Models ◽  
Goodness Of Fit ◽  
Household Wealth ◽  
Demographic And Health Surveys ◽  
Negative Consequences ◽  
Logistic Regression Models ◽  
Childhood Anemia ◽  
Prevalence Of Anemia

Objective. Childhood anemia remains a significant public health challenge in developing countries, and it has negative consequences on the growth of the children. Therefore, it is essential to identify the determinants of childhood anemia, as these will help in formulating appropriate health policies in order to meet the United Nations MDG goal. This study aims to assess and model the determinants of the prevalence of anemia among children aged 6–59 months in Nigeria. To accomplish the aims of the study, the authors applied single-level and multilevel binary logistic regression models. Methods. To measure the relative impact of individual and household-level factors for childhood anemia among children aged 6–59 months, this study undertakes data from Nigeria Demographic and Health Surveys with both binary logistic and multilevel logistic regression models. The fit of the model was assessed by Hosmer–Lemeshow goodness-of-fit, variance inflation factor, and likelihood ratio tests. Results. The study established that about 67.01% of the children were anemic and identified sex of children, mother’s education, religion, household wealth status, total children ever born, age of children, place of residence, and region to have a statistical significant effect on the prevalence of anemia. The adjusted odds ratio (aOR) for anemia was 0.56 (95% CI = 0.50, 0.63) in children aged from 24 to 42 months and 0.40 (95% CI = 0.36, 0.45) in children aged from 43 to 59 months. Also, children who reside in certain geographical-political zones of Nigeria are associated with increased childhood anemia. Conclusion. This study has highlighted the high prevalence of childhood anemia in Nigeria and indicated the need to improve mothers’ education and regional variations. Findings from this study can help policymakers and public health institutions to map out programs targeting these regions as a measure of tackling the prevalence of anemia among the Nigerian populace.

Model of Biomass Concentration in Membrane Filtration Recycling Systems Subject to Single Substrate-Limited Growth Kinetics

2000 ◽  
Author(s):  
Steven J. Skerlos ◽  
N. Rajagopalan ◽  
Richard E. DeVor ◽  
Shiv G. Kapoor ◽  
Robert A. Sanford
Keyword(s):  
Membrane Filtration ◽  
Microbial Growth ◽  
Nonlinear Differential Equations ◽  
Biomass Concentration ◽  
Metalworking Fluids ◽  
Biomass Growth ◽  
Growth Data ◽  
Monod Equation ◽  
Single Substrate ◽  
Rejection Coefficient

Abstract Membrane filtration has the ability to limit microbiological growth in metalworking fluids (MWFs). To appropriately design and size a membrane filtration system for this application, the rate of microbial removal must be assessed relative to microbial population (biomass) growth. This research utilizes the Monod Equation describing biomass growth limited by a single substrate to evaluate if biomass levels can be maintained below a prescribed level in a perfectly mixed MWF system. The model for predicting biomass in the MWF system is obtained by numerical solution of a system of coupled nonlinear differential equations. The model solution permits membrane filtration design and sizing decisions based on microbial growth data specific to MWF chemistries, microbial species, and manufacturing facilities. It is revealed that the ratio of the filtration rate to the MWF volume must exceed the maximum specific growth rate of microorganisms to control biomass concentrations in the system under arbitrary initial substrate and contamination levels. The control of microbial growth in the system also requires that appropriate cleaning intervals be selected for the membrane filtration process tank. The microbial rejection coefficient, which is characteristic to a given membrane, has a dominant impact on the required cleaning interval.

scholarly journals Stoic beliefs and health: development and preliminary validation of the Pathak-Wieten Stoicism Ideology Scale

BMJ Open ◽  
2017 ◽  
Vol 7 (11) ◽  
pp. e015137 ◽  
Author(s):  
Elizabeth B Pathak ◽  
Sarah E Wieten ◽  
Christopher W Wheldon
Keyword(s):  
Content Validity ◽  
Help Seeking ◽  
Goodness Of Fit ◽  
Pain Treatment ◽  
A Priori ◽  
Internal Resistance ◽  
Economic Stress ◽  
Negative Consequences ◽  
Wide Range ◽  
Personal Ideology

