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  • Articles  (123)
  • Biochemistry and Biotechnology  (123)
  • 1990-1994  (123)
  • 1935-1939
  • 1992  (123)
  • 1
    Electronic Resource
    Electronic Resource
    Application of empirical design methodologies to the study of the influence of reaction conditions and N-α-protecting group structure on the enzymatic X-Phe-Leu-NH2 dipeptide synthesis in buffer/dimethylformamide solvents systems (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 539-549 
    Details
    ISSN: 0006-3592
    Keywords: enzymatic peptide synthesis ; N-terminal protecting groups ; α-chymotrypsin ; experimental design ; partition constant ; reaction rate ; log P ; molecular refractivity ; response surfaces ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of five different N-terminal protecting groups (For, Ac, Boc, Z, and Fmoc) and reaction conditions (temperature and dimethylformamide content) on the α-chymotrypsin-catalyzed synthesis of the dipeptide derivative X-Phe-Leu-NH2 was studied. Groups such as For, Ac, Boc, and Z always rendered good peptide yields (82% to 85%) at low reaction temperatures and DMF concentrations, which depended on the N-α protection choice. Boc and Z were the most reactive N-α groups and, in addition, the most suitable for peptide synthesis. On the other hand, the use of empirical design methodologies allowed, with minimal experimentation and by multiple regression, to deduce an equation, which correlates the logarithm of the first order kinetic constant (log k') with reaction temperature, DMF concentration, and hydrophobicity (log P values) of the different protecting groups. The predictive value of the equation was tested by comparing the performance of another protective group, such as Aloc, with the performance predicted by said equation. Experimental and calculated k' values were found to be in good agreement.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390509
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  • 2
    Electronic Resource
    Electronic Resource
    In search of a thermodynamic description of biomass yields for the chemotrophic growth of microorganisms (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 833-858 
    Details
    ISSN: 0006-3592
    Keywords: biomass yield ; chemotrophic growth ; Gibbs energy dissipation ; thermodynamic efficiencies ; energy convertor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Correlations for the prediction of biomass yields are valuable, and many proposals based on a number of parameters (YATP, YAve, ηo, Yc, Gibbs energy efficiencies, and enthalpy efficiencies) have been published. This article critically examines the properties of the proposed parameters with respect to the general applicability to chemotrophic growth systems, a clear relation to the Second Law of Thermodynamics, the absence of intrinsic problems, and a requirement of only black box information. It appears that none of the proposed parameters satisfies all these requirements. Particularly, the various energetic efficiency parameters suffer from major intrinsic problems. However, this article will show that the Gibbs energy dissipation per amount of produced biomass (kJ/C-mod) is a parameter which satisfies the requirements without having intrinsic problems. A simple correlation is found which provides the Gibbs energy dissipation/C-mol biomass as a function of the nature of the C-source (expressed as the carbon chain length and the degree of reduction). This dissipation appears to be nearly independent of the nature of the electron acceptor (e.g., O2, No3-, fermentation). Hence, a single correlation can describe a very wide range of microbial growth systems. In this respect, Gibbs energy dissipation is much more useful than heat production/C-mol biomass, which is strongly dependent on the electron acceptor used. Evidence is presented that even a net heat-uptake can occur in certain growth systems.The correlation of Gibbs energy dissipation thus obtained shows that dissipation/C-mol biomass increases for C-sources with smaller chain length (C6 → C1), and increases for both higher and lower degrees of reduction than 4. It appears that the dissipation/C-mol biomass can be regarded as a simple thermodynamic measure of the amount of biochemical “work” required to convert the carbon source into biomass by the proper irreversible carbon-carbon coupling and oxidation/reduction reactions. This is supported by the good correlation between the theoretical ATP requirement for biomass formation on different C-sources and the dissipation values (kJ/C-mol biomass) found. The established correlation for the Gibbs energy dissipation allows the prediction of the chemotrophic biomass yield on substrate with an error of 13% in the yield range 0.01 to 0.80 C-mol biomass/(C)-mol substrate for aerobic/anaerobic/denitrifying growth systems.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390806
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetics and stoichiometry of growth of plant cell cultures of Catharanthus roseus and Nicotiana tabacum in batch and continuous fermentors (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 863-874 
    Details
    ISSN: 0006-3592
    Keywords: plant cell suspension cultures ; chemostat culture ; growth kinetics ; stoichiometry ; Catharanthus roseus ; Nicotiana tabacum ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Plant cell suspension cultures of Catharanthus roseus and Nicotiana tabacum were grown in stirred tank bioreactors operated in batch and continuous mode. The stoichiometry of growth of both species in steady-state glucose limited chemostats was studied at a range of different dilution rates. A linear relation was applied to describe specific glucose uptake, oxygen consumption, and carbon dioxide production as a function of the growth rate. Specific respiration deviated greatly from the linear relation. An unstructured mathematical model, based on the observed stoichiometry in the glucose limited chemostats, was applied to describe the growth in batch culture. From a comparison between the observed growth pattern in batch fermentors and computer simulations it appeared that the stoichiometry of growth of the C. roseus culture was different under steady-state and dynamic conditions. It was concluded that a mathematical model for the growth of suspension culture plant cells in which the biomass is considered to be a single compound with an average chemical composition is of limited value because large changes in the conmposition of the biomass may occur. © 1992 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400802
