Search

Introduction: Industrially, the use of enzymes has increased over time, as their production processes, stabilization and operating conditions have been optimized. Meanwhile associated with their use are minimized with environmental sustainability. The use of mathematical modeling has been a key factor in this advance, making it an great scientific interest area. Objective: To know the state of the art in this area of knowledge, highlighting the most successful and promising findings at present. Materials and Methods: A systematic search of recent high-impact publications between 2015 and 2021 was carried out in internationally recognized databases. A qualitative/comparative analysis of the approaches and contributions of the selected literature was carried out. Results and Discussion: It was evidenced that most of the mathematical models was developed from the Michaelis-Menten kinetic equation, but the simplifications assumed, the operating conditions and the mathematical methods used to solve these systems define the singularity and complexity of each investigation, which makes complex their comparison or implementation in a standardized way. Conclusions: In all cases, the proposed models were adjusted to experimental results or they agreed when different mathematical resolution methods were used. These results can provide valuable information for processes improvement and for equipment design, minimizing costs and time of experimentation and being more friendly to the environment. [ABSTRACT FROM AUTHOR]

Determination of optimum temperature in the (PFasa) cellulase production, by a strain of Aspergillus niger in solid fermentationis presented in this paper, using data from a previously proposed kinetic model. Dependence of the 16 kinetic parameters with temperature (in the range of 20 °C to 40 °C), was established. For µmax and xmax parameters, the adjustment was achieved using the Rosso and Ratkowsky models respectively. Cubic interpolation models was needed to adjust the rest of kinetic parameters. The dependence of the kinetic model parameters with temperature allowed the estimation of temperature and optimum fermentation time to maximize the productivity in the production of true protein and the activity of the three studied enzymes. As result, the optimum temperature rangeisbetween 30°C and 32°C. For the production of true protein and CMcasa, the optimum fermentation time is located within the19 and 22 hours respectively, but for the production of PFasa, is 33 hours. The protease activity presented several local maxima in terms of optimal temperatures ranging from 25 to 40 °C. Although the maximum activity levels are 64 UI/gdm, which, according to literature, is an intermediate value, the level of productivity of PFasa is the highest found (3.84 times superior to average activity), when compared with another 20 reports consulted since 2004. [ABSTRACT FROM AUTHOR]

In this work a kinetic model proposal is presented for describing cellulase production in a solid-state fermentation process of an Aspergillus niger strain. The validation of the model was carried out at five temperatures: 20, 25, 30, 35 and 40°C. In the validation the characteristic parameters of the model were identified using a dynamic data generated at constant temperature. The response variables described by the model are: concentration of biomass of fungus measured as true protein, total reducing sugars, crude fiber, FPase activity, CMCase activity and the activity of proteases in the medium. For parameters identification the process model was programmed in MATLAB. The results indicate that the model is perfectly capable describing the cellulase production kinetics under these conditions. The temperatures where cellulase production was higher were 30°C and 35°C. The experimental levels of FPase and CMCase are significant because maxim values of FPase of 60 UI gDW-1 and of CMCase of 50 UI gDW-1 are reached in a fermentation time ranging from 24 to 30 hours. The identified parameters are strongly associated to temperature. [ABSTRACT FROM AUTHOR]

Bioethanol production from lignocellulose biomass is becoming of increasing importance because of its low-cost, widely available, non-food competence and high sugar content. However, lignocellulose is more difficult to convert than sugars, starches and oils because it consists of a complex mixture of cellulose, hemicellulose and lignin. To break down its complex structure, a pretreatment step is required. For that purpose physical, physico-chemical, chemical, biological or a combination of pretreatment steps have been proposed to process the raw materials [23]. Pretreatment is essential for the economic success of the entire system because the pretreatment may represent up to one-third of the overall processing cost [14]. The impact of the pretreatment step on the overall process motivates the development of models suitable for process design and optimization. This study presents the modelling and optimization of the pretreatment of sugarcane bagasse for bioethanol production. Alternative pretreatment steps are considered, including dilute-acid hydrolysis (with different acids) and processing with liquid hot water. Models for each pretreatment step are derived from experimental data from the literature, based on an understanding of the kinetics involved in the different reactions and incorporating the kinetics into mass balances models to quantify the consumption and generation of the different components. The models are implemented in the Jacaranda system for process design and optimisation [8] to identify the optimal process conditions for each pretreatment. Results show the interaction between design variables (i.e. residence time, operating temperature or acid concentration) and optimal conditions. [ABSTRACT FROM AUTHOR]

The acid compounds (H2S y CO2) removal from gaseous streams is traditionally carried out in an absorption system based on alkanolamines. The present paper deals with the evaluation of a gas sweetening plant for the H2S removal from hidrotreating products in a heavy oil industry. The efficiency of a typical absorption system running on MDEA/MEA and MDEA/DEA is proved to obtain a lean gas with 40 to 60ppm of H2S. The 90% of the H2S is recovered and the sweet gas can be recirculated to the hidrotreating stage. The modeling and simulation of the process is implemented on Aspen-Hysys software. [ABSTRACT FROM AUTHOR]

