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  • 1
    Electronic Resource
    Electronic Resource
    Intracellular pH Responses of Hybridoma and Yeast to Substrate Addition and Acid Challenge (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 745 (1994), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1994.tb44367.x
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  • 2
    Electronic Resource
    Electronic Resource
    Oxidative-stress-induced production of pyocyanin by Xanthomonas campestris and its effect on the indicator target organism, Escherichia coli (2000)
    Springer
    Journal of industrial microbiology and biotechnology 25 (2000), S. 266-272 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: pyocyanin; free radicals; HOCl; oxidative stress; Xanthomonas campestris
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pyocyanin, a potential antimicrobial agent, was secreted by Xanthomonas campestris. Treatments with agents causing oxidative stress in the organism caused up to 4.4-fold increase in pyocyanin production. Pyocyanin added in the extracellular space did not affect growth rate of X. campestris, but decreased maximum cell concentration and specific product formation. However, the growth of Escherichia coli, the indicator target organism, was affected by pyocyanin. There was also a significant increase in the intracellular reactive oxygen species (ROS) concentration and antioxidant enzyme [catalase, superoxide dismutase (SOD)] concentrations, in the presence of pyocyanin. The intracellular ROS concentrations in E. coli formed upon exposure to pyocyanin, which is an indicator of the toxicity, was dependent on the growth phase of the organism. Studies with mutants of E. coli showed that intracellular ROS concentration was not significantly affected by the absence of the regulon OxyR, but, was significantly higher in cases when the regulon rpoS or the genes katG or katE were absent. Journal of Industrial Microbiology & Biotechnology (2000) 25, 266–272.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.7000067
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  • 3
    Electronic Resource
    Electronic Resource
    Intracellular pH-based controlled cultivation of yeast cells: II. Cultivation methodology (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 295-302 
    Details
    ISSN: 0006-3592
    Keywords: intracellular pH ; bioreactors ; cultivation ; yeast ; 9-aminoacridine ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Intracellular pH (pHi) was measured on-line in a bioreactor using a fluorescent pHi indicator, 9-aminoacridine, and controlled fed-batch cultivations of yeast cells based on pHi (FB-pHi) were performed. In FB-pHi cultivations, automated glucose additions were made to the culture in response to culture pHi. The average ethanol (an-aerobic product) yield was significantly lower [0.12 g g-1 glucose in fed-batch pHi cultivations with 100 ppm glucose additions (FB-pHi-100 cultivation) vs. 0.48 g g-1 glucose in batch] and cell yield was higher (0.54 g g-1 glucose in FB-pHi-100 cultivation vs. 0.3 g g-1 glucose in batch) compared to batch cultivation. An expression has been derived to calculate changes in pHi from measured fluorescence values when the cell concentration increases during growth. Cultivations based on pHi, performed with different magnitudes of glucose addition (100, 50, and 10 ppm additions), showed that lower magnitudes of glucose addition resulted in lower ethanol yields while cell yield remained unaffected. The ratio of specific oxygen uptake rate to specific glucose uptake rate (OUR/GUR) increased with decreased in magnitude of glucose additions in FB-pHi cultivations, suggesting that the culture aerobic state was higher when the magnitude of glucose addition was lower. The average cell productivity in FB-pHi cultivations was 29% higher than in batch cultivation. Cells were also cultivated at high OUR conditions, and the results are compared with other cultivations. © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420305
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  • 4
    Electronic Resource
    Electronic Resource
    The influence of temperature on a mouse-mouse hybridoma growth and monoclonal antibody production (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 292-295 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370313
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  • 5
    Electronic Resource
    Electronic Resource
