Volume 4
Editorial
Worldwide Scientists
Forthcoming Events
Second call for the 19th International Symposium "Bioprocess Systems 2007 - BioPS'07"
Modelling and Optimization of Biotechnological Systems
Modelling of Escherichia coli Cultivations: Acetate Inhibition in a Fed-batch Culture1-11
Olympia Roeva, Stoyan Tzonkov
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A set of three competing, unstructured models has been proposed to model biomass growth, glucose utilization, acetate formation, dissolved oxygen consumption and carbon dioxide accumulation of a fed-batch cultivation process of Escherichia coli. The inhibiting effect of acetate on growth of E. coli cultures is included in the considered models. The model identification is carried out using experimental data from the cultivation process. Genetic algorithms are used for parameter estimation. The model discrimination is based on the four criteria, namely sum of square errors, Fisher criterion, Akaike information criterion and minimum description length criterion. The most suitable model is identified that reflects the state variables curves adequately by considering acetate inhibited growth according to the Jerusalimsky approach.
Modelling of Fed-batch Fermentation Process with Droppings for L-lysine Production12-23
Tzanko Georgiev, Velitchka Ivanova, Julia Kristeva, Kalin Todorov, Ignat Dimov, Alexander Ratkov
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The aim of the article is the development of dynamic unstructured model of L-lysine fed-batch fermentation process with droppings. This approach includes the following procedures: description of the process by generalized stoichiometric equations; preliminary data processing; identification of the specific rates (growth rate (μ), substrate utilization rate (ν), production rate (ρ)); establishment and optimization of the dynamic model of the process; simulation researches.
Time Series Analysis of Fed-batch Fermentation Process for L-valine Production24-29
KalinTodorov, Tzanko Georgiev, Velitchka Ivanova, Julia Kristeva, Ignat Dimov, Alexander Ratkov
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Fed-batch fermentation processes are some of the most efficient and wildly applied types of cultivation for industrial production of most amino acids including L-valine. Time series analysis is an important tool for description of the experimental data. This article deals with statistical inference from the time series analysis of generalised stoichiometric equations as a hypothesis for modelling and optimisation. The aim of the article is to develop some time series models of generalized stoichiometric equations. The identification procedure includes the following steps: description of the process by generalized stoichiometric equations; preliminary data processing; model structure selection for each stoichiometric equation; estimation of the modelís parameters; verification of the derived models.
Bioprocess Systems
Environmental Process Control: Strategies and Implementation30-40
Jurgis Staniskis
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The structure and mathematical presentation of the optimal strategy for environmental process control is presented. This approach covers a wide variety of control systems, which have been constructed and analysed at the Institute of Environmental Engineering during the last fifteen years. Special attention is paid to the preventive environmental control and its tools: pollution prevention, life cycle assessment. The implementation results of preventive environmental control from more than 150 companies are presented in the paper.
The investigations on water quality control issues are evaluated from the point of view of the interface between physico-ecological and socio-economical systems and decision support system based on river water quality model is suggested.
Extracellular Polysaccharide Production and Biofilm Formation by Coagulase-negative Staphylococci41-44
Aija Žileviča, Rita Treimane, Uldis Viesturs
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Coagulase-negative Staphylococci (CoNS) form a part of the skin flora and commonly cause nosocomial bloodstream and catheter- related infections. According to their relatively low virulence, it is important to detect the virulence factors of clinical isolates. The production of extracellular polymers and formation of biofilms belong to virulence factors. We studied clinical isolates of CoNS and compared them with isolates from the healthy skin. The species distribution did not differ significantly. Slime production in clinical strains was more often and more intense. A comparison of methicillin-resistant (MR) and methicillinsensitive (MS) clinical strains has revealed that slime production is more active in MR strains.
Neural Network Configurations for Filtering of Feed Stream Noise from Oscillating Continuous Microbial Fermentations45-56
Pratap Patnaik
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Some microbial systems exhibit sustained oscillations under certain conditions. The maintenance and the suppression of oscillations are both important in different situations. While oscillations are clearly identifiable in small bioreactors, the influx of noise fuzzifies the oscillations in larger vessels. So, noise-filtering devices are employed to recover clear oscillating profiles. Recent work has shown that an auto-associative (AA) neural network is a better than standard algorithmic filters. In this study, nine neural network designs are compared for their ability to filter Gaussian noise in the substrate inflow rate of a continuous fermentation containing Saccharomyces cerevisiae. While the AA network is the best overall, specific performance criteria favor other designs. Thus the choice of a neural filter depends on the evaluation criterion, which is guided by the application.
