Change search
Refine search result
1 - 16 of 16
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Boer, H.
    et al.
    Teeri, Tuula T.
    KTH, Superseded Departments, Biotechnology.
    Koivula, A.
    Characterization of Trichoderma reesei cellobiohydrolase CeI7A secreted from Pichia pastoris using two different promoters2000In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 69, no 5, p. 486-494Article in journal (Refereed)
    Abstract [en]

    Heterologous expression of T. reesei cellobiohydrolase Cel7A in a methylotrophic yeast Pichia pastoris was tested both under the P. pastoris alcohol oxidase (AOX1) pro meter and the glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter in a fermenter. Production of Ce17A with the AOX1 promoter gave a better yield, although part of the enzyme expressed was apparently not correctly folded. Cel7A expressed in P. pastoris is overglycosylated at its N-glycosylation sites as compared to the native T. reesei protein, but less extensive than Cel7A expressed in Saccharomyces cerevisiae. The k(cat) and K-m values for the purified protein on soluble substrates are similar to the values found for the native Trichoderma Cel7A, whereas the degradation rate on crystalline substrate (BMCC) is somewhat reduced. The measured pH optimum also closely resembles that of purified T. reesei Cel7A. Furthermore, the hyperglycosylation does not affect the thermostability of the enzyme monitored with tryptophane fluorescence and activity measurements. On the other hand, CD measurements indicate that the formation of disulfide bridges is an important step in the correct folding of Cel7A and might explain the difficulties encountered in heterologous expression of T. reesei Cel7A. The constitutive GAP promoter expression system of P. pastoris is nevertheless well suited for activity screening of cellulase activities in microtiter plates. With this type of screening method a faster selection of site-directed and random mutants with, for instance, an altered optimum pH is possible, in contrast to the homologous T. reesei expression system.

  • 2. Bylund, F.
    et al.
    Castan, A.
    Mikkola, R.
    Veide, Andres
    KTH, Superseded Departments, Biotechnology.
    Larsson, G.
    Influence of scale-up on the quality of recombinant human growth hormone2000In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 69, no 2, p. 119-128Article in journal (Refereed)
    Abstract [en]

    The aerobic fed-batch production of recombinant human growth hormone (rhGH) by Escherichia coli was studied. The goal was to determine the production and protein degradation pattern of this product during fed-batch cultivation and to what extent scale differences depend on the presence of a fed-batch glucose feed zone. Results of laboratory bench-scale, scale-down (SDR), and industrial pilot-scale (3-m(3)) reactor production were compared. In addition to the parameters of product yield and quality, also cell yield, respiration, overflow, mixed acid fermentation, glucose concentration, and cell lysis were studied and compared. The results show that oxygen limitation following glucose overflow was the critical parameter and not the glucose overflow itself. This was verified by the pattern of byproduct formation where formate was the dominating factor and not acetic acid. A correlation between the accumulation of formate, the degree of heterogeneity, and cell lysis was also visualized when recombinant protein was expressed. The production pattern could be mimicked in the SDR reactor for all parameters, except for product quantity and quality, where 30% fewer rhGH-degraded forms were present and where about 80% higher total yield was achieved, resulting in 10% greater accumulation of properly formed rhGH monomer.

  • 3.
    Cassimjee, Karim Engelmark
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Trummer, Martin
    KTH, School of Biotechnology (BIO), Biochemistry.
    Branneby, Cecilia
    KTH, School of Biotechnology (BIO), Biochemistry.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry.
    Silica-immobilized His(6)-tagged enzyme: Alanine racemase in hydrophobic solvent2008In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 99, no 3, p. 712-716Article in journal (Refereed)
    Abstract [en]

    A new immobilization method for enzymes is presented to facilitate synthetic applications in aqueous as well as organic media. The enzyme Alanine racemase (AlaR) from Geobacillus stearothermophilus was cloned, overexpressed and then immobilized on a silica-coated thin-layer chromatography plate to create an enzyme surface. The enzyme, fused to a His(6)-tag at its N-terminal, was tethered to the chemically modified silica-coated TLC plate through cobalt ions. The immobilized enzyme showed unaltered kinetic parameters in small-scale stirred reactions and retained its activity after rinsing, drying, freezing or immersion in n-hexane. This practical method is a first step towards a general immobilization method for synthesis applications with any enzyme suitable for His(6)-tagging.

