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  • 1
    Electronic Resource
    Electronic Resource
    Biosynthesis of Phenylalanine in Bakers' Yeast1,2 (1955)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 77 (1955), S. 5448-5449 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja01625a093
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  • 2
    Electronic Resource
    Electronic Resource
    Characterising latex particles and fractal aggregates using image analysis (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 325-333 
    Details
    ISSN: 1435-1536
    Keywords: Key words Latex particles ; Aggregates ; Fractal dimensions ; Image analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The fractal nature of latex particles and their aggregates was characterised by image analysis in terms of fractal dimensions. The one- and two-dimensional fractal dimensions, D 1 and D 2, were estimated for polystyrene latex aggregates formed by flocculation in citric acid/phosphate buffer solutions. The dimensional analysis method was used, which is based on power law correlations between aggregate perimeter, projected area and maximum length. These aggregate characteristics were measured by image analysis. A two-slopes method using cumulative size distributions of aggregate length and solid volume has been developed to determine the three-dimensional fractal dimension (D 3) for the latex aggregates. The fractal dimensions D 1, D 2 and D 3 measured for single latex particles in distilled water agreed well with D 1 = 1, D 2 = 2 and D 3 = 3 expected for Euclidean spherical objects. For the aggregates, the fractal dimension D 2 of about 1.67 ± 0.04 (±standard deviation) was comparable to the fractal dimension D 3 of approximately 1.72 ± 0.13 (±standard deviation), taking the standard deviations into account. The measured three-dimensional fractal dimension for latex aggregates is within the fractal dimension range 1.6–2.2 expected for aggregates formed through a cluster-cluster mechanism, and is close to the D 3 value of about 1.8 indicated for cluster formation via diffusion-limited colloidal aggregation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050388
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  • 3
    Electronic Resource
    Electronic Resource
    Dispersion of chlorpyrifos in soil beneath concrete slabs (1994)
    Springer
    Bulletin of environmental contamination and toxicology 53 (1994), S. 1-6 
    Details
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00205130
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  • 4
    Electronic Resource
    Electronic Resource
    A novel micromanipulation technique for measuring the bursting strength of single mammalian cells (1991)
    Springer
    Applied microbiology and biotechnology 36 (1991), S. 208-210 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Information about the bursting strength of animal cells is essential if the mechanisms of cell damage in bioreactors are to be understood, and if cell mechanical properties are ever to be related to cell structure and physiology. We have developed a novel cell compression technique that makes it possible to directly measure the bursting strength of single mammalian cells, and to infer information about cell mechanical properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164421
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  • 5
    Electronic Resource
    Electronic Resource
    Action of shear on enzymes: Studies with alcohol dehydrogenase (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 2263-2278 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Yeast alcohol dehydrogenase (ADH) solutions (approximately 1 mg/ml, pH 7) were sheared in a coaxial cylindrical viscometer. This was fitted with a lid sealing the contents from the atmosphere and preventing evaporation. At 30°C after a total of 5 hr intermittent shearing at 683 sec-1 no losses of activity were observed. No losses were found after 5 hr continuous shearing and in a no-shear control. At 40°C and 683 sec-1 there were only small activity losses in 5 hr. Shearing at 3440 sec-1 no measurable losses of activity were found with a 1.03 mg/ml solution in 5 hr at 30°C, a 1.03 mg/ml solution in 8 hr at 5°C, and with a 3.89 mg/ml solution in 3 hr at 5°C. In all these cases, however, a white precipitate formed that was not observed in zero shear control experiments. The sheared 3.89 mg/ml solution was clarified by centrifugation. It was shown that there were no ADH aggregates in the supernatant and that the precipitate was less than 2% of the original protein. At 30°C under adverse pH conditions (pH 8.8) there was no significant difference in activity losses of an approximately 1 mg/ml solution sheared at 65 and 744 sec-1. An approximately 0.5 mg/ml ADH solution, pH 7, was agitated in a small reactor with no free air-liquid interface. Peak shear rates near the impeller were estimated to be about 9000 sec-1. Only a small decrease in specific activity was observed until over 15 hr total running at 5°C.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260211208
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  • 6
    Electronic Resource
    Electronic Resource
    Action of shear on enzymes: Studies with catalase and urease (1979)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 21 (1979), S. 2279-2302 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Intermittent shear was applied to approximately 1 mg/ml solutions of bovine liver catalase in a coaxial cylindrical viscometer at temperatures from 20 to 60°C and shear rates up to 683 sec-1. The viscometer was sealed to prevent evaporation. Up to 40°C there were no activity losses during 3 hr total shearing. Above 40°C shearing reduced losses due to thermal inactivation, possibly by interfering with precipitation. At 3440 sec-1 and 40°C fine precipitates formed but little activity was lost. No activity losses were found with experimental conditions under which Taylor vortexing occurred, nor when shear stresses were increased up 57 times by adding glycerol to raise the, viscosity. There were no significant losses in a capillary rheometer at shear rates up to 106 sec-1. When low concentration (6 μg/ml) catalase solutions were sheared there was little loss in sealed systems, but there were losses in “open” systems even in low-temperature nonshear experiments. Although there were no losses with 1 mg/ml solutions, 6 μg/ml catalase solutions from an alternative source did lose activity in sealed systems but much less than expected from previously published work. Approximately 1 mg/ml jack bean urease solutions were sheared in the sealed system at 23°C and 683 sec-1 for 3 hr. No losses were found. No evidence of temporary or permanent inactivation was found with 28°g/ml solutions sheared in the presence of urea. Shear forces alone were not found to be as effective in causing enzyme inactivation as is generally believed and alternative mechanisms for damage are discussed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260211209
