Nestrukturirani modeli mliječno-kiselog vrenja

To describe a microbial process, two kinds of models can be developed, structured and unstructured models. Contrary to structured models, which take into account some basic aspects of cell structure, their function and composition, no physiological characterization of cells is considered in unstructured models, which only consider total cellular concentration. However, in spite of their simplicity, unstructured models have proven to accurately describe lactic acid fermentation in a wide range of experimental conditions and media. A partial link between cell growth and production, namely the Luedeking and Piret model, is mostly considered by the authors. Culture pH is the main parameter to be considered for model development. Acidic pH leads to inhibitory concentrations of undissociated lactic acid, the main inhibitory component, which causes cessation of growth and then production. On the other hand, pH control at optimal value for LAB growth allows to overcome product inhibition (by the total lactic acid produced or its undissociated part); hence nutritional limitations have to be considered for model development. Nitrogen is mainly involved in cessation of growth, owing to the fastidious nutritional requirements of LAB, while lactic acid production ceased when carbon was exhausted from the medium. The lack of substrate inhibition when usual concentrations of carbon substrate are used should be noted.Da bi se opisao mikrobni proces, upotijebljeni su strukturirani i nestrukturirani modeli. Strukturirani modeli uzimaju u obzir strukturu, funkciju i raspored stanica, a nestrukturirani ne uzimaju fiziološka svojstva, već samo ukupnu koncentraciju stanica. Ipak, usprkos njihovoj jednostavnosti, nestrukturirani modeli precizno opisuju mliječno-kiselo vrenje u različitim eksperimentalnim uvjetima i na raznim podlogama. Autori najčešće koriste Luedekingov i Piretov model, koji opisuje djelomičnu vezu između rasta stanica i proizvodnje mliječne kiseline. U razvoju ovoga modela najčešće je pH-vrijednost glavni parametar. Pri niskoj pH-vrijednosti nastaju inhibicijske koncentracije nedisocirane mliječne kiseline, što zaustavlja rast mliječno-kiselih bakterija, a time i proizvodnju mliječne kiseline. Taj se inhibicijski učinak može prevladati održavanjem optimalne pH-vrijednosti, ali pritom treba uzeti u obzir utjecaj hranjivih tvari na rast mliječno-kiselih bakterija. Nedostatak dušika je najčešći uzrok inhibicije mliječno-kiselih bakterija, jer im je prijeko potreban za rast, dok nakon iscrpljivanja ugljika iz podloge prestaje proizvodnja mliječne kiseline, što se može izbjeći korištenjem odgovarajućih koncentracija ugljika

Improved growth model for two-stage continuous cultures of Lactobacillus helveticus

An unstructured model for growth and lactic acid production during two-stage continuous cultures of Lactobacillus helveticus was previously developed. The Verlhust model was considered to describe growth kinetics. Production models was based on modified Luedeking-Piret expressions involving an inhibitory effect for the first stage (seed culture) and a nutritional limitation effect for the second stage (culture). To account for the decrease of the biomass concentration observed in the second stage, the dilution rate Dc was replaced by an exponential term of the dilution rate \u3b1 exp (Dc/\u3b2 ) in the growth and product relations. Contrarily to the previous model, the important decrease of the biomass concentration observed at steady state in the second stage at high dilution rates, namely close to wash out, was correctly described by the new model. It also proved to satisfactory describes production data and volumetric productivity

Enhanced photocatalytic degradation of methylene blue: Preparation of TiO2/reduced graphene oxide nanocomposites by direct sol-gel and hydrothermal methods

In this study, two different preparation methods of titanium dioxide nanoparticles/reduced graphene oxide nanocomposites were investigated using direct sol-gel method followed by hydrothermal treatment or simple hydrothermal route. A different amount of graphene (1- 20%) was mixed with TiO2 for both series of samples in order to improve the photocatalytic activity. The influence of the preparation method on the physico-chemical properties was established by different characterization methods and the photocatalytic degradation of methylene blue (MB) under UV light irradiation was used as test reaction. The highest photocatalytic activity was observed for the nanocomposites containing 10 wt% of graphene. The elimination of MB can reach 93% and 82% for the nanocomposites with 10 wt% graphene prepared by the sol-gel and hydrothermal methods, respectively. These photocatalysts are promising for practical application in nanotechnology.Postprint (author's final draft

The Enhanced Adsorption Capacity of <em>Ziziphus jujuba</em> Stones Modified with Ortho-Phosphoric Acid for Organic Dye Removal: A Gaussian Process Regression Approach