  • 4. Castan, A.
    et al.
    Enfors, Sven-Olof
    KTH, Superseded Departments, Biotechnology.
    Formate accumulation due to DNA release in aerobic cultivations of Escherichia coli2002In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 77, no 3, p. 324-328Article in journal (Refereed)
    Abstract [en]

    Three different aerobic fed-batch processes of Escherichia coli were studied, two for the production of a recombinant protein and one process with a wild-type E. coli strain. In all three processes, an accumulation of formate could be observed in the latter part of the process. Analysis of the concentration of DNA in the medium revealed that the release of DNA coincided with the accumulation of formate. It was found that increasing concentrations of DNA correlated in almost linearly increasing concentrations of formate. Formate accumulation is caused by mixed acid fermentation, although no oxygen limitation was measured with the DO electrode. It is proposed that extracellular DNA restrained mass transfer between the bulk medium and the cell. To investigate if the DNA accumulation caused formate production, DNA was removed by continuous feeding of a DNA binding polymer to the medium. The addition of the polymer decreased the content of free DNA in the broth and the formate was reassimilated. Furthermore, additional DNA early in the process resulted in early formate accumulation.

  • 5. Jahic, M.
    et al.
    Knoblechner, J.
    Charoenrat, T.
    Enfors, Sven-Olof
    KTH, School of Biotechnology (BIO), Bioprocess Technology.
    Veide, Andres
    KTH, School of Biotechnology (BIO), Bioprocess Technology.
    Interfacing Pichia pastoris cultivation with expanded bed adsorption2006In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 93, no 6, p. 1040-1049Article in journal (Refereed)
    Abstract [en]

    For improved interfacing of the Pichia pastoris fed-batch cultivation process with expanded bed adsorption (EBA) technique, a modified cultivation technique was developed. The modification included the reduction of the medium salt concentration, which was then kept constant by regulating the medium conductivity at low value (about 8 mS/cm) by salt feeding. Before loading, the low conductivity culture broth was diluted only to reduce viscosity, caused by high cell density. The concept was applied to a one-step recovery and purification procedure for a fusion protein composed of a cellulose-binding module (CBM) from Neocallimastix patriciarum cellulase 6A fused to lipase B from Candida antarctica (CALB). The modified cultivation technique resulted in lower cell death and consequently lower concentration of proteases and other contaminating proteins in the culture broth. Flow cytometry analysis showed 1% dead (propidium-stained) cells compared to 3.5% in the reference process. During the whole process of cultivation and recovery, no proteolysis was detected and in the end of the cultivation, the product constituted 87% of the total supernatant protein. The lipase activity in the culture supernatant increased at an almost constant rate up to a value corresponding to 2.2 g/L of CBM-CALB. In the EBA process, no cell-adsorbent interaction was detected but the cell density had to be reduced by a two-times dilution to keep a proper bed expansion. At flow velocity of 400 cm/h, the breakthrough capacity was 12.4 g/L, the product yield 98%, the concentration factor 3.6 times, the purity about 90%, and the productivity 2.1 g/L (.) h.

  • 6.
    Jarmander, Johan
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Hallström, Björn M.
    KTH, School of Biotechnology (BIO), Proteomics and Nanobiotechnology. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Larsson, Gen
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Simultaneous Uptake of Lignocellulose- Based Monosaccharides by Escherichia Coli2014In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 111, no 6, p. 1108-1115Article in journal (Refereed)
    Abstract [en]

