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Dive into the research topics where Peter Czermak is active.

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Featured researches published by Peter Czermak.


Open Environmental Sciences | 2007

Ceramic Ultra- and Nanofiltration Membranes for Oilfield Produced Water Treatment: A Mini Review

K. Shams Ashaghi; Mehrdad Ebrahimi; Peter Czermak

Produced water is any fossil water that is brought to the surface along with crude oil or natural gas. By far, pro- duced water is the largest by-product or waste stream by volume associated with oil and gas production. The volume of produced water is dependent upon the state of maturation of the field. There is a need for new technologies for produced water treatment due to increased focus on water conservation and environmental regulation. Each time regulatory agencies initiate more stringent environmental control treatment technologies are refined to meet the updated standards. The Euro- pean standard for effluent from onshore petroleum activities requires less than 5 mg/l total hydrocarbons (HC) and less than 10 mg/l suspended solids; such low concentrations are unattainable when classical separation processes are used. To overcome the challenges posed by more stringent regulations, operators have turned to membrane filtration schemes which have the potential to minimize additional costs and disposal issues. Ceramic ultra- and nanofiltration membranes represent a relatively new class of materials available for the treatment of produced water. They can be manufactured from a variety of starting materials and can be processed in different ways to yield products with broad ranges of physical- chemical advantages and applications. While these membranes are effective in the separation of oils, emulsions and silts, they are prone to fouling by waxes and asphaltenes. The issues needing to be addressed are the prevention of membrane fouling during operation and the provision of an expedient, cost-effective and non-hazardous means of cleaning fouled membranes. Currently, there are not enough existing studies related to the treatment of oilfield produced water using ce- ramic membranes.


The Open Biomedical Engineering Journal | 2007

Expansion and Harvesting of hMSC-TERT

Christian Weber; Sebastian Pohl; Ralf Pörtner; Christine Wallrapp; Moustapha Kassem; Peter Geigle; Peter Czermak

The expansion of human mesenchymal stem cells as suspension culture by means of spinner flasks and microcarriers, compared to the cultivation in tissue culture flasks, offers the advantage of reducing the requirements of large incubator capacities as well as reducing the handling effort during cultivation and harvesting. Nonporous microcarriers are preferable when the cells need to be kept in viable condition for further applications like tissue engineering or cell therapy. In this study, the qualification of Biosilon, Cytodex 1, Cytodex 3, RapidCell and P102-L for expansion of hMSC-TERT with an associated harvesting process using either trypsin, accutase, collagenase or a trypsin-accutase mixture was investigated. A subsequent adipogenic differentiation of harvested hMSC-TERT was performed in order to observe possible negative effects on their (adipogenic) differentiation potential as a result of the cultivation and harvesting method. The cultivated cells showed an average growth rate of 0.52 d-1. The cells cultivated on Biosilon, RapidCell and P102-L were harvested succesfully achieving high cell yield and vitalities near 100%. This was not the case for cells on Cytodex 1 and Cytodex 3. The trypsin-accutase mix was most effective. After spinner expansion and harvesting the cells were successfully differentiated to adipocytes.


Journal of Biotechnology | 2015

Expression of enzymes for the usage in food and feed industry with Pichia pastoris.

Sebastian C. Spohner; Hagen Müller; Hendrich Quitmann; Peter Czermak

The methylotrophic yeast Pichia pastoris is an established protein expression host for the production of industrial enzymes. This yeast can be grown to very high cell densities and produces high titers of recombinant protein, which can be expressed intercellularly or be secreted to the fermentation medium. P. pastoris offers some advantages over other established expression systems especially in protein maturation. In food and feed production many enzymatically catalyzed processes are reported and the demand for new enzymes grows continuously. For instance the unique catalytic properties of enzymes are used to improve resource efficiency, maintain quality, functionalize food, and to prevent off-flavors. This review aims to provide an overview on recent developments in heterologous production of enzymes with P. pastoris and their application within the food sector.