\ua9 2024 by the authors. Here, the chemical modification of Ziziphus jujuba stones (ZJS) treated with ortho-phosphoric acid (ZJS-H3PO4) is investigated to enhance its adsorption properties for organic dyes. The physicochemical properties of ZJS-H3PO4 reveal increased porosity (87.29%), slightly higher bulk density (0.034 g mL−1), and enhanced acidity (31.42 m eq g g−1) compared to untreated ZJS. XRF analysis confirms the successful incorporation of orthophosphoric acid during treatment due to a significant increase in phosphorus content. The maximum adsorption capacity of methylene blue on ZJS-H3PO4 is found to be 179.83 mg g−1, demonstrating its efficacy as a potential adsorbent for organic dyes. These findings suggest that modifying ZJS with orthophosphoric acid could be a promising strategy to enhance its adsorption performance in various environmental applications. Furthermore, Gaussian process regression (GPR) is employed to model MB adsorption by ZJS-H3PO4. Optimization of the GPR model involves evaluating different kernel functions and meticulously adjusting parameters to maximize its ability to capture complex relationships in the data. The obtained GPR model demonstrates remarkable performance with high correlation coefficients (R) and low root mean square errors (RMSEs) across all study phases. Model validation is performed through residual analysis, confirming its effectiveness and accuracy in predicting MB adsorption. Finally, a user-friendly interface is developed to facilitate the usage of the GPR model in future applications, representing a significant advancement in environmental process modeling and ecosystem management

Microscopic Study of Superdeformed Rotational Bands in 151Tb

Structure of eight superdeformed bands in the nucleus 151Tb is analyzed using the results of the Hartree-Fock and Woods-Saxon cranking approaches. It is demonstrated that far going similarities between the two approaches exist and predictions related to the structure of rotational bands calculated within the two models are nearly parallel. An interpretation scenario for the structure of the superdeformed bands is presented and predictions related to the exit spins are made. Small but systematic discrepancies between experiment and theory, analyzed in terms of the dynamical moments, J(2), are shown to exist. The pairing correlations taken into account by using the particle-number-projection technique are shown to increase the disagreement. Sources of these systematic discrepancies are discussed -- they are most likely related to the yet not optimal parametrization of the nuclear interactions used.Comment: 32 RevTeX pages, 15 figures included, submitted to Physical Review

Evaluating the Effectiveness of Coagulation–Flocculation Treatment Using Aluminum Sulfate on a Polluted Surface Water Source: A Year-Long Study

\ua9 2024 by the authors.Safeguarding drinking water is a major public health and environmental concern because it is essential to human life but may contain pollutants that can cause illness or harm the environment. Therefore, continuous research is necessary to improve water treatment methods and guarantee its quality. As part of this study, the effectiveness of coagulation–flocculation treatment using aluminum sulfate (Al2(SO4)3) was evaluated on a very polluted site. Samplings were taken almost every day for a month from the polluted site, and the samples were characterized by several physicochemical properties, such as hydrogen potential (pH), electrical conductivity, turbidity, organic matter, ammonium (NH+4), phosphate (PO43−), nitrate (NO3−), nitrite (NO2−), calcium (Ca2+), magnesium (Mg2+), total hardness (TH), chloride (Cl−), bicarbonate (HCO3−), sulfate (SO42−), iron (Fe3+), manganese (Mn2+), aluminum (Al3+), potassium (K+), sodium (Na+), complete alkalimetric titration (TAC), and dry residue (DR). Then, these samples were treated with Al2(SO4)3 using the jar test method, which is a common method to determine the optimal amount of coagulant to add to the water based on its physicochemical characteristics. A mathematical model had been previously created using the support vector machine method to predict the dose of coagulant according to the parameters of temperature, pH, TAC, conductivity, and turbidity. This Al2(SO4)3 treatment step was repeated at the end of each month for a year, and a second characterization of the physicochemical parameters was carried out in order to compare them with those of the raw water. The results showed a very effective elimination of the various pollutions, with a very high rate, thus demonstrating the effectiveness of the Al2(SO4)3. The physicochemical parameters measured after the treatment showed a significant reduction in the majority of the physicochemical parameters. These results demonstrated that the coagulation–flocculation treatment with Al2(SO4)3 was very effective in eliminating the various pollutions present in the raw water. They also stress the importance of continued research in the field of water treatment to improve the quality of drinking water and protect public health and the environment