    Lignocellulosic waste is a naturally abundant biomass and is therefore an attractive material to use in second generation biorefineries. Microbial growth on the monosaccharides present in hydrolyzed lignocellulose is however associated with several obstacles whereof one is the lack of simultaneous uptake of the sugars. We have studied the aerobic growth of Escherichia coli on D-glucose, D-xylose, and L-arabinose and for simultaneous uptake to occur, both the carbon catabolite repression mechanism (CCR) and the AraC repression of xylose uptake and metabolism had to be removed. The strain AF1000 is a MC4100 derivative that is only able to assimilate arabinose after a considerable lag phase, which is unsuitable for commercial production. This strain was successfully adapted to growth on L-arabinose and this led to simultaneous uptake of arabinose and xylose in a diauxic growth mode following glucose consumption. In this strain, a deletion in the phosphoenolpyruvate:phosphotransferase system (PTS) for glucose uptake, the ptsG mutation, was introduced. The resulting strain, PPA652ara simultaneously consumed all three monosaccharides at a maximum specific growth rate of 0.59h(-1), 55% higher than for the ptsG mutant alone. Also, no residual sugar was present in the cultivation medium. The potential of PPA652ara is further acknowledged by the performance of AF1000 during fed-batch processing on a mixture of D-glucose, D-xylose, and L-arabinose. The conclusion is that without the removal of both layers of carbon uptake control, this process results in accumulation of pentoses and leads to a reduction of the specific growth rate by 30%.

  • 7. Lin, H. Y.
    et al.
    Hoffmann, F.
    Rozkov, Aleksei
    KTH, Superseded Departments, Biotechnology.
    Enfors, Sven-Olof
    KTH, Superseded Departments, Biotechnology.
    Rinas, U.
    Neubauer, P.
    Change of extracellular cAMP concentration is a sensitive reporter for bacterial fitness in high-cell-density cultures of Escherichia coli2004In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 87, no 5, p. 602-613Article in journal (Refereed)
    Abstract [en]

    Guanosine-3'5'-tetraphosphate (ppGpp) and as, two regulators of the starvation response of Escherichia coli, have received increasing attention for monitoring cell physiological changes in production processes, although both are difficult to quantify. The kinetics of cAMP formation and degradation were not yet investigated in such processes, although the complex regulation of cAMP by synthesis, release, and degradation in connection with straightforward methods for analysis renders it a highly informative target. Therefore, we followed the cAMP concentration in various nonrecombinant and in four different recombinant glucose-limited fed-batch processes in different production scales. The intracellular cAMP concentration increases strongly at the end of the batch phase. Most cAMP is released to the cultivation medium. The rates of accumulation and degradation of extracellular cAMP are growth-rate-dependent and show a distinct maximum at a growth rate of about 0.35 h(-1). At very low growth rates, below 0.05 h(-1), extracellular cAMP is not produced but rather degraded, independent of whether this low growth rate is caused by glucose limitation or by the high metabolic load of recombinant protein production. In contrast to intracellular cAMP, which is highly unstable, analysis of extracellular cAMP is simpler and the kinetics of accumulation and degradation reflect well the physiological situation, including unlimited growth, limitation, and severe starvation of a production host.

  • 8. Lin, H. Y.
    et al.
    Mathiszik, B.
    Xu, B.
    Enfors, Sven-Olof
    KTH, Superseded Departments, Biotechnology.
    Neubauer, P.
    Determination of the maximum specific uptake capacities for glucose and oxygen in glucose-limited fed-batch cultivations of Escherichia coli2001In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 73, no 5, p. 347-357Article in journal (Refereed)
    Abstract [en]

    A simple pulse-based method for the determination of the maximum uptake capacities for glucose a nd oxygen in glucose limited cultivations of E. coli is presented. The method does not depend on the time-consuming analysis of glucose or acetate, and therefore can be used to control the feed rate in glucose limited cultivations, such as fed-batch processes. The application of this method in fed-batch processes of E. coli showed that the uptake capacity for neither glucose nor oxygen is a constant parameter, as often is assumed in fed-batch models. The glucose uptake capacity decreased significantly when the specific growth rate decreased below 0.15 h(-1) and fell to about 0.6 mmol g(-1) h(-1) (mmol per g cell dry weight and hour) at the end of fed-batch fermentations, where mu was approximately 0.02 h(-1). The oxygen uptake capacity started to decrease somewhat earlier when mu declined below 0.25 h(-1) and was 5 mmol g(-1) h(-1) at the end of the fermentations. The behavior of both uptake systems is integrated in a dynamic model which allows a better fitting of experimental values for glucose in fed-batch processes in comparison to generally used unstructured kinetic models.