Biomedical Systems
Transthoracic Impedance Study with Large Self-adhesive Electrodes57-68
Vessela Krasteva, Mikhail Matveev, Nikolay Mudrov, Rada Prokopova
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The external electrical therapy of the heart requires the application of high voltage electrical pulses via large external electrodes, placed on selected locations on the thorax surface. The position of the electrodes is one of the major determinants of the transthoracic impedance (TTI), which influences the intracardiac current flow during electric shock and therefore affects the defibrillation success. The indefinite nature of the factors affecting TTI raised our interest in clinical study of the TTI behavior during long-term applications of the defibrillation pads in different positions on the patient's chest. The study involved 86 randomly selected patients (39 male and 49 female, age (20-83) years, height (150-190) cm, weight (50-110) kg, chest size (86-130) cm, 67 patients with normal skin, 13 patients with dry skin and 6 patients with greasy skin, 70 patients without and 16 patients with chest pilosity). TTI was measured by passing of a low-amplitude high-frequency (23 kHz) current between the two PADs (active area about 92 cm2). For each patient, the TTI was measured 10 s, 1 min and 5 min after sticking on the electrodes to the skin surface, separately for the two tested electrode positions - Position 1 (sub-clavicular/sub-axillar position) and Position 2 (antero-posterior position). TTI range is comparable for the two tested PAD positions - between 58 Ω and 152 Ω for Position1 and between 55 Ω and 149 Ω for Position 2. TTI mean±SD value in Position 1 (107,2±22,3) Ω is significantly higher than TTI in Position 2 (96,6±19,2) Ω. Both the pilosity and the skin type do not change significantly the TTI value, however the patients with chest pilosity presented slightly higher TTI than those without pilosity. The TTI was higher for normal skin, followed by dry and greasy skin. TTI presented weak correlation with both the patient chest size and weight (r<0,5, p<0,05). The mean value of the TTI decreases in time. In time-interval (10s to 1min) after sticking on the electrodes, TTI drops with about (3,8±4,03) Ω for Position 1 and (2,44±3,75) Ω for Position 2. The TTI drop (10s-5min) is (7,36±5,33) Ω for Position 1 and (5,06±7,08) Ω for Position 2.
Robust Approximation to Adaptive Control by Use of Representative Parameter Sets with Particular Reference to Type 1 Diabetes69-72
Richard Ollerton, Anthony Shannon
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This paper describes an approach to adaptive optimal control in the presence of model parameter calculation difficulties. This has wide application in a variety of biological and biomedical research and clinical problems. To illustrate the techniques, the approach is applied to the development and implementation of a practical adaptive insulin infusion algorithm for use with patients with Type 1 diabetes mellitus.
A New Parameter for Improved Assessment of the Tracing Repeatability for Area Measurements of the Left Ventricle73-79
Wai-Tak (Arthur) Hung
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In order to validate an automated border detection (ABD) algorithm for obtaining a cross-sectional area of the left ventricle of heart, the areas obtained by ABD need to be compared with the areas obtained by a trained tracer as the latterís measurements are regarded as gold standard. Before performing an agreement analysis between the areas obtained by the ABD and that of the tracer, we need to know how well the tracer can repeat the tracing of the same image. A new parameter is proposed to assess the repeatability of this tracing. The results of three sets of 30x2 measurements have been analyzed. It was found that this new parameter can reveal the true difference in two tracings of the same image both spatially and numerically on a scale of 0 to 1. It can also yield the area differences between the ABD and traces.
Monolithic Controlled Delivery Systems: Part I. Basic Characteristics and Mechanisms80-88
Rumiana Blagoeva, Assen Nedev
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The article considers contemporary systems for controlled delivery of active agents, such as drugs, agricultural chemicals, pollutants and additives in the environment. A useful classification of the available controlled release systems (CRS) is proposed according to the type of control (passive, active or self-preprogrammed) and according to the main controlling mechanism (diffusion, swelling, dissolution or erosion). Special attention is given to some of the most used CRS Ė polymer monoliths. The structural and physical-chemical characteristics of CRS as well as the basic approaches to their production are examined. The basic mechanisms of controlled agent release are reviewed in detail and factors influencing the release kinetics are classified according to their importance. The present study can be helpful for understanding and applying the available mathematical models and for developing more comprehensive ones intended for design of new controlled delivery systems.

© 2006, BAS, Institute of Biophysics and Biomedical Engineering