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  • 4
    Electronic Resource
    Electronic Resource
    Changes of lipase-catalyzed lipolytic rates in a batch reactor (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 1128-1132 
    Details
    ISSN: 0006-3592
    Keywords: lipolytic rates ; hydrolysis ; tributyrin ; Candida rugosa ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dramatic change of the reaction rate was observed for the lipase-catalyzed hyrolysis of tributyrin in a batch reactor. Immediately after the addition of the enzyme, the lipolysis rate increased continuously until a maximal reaction rate was reached. The duration of the induction was mainly controlled by the bulk enzyme concentration and the reactor stirring speed. The reaction rate dropped sharply after reaching its maximal value. The lipolysis decayed at a rate of about 0.012 min-1, and was not affected by changes of the stirring speed. This decay was attributed to the fast deactivation of the surface-adsorbed lipase, and possibly to the extremely slow desorption of the inactivated species. For reaction time longer than 120 minutes, the lipolysis decreased at a much slower rate. Several mechanisms for the decay of the lipolysis rate were discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260391108
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  • 5
    Electronic Resource
    Electronic Resource
    Modeling and experimental validation of carbon dioxide evolution in alkalophilic cultures (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 1069-1079 
    Details
    ISSN: 0006-3592
    Keywords: carbon dioxide ; bicarbonate ; alkalophilic cultures ; nonideal solutions ; continuous culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The chemical reactions involving carbon dioxide in mineral culture media are considered. A mathematic model is set up, based on published data, which is valid at pH values below 9, and in which the nonideality of the solution is taken into account. The crucial parameter is the constant expressing the equilibrium between carbon dioxide and bicarbonate, K1.The reactions were studied in three different aqueous solutions: water, mineral salt medium, and a suspension with nongrowing bacterial cells. For each situation, three methods were compared for the determination of the bicarbonate concentration in the solution: equilibrium state total carbon analysis, dynamic monitoring of the rate of acid or alkali addition, and dynamic measurement of the carbon dioxide gas phase mole fraction.In a batch-stirred tank reactor, the equilibrium constant K1 agreed with the published value, and the three bicarbonate analysis methods give the same results. If the nonideality is not taken into account, the result significantly differed from the published value and is likely to be incorrect.A real alkalophilic process, using Acinetobacter calcoaceticus in a continuous stirred tank reactor at steady state, also gave results that are in accord with the literature. However, the results do not allow validation of the equation expressing the nonideality.The steady state in the batch system and in continuous culture can be well described with the mathematical model. However, in the transient state there are some unexplained differences between simulation and measurement.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260391102
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  • 6
    Electronic Resource
    Electronic Resource
    Formamide modified polyacrylamide gels for DNA sequencing by capillary gel electrophoresis (1992)
    Weinheim : Wiley-Blackwell
    Electrophoresis 13 (1992), S. 484-486 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Compressions are occasionally found during the separation of DNA sequencing fragments, particularly in G/C-rich regions and in gels operated at room temperature. Addition of at least 10% formamide to urea/polyacrylamide sequencing gels improves the denaturing capacity of the gel, minimizing compressions. Addition of 20% or more formamide decreases the separation rate, theoretical plate count, and resolution for normally migrating fragments. An optimum concentration of 10% formamide improves resolution of compressed regions without degrading the other characteristics of the gel. Operation of gels at room temperature simplifies the engineering associated with automated sequencers based on capillary gel electrophoresis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.11501301102
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of enzymatic degradation of cyanide (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 629-634 
    Details
    ISSN: 0006-3592
    Keywords: biocatalyst ; cyanide degradation ; immobilized enzyme ; wastewaters ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: CYANIDASE@ is a new enzyme preparation capable of degrading cyanide in industrial wastewaters to ammonia and formate in an apparently one-step reaction, down to very low concentrations. This enzyme has both a high selectivity and affinity toward cyanide. A granular form of the biocatalyst was used in a recirculation fixed bed reactor in order to characterize the new biocatalyst with respect to pH, ionic strength, common ions normally present in wastewaters, mass transfer effects, and temperature. Long term stability was investigated. The kinetics of the enzymatic degradation of cyanide were studied in a batch reactor using the powdered immobilized enzyme preparation and modeled using a simple Michaelis-Menten equation.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390607
