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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 750 (1995), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 369 (1981), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 18 (1983), S. 75-85 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary To initiate studies of the stereospecific reduction of pyruvate and phenylpyruvate to the corresponding d-2-hydroxyacids a limited screening was carried out for microorganisms possessing a high NADH-dependet d-lactate dehydrogenase activity. Lactobacillus confusus was found to produce the desired dehydrogenase, which showed also relatively high activity towards phenylpyruvate, so this strain was selected for large scale production of the enzyme. A procedure for large scale purification of the enzyme starting with 24 kg wet cells is described including liquid-liquid extraction, ultrafiltration and chromatography on DEAE-cellulose, yielding a catalyst with specific activities of 216 U×mg−1 for pyruvate reduction and 15 U×mg−1 for phenyl-pyruvate reduction. A further tenfold purification can be achieved by affinity chromatography on Blue-Sepharose C-6B. Parameters which are important for industrial application of the enzyme were determined: substrate specifity, pH and temperature optimum, temperature stability, stability at different pH-values, and the storage stability of the enzyme in crude extracts.
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary To develop a large-scale isolation of leucine dehydrogenase (E.C. 1.4.1.9) as industrial catalyst we carried out a limited screening for microorganisms with high leucine dehydrogenase activity. Conditions for the growth and enzyme formation of Bacillus sphaericus (DSM 396) which proved to be the best enzyme producer were optimized. The highest yield in volume and specific activity were obtained using glucose and yeast-extract in the medium. The highest specific enzyme activity was found at the end of the exponential growth phase. Cultivation of Bacillus sphaericus under optimal conditions increased the yield to about 3 U mg−1. The heat stability of the enzyme was exploited to develop a simple large-scale purification. Together with an ultrafiltration step, the enzyme could be enriched 9fold in a short time. After further purification using DE-cellulose an enzyme preparation (25fold enriched) was obtained; suitable as a technical catalyst in amino acid production.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 137 (1984), S. 47-52 
    ISSN: 1432-072X
    Keywords: Phenylalanine dehydrogenase ; NAD+-dependence ; Reductive aminoation ; Brevibacterium spec. ; Selective enrichment with L-phenylalanine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The new enzyme phenylalanine dehydrogenase [L-phenylalanine: NAD+-oxidoreductase (deaminating)] was detected in the crude extract of a strain of Brevibacterium spec. The bacterium was isolated from a soil sample by enrichment with phenylalanine. This strain was the only one containing phenylalanine dehydrogenase out of 173 tested strains, among them 22 of the genus Brevibacterium, 74 strains from soil samples and 77 strains from a culture collection belonging to several genera. The enzyme is involved in the degradation of phenylalanine and could be induced by addition of L-, D-, D,l-phenylalanine or L-histidine, the optimum inducer concentration of phenylalanine being 1%. The reaction mechanism of a reductive amination was confirmed by demonstrating the close coupling between NADH-consumption and phenylalanine production; ammonia could not be replaced by L-glutamate or L-aspartate as amino donor. The α-keto acid of L-tyrosine was converted too, while the corresponding compound of histidine was inactive. The optimum pH value for reductive amination in the crude extract was 8.5 and for oxidative desamination 10.5.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Glycoconjugate journal 15 (1998), S. 139-145 
    ISSN: 1573-4986
    Keywords: activated deoxysugars ; preparative enzymatic synthesis ; sucrose synthase ; dehydratase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract dTDP–6–deoxy–4–keto–D–glucose (1), the common intermediate in the biosyntheses of the mainfold deoxysugars, was synthesized on a gram–scale by the combination of sucrose synthase and dTDP–D–glucose 4,6–dehydratase in a fed batch, starting the reaction with dTDP. This process allowed a dTDP conversion with a 100% rate. An easy and efficient three–step purification with anion–exchange chromatography and gel filtration gave 1.1 g of 1 in an overall yield of 73%. This work realizes a first step for an economic access to activated deoxysugars.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 23 (1981), S. 2789-2802 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Multienzyme reaction systems with simultaneous coenzyme regeneration have been investigated in a continuously operated membrane reactor at bench scale. NAD(H) covalently bound to polyethylene glycol with a molecular weight of 104 [PEG-10,000-NAD(H)] was used as coenzyme. It could be retained in the membrane reactor together with the enzymes. L-leucine dehydrogenase (LEUDH) was used as catalyze for the reductive amination of α-ketoisocaproate (2-oxo-4-methylpentanoic acid) to L-leucine. Format dehydrogenease (FDH) was used for the regeneration of NADH. Kinetic experiments were carried out to obtain data which could be used in a kinetic model in order to predict the performance of an enzyme membrane reactor for the continuous production of L-leucine. The kinetic constants Vmax and Km of enzymes are all in the same range regardless of whether native NAD(H) or PEG-10,000-NAD(H) is used as coenzyme. L-leucine was produced continuously out of α-ketoisocaproate for 48 days; a maximal conversion of 99.7% was reached. The space-time yield was 324 mmol/L day (or 42.5 g/L day).
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 301-301 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 45 (1995), S. 205-211 
    ISSN: 0006-3592
    Keywords: monoclonal antibodies ; fermentation ; fluidized bed adsorption ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To achive the coarse purification of a monoclonal antibody from whole hybridoma fermentation broth a fluidized bed cation exchange process was used. The procedure consisted of application of the crude sample and washing of the bed in a fluidized mode and elution in a fixed bed mode. A completely clarified eluate was obtained with purification factors between 4 and 8 and a concentration of the desired product (monoclonal antibody) by a factor of more than 3 was achived. Thus, a combination of the three early steps of the downstream process clarification, concentration and coarse purification was possible. Two different materials were tested: a commercially available agarose-based matrix (Stream-line-SP), and a self-derivatized material based on controlled-pore glass (Bioran). Initial experiments were performed to describe the fluidization of the glass material. Comparison with the agarose material showed several differences, the agarose matrix allowing liquid flow closer to plug flow than the glass material. Increased backmixing in the liquid phase was detected when fluidizing the glass adsorbent compared with the agarose-based matrix. Despite this fact, comparison of the two materials with respect to antibody binding and elution demonstrated a similar performance. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 367-374 
    ISSN: 0006-3592
    Keywords: adsorption ; fluidization ; hydrodynamics ; proteinpurification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of fluidized bed adsorption is strongly influenced by the hydrodynamics of the fluidization process. Especially axial mixing in the liquid and solid phase may lead to reduced capacity and resolution. In this article axial mixing in the liquid phase of a classified fluidized bed based on porous glass granules is presented. Axial mixing was analyzed by measurements of residence time distributions in a fluidized bed, showing a reduction of mixing at increased ratio of bed height to diameter as well as at increased linear velocity of the liquid stream. These results were transferred to two real adsorption systems on two different scales: In a bench scale (up to 15 mL of adsorbent) the purification of monoclonal antibodies from hybridoma supernatant was performed with a cation exchanger, in a larger scale (up to 750 mL of matrix) the adsorption of bovine serum albumin (BSA) on the same matrix was investigated. The results showed an increase of capacity at increased bed height-to-diameter ratio; with regard to linear velocity a broad range of only slightly changed capacity was found. A shift from dispersion controlled to diffusion controlled adsorption at intermediate linear velocity was proposed by isolating the effect of pore diffusion from the effect of dispersion. © 1995 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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