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  • 7
    Electronic Resource
    Electronic Resource
    Estimation of cell volume and biomass of penicillium chrysogenum using image analysis (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 384-391 
    Details
    ISSN: 0006-3592
    Keywords: biomass ; cell volume ; image analysis ; Penicillium chrysogenum ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A methodology for the estimation of biomass for the penicillin fermentation using image analysis is presented. Two regions of hyphae are defined to describe the growth of mycelia during fermentation: (1) the cytoplasmic region, and (2) the degenerated region including large vacuoles. The volume occupied by each of these regions in a fixed volume of sample is estimated from area measurements using image analysis. Areas are converted to volumes by treating the hyphae as solid cylinders with the hyphal diameter as the cylinder diameter. The volumes of the cytoplasmic and degenerated regions are converted into dry weight estimations using hyphal density values available from the literature. The image analysis technique is able to estimate biomass even in the presence of nondissolved solids of a concentration of up to 30 gL-1. It is shown to estimate successfully concentrations of mycelia from 0.03 to 38 gL-1. Although the technique has been developed for the penicillin fermentation, it should be applicable to other (nonpellected) fungal fermentations.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390404
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  • 8
    Electronic Resource
    Electronic Resource
    Classification and measurement of fungal pellets by automated image analysis (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 945-952 
    Details
    ISSN: 0006-3592
    Keywords: pellet characterization ; pellet measurement ; image analysis ; Aspergillus niger ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An automated image analysis method for classifying and measuring pellets of filamentous fungi growing in submerged fermentations has been developed. The method discriminates between pelleted mycelial growth and loose aggregates of dispersed hyphae. Pellets are classified into smooth and hairy types. In both cases, the core of the pellet is identified and its shape and size characterized. For hairy pellets the annular region is also characterized. The method was tested on pellets of Aspergillus niger ATCC 11414 grown in a defined medium in shake flasks. This rapid method makes practical extensive studies on the morphology of pellets in submerged fermentations and the influence of fermentation conditions on that morphology.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390909
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  • 9
    Electronic Resource
    Electronic Resource
    Estimation of disruption of animal cells by laminar shear stress (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 1004-1010 
    Details
    ISSN: 0006-3592
    Keywords: mammalian cell ; disruption ; shear stress ; mechanical properties ; micromanipulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using mechanical cell properties measured by micromanipulation, and a model of cell distortion in laminar flow fields, a method has been developed for predicting disruption of animal cells by laminar shear stresses. Predictions of the model were compared with measured losses of cell number and viability of TB/C3 murine hybridomas sheared in a cone and plate viscometer at shear rates up to 3950 s-1, and shear stresses up to 600 Nm-2, achieved by enhancement of viscosity with dextran. In all cases, the experimental, results and predictions were within 30%. Such excellent agreement suggests it might be possible to use micromanipulation measurements of animal cell mechanical properties to predict cell damage in more complex flow fields, such as those in bioreactors. © 1992 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400903
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of Penicillium chrysogenum physiology in submerged cultures by color and monochrome image analysis (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 1-11 
    Details
    ISSN: 0006-3592
    Keywords: Penicillium chrysogenum ; physiology ; image analysis ; differentiation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Although filamentous microorganisms are widely used in industrial fermentation processes, their growth and differentation are not yet fully understood, because their biomass is structured, and therefore difficult to descrbie and to quantify. This lack of appropriate tools can hinder the optimization and control of the fermentation. A quantitative image analysis method was therefore developed for characterizing the physiology of the penicillin-producing mold Penicillium chrysogenum. This method is based on a differntial staining procedure showing six physiological states: growing material, three differentiated states characterzied by an increasing granulation, a highly vacuolized state, and dead segments having lost their cytoplasm. The image analysis software, with versions written for monochrome and color images, consisted of a semiautomatic binary mask computation step and a fully automatic segmentation step based on a fuzzy classification. © 1995 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480103
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