International Journal of Artificial Organs | 2010

Expansion of human mesenchymal stem cells in a fixed-bed bioreactor system based on non-porous glass carrier – Part A: Inoculation, cultivation, and cell harvest procedures

Christian Weber; Denise Freimark; Ralf Pörtner; Pablo Pino-Grace; Sebastian Pohl; Christine Wallrapp; Peter Geigle; Peter Czermak

Human mesenchymal stem cells (hMSC) are a promising cell source for several applications of regenerative medicine. The cells employed are either autologous or allogenic; by using stem cell lines in particular, allogenic cells enable the production of therapeutic cell implants or tissue engineered implants in stock. For these purposes, the generally small initial cell number has to be increased; this requires the use of bioreactors, which offer controlled expansion of the hMSC under GMP-conform conditions. In this study, divided into part A and B, a fixed bed bioreactor system based on non-porous borosilicate glass spheres for the expansion of hMSC, demonstrated with the model cell line hMSC-TERT, is introduced. The system offers convenient automation of the inoculation, cultivation, and harvesting procedures. Furthermore, the bioreactor has a simple design which favors its manufacturing as a disposable unit. Part A is focused on the inoculation, cultivation, and harvesting procedures. Cultivations were performed in lab scales up to a bed volume of 300 cm³. The study showed that the fixed bed system, based on 2-mm borosilicate glass spheres, as well as the inoculation, cultivation, and harvesting procedures are suitable for the expansion of hMSC with high yield and vitality.


Cryobiology | 2011

Systematic parameter optimization of a Me2SO- and serum-free cryopreservation protocol for human mesenchymal stem cells

Denise Freimark; Constanze Sehl; Christian Weber; Klaus Hudel; Peter Czermak; Nicola Hofmann; Ralf Spindler; Birgit Glasmacher

Human mesenchymal stem cells (hMSCs) have great potential for clinical therapy and regenerative medicine. One major challenge concerning their application is the development of an efficient cryopreservation protocol since current methods result in a poor viability and high differentiation rates. A high survival rate of cryopreserved cells requires an optimal cooling rate and the presence of cryoprotective agents (CPA) in sufficient concentrations. The most widely used CPA, dimethylsulfoxide (Me(2)SO), is toxic at high concentrations at temperatures >4°C and has harmful effects on the biological functionality of stem cell as well as on treated patients. Thus, this study investigates different combinations of non-cytotoxic biocompatible substances, such as ectoin and proline, as potential CPAs in a systematic parametric optimization study in comparison to Me(2)SO as control and a commercial freezing medium (Biofreeze®, Biochrom). Using a freezing medium containing a low proline (1%, w/v) and higher ectoin (10%, w/v) amount revealed promising results although the highest survival rate was achieved with the Biofreeze® medium. Cryomicroscopic experiments of hMSCs revealed nucleation temperatures ranging from -16 to -25°C. The CPAs, beside Me(2)SO, did not affect the nucleation temperature. In most cases, cryomicroscopy revealed intracellular ice formation (IIF) during the cryopreservation cycle for all cryoprotocols. The occurence of IIF during thawing increased with the cooling rate. In case of hMSC there was no correlation between the rate of IIF and the post-thaw cell survival. After thawing adipogenic differentiation of the stem cells demonstrated cell functionality.


