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Optimization of cultivation conditions for mammalian cell lines producing complex biosimilars
Jure Strnad, 2011, doktorska disertacija

Opis: EXTENDED ABSTRACT The possibility to replace standard single use 250 mL shake flasks with single use 50 mL spin tubes was investigated using the design of experiments methodology. Experimental throughput could be tripled to a maximum of 120 spin tubes per shaker-incubator unit if similar process performance could be proven in shake flasks and spin tubes. A D-optimal response surface design was used to model titer values in a seven day batch process producing recombinant erythropoietin. Shaking rate and working volume in spin tubes were adjusted to simulate titers that are produced in shake flasks at the reference setting. Research results indicated that equivalent titers as in shake flasks at the reference setting can be produced in spin tubes; moreover, even higher titers are possible. The maximal titers in spin tubes reached values as observed in 6 L bioreactors. Furthermore, a comparison of process performance and product quality attributes between two spin tube settings, the reference shake flask setting, a standard bioreactor run and a bioreactor run without pH control was made. Process performance and product quality attributes in spin tubes at the equality setting (shaking rate of 180 rpm and 30 mL working volume) were comparable to the ones derived from the reference shake flask setting. Results derived for both bioreactor runs were not fully comparable to the spin tube and shake flask systems. The statistical model for calculating titers on day seven of a batch process in spin tubes was successfully validated and can be used for titer prediction in the proposed design space. The optimized spin tube settings were further used in a repetitive batch process where in the harvest phase of the process medium was daily exchanged to prevent component depletion or build-up of inhibitors. Spin tubes and shake flasks were used to simulate the industrial process of erythropoietin production. The effect of process mode change from seven-day batch to repetitive batch was investigated on process performance and product quality attributes, such as isoform distribution and glycan group distribution. Spin tube performance at the equality setting was comparable to the shake flask performance also in the repetitive batch process. Performance, especially titers at the maximal titer spin tube setting was, however, not fully comparable to the results obtained in previous optimization experiments. The spin tube equality setting was also used for cultivating two cell lines producing different monoclonal antibodies. The goal was to investigate how different cell lines influence process performance and product quality attributes, such as monoclonal antibody charge variant distribution and glycan group distribution. Both cell lines were derived from a Chinese hamster ovary parental cell line, therefore, it was proposed that maybe the optimal spin tube setting derived for the erythropoietin producing cell line, which was also derived from the Chinese hamster ovary parental cell line, could also be used for these subtypes. Cell growth of the monoclonal antibody producing cell lines was extensively better as observed for the erythropoietin producing cell line, which meant that culture demands were more pronounced, such as oxygen transfer or mass transfer. It was observed that the erythropoietin derived equality spin tube setting did not produce similar process responses as shake flask at the reference setting for both monoclonal antibodies. The foremost difference was that the metabolite lactate was being consumed in shake flasks after it reached a maximum value but was not consumed in spin tubes for both monoclonal antibody producing cell lines. In these experiments also amino acid time profiles during a seven day batch process were monitored and subsequently compared. It was seen that several amino acids seemed to be in excess as most of them were only half way consumed. Product quality attributes also differed between the spin tube and the shake flask setting. The conclusion of the experimental work was that some fine tuning of th
Ključne besede: design of experiments, spin tube, shake flask, optimization, erythropoietin, monoclonal antibodies
Objavljeno: 22.12.2011; Ogledov: 2602; Prenosov: 135
.pdf Celotno besedilo (6,72 MB)

Volumetric properties of ethanol-water mixtures under high temperatures and pressures
Darja Pečar, Valter Doleček, 2005, izvirni znanstveni članek

Opis: The densities of ethanol and ethanol-water mixtures were measured with a vibrating tube densimeter at 25.0, 50.0 and 75.0°C in the pressure range from 0.10 to 40.00 MPa. Densities were correlated using an empirical model. Partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures were calculated from obtained densities. This study reports the dependence of densities, partial molar volumes, excess molar volumes, isothermal compressibilities, cubic expansion coefficients and internal pressures on composition, temperature and pressure.
Ključne besede: ethanol, ethanol-water mixtures, density measurements, vibrating U tube densimeter, partial molar volumes, isothermal compressibility, isobaric expansibility, cubic expansion coefficient, internal pressure
Objavljeno: 01.06.2012; Ogledov: 1677; Prenosov: 70
URL Povezava na celotno besedilo