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  • 8
    Electronic Resource
    Electronic Resource
    Influence of expression of the pet operon on intracellular metabolic fluxes of Escherichia coli (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 59-65 
    Details
    ISSN: 0006-3592
    Keywords: pet operon ; E. coli ; metabolic fluxes ; metabolic engineering ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fermentation patterns of Escherichia coli HB101 carrying plasmids expressing cloned genes of Zymomonas mobilis pyruvate decarboxylase (PDC) and alcohol dehydrogenase li (ADH) were determined in glucose-limited complex medium in pH-controlled anaerobic batch cultivations. Time profiles of glucose, dry cell weight, succinate, formate, acetate, and ethanol were determined, as were the activities of ADH and PDC. Fluxes through the central carbon pathways were calculated for each construct utilizing exponential phase data on extracellular components and assuming quasi-steady state for intermediate metabolites. Overall biomass yields were greatest for cells expressing both PDC and ADH activities. Yields of carbon catabolite end products were similar for all PDC-expressing strains and different from those for other strains. Relative to its glucose uptake rate, the strain with greatest PDC and ADH activities produces formate and acetate more slowly and ethanol more rapidly than other strains. Strong influences of plasmid presence and metabolic coupling complicate detailed interpretations of the data.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390110
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  • 9
    Electronic Resource
    Electronic Resource
    Biological method for protection of 6-position of sucrose and its use in synthesis of disaccharide high-intensity sweetener (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 203-210 
    Details
    ISSN: 0006-3592
    Keywords: glucose-6-acetate ; B. megaterium ; fructosyl transferase ; conversion ; sucrose-6-acetate ; sucralose ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A general method for protecting the 6 primary hydroxyl position of sucrose is described. It involves the production of glucose-6-acetate by fermentation of glucose using a strain of Bacillus megaterium followed by conversion to sucrose-6-acetate as a kinetic product using a specially selected fructosyl transferase producted by a newly isolated strain of Bacillus subtilis. The sucrose-6-acetate was found to be more lipophilic than expected, and this property aided its purification by chromatography. Pure sucrose-6-acetate may then be chlorinated and subsequently deacetylated to give the high-intensity sweetener 4,1′,6′-trichlo-4,1′,6′-trideoxygalactosucrose (sucralose) in high yields. This process involves fewer steps than are required for chemical synthesis using trityl chloride and acetic anhydride. Related intensely sweet molecules which were synthesized by similar methods included 4,1′,6′-trichloro, 4,1′,6′-trideoxy L-arabinosucrose, and 4,1′,6′-trichloro-4,6,1′,6′-tetradeoxy-galactosucrose. They were obtained from xylose and 6-deoxyglucose, respectively, via the intermediates xylsucrose and 6-deoxysucrose, formed by the reaction of the fructosyl transferase on the monosaccharide acceptors.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390212
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  • 10
    Electronic Resource
    Electronic Resource
    Development of a helical-ribbon impeller bioreactor for high-density plant cell suspension culture (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 511-521 
    Details
    ISSN: 0006-3592
    Keywords: plant cell ; Catharanthus roseus ; suspension ; culture ; mixing ; helical ribbon impeller ; bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A double helical-ribbon impeller (HRI) bioreactor with a 11-L working volume was developed to grow high-density Catharanthus roseus cell suspensions. The rheological behavior of this suspension was found to be shear-thinning for concentrations higher than 12 to 15 g DW · L-1. A granulated agar suspension of similar rheological properties was used as a model fluid for these suspensions. Mixing studies revealed that surface baffling and bottom profiling of the bioreactor and impeller speeds of 60 to 150 rpm ensured uniform mixing of suspensions. The HRI power requirement was found to increase singnificantly for agar suspensions higher than 13 g DW · L-1, in conjunction with the effective viscosity increase. Oxygen transfer studies showed high apparent surface oxygen transfer coefficients (kLa ∼4 to 45 h-1) from agar suspensions of 30 g DW · L-1 to water and for mixing speeds ranging from 120 to 150 rpm. These high surface kIa values were ascribed to the flow pattern of this bioreactor configuration combined with surface bubble generation and entrainment in the liquid phase caused by the presence of the surface baffles. High-density C. roseus cell suspension cultures were successfully grown in this bioreactor without gas sparging. Up to 70% oxygen enrichment of the head space was required to ensure sufficient oxygen supply to the cultures so that dissolved oxygen concentration would remain above the critical level (≥10% air saturation). The best mixing speed was 120 rpm. These cultures grew at the same rate (∼0.4 d-1) and attained the same high biomass concentrations (∼25 to 27 g DW · L-1, 450 to 500 g filtered wet biomass · L-1, and 92% to 100% settled wet biomass volume) as shake flask cultures. The scale-up potential of this bioreactor configuration is discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390506
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