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| 3. |
- Bachinger, Thomas
(författare)
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Multisensor arrays : for bioprocess monitoring
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bioprocess engineering, the technology that is focused on the exploitation of the metabolic potential of biological agents, has attracted growing interest throughout the past 50 years from both scientific and industrial communities. The products that have been brought to market range from pharmaceuticals and enzymes to food products and vitamins. The quality of human life has been improved through these efforts in many ways.Despite a strong research effort and the fact that microbial transformations often reach yields close to the theoretical maximum. many bioprocesses still operate at relatively low yields. One of the obstacles in effective operation is the extraction of useful information from the bioprocess. Sensors that acquire real-time information about the cells' state and their interaction with the environment in the bioreactor are seldom available. Hence, the implementation of sophisticated process control is prevented.In this thesis a new approach of non-invasive on-line bioprocess monitoring is evaluated. Chemical multisensor arrays (i.e. electronic noses) are used to extract information from the composition of volatiles emitted from the cell culture. The focus is on two specific areas: (i) monitoring of key variables in the bioreactor environment and (ii) monitoring of cell states and physiological events. The overall concern is, besides the increase of yield and reproducibility, the safety operation of bioprocesses.To cover a comprehensive area of modern bioprocessing, several organisms are investigated under different modes of operation in laboratory- and production scale processes. In repeated batch cultivations of recombinant Escherichia coli it is shown that an electronic nose can monitor biomass and specific growth rate with high accuracy. Glucose and ethanol concentration are monitored in batch cultivations of Saccharomyces cerevisiae. Bioproduct monitoring is presented in production-scale mammalian cell cultivation. The concentration of a therapeutic protein is monitored on-line in this long-term bioprocess thereby also outlining the stability of the sensor technique.In production-scale mammalian cell culture it is possible to follow cell transition states and monitor the reproducibility of the process. The physiological state of the cell population is revealed in laboratory-scale cultivations. It is shown that microbial contamination can be identified earlier than with conventional methods. Finally, the metabolic burden imposed on bacterial cells through strong overexpression of recombinant protein is monitored in fed-batch cultivation.
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- Behravan, Gity, et al.
(författare)
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Formation of a free radical of the sulfenylimine type in the mouse ribonucleotide reductase reaction with 2'-azido-2'-deoxycytidine 5'-diphosphate
- 1995
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Ingår i: Biochimica et Biophysica Acta, Gene Structure and Expression. - : Elsevier BV. - 0167-4781 .- 1879-2634. ; 1264:3, s. 323-329
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Tidskriftsartikel (refereegranskat)abstract
- Mouse and Escherichia coli ribonucleotide reductases (RR) both belong to the same class of RR, where the enzyme consists of two non-identical subunits, proteins R1 and R2. A transient free radical was observed by EPR spectroscopy in the mouse RR reaction with the suicidal inhibitor 2′-azido-2′-deoxycytidine 5′-diphosphate. The detailed hyperfine structure of the EPR spectrum of the transient radical is somewhat different for the mouse and previously studied E. coli enzymes. When the positive allosteric effector ATP was replaced by the negative effector dATP, no transient radical was observed, showing that ‘normal' binding of the inhibitor to the substrate binding site is required. Using the mouse protein R2 mutants W 103Y and D266A, where the mutations have been shown to specifically block long range electron transfer between the active site of the R1 protein to the iron/radical site in protein R2, no evidence of transient radical was found. Taken together, the data suggest that the radical is located at the active site in protein R1, and is probably of the sulfenylimine type
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- Bülow, Leif, et al.
(författare)
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The metabolic effects of native and transgenic hemoglobins on plants
- 1999
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Ingår i: Trends in Biotechnology. - 0167-7799. ; 17:1, s. 4-21
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Tidskriftsartikel (refereegranskat)abstract
- The strictly aerobic bacterium Vitreoscilla expresses a hemoglobin-like protein, VHb, when subjected to oxygen stress. When expressed in plants, this has several intriguing physiological effects, such as improving the overall growth rate, speeding germination and flowering, and increasing the productivity of certain oxygen-requiring metabolic pathways. Although the mechanisms behind the effects of VHb in heterologous hosts are not yet fully characterized, it has been suggested that VHb facilitates oxygen transport and/or storage. This hypothesis is supported by the kinetic properties of VHb, which allow very rapid dissociation of oxygen from the protein.
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- Dunuwila, D.D., et al.
(författare)
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ATR FTIR spectroscopy for in situ measurement of supersaturation
- 1997
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 179:1-2, s. 185-193
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Tidskriftsartikel (refereegranskat)abstract
- The current contribution establishes the technical feasibility of Attenuated Total Reflection (ATR) Fourier transform infrared (FTIR) spectroscopy for the in situ measurement of supersaturation in crystallization processes. The approach was inspired by recent advancements in ATR spectroscopy by way of various light transfer systems for remote sensing and by the increasing availability of ATR configurations well suited for remote, in situ measurements. The feasibility of the technique was investigated using a DIPPER-210® immersion probe manufactured by Axiom Analytical, Inc. Initial experiments conducted using aqueous maleic acid proved that ATR FTIR spectroscopy can be successfully employed to measure supersaturation, solubility and the metastable limit, in situ, with sufficient accuracy and precision.
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- Glassner, David A., et al.
(författare)
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Purification process for succinic acid produced by fermentation
- 1995
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Ingår i: Applied Biochemistry and Biotechnology. - 0273-2289 .- 1559-0291. ; 51-52:1, s. 73-82
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Tidskriftsartikel (refereegranskat)abstract
- Succinic acid is a versatile four-carbon dicarboxylic acid. It can be used commerically as an intermediate chemical for the manufacture of 1,4-butanediol, maleic anhydride, and many other chemicals. Succinic acid can be produced by the fermentation of carbohydrates. A complete process for the production and purification of succinic acid from carbohydrates has been developed. The process includes fermentation, desalting electrodialysis, water-splitting electrodialysis, and crystallization to produce a pure crystalline succinic acid. This article will present experimental work performed in the development of this process.
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- Kwon, Yun Joong, et al.
(författare)
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Protein separation using metal ion-bound particles in aqueous two-phase system
- 1999
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Ingår i: Biotechnology Techniques. - 0951-208X. ; 13:2, s. 145-148
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Tidskriftsartikel (refereegranskat)abstract
- Metal ion affinity partitioning of protein in aqueous two-phase systems was studied using Sepharose as ligand carrier as an integrated adsorption partitioning. Cu(II)-bound Sepharose was mixed with protein solution and an aqueous two-phase system. The affinity sorbent was distributed quantitatively to the upper side or the interface. The binding studies of lysozyme to copper-bound gel in PEG/dextran two-phase systems demonstrate the feasibility of this bioseparation process. PEG/dextran system did not affect binding and elution of lysozyme to and from the Cu(II)-Sepharose particles.
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- LeCaptain, D.J., et al.
(författare)
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Applicability of second harmonic generation for in situ measurement of induction time of selected crystallization systems
- 1999
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 203:4, s. 564-569
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Tidskriftsartikel (refereegranskat)abstract
- The nonlinear optical technique of second harmonic generation (SHG) is introduced as a novel technique for monitoring particle formation in batch crystallizations. SHG is more sensitive and is less prone to interference than turbidometric methods. The studies presented show the applicability of SHG as a method for in situ measuring the induction time of a number of noncentrosymmetric crystal systems.
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