Transfusion Medicine and Hemotherapy | 2010

Use of encapsulated stem cells to overcome the bottleneck of cell availability for cell therapy approaches

Denise Freimark; Pablo Pino-Grace; Sebastian Pohl; Christian Weber; Christine Wallrapp; Peter Geigle; Ralf Pörtner; Peter Czermak

Nowadays cell-based therapy is rarely in clinical practice because of the limited availability of appropriate cells. To apply cells therapeutically, they must not cause any immune response wherefore mainly autologous cells have been used up to now. The amount of vital cells in patients is limited, and under certain circumstances in highly degenerated tissues no vital cells are left. Moreover, the extraction of these cells is connected with additional surgery; also the expansion in vitro is difficult. Other approaches avoid these problems by using allo-or even xenogenic cells. These cells are more stable concerning their therapeutic behavior and can be produced in stock. To prevent an immune response caused by these cells, cell encapsulation (e.g. with alginate) can be performed. Certain studies showed that encapsulated allo-and xenogenic cells achieve promising results in treatment of several diseases. For such cell therapy approaches, stem cells, particularly mesenchymal stem cells, are an interesting cell source. This review deals on the one hand with the use of encapsulated cells, especially stem cells, in cell therapy and on the other hand with bioreactor systems for the expansion and differentiation of mesenchymal stem cells in reproducible and sufficient amounts for potential clinical use.


Advances in Biochemical Engineering \/ Biotechnology | 2010

Production Process for Stem Cell Based Therapeutic Implants: Expansion of the Production Cell Line and Cultivation of Encapsulated Cells

Christian Weber; Sebastian Pohl; R. Poertner; Pablo Pino-Grace; Denise Freimark; Christine Wallrapp; Peter Geigle; Peter Czermak

Cell based therapy promises the treatment of many diseases like diabetes mellitus, Parkinson disease or stroke. Microencapsulation of the cells protects them against host-vs-graft reactions and thus enables the usage of allogenic cell lines for the manufacturing of cell therapeutic implants. The production process of such implants consists mainly of the three steps expansion of the cells, encapsulation of the cells, and cultivation of the encapsulated cells in order to increase their vitality and thus quality. This chapter deals with the development of fixed-bed bioreactor-based cultivation procedures used in the first and third step of production. The bioreactor system for the expansion of the stem cell line (hMSC-TERT) is based on non-porous glass spheres, which support cell growth and harvesting with high yield and vitality. The cultivation process for the spherical cell based implants leads to an increase of vitality and additionally enables the application of a medium-based differentiation protocol.


International Journal of Artificial Organs | 2012

Microcarrier-based expansion process for hMSCs with high vitality and undifferentiated characteristics.

Christiane Elseberg; Jasmin Leber; Denise Salzig; Christine Wallrapp; Moustapha Kassem; Matthias Kraume; Peter Czermak

For cell therapy, a high biomass of human mesenchymal stem cells (hMSCs) is required for clinical applications, such as in the form of encapsulated implants. An easy and reproducible microcarrier-based stirred tank reactor cultivation process for hMSCs in 1.68 L scale is described. To avoid medium changes, studies comparing high-glucose DMEM (DMEM-HG) with low-glucose EMEM were performed showing that high-glucose medium has positive effects on cell proliferation and that cell differentiability remains. Studies on the inoculation strategy and cell density, carrier concentration, volume, and stirrer speed were performed and resulted in a set of optimized parameters, inoculation strategy was found to be 45 minutes of static state and 2 minutes of stirring repeated in 4 cycles. The inoculation density was chosen to be 7×103 cells/cm2, and the carrier concentration of glass surface carrier was 25 g/L. For the described reactor system, a stirrer speed of 120 rpm for the inoculation process and a daily increase of 10 rpm up to 160 rpm were found to be suitable. Process reproducibility was shown by 3 repeated cultivations at the determined set of parameters allowing high biomass values of up to 7×108 cells per batch. With DMEM-HG, no limitation of glucose was found, and lactate and ammonia remained lower than critical inhibitory concentrations. Comparison of the static (T-flask) and dynamic cultures in the stirred tank reactor showed for both cases, that cells were of high vitality and both maintained differentiability. In both cases, encapsulation of the cells resulted in high bead vitality, a basic requirement for cell therapy application.


