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1

Problems in design and operation of bioreactors for plant and animal cell cultures

100%
Pohorecki R.
Biotechnologia
|
1996
|
issue 2
125-135
EN
Basic modes of bioreactor operation (bath, semicontinuous and continuous), and main culture systems (suspended growth, attached growth on microcarriers) are shortly described.Main problem in bioreactor design and operation, including hydrodynamics, heat and mass transfer, cell viability, measurement and control, are discussed.Some particular problems: mixing systems, air supply systems, power dissipation, external and internal diffusion are discussed in a greater detail.Examples of specific reactor design are given, namely: stirred tank reactors, bubble columns, gas lift reactors, liquid jet reactors, packed bed reactors fluidised bed reactors, membrane reactors.New research problem are outlined.
2

Fluid mechanical problems in biotechnology

100%
Pohorecki R.
Biotechnologia
|
2002
|
issue 2
60-77
EN
The rapid development of biotechnology we are witnessing nowadays is strongly related to the advances in bioprocess engineering. This field of engineering, including both bioreactor engineering and down-stream processing, is an integration of biological, biochemical and engineering principles, leading to the quantitative description and development of biotechnological processes carried out on an industrial scale. A very important part of bioprocess engineering problems involves the fluid mechanics problems occurring in biotechnological equipment. These are both the problems related to bioreactor design and operation, and to down-stream processing operations, such as micro- and ultrafiltration, centrifugation, precipitation, extraction, sorptions, flocculation, mixing, fluid transportation, etc. This paper is focused mainly on fluid mechanical problems in bioreactor engineering. It begins with a brief reminder of some basic concepts in fluid flow, rheology and turbulence, of relevance to bioreactors. Then the main types of bioreactor design are reviewed, including stirred bioreactors and pneumatically driven bioreactors. The hydrodynamic characteristics of different types of reactors are then outlined, including power consumption, mixing, heat and mass transfer, aeration, and cell demage by hydrodynamic stresses. Finally, some new developments are discussed, including the use of computer fluid dynamics (CFD) to describe hydrodynamics of bioreactors, and the use of the multifractal theory of turbulence to describe some cell damaging effects.
3

Kinetic study of enzymatic hydrolysis of tannins

63%
Pohorecki R., Galwas-Zakrzewska M.
Biotechnologia
|
2002
|
issue 2
184-192
EN
Tannins are present in many plant foods. Tannase (EC 3.1.1.20) catalyses hydrolysis of ester bonds in hydrolysable gallotannins releasing glucose and gallic acid. Enzyme was produced by Penicillium chrysogenum cultured in Czapek-Dox medium containing tannic acid. The tannic acid was used as a substrate in the enzymatic reactions. The product inhibits the enzymatic reaction. It was determined that inhibition was of the competitive type. The mathematical model (Eg. 7) and kinetic constancy describing the process were determined: KM=0,5310-4[mol/dm3], RM=1,2610-3 [mol/dm3 min], KP=2,0410-4 [mol/dm3]. The results obtained from the model well agree with those obtained experimentally.
4

Enzymatic hydrolysis in multifunctional reactor

63%
Galwas M., Pohorecki R.
|
2007
|
issue 2
149-160
EN
The aim of this work was to develop a multifunctional reactor to carry out the enzymatic process of biodegradation of tannins. An integrated reaction system consists of a stirred tank reactor and a spiral-wound membrane module. The system was used for simultaneous reaction and product separation during the enzymatic hydrolysis of tannic acid. On the basis of kinetic investigations, a kinetic equation for the enzymatic hydrolysis of tannic acid to gallic acid by tannase was developed. It was demonstrated that the kinetics of enzymatic hydrolysis of tannic acid catalyzed by tannase can be described by a kinetic equation of the Michaelis-Menten type with the competitive product inhibition. The design of the reactor ensured the entrapment of enzyme within the reactor volume, and, in the same time, continuous separation of gallic acid. A multifunctional membrane reactor has been designed. The reactor consisted of a stirred vessel and a spiral-wound membrane module. The process was run under optimal conditions for the enzyme activity (pH 5.5, 30oC). Prolonged use of the enzyme was achieved with good efficiency. A mathematical model describing the process in the reactor has been developed. The model, based on kinetic studies, has been demonstrated to describe properly the behavior of the reactor. A good agreement of the experimental results with the calculated ones was obtained. The experimental results were also compared with the existing literature data concerning the mass transfer in spiral membrane modules. A dimensionless correlation of the Sh=f(Re,Sc) type was used to describe the data obtained. A good agreement of the literature results with own data was observed.
5

Erythrocyte destruction under shear stresses

51%
Pohorecki R., Ryszczuk A., Baldyga J., Motyl T.
Biotechnologia
|
2002
|
issue 2
33-47
EN
Erythrocyte destruction in laminar (Couette) flow was investigated. Critical values of the shear stress for ovine erythrocytes from two donors were determined. Large individual differences between erythrocytes from the two donors suggest that individual determination of shear stress resistance for each donor is necessary, and that the determination of shear stress resistance might be of diagnostic value.
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