Porosity sensor by using quartz crystals and two excitation signals
Vojko Matko, 2003, objavljeni znanstveni prispevek na konferenci

Opis: In response to a need for a more accurate porosity measuring method for small solid samples (app. 1 g in mass) the porosity measurement sensor using a sensitive capacitive-dependent crystal was developed. This paper presents the new sensor and the probe sensitivity, frequency dependence on the volume. In addition, the new idea of excitation of the entire sensor with stochastic test signals is described, and the porosity measuring method is provided. The latter includes the influence of test signals on the weighting function uncertainty. The experimental results of the porosity determination in volcanic rock samples are presented. The uncertainty of porosity measurements is less than 0.1% in the temperature range 10 - 30°C.
Ključne besede: electrical measurements, porosity, soil, capacitive dependent crystals, sensor, glass test tube, direct digital method
Objavljeno: 01.06.2012; Ogledov: 1362; Prenosov: 83
URL Povezava na celotno besedilo

Experimental models of medium break loss of coolant accidents with and without steam generator tube rupture
Jure Marn, Marjan Delić, Leopold Škerget, 2003, izvirni znanstveni članek

Opis: This paper reports model experiments simulating medium break loss of coolant accidents, with and without steam generator tube rupture (SGTR), in pressurized water reactors. Apart from a significant influence on the pressure in the reactor coolant system in the early parts of the accident, SGTR generally has only a small effect on the pressures and temperatures during the accident. The initial reactor conditions are found to be more significant. Some results of preliminary numerical models are briefly presented and these are broadly in agreement with the experimental measurements.
Ključne besede: nuclear engineering, nuclear accidents, steam generator tube rupture, loss of coolant, medium break loss of coolant accident, computer program, Melcor, MELCOR computer code, integral test facility
Objavljeno: 01.06.2012; Ogledov: 991; Prenosov: 83
URL Povezava na celotno besedilo

Parameter optimization of tube hydroforming
Edina Karabegović, Miran Brezočnik, 2012, izvirni znanstveni članek

Opis: Tube hydroforming is mostly applied in automotive industry. In this respect, necessity for the procedure improvement of fluid forming is constant. One of the reasons of its improvement is the procedure performance in optimal conditions. The process parameters have the direct influence on quality and optimal of forming procedure. This paper provides an example of the fluid pressure optimization in T-shape tube hydroforming. Three types of material have been analysed, with three wall thickness and three course levels of axial printers. For the optimization, the evolutional method with applied genetic algorithm (GA) was utilized. The application of GA is significant in solving of many problems in engineering practice. The simplicity and adaptability of the genetic algorithm to the engineering problem results with the increasing volume of applications in a research work. In this paper we investigated interactions of the internal parameters of the T tube hydroforming process, towards achieving the GA model for the optimal internal pressure, necessary for hydroforming.
Ključne besede: hydroforming, tube, modelling, optimization, parameter, genetic algorithm, T-shape
Objavljeno: 10.07.2015; Ogledov: 1168; Prenosov: 34
URL Povezava na celotno besedilo

Volumetric properties of ethanol-water mixtures under high pressure
Aljana Petek, Darja Pečar, Valter Doleček, 2001, izvirni znanstveni članek

Opis: Densities of ethanol-water mixtures have been measured using a vibrating tube densimeter and a different arrangement high-pressure experimental set-up. Measurements were carried out at 298,15 K in a pressure range from 0.1 MPa to 5MPa. Partial molar volumes, excess molar volumes and coefficients of isothermal compressibility were calculated. The molar volumes of alcohol and its partial molar volumes in mixtures with water are found to decrease monotonously with increasing pressure. Excess molar volumes are negative at all pressures. The numerical P-V relations at each composition are correlated satisfactorily as a function of pressure by the Hayward equation.
Ključne besede: chemistry, high-pressure vibrating tube densimeter, excess molar values, isothermal compressibility
Objavljeno: 10.07.2015; Ogledov: 658; Prenosov: 46
.pdf Celotno besedilo (424,02 KB)
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