International Journal of Artificial Organs | 2010

Intervertebral disc regeneration: Influence of growth factors on differentiation of human mesenchymal stem cells (hMSC)

Franziska Ehlicke; Denise Freimark; Birthe Heil; Adriaan Dorresteijn; Peter Czermak

INTRODUCTION One common cause of disability in modern society is low back pain. The main reason for this pain is the degeneration of the intervertebral disc (IVD), particularly of the nucleus pulposus (NP). For the early degeneration stage, a cell-based therapy could constitute a minimally invasive method of treatment. Therefore, adequate cells are needed. As the usage of NP cells is limited because of their insufficient amount or vitality, a promising alternative is the application of human mesenchymal stem cells (hMSCs) OBJECTIVE To investigate the potential of various growth factors to induce the differentiation of hMSCs into NP cells and thereby to obtain an alternative cell source for the treatment of IVD degeneration. METHODS hMSC-TERT were cultivated three-dimensionally in a hydrogel for 21 days to form NP cells. Cell survival and proliferation were determined using SybrGreen/propidium iodide double staining and the WST-test. To investigate the ability of several growth factors to differentiate hMSCs into NP cells, fluorescence immunostaining of NP-specific marker proteins (e.g., chondroadherin (CHAD) and the recently discovered cytokeratin 19) were performed. RESULTS Following the procedure described above, cells are able to maintain their viability and proliferation capacity throughout the cultivation time. By using a previously established immunofluorescence protocol, we were able to indicate the ability of three different growth factors for differentiating hMSCs into NP-like cells. CONCLUSION The expression of several marker proteins in all differentiation experiments indicates the ability of IGF-1, FGF-2 and PDGF-BB to differentiate hMSCs into NP-like cells apart from the usually applied TGF-beta3. Furthermore, our findings preclude the application of Cytokeratin 19 as a specific marker protein for NP cells. Further experiments have to be done to find real specific NP marker proteins to indisputably verify the differentiation of hMSCs into NP cells. If so, application of these three growth factors would possibly be an option to obtain sufficient NP cells for minimally invasive IVD regeneration.


Biotechnology Progress | 2004

Experimental Study of a Ceramic Microsparging Aeration System in a Pilot‐Scale Animal Cell Culture

Dirk Nehring; Peter Czermak; Jürgen Vorlop; Holger Lübben

The oxygen supply of cell cultures with the aid of free gas bubbles is an efficient process strategy in pharmaceutical production. If the cell‐damaging impact of gas bubbles is reduced, direct aeration becomes a practical solution with scale‐up potential and comparatively high oxygen transfer rates. In this paper a microsparging aeration system made of porous ceramic was compared with bubble‐free membrane aeration. The sparging system was used for the long‐term cultivation of mammalian cells in 2‐to 100‐L scale bioreactors and produced bubble sizes of 100–500 μm in diameter. Using a scale of 2.5 and 30 L, a cell density of 2.6 × 106 cells/mL was attained. When a 100‐L scale was used, a density of 1.1 × 106 cells/mL was achieved, whereas a comparable membrane‐aerated system showed a cell density of 2.2 × 106 cells/mL. At relatively low agitation rates of less than 70 rpm in the sparged bioreactors, a homogeneous and constant oxygen concentration was kept in the medium. As a result of the different foam‐forming tendency caused by the lower gas flow of the ceramic sparger compared to that of the standard aeration systems, we were able to develop an appropriate process control strategy. Furthermore, oxygen transfer measurements for the common stainless steel sparger and the ceramic sparger showed a 3‐fold higher oxygen transfer coefficient for the ceramic sparger.

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Mehrdad Ebrahimi

Technische Hochschule Mittelhessen

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Denise Salzig

Technische Hochschule Mittelhessen

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Ralf Pörtner

Hamburg University of Technology

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Christian Weber

Technische Hochschule Mittelhessen

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Zoltán Kovács

Corvinus University of Budapest

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Denise Freimark

Technische Hochschule Mittelhessen

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Tobias Weidner

Technische Hochschule Mittelhessen

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