    Bovine colostrum or milk as a serum substitute for the cultivation of a mouse hybridoma (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 882-889 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mouse-mouse hybridoma was grown in serum-free medium supplemented with bovine milk or colostrum. Bovine colostrum supported growth of the hybridoma whereas bovine milk alone did not support cellular proliferation. For growth in medium supplemented with colostrum, the maximum cell concentration achieved was 1.4 × 106 cells/mL in 2.2% colostrum, which is 44% of that obtained in 9% serum. When cells were grown in media containing milk and low amounts of serum (〈1%) the maximum cell concentration in 2.2% milk with 0.4% serum was 2 × 106 cells/ml, whereas it was only 0.2 × 106 cells/ml and 1.3 × 106 cells/ml in 2.2% milk alone and 0.4% serum alone, respectively. Similar behavior was observed for growth in media containing colostrum and low amounts of serum. The monoclonal antibody production in media containing combinations of serum and milk or colostrum was comparable to that obtained in media with higher serum concentrations. Experiments performed with conditioned media suggest that the rapid decrease in viability, after the maximum cell concentration has been reached, is partially due to the presence of some inhibitory components generated during the cell culture rather than due to depletion of some serum components.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350905
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  • 6
    Electronic Resource
    Electronic Resource
    Intracellular pH based controlled cultivation of yeast cells: I. Measurement methodology (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 118-128 
    Details
    ISSN: 0006-3592
    Keywords: intracellular pH ; 9-aminoacridine ; bioreactor ; on-line measurement ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method has been developed to continuously measure the intracellular pH (pHi) of cells cultivated in a bioreactor in an on-line fashion over extend time periods. The methods is attractive in its simplicity and involves the use of a fluorescent pHi indicator 9-aminoacridine (9A A) which is a week base. An expression has been derived to calculate changes in pHi from measured 9AA-fluorescence changes. The indicator 9AA was found t be nontoxic to yeast cells at concentrations used to measure pHi (7 μM). The fluorescence of nicotinamide adenine dinucleotide (NADH) molecules did not interfere significantly with the measurement of 9AA-fluorescence. The pHi change in yeast cell following the addition of a proton ionophore carbonyl cyanide m-chlorophenyl hydrazone (CCCP) measured by 9AA compared favorably with that measured by the well-established pHi, indicator (which is however unsuitable for on-line applications in a bioreactor) bis-carboxyethyl carboxy fluorescein (BCECF). The pHi of yeast under substrate starved conditions was 6.4 units. The responses of pHi of yeast cells to induced metabolic transitions were studied. Under aerobic condition, pHi increased by 0.12 unit following a 100-ppm glucose pulse addition and by 0.25 unit following a 300-ppm ethanol pulse addition. Under anaerobic condition, pHi increased by 0.1 unit following a 500-ppm glucose pulse addition. Comparison of pHi with other indicators of cellular metabolic state suggests that pHi is a cellular metabolic state indicator. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260410116
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  • 7
    Electronic Resource
    Electronic Resource
    Oxygen supply without gas-liquid film resistance to Xanthomonas campestris cultivation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 714-723 
    Details
    ISSN: 0006-3592
    Keywords: oxygen-supply ; bioreactors ; H2O2 decomposition ; xanthomonas ; catalase ; HOCl pretreatment ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alternative methods of oxygen supply are of crucial importance, especially in viscous fermentations and shear-sensitive fermentations. A method of oxygen supply that completely eliminates the gas-liquid transport resistance has been presented. The method involves a need-based liquid-phase decomposition of hydrogen peroxide to provide the necessary oxygen. When Xanthomonas campestris was cultivated (viscous cultivation) using this method of oxygen supply, dissolved oxygen (DO) levels were maintained above the setpoint of 50% throughout the cultivation, whereas the conventional cultivation was able to meet culture oxygen demand only for about 6 h in a 72-h fermentation. Furthermore, the maximum specific growth rate and xanthan yields in the novel cultivation were 89% and 169%, respectively, of those obtained in conventional cultivation. A mathematical model was also developed to simulate and predict results in fermentations employing the presented methodology. In addition, studies with HOCl pretreatments indicated that monofunctional catalase may be responsible for the decomposition of H2O2 supplied externally to cells; HOCl pretreatments also increased the tolerance of cells to H2O2. The decomposition kinetics of externally supplied H2O2 was Michaelis-Menten in nature with vmax = 1.196 × 10-6M s-1 and Km = 0.21 mM. The catalase concentration was estimated to be 3.4 × 10-10 mol/g of cells. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:714-723, 1988.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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