IntroductionWe developed and validated a new parsimonious scale to measure stoic beliefs. Key domains of stoicism are imperviousness to strong emotions, indifference to death, taciturnity and self-sufficiency. In the context of illness and disease, a personal ideology of stoicism may create an internal resistance to objective needs, which can lead to negative consequences. Stoicism has been linked to help-seeking delays, inadequate pain treatment, caregiver strain and suicide after economic stress.MethodsDuring 2013–2014, 390 adults aged 18+ years completed a brief anonymous paper questionnaire containing the preliminary 24-item Pathak-Wieten Stoicism Ideology Scale (PW-SIS). Confirmatory factor analysis (CFA) was used to test an a priori multidomain theoretical model. Content validity and response distributions were examined. Sociodemographic predictors of strong endorsement of stoicism were explored with logistic regression.ResultsThe final PW-SIS contains four conceptual domains and 12 items. CFA showed very good model fit: root mean square error of approximation (RMSEA)=0.05 (95% CI 0.04 to 0.07), goodness-of-fit index=0.96 and Tucker-Lewis Index=0.93. Cronbach’s alpha was 0.78 and ranged from 0.64 to 0.71 for the subscales. Content validity analysis showed a statistically significant trend, with respondents who reported trying to be a stoic ‘all of the time’ having the highest PW-SIS scores. Men were over two times as likely as women to fall into the top quartile of responses (OR=2.30, 95% CI 1.44 to 3.68, P<0.001). ORs showing stronger endorsement of stoicism by Hispanics, Blacks and biracial persons were not statistically significant.DiscussionThe PW-SIS is a valid and theoretically coherent scale which is brief and practical for integration into a wide range of health behaviour and outcomes research studies.

Determining Emotional Tone and Verbal Behavior in Patients With Tinnitus and Hyperacusis: An Exploratory Mixed-Methods Study

2019 ◽  
Vol 28 (3) ◽  
pp. 660-672
Author(s):  
Suzanne H. Kimball ◽  
Toby Hamilton ◽  
Erin Benear ◽  
Jonathan Baldwin
Keyword(s):  
Mixed Methods ◽  
Verbal Behavior ◽  
Coping Strategies ◽  
Mixed Methods Study ◽  
Self Report ◽  
Anxiety And Depression ◽  
Negative Consequences ◽  
Emotional Tone ◽  
Explanatory Mixed Methods ◽  
Quantitative Results

Purpose The purpose of this study was to evaluate the emotional tone and verbal behavior of social media users who self-identified as having tinnitus and/or hyperacusis that caused self-described negative consequences on daily life or health. Research Design and Method An explanatory mixed-methods design was utilized. Two hundred “initial” and 200 “reply” Facebook posts were collected from members of a tinnitus group and a hyperacusis group. Data were analyzed via the LIWC 2015 software program and compared to typical bloggers. As this was an explanatory mixed-methods study, we used qualitative thematic analyses to explain, interpret, and illustrate the quantitative results. Results Overall, quantitative results indicated lower overall emotional tone for all categories (tinnitus and hyperacusis, initial and reply), which was mostly influenced by higher negative emotion. Higher levels of authenticity or truth were found in the hyperacusis sample but not in the tinnitus sample. Lower levels of clout (social standing) were indicated in all groups, and a lower level of analytical thinking style (concepts and complex categories rather than narratives) was found in the hyperacusis sample. Additional analysis of the language indicated higher levels of sadness and anxiety in all groups and lower levels of anger, particularly for initial replies. These data support prior findings indicating higher levels of anxiety and depression in this patient population based on the actual words in blog posts and not from self-report questionnaires. Qualitative results identified 3 major themes from both the tinnitus and hyperacusis texts: suffering, negative emotional tone, and coping strategies. Conclusions Results from this study suggest support for the predominant clinical view that patients with tinnitus and hyperacusis have higher levels of anxiety and depression than the general population. The extent of the suffering described and patterns of coping strategies suggest clinical practice patterns and the need for research in implementing improved practice plans.

Serum Vitamin B12 Concentrations among Mothers and Newborns and Follow-up Study to Assess Implication on the Growth Velocity and the Urinary Methylmalonic Acid Excretion

2009 ◽  
Vol 79 (56) ◽  
pp. 297-307 ◽  
Author(s):  
Laila Hussein ◽  
Sahar Abdel Aziz ◽  
Salwa Tapouzada ◽  
Boehles
Keyword(s):  
Early Diagnosis ◽  
Growth Velocity ◽  
Methylmalonic Acid ◽  
Post Partum ◽  
Serum Vitamin ◽  
Vitamin B ◽  
Postnatal Life ◽  
Negative Consequences ◽  
Metabolic Marker ◽  
Biochemical Measurement