  • 9. Lindberg, Anna
    et al.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Selective desorption of carbon dioxide from sewage sludge for in situ methane enrichment - Part 1: Pilot-plant experiments2006In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 95, no 5, p. 794-803Article in journal (Refereed)
    Abstract [en]

    In situ methane enrichment in anaerobic digestion of sewage sludge has been investigated by experiments and by modeling. In this first part, the experimental work on the desorption of carbon dioxide and methane from sewage sludge is reported. The bubble column, had a diameter of 0.3 m and a variable height up to 1.8 m. At operation the dispersion height in the column was between 1 and 1.3 m. Outdoor air was used. The column was placed close to a full-scale sewage sludge digester, at a municipal wastewater treatment plant. The digester was operated at mesophilic conditions with a hydraulic retention time of about 20 days. The bubble column was operated to steady-state, at which carbon dioxide concentration and alkalinity were determined on the liquid side, and the concentration of carbon dioxide and methane on the gas side. Thirty-eight experiments were performed at various liquid and gas flow rates. The experimental results show that the desorption rates achieved for carbon dioxide ranges from 0.07 to 0.25 m(3) CO2/m(3) sludge per day, which is comparable to the rate of generation by the anaerobic digestion. With increasing liquid flow rate and decreasing gas flow rate the amount of methane desorbed per amount of carbon dioxide desorbed increases. The lowest methane loss achieved is approximately 2% of the estimated methane production in the digestion process.

  • 10. Lindberg, Anna
    et al.
    Rasmuson, Åke C.
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Transport Phenomena.
    Selective desorption of carbon dioxide from sewage sludge for in situ methane enrichment - Part II: Modelling and evaluation of experiments2007In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 97, no 5, p. 1039-1052Article in journal (Refereed)
    Abstract [en]

    In situ methane enrichment in anaerobic digestion of sewage sludge has been investigated by experiments and by modelling. Sludge from a full scale digester was fed to a pilot scale bubble column having 0.3 m diameter for preferential desorption of carbon dioxide. In this second part, a model describing the steady-state performance of the bubble column for desorption of carbon dioxide and methane has been developed. The column is assumed to operate in the homogeneous flow regime, and with respect to carbon dioxide and methane both phases are described by the axial dispersion model.. The model treats the chemical reaction equilibrium between carbon dioxide and bicarbonate as being slow and the bicarbonate concentration as being constant. The model is correlated to previously reported experimental, results to determine the liquid side mass transfer coefficient in each experiment. A simple power law model is used to correlate, the mass transfer coefficient to the gas flow rate. In general, the model allows for a reasonable qualitative description of the behaviour of the bubble column performance but the quantitative agreement with experimental results is not satisfactory. It is believed, though that the main. problem is actually not in the model but is related to experimental uncertainties concerning inlet concerttrations of liquid phase methane and bicarbonate..

  • 11.
    Prytz, Ingela
    et al.
    KTH, Superseded Departments, Biotechnology.
    Sandén, Anna Maria
    KTH, Superseded Departments, Biotechnology.
    Nyström, Thomas
    Farewell, Anne
    Wahlström, Åsa
    Förberg, Cecilia
    Pragai, Zoltan
    Barer, Mike
    Harwood, Colin
    Larsson, Gen
    KTH, Superseded Departments, Biotechnology.
    Fed-batch production of recombinant beta-galactosidase using the universal stress promoters uspA and uspB in high cell density cultivations2003In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 83, no 5, p. 595-603Article in journal (Refereed)
    Abstract [en]

    A high-level production system using the universal stress promoters uspA and uspB in a fed-batch cultivation based on minimal medium was designed. In development it was shown that a standard industrial fed-batch protocol could not be used for this purpose since it failed to induce the levels of product as compared to the basal level. Instead, a batch protocol followed by a low constant feed of glucose was shown to give full induction. The levels of the product protein, beta-galactosidase, corresponded to approximately 25% of the total protein. Higher levels were found using the uspA than uspB vectors where uspA showed considerably higher basal level. The data indicate that the sigma(70) regulated promoter, uspA, although affected by the alarmone guanosine tetraphosphate, ppGpp, worked partly in a similar manner to constitutive promoters. An industrial high cell density fedbatch cultivation on the basis of the suggested fed-batch protocol and the uspA promoter gave a final beta-galatosidase concentration of 7 g/L and a final cell concentration of 65 g/L. The heterogeneity in production of the individual cell was measured by fluorescence microscopy. The data show that there is a process time independent heterogeneity in production, which is suggested to be caused by heterogeneity in the substrate uptake rate of the individual cell.

