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  • 1
    Electronic Resource
    Electronic Resource
    13C tracer experiments and metabolite balancing for metabolic flux analysis: Comparing two approaches (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 58 (1998), S. 254-257 
    Details
    ISSN: 0006-3592
    Keywords: metabolic flux analysis ; 13C tracer experiments ; fractional enrichment ; NADH ; NADPH ; pentose phosphate pathway ; Aspergillus oryzae ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conventional metabolic flux analysis uses the information gained from determination of measurable fluxes and a steady-state assumption for intracellular metabolites to calculate the metabolic fluxes in a given metabolic network. The determination of intracellular fluxes depends heavily on the correctness of the assumed stoichiometry including the presence of all reactions with a noticeable impact on the model metabolite balances. Determination of fluxes in complex metabolic networks often requires the inclusion of NADH and NADPH balances, which are subject to controversial debate. Transhydrogenation reactions that transfer reduction equivalents from NADH to NADPH or vice versa can usually not be included in the stoichiometric model, because they result in singularities in the stoichiometric matrix. However, it is the NADPH balance that, to a large extent, determines the calculated flux through the pentose phosphate pathway. Hence, wrong assumptions on the presence or activity of transhydrogenation reactions will result in wrong estimations of the intracellular flux distribution. Using 13C tracer experiments and NMR analysis, flux analysis can be performed on the basis of only well established stoichiometric equations and measurements of the labeling state of intracellular metabolites. Neither NADH/NADPH balancing nor assumptions on energy yields need to be included to determine the intracellular fluxes. Because metabolite balancing methods and the use of 13C labeling measurements are two different approaches to the determination of intracellular fluxes, both methods can be used to verify each other or to discuss the origin and significance of deviations in the results. Flux analysis based entirely on metabolite balancing and flux analysis, including labeling information, have been performed independently for a wild-type strain of Aspergillus oryzae producing α-amylase. Two different nitrogen sources, NH4+ and NO3-, have been used to investigate the influence of the NADPH requirements on the intracellular flux distribution. The two different approaches to the calculation of fluxes are compared and deviations in the results are discussed. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:254-257, 1998.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Response of the central metabolism of Corynebacterium glutamicum to different flux burdens (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 168-180 
    Details
    ISSN: 0006-3592
    Keywords: metabolic fluxes ; metabolite balance ; NMR spectroscopy ; amino acid production ; bidirectional fluxes ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To evaluate the importance of reactions within the central metabolism under different flux burdens the fluxes within the pentose phosphate pathway (PPP), as well as the other reactions of the central metabolism, were intensively analyzed and quantitated. For this purpose, Corynebacterium glutamicum was grown with [1-13C]glucose to metabolic and isotopic steady state and the fractional enrichments in precursor metabolites (e.g., pentose 5-phosphate) were quantified. Matrix calculus was used to express these data together with metabolite mass data. The detailed analysis of the dependence of 13C enrichments on exchange fluxes enabled the transketolase-catalyzed exchange rate (2 pentose 5-phosphate ↔ sedoheptulose 7-phosphate + glyceraldehyde 3-phosphate) to be quantified as 74.3% (molar metabolite flux) at a net flux of 10.3% and the exchange rate (pentose 5-phosphate + erythrose 4-phosphate ↔ fructose 6-phosphate + glyceraldehyde 3-phosphate) to be quantified as 5.6% at a net flux of 8.1%. The flux entering the tricarboxylic acid cycle was 93.3%. The same comprehensive flux analysis as performed for the nonexcreting condition was done with the identical strain that had been forced to excrete L-glutamate. Because we had already quantified the fluxes for L-lysine excretion with an isogenic strain, three directly comparable flux situations are thus available. Consequently, this comparison permits a direct cause-and-effect relationship to be specified. In response to the different flux burdens of the cell, the PPP flux decreased from a maximum of 67% to 26%, with the glycolytic flux increasing accordingly. The carbon flux through isocitrate dehydrogenase increased from 20% to 36%. The bidirectional carbon flux between pyruvate and oxaloacetate decreased from 36% to 9%. Since the cause of the three different flux states was the allelic exchange in the final L-lysine assembling pathway or the glutamate export activity, respectively, the flexible response is the effect. This shows conclusively the enormous flexibility within the central metabolism of C. glutamicum to supply precursors upon their withdrawal for the synthesis of amino acids. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 168-180, 1997.