Unstructured Models for Lactic Acid Fermentation – A Review

To describe a microbial process, two kinds of models can be developed, structured and unstructured models. Contrary to structured models, which take into account some basic aspects of cell structure, their function and composition, no physiological characterization of cells is considered in unstructured models, which only consider total cellular concentration. However, in spite of their simplicity, unstructured models have proven to accurately describe lactic acid fermentation in a wide range of experimental conditions and media. A partial link between cell growth and production, namely the Luedeking and Piret model, is mostly considered by the authors. Culture pH is the main parameter to be considered for model development. Acidic pH leads to inhibitory concentrations of undissociated lactic acid, the main inhibitory component, which causes cessation of growth and then production. On the other hand, pH control at optimal value for LAB growth allows to overcome product inhibition (by the total lactic acid produced or its undissociated part); hence nutritional limitations have to be considered for model development. Nitrogen is mainly involved in cessation of growth, owing to the fastidious nutritional requirements of LAB, while lactic acid production ceased when carbon was exhausted from the medium. The lack of substrate inhibition when usual concentrations of carbon substrate are used should be noted

Optimization of production of lactic acid fermentation

During lactic acid fermentation in batch and continuous culture using Lactobacillus helveticus, seed culture is usually carried out without pH control, while culture is carried out at pH controlled at the optimal value to overcome inhibitory effects. In this study, novel mathematical models are set up to describe lactic acid production in batch and continuous fermentation. The Luedeking-Piret expression was therefore previously modified by introducing additional terms involving the undissociated form of the lactic acid, the main inhibitory species, in case of batch cultures without pH control. To describe growth, the Verlhust model which proved to describe satisfactory growth kinetics was considered. The model was found to match both experimental growth and production data. Another model was also developed involving the residual lactose concentration to account for carbon substrate limitation, responsible for cessation of production during batch cultures of Lactobacillus helveticus at controlled pH. This model matched experimental data accurately. Two generalized models were then deduced from the above expressions. The results obtained show that the generalized models gave a satisfactory description of experimental data in various culture conditions, since they were validated during cultures at pH control and in absence of pH control, as well as for different nitrogen supplementation of culture media. Both models, as well as the Luedeking-Piret model, were developed to describe successfully continuous two-stage culture of L. helveticusAu cours de la fermentation lactique en discontinu ou en continu, la préculture se fait généralement à pH libre tandis que la culture se fait à pH régulé, et ce pour éviter une inhibition par l acide formé. Dans ce travail, de nouveaux modèles mathématiques ont été développés pour décrire la croissance et la production d'acide lactique. Le modèle de Luedeking-Piret a été modifié en introduisant, d'une part, l'effet inhibiteur de l'acide lactique non dissocié dans le cas de la préculture. Pour la croissance, le modèle de Verlhust a été utilisé dans ce travail. Le modèle développé décrit correctement les résultats expérimentaux jusqu'à la fin de la fermentation. D'autre part, afin de rendre compte d une limitation nutritionnelle, ce qui est le cas lors de l étape de culture (à pH régulé) un second modèle a été développé en introduisant la concentration résiduelle en substrat carboné. Pour éviter l'utilisation des deux modèles précités, deux modèles généralisés ont été développés qui tiennent compte à la fois de l'effet inhibiteur de l'acide lactique non dissocié et des limitations nutritionnelles. Ces modèles décrivent bien les résultats expérimentaux à pH libre et à pH régulé. Ces modèles ont été appliqués avec succès au cas d'un bioréacteur biétagé en continu.RENNES1-BU Sciences Philo (352382102) / SudocSudocFranceF

Adsorption of the Cationic Dye Ethyl Violet on Acid and Alkali-Treated Wild Carob Powder, A Low-Cost Adsorbent Derived from Forest Waste

International audienceThe effect of acid-alkaline treatment of lignocellulosic material (wild carob forest wastes) on Ethyl violet adsorption was investigated. It was found that surface chemistry plays an important role in Ethyl Violet (EV) adsorption. HCl treatment produces more active acidic surface groups such as carboxylic and lactone, resulting in an increase in the adsorption of EV dye. The adsorption efficiency was higher for treated lignocellulosic material with HCl (WCHCl) compared to that treated with KOH (WCKOH); maximum biosorption capacities were 170 and 130 mg/g for WCHCl and WCKOH at pH 6, respectively. It was also found that for both treated materials less than 150 min was needed to reach equilibrium. The adsorption of a basic dye (i.e. ethyl violet or basic violet 4) was carried out by varying some process parameters, such as the initial concentration and pH. The adsorption process can be well described by means of a pseudo-second-order reaction model and experimental data were accurately expressed by the Sips and Langmuir models for both WCHCl and WCKOH