In the work the methodology is exposed to carry out the necessary modifications to adapt a mathematical model with phenomenological character that describes the real process of cooking of massecuite "A", with view to that could be used with the objective of to optimize and to control this process, supported in the online simulation. The methodology is distinguished for three fundamental stages: Determination of sensibility of entrance variables to the process of optimization, the optimization and the control stage. The aspects fundamental analysis object are offered that should be had in bill in each one of the stages of the methodology, to be able to achieve that the created pattern of phenomenological character satisfies the objectives of optimization and control of the discontinuous crystallization process in vacuum pan for the obtaining of massecuite "A", that which can be extrapolated to any process study object. [ABSTRACT FROM AUTHOR]

The present work was carried out in the CAI "George Washington", to establish the mathematical model of the Stage of cooking of the massecuite A, under industrial conditions, with the purpose of carrying out an operational analysis of this, leaving of the measurements of the main operational variables. In this it is, exposed the adaptation and development of the phenomenological mathematical model that it characterizes this process, as well as the adjustment of the same ones with the obtained industrial experimental data. It was also carried out a statistical analysis of this process to corroborate the existence or not of significant differences among the experimental results and the results toasted once by the model adjusted, where satisfactory results were obtained; also the statistical analysis of frequency of all it dates it experimental obtained during the time of study of the stage of cooking of massecuite of first, it allowed to establish 12 different types of conditions of feeding of the raw material (molasses and seed B) to the cross out evaporation tank of first, which were simulated with the mathematical phenomenological model obtained, being achieved the behavior of the variables that characterize to the crystallization process to hole, such (variation half diameter of the crystal, content of crystals, efficiency, etc), as well as an economic analysis of each one. To conclude, that these model is valid for the studied experimentation range and that they represent the behavior of this stage appropriately. They are also appropriate for the simulation of this process. [ABSTRACT FROM AUTHOR]

A former job dealing with the scheduling of operations (synthesis of boiling schemes) in raw sugar production from cane has been done using a simulation approach, Tasks were assigned to the available equipment before the scheduling analysis was done with a simulation approach. Now, a direct optimization approach is used for the synthesis of boiling schemes in raw sugar production. This approach, described by Kondili et. al. is based on the state task network representation (STN) and allows studying the production strategy without assigning, a priori, tasks to equipment. In this paper, a case study in sugar production is described. [ABSTRACT FROM AUTHOR]

A former job dealing with the scheduling of operations (synthesis of boiling schemes) in raw sugar production from cane has been done using a simulation approach (3). Tasks were assigned to the available equipment before the scheduling analysis was done with a simulation approach. Now, a direct optimization approach is used for the synthesis of boiling schemes in raw sugar production. This approach, described by Kondili et al., is based on the state task network representation (STN) and allows studying the production strategy without assigning, a priori, tasks to equipment. In this first part of the paper, the mixed integer linear programming (MILP) model is described. [ABSTRACT FROM AUTHOR]

This paper deals with the physical modeling of one of the reduction stages of big-size speed reducer for the cane mills of Cuban sugar power stations. The theory of modeling is approached regarding mathematical modeling applied to transmissions by cylindrical gear, and especially to the planetary transmissions of the type 2R-P/A. An example is shown, where the similarity between the model and the speed reducer is evident. [ABSTRACT FROM AUTHOR]

In the present work the modeling of the foundations is approached on piles of great use in the foundations in chimneys and structures of great height in the sugar industry. New design coefficients are proposed and compared that allow using the design of rational and safe foundations as well. It is exemplified through comparisons the results obtained through the modeling with other formulations, assessing the validation of the proposed pattern and their possible application. [ABSTRACT FROM AUTHOR]

The baskets of the centrifugal machines of the sugar plants have a useful life that the vendor determines by the thickness of their walls. This thickness decreases during their exploitation. This paper is intended to give a way to increase the life of these baskets by means of the reinforcement of their walls. Calculations are carried out applying the techniques of the Finite Element Method. [ABSTRACT FROM AUTHOR]

This work describes the mathematical modelling and simulation of a wastewater anaerobic treatment system from a yeast plant. The system consists of two tubular reactors in series, which have been used both at laboratory and pilot plant scale. The main objective of the modelling stage was the subsequent scale -- up of this system to increase the volume of wastewater to process. The reactors mentioned above were used in previous tests in which the feasibility of utilization of anaerobic treatment in the decontamination of these wastes was studied. These reactors could be classified as hybrid or non -- conventional reactors since they combine features of the traditional reactors. In this case we dealt with upflow tubular reactors in which a fibrilar support was included. Due to that fact, another objective of this modelling was to learn the mechanisms that governs at least those parts of the process, if not the whole of it, that have to do with the anaerobic digestion, in this particular case the decontamination (understood as the reduction of the value of the Chemical Oxygen Demand: COD), for its later dumping. The first stage of modelling, at laboratory scale, had as a result that the model that reflects the COD removal at this level is: dS/dz = - 1/v ⋅ μ/YX/S ⋅ γ with particular definitions for μ and the factor γ. The latter constitutes a parameter including typical features of bioprocess developing on supports. At pilot plant scale, one could observe the influence of transport phenomena, which is not reflected in the preceding stage and become evident with scale changes. It is concluded that the transport phenomena affecting the process is of the convective type, not diffusional. The model to reflect COD removal at this scale is: dS/dz = - 1/v ⋅ μ ⋅ γ/YX/S ⋅ (a1 + b1 ⋅ v0.5) The simulation using these models was carried out by means of the simulator ISIM and its main goal was to validate the models, which are going to be used to scale-up the process. In this model an effectiveness factor η (potential expression) is included to reflect the influence of the phenomena mentioned above. [ABSTRACT FROM AUTHOR]