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Production L-tryptophan by Escherichia coli cells (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 25 (1983), S. 999-1011 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Whole cells of Escherichia coli B 10 having high tryptophan synthetase activity were used directly as an enzyme source to produce L-tryptophan from indole and L- or D,L-serine. This strain is tryptophan auxotrophic, which is tryptophanase negative and, in addition, L- and D-serine deaminase negative under production conditions. To avoid inhibition of tryptophan synthetase by a high concentration of indole, nonaqueous organic solvents, Amberlite XAD-2 adsorbent, and nonionic detergents were used as reservoirs of indole in the reaction mixture for the production of L-tryptophan. As a result, different effects were observed on the production of L-tryptophan. Particularly, among the nonionic detergents, Triton X-100 was very efficient. Using Triton X-100 for production of L-tryptophan from indole and L- or D,L-serine by whole cells of Escherichia coli B 10, 14.14 g/100 mL and 14.2 g/100 mL of L-tryptophan were produced at 37°C for 60 h.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260250410
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  • 4
    Electronic Resource
    Electronic Resource
    Incapability of Gluconobacter oxydans to produce tartaric acid (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 183-186 
    Details
    ISSN: 0006-3592
    Keywords: Gluconobacter oxydans ; 5-ketogluconic acid ; tartatic acid ; vanadate ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dependence of tartaric acid production by Gluconobacter oxydans ssp. oxydans ATCC 19357 and G. oxydans ssp. suboxydans ATCC 621 on vanadate was investigated. It was found with both organisms that trataric acid could only be produced in a medium containing vanadate (NH4VO3). A proposed intermediate of the tartaric acid metabolism in G. oxydans, 5-ketogluconic acid, was tested on its reactivity in the presence of the oxidizing catalyst vanadate. It could be shown that 5-ketogluconic acid and the catalyst vanadate, but not the activity of G. oxydans, were responsible for the formation of tartaric acid. G. oxydans was not able to produce tartaric acid by itself. The stereochemical identity of the formed tartaric acid could be identified as the L-(+)-type. Oxalic acid was formed from 5-ketogluconic acid with vanadate in the absence and in the presence of G. oxydans. The ratio of oxalic acid to tartaric acid was 1:1.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400126
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of the fluxes in the central metabolism of Corynebacterium glutamicum by nuclear magnetic resonance spectroscopy combined with metabolite balancing (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 111-129 
    Details
    ISSN: 0006-3592
    Keywords: intracellular fluxes ; metabolite balance ; carbon labeling balance ; lysine ; anaplerotic reactions ; NMR spectroscopy ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To determine the in vivo fluxes of the central metabolism we have developed a comprehensive approach exclusively based on the fundamental enzyme reactions known to be present, the fate of the carbon atoms of individual reactions, and the metabolite balance of the culture. No information on the energy balance is required, nor information on enzyme activities, or the directionalities of reactions. Our approach combines the power of 1H-detected 13C nuclear magnetic resonance spectroscopy to follow individual carbons with the simplicity of establishing carbon balances of bacterial cultures. We grew a lysine-producing strain of Corynebacterium glutamicum to the metabolic and isotopic steady state with [1-13C]glucose and determined the fractional enrichments in 27 carbon atoms of 11 amino acids isolated from the cell. Since precursor metabolites of the central metabolism are incorporated in an exactly defined manner in the carbon skeleton of amino acids, the fractional enrichments in carbons of precursor metabolites (oxaloacetate, glyceraldehyde 3-phosphate, erythrose 4-phosphate, etc.) became directly accessible. A concise and generally applicable mathematical model was established using matrix calculus to express all metabolite mass and carbon labeling balances. An appropriate all-purpose software for the iterative solution of the equations is supplied. Applying this comprehensive methodology to C. glutamicum, all major fluxes within the central metabolism were determined. The result is that the flux through the pentose phosphate pathway is 66.4% (relative to the glucose input flux of 1.49 mmol/g dry weight h), that of entry into the tricarboxylic acid cycle 62.2%, and the contribution of the succinylase pathway of lysine synthesis 13.7%. Due to the large amount and high quality of measured data in vivo exchange reactions could also be quantitated with particularly high exchange rates within the pentose phosphate pathway for the ribose 5-phosphate transketolase reaction. Moreover, the total net flux of the anaplerotic reactions was quantitated as 38.0%. Most importantly, we found that in vivo one component within these anaplerotic reactions is a back flux from the carbon 4 units of the tricarboxylic acid cycle to the carbon 3 units of glycolysis of 30.6%. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Ethanol-Herstellung mit Bakterien (1987)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 59 (1987), S. 695-700 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Ethanol production with bacteria. Strains of Saccharomyces cerevisiae have mostly been used for the production of ethanol from sugar by yeasts. Recently it was shown that the bacterium Zymomonas mobilis has some advantages compared to yeast for the production of industrial alcohol. Compared to traditional yeast fermentation, ethanol yield is about 5% higher than with yeast, since less sugar is incorporated into cell material by this bacterium. Like yeast, Zymomonas mobilis has remarkably high ethanol tolerance which enables the bacterium to produce ethanol concentrations of more than 13 vol.-% from sugar solutions of appropriate concentration. Investigations of the spectrum of lipids present have shown that this bacterium contains large quantities of hopanoids which are presumably of significance for the stabilization of cell membranes in the presence of ethanol. Since the cost of the sugar greatly influences the profitability fraction formed in the production of glucose syrup from wheat flour was investigated. It was shown that after enzymatic saccharification of this waste starch the glucose was efficiently fermented to ethanol by Zymomonas mobilis. It is planned to broaden the substrate spectrum of Zymomonas mobilis by gene cloning techniques so that in future pentoses, e. g. xylose or arabinose, can also be fermented to ethanol by this organism.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330590904
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  • 7
    Electronic Resource
    Electronic Resource
    Anaerober mikrobieller Abbau von halogenierten Aromaten zu BiogasVortrag von M. Brunner auf der 4. Dechema-Jahrestagung der Biotechnologen, 3./4. Juni 1986 in Frankfurt/M. (1987)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 59 (1987), S. 55-57 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330590110
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  • 8
    Electronic Resource
    Electronic Resource
    Kontinuierlicher anaerober Abbau von 3-Chlorbenzoesäure in Festbettumlaufreaktoren (1991)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 63 (1991), S. 1238-1240 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330631217
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  • 9
    Electronic Resource
    Electronic Resource
    Mikrobielle Protein-Gewinnung auf Methanol-Basis (1974)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 46 (1974), S. 669-676 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In einer ökonomischen Betrachtung wird Methanol als Substrat für die Produktion von Einzeller-Protein (SCP) mit anderen Rohstoffen an Hand von publizierten Daten verglichen. Die Kriterien sind einerseits der Preis des Substrates und andererseits die Substrat-Zellausbeute, der Sauerstoff-Bedarf und die Wärme-Entwicklung im Fermentationsprozeß. Weiterhin wird ein Überblick über methanol-verwertende Mikroorganismen und über die Kriterien für ihre Eignung zur SCP-Produktion gegeben. Bei der Hefe Candida boidinii wurde der Methanol-Stoffwechsel untersucht und mit dem von Bakterien verglichen. Methanol wird wie bei Bakterien über Formaldehyd und Formiat zu CO2 oxidiert. Das C1-Substrat scheint bei Hefen über einen Zucker-phosphat-Weg assimiliert zu werden, der ähnlich dem Ribose-phosphat-Weg in Bakterien ist. Das Problem der Prozeßtechnik wird unter dem Gesichtspunkt der Prozeßführung, Reaktortechnik und mathematischen Modellierung der Prozesse diskutiert.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330461602
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  • 10
    Electronic Resource
    Electronic Resource
    Biologie der Methan-Bildung (1981)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 53 (1981), S. 854-863 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Description / Table of Contents: Biology of methane formation. It has long been known that methane is produced in nature where organic compounds are degraded by microorganisms under anaerobic conditions. On an industrial scale, this process has been used for more than 50 years in the stabilization of sewage sludge from municipal waste water treatment plants. Recently it could be demonstrated that at least three different groups of bacteria are involved in the degradation of organic material into methane and CO2. Hydrolytic and fermentative bacteria first degrade the organic compounds into various alcohols, fatty acids, hydrogen and CO2. The second group of bacteria convert these metabolites into acetic acid, hydrogen, and CO2, which are then utilized by the methanogenic bacteria to produce methane and CO2.
    Notes: Es ist seit langem bekannt, daß überall in der Natur, wo organisches Material unter anaeroben Bedingungen mikrobiell abgebaut wird, Methan entsteht. Diese Fähigkeit anaerober Bakterien, organische Substanzen zu Methan und Kohlendioxid abzubauen, wird im großtechnischen Maßstab seit über 50 Jahren zur Stabilisierung von Klärschlamm genutzt. In jüngster Zeit konnte nachgewiesen werden, daß bei diesem Prozeß mindestens drei verschiedene Gruppen von Bakterien beteiligt sind. Bei dieser Abbau- bzw. Nahrungskette werden zunächst die verschiedenen organischen Verbindungen zu niedrigen Alkoholen, Fettsäuren, Wasserstoff und Kohlendioxid von einer Bakteriengruppe abgebaut. Die zweite Mikroorganismen-Gruppe setzt diese Alkohole, Säuren etc. weiter zu Essigsäure, Wasserstoff und Kohlendioxid um, welche dann von den Methan-Bakterien als Substrat verwertet und in Methan und Kohlendioxid (Biogas) umgewandelt werden.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330531105
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