  • 12.
    Sandén, Anna Maria
    et al.
    KTH, School of Biotechnology (BIO), Centres, Centre for Bioprocess Technology, CBioPT.
    Boström, Maria
    KTH, School of Biotechnology (BIO), Centres, Centre for Bioprocess Technology, CBioPT.
    Markland, Katrin
    KTH, School of Biotechnology (BIO), Centres, Centre for Bioprocess Technology, CBioPT.
    Larsson, Gen
    KTH, School of Biotechnology (BIO), Centres, Centre for Bioprocess Technology, CBioPT.
    Solubility and proteolysis of the Zb-MaIE and Zb-MaIE31 proteins during overproduction in Escherichia coli2005In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 90, no 2, p. 239-247Article in journal (Refereed)
    Abstract [en]

    From the hypothesis that the rate of expression of a nascent polypeptide controls the accumulation of soluble full-length protein, accumulation of the model fusion proteins Zb-MalE and Zb-MalE31, were studied. MalE and MalE31 are two isoforms of the maltose binding protein, differing only in two consecutive amino acids. Parameters controlling the expression rate were the transcription rate, which was controlled by IPTG induction of the lacUV5 promoter and the substrate addition levels during fed-batch cultivation.

    Results show that the two product proteins appear in both soluble and insoluble fractions during cultivation and are both subjected to proteolysis. However, the accumulation of the soluble form of Zb-MalE31 protein is radically lower, at all conditions, due to the small difference in primary structure.

    It was shown that both proteolysis and inclusion body formation could be influenced by the selected parameters although a change in feed rate had a considerably higher effect. A high concentration of inducer and a "high" feed rate result in a low accumulation of soluble product, due to a high proteolysis. The concentration of inducer leading to different levels of transcription is, however, an efficient tool to influence inclusion body formation. At low IPTG concentrations (<= 5 mu M), this formation is almost abolished while at a comparatively high concentration (>= 300 mu M) 50% of the total product accumulated was in the form of inclusion bodies.

  • 13.
    Sandén, Anna Maria
    et al.
    KTH, Superseded Departments, Biotechnology.
    Prytz, Ingela
    KTH, Superseded Departments, Biotechnology.
    Larsson, Gen
    KTH, Superseded Departments, Biotechnology.
    The influence of time and method of induction on recombinant protein productivity and acetic acid formation in Escherichia coli2004In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290Article in journal (Other academic)
  • 14.
    Sandén, Anna Maria
    et al.
    KTH, Superseded Departments, Biotechnology.
    Prytz, Ingela
    KTH, Superseded Departments, Biotechnology.
    Tubulekas, I.
    Förberg, C.
    Le, H.
    Hektor, A.
    Neubauer, P.
    Pragai, Z.
    Harwood, C.
    Ward, A.
    Picon, A.
    de Mattos, J. T.
    Postma, P.
    Farewell, A.
    Nyström, T.
    Reeh, S.
    Pedersen, S.
    Larsson, Gen
    KTH, Superseded Departments, Biotechnology.
    Limiting factors in Escherichia coli fed-batch production of recombinant proteins2003In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 81, no 2, p. 158-166Article in journal (Refereed)
    Abstract [en]