Objective:Cobalamin (B12) deficiency has been reported in infants born to mothers with low cobalamin intake. Early diagnosis of vitamin B12 deficiency in infants is critical for the prevention of neurobehavioral disorders. We investigated the relationship between serum vitamin B12 level in newborns and in their healthy mothers who consumed an omnivorous diet. Anthropometry was studied longitudinally to assess the growth velocity of the infants. Urinary methylmalonic acid (MMA) excretion of 6-month old infants was compared retrospectively as the biomarker correlated with the initial serum vitamin B12 concentrations. Methods: Serum cobalamin and blood hemoglobin were determined in 84 pairs of newborns and their mothers. Urinary MMA excretion was measured in the same subjects during the first 6 months of the post partum period. Results: At birth, median serum cobalamin levels were 152.0 pmol/L in the mothers and 296.6 pmol/L in the newborns. Maternal and neonatal serum cobalamin levels had no effect on growth velocity during the first six months of postnatal life. Serum maternal and neonatal cobalamin levels were inversely associated with urinary MMA excretion. Conclusion: Early diagnosis of vitamin B12 status in neonates and infants is crucial, particularly in nutritionally deprived areas. Biochemical measurement of plasma cobalamin or its metabolic marker MMA is highly recommended. Urinary MMA measurement in cobalamin diagnostics provides an advantage in that blood sampling is not required. A vitamin B12 taskforce should be created to alleviate vitamin deficiency and its negative consequences.

Applying the Anderson-Darling Test to Suicide Clusters

Crisis ◽  
2013 ◽  
Vol 34 (6) ◽  
pp. 434-437 ◽  
Author(s):  
Donald W. MacKenzie
Keyword(s):  
Poisson Process ◽  
Goodness Of Fit ◽  
Small Samples ◽  
Massachusetts Institute Of Technology ◽  
Homogeneous Poisson Process ◽  
Cornell University ◽  
The Difference ◽  
Suicide Clusters ◽  
Institute Of Technology ◽  
Anderson Darling

Background: Suicide clusters at Cornell University and the Massachusetts Institute of Technology (MIT) prompted popular and expert speculation of suicide contagion. However, some clustering is to be expected in any random process. Aim: This work tested whether suicide clusters at these two universities differed significantly from those expected under a homogeneous Poisson process, in which suicides occur randomly and independently of one another. Method: Suicide dates were collected for MIT and Cornell for 1990–2012. The Anderson-Darling statistic was used to test the goodness-of-fit of the intervals between suicides to distribution expected under the Poisson process. Results: Suicides at MIT were consistent with the homogeneous Poisson process, while those at Cornell showed clustering inconsistent with such a process (p = .05). Conclusions: The Anderson-Darling test provides a statistically powerful means to identify suicide clustering in small samples. Practitioners can use this method to test for clustering in relevant communities. The difference in clustering behavior between the two institutions suggests that more institutions should be studied to determine the prevalence of suicide clustering in universities and its causes.

The Hierarchical Model of Exercise Dependence

2015 ◽  
Vol 36 (4) ◽  
pp. 247-257 ◽  
Author(s):  
Gayatri Kotbagi ◽  
Laurence Kern ◽  
Lucia Romo ◽  
Ramesh Pathare
Keyword(s):  
Factor Analysis ◽  
Confirmatory Factor Analysis ◽  
Physical Exercise ◽  
Exploratory Factor Analysis ◽  
Convergent Validity ◽  
Large Population ◽  
Assessment Tools ◽  
Negative Consequences ◽  
Confirmatory Factor ◽  
Preliminary Version

Abstract. Physical exercise when done excessively may have negative consequences on physical and psychological wellbeing. There exist many scales to measure this phenomenon. The purpose of this article is to create a scale measuring the problematic practice of physical exercise (PPPE Scale) by combining two assessment tools already existing in the field of exercise dependency but anchored in different approaches (EDS-R and EDQ). This research consists of three studies carried out on three independent sample populations. The first study (N = 341) tested the construct validity (exploratory factor analysis); the second study (N = 195) tested the structural validity (confirmatory factor analysis) and the third study (N = 104) tested the convergent validity (correlations) of the preliminary version of the PPPE scale. Exploratory factor analysis identified six distinct dimensions associated with exercise dependency. Furthermore, confirmatory factor analysis validated a second order model consisting of 25 items with six dimensions and four sub-dimensions. The convergent validity of this scale with other constructs (GLTEQ, EAT26, and The Big Five Inventory [BFI]) is satisfactory. The preliminary version of the PPPE must be administered to a large population to refine its psychometric properties and develop scoring norms.

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