    Fed-batch production of recombinant beta-galactosidase in E. coli was studied with respect to the specific growth rate at induction. The cultivations were designed to induce protein production by IPTG at a glucose feed rate corresponding to high (mu = 0.5 h(-1)) or low (mu = 0.1 h(-1)) specific growth rate. Protein production rate was approximately 100% higher at the higher specific growth rate, resulting in the accumulation of beta-galactosidase up to 30% of the total cell protein. Transcription analysis showed that beta-galactosidase-specific messenger RNA was immediately formed after induction (<5 min), but the amount was the same in both cases and was thus not the initial limiting factor. The content of ribosomes, as represented by rRNA, rapidly decreased with specific growth rate from a relative level of 100%, at the high specific growth rate, to 20% at the low specific growth rate. At high specific growth rate, ribosomes were additionally degraded upon induction due to the high production level. Translation therefore seemed to be the initial limiting factor of the protein synthesis capacity. The alarmone guanosine tetraphosphate increased at both high and low feed level inductions, indicating an induction-forced starvation of charged tRNA and/or glucose. The altered physiological status was also detected by the formation of acetic acid. However, the higher production rate resulted in high-level accumulation of acetic acid, which was absent at low feed rate production. Acetic acid production is thus coupled to the high product formation rate and is proposed to be due either to a precursor drain of Krebs cycle intermediates and a time lag before induction of the glyoxalate shunt, or to single amino acid overflow, since the model product is relatively poor in glycin and alanin. In conclusion, it is proposed that production at high specific growth rate becomes precursor-limited, while production at low specific growth rate is carbon- and/or energy-limited.

  • 15.
    Spens, Erika
    et al.
    KTH, School of Biotechnology (BIO), Bioprocess Technology.
    Häggström, Lena
    KTH, School of Biotechnology (BIO), Bioprocess Technology.
    Defined protein and animal component-free NS0 fed-batch culture2007In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 98, no 6, p. 1183-1194Article in journal (Refereed)
    Abstract [en]

    A chemically defined protein and animal component-free fed-batch process for an NS0 cell line producing a human IgG(1) antibody has been developed. The fed-batch feed profile was optimised in a stepwise manner. Depletion of measurable compounds was determined by direct analysis. The cellular need for nonmeasurable compounds was tested by continued culturing of cell suspension, removed from the bioreactor, in shake-flasks supplemented with critical substances. In the final fed-batch culture, 8.4 x 10(6) viable cells mL(-1) and 625 mg antibody L-1 was obtained as compared to 2.3 X 10(6) cells mL(-1) and 70 mg antibody L-1 in batch. The increase in cell density, in combination with a prolonged declining phase where antibody formation continued, resulted in a 6-fold increase in total cell yield, a 10.5-fold increase 6.2 in viable cell hours and an 11.4-fold increase in product yield. These improvements were obtained by using a feed with glucose, glutamine, amino acids, lipids, sodium selenite, ethanolamine and vitamins. Specifically, supplementation with lipids (cholesterol) had a drastic effect on the maximum viable cell density. Calcium, magnesium and potassium were not depleted and a feed also containing iron, lithium, manganese, phosphorous and zinc did not i significantly enhance the cell yield. The growth and death profiles in the final fed-batch indicated that nutrient deprivation was not the main cause of cell death. The ammonium concentration and the osmolality increased to potentially inhibitory levels, but an imbalance in the supply of growth/survival factors may also contribute to termination of the culture.

  • 16.
    Svennebring, Jessica
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Manneberg, Otto
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Skafte-Pedersen, Peder
    Bruus, Henrik
    Wiklund, Martin
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Selective bioparticle retention and characterization in a chip-integrated confocal ultrasonic cavity2009In: Biotechnology and Bioengineering, ISSN 0006-3592, E-ISSN 1097-0290, Vol. 103, p. 323-328Article in journal (Refereed)
    Abstract [en]

    We demonstrate selective retention and positioning of cells or other bioparticles by ultrasonic manipulation in a microfluidic expansion chamber during microfluidic perfusion. The chamber is designed as a confocal ultrasonic resonator for maximum confinement of the ultrasonic force field at the chamber center, where the cells are trapped. We investigate the resonant modes in the expansion chamber and its connecting inlet channel by theoretical modeling and experimental verification during no-flow conditions. Furthermore, by triple-frequency ultrasonic actuation during continuous microfluidic sample feeding, a set of several manipulation functions performed in series is demonstrated: sample bypass-injection-aggregation and retention-positioning. Finally, we demonstrate transillumination microscopy imaging Of Ultrasonically trapped COS-7 cell aggregates.

1 - 16 of 16
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf