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  • Biochemistry and Biotechnology  (2,788)
  • Animals  (1,937)
  • 1985-1989  (4,725)
  • 1950-1954
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 1-10 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The optimal glucose feeding policy for the fed-batch culture of Saccharomyces carlsbergensis is presented. The biphasic nature of growth results in a singular feed rate policy that is unique to this organism. When the operating cost is high, the reduction in operating time forces the cells to utilize both glucose and ethanol toward the end of fermentation time and results in a decreasing rate of glucose addition, unlike the normally observed in creasing feed rate. The optimal feeding policy depends heavily on the initial conditions and is highly sensitive to changes in kinetic parameters. A semiempirical scheme for feedback optimization is suggested for the fed-batch yeast culture.
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  • 2
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    Biotechnology and Bioengineering 33 (1989), S. 62-71 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several independent experimental techniques, including nondenaturing and denaturing isoelectric focusing, spin labeling, and enzyme immobilization, indicate that four ethanol-active subunits of horse liver alcohol dehydrogenase (LADH) can be classified as one of two types, designated E1 and E2. Thermal inactivation studies of LADH in solution and immobilized to two different supports demonstrate that the first-order rate constants of deactivation of E1 and E2 differ by more than an order of magnitude. Furthermore, E1, and E 2 can be distinguished by EPR spectroscopy, with the less stable subunit type, E2, appearing to have the less compactly structured active-site environment. The less stable enzyme form also loses catalytic activity upon covalent attachment to CNBr-Sepharose but remains active when adsorbed to Octyl-Sepharose. Moreover, the immobilization results in conjunction with lysine modification studies suggest that E2 immobilized to CNBr-Sepharose cannot bind coenyzme. Overall, these results illustrate how EPR measurements in concert with activity assays can pro vide insights into the molecular mechanisms of enzyme stabilization.
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  • 3
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alginates, both commercial and laboratory made, are strongly fluorescent due to small amounts of polyphenolic materials. These contaminants can be detected by fluorescence spectroscopy in concentrations lower than 1 ppm. This technique has been used to measure polyphenols in a wide range of alginates and various procedures for preparation of biotechnological-grade alginates have been evaluated.
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  • 4
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 79-89 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Calcium alginate gel beads were prepared from a range of well characterized alginates. The physical properties of beads depended strongly on the composition, sequential structure, and molecular size of the polymers. Beads with the highest mechanical strength, lowest shrinkage, best stability towards monovalent cations, and highest porosity were made from alginate with a content of L-guluronic acid higher than 70% and an average length of the G-blocks higher than 15. For these “high G” alginates the critical overlap intrinsic viscosities have been determined, and for molecular weight higher than 2.4 × 105, the gel strength was independent of the molecular weight.
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  • 5
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    Biotechnology and Bioengineering 33 (1989), S. 126-128 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 6
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 95-103 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The breakage of nylon membrane microcapsules is proposed as a new method to study and quantify shear effects in biological systems. A critique of this method shows that a narrower particle size distribution may be an important improvement in the breakage study as well as breakage control in many bioreactor and biotechnological applications. In a turbine reactor, it was shown that the primary process which determines the microcapsule breakage is the shear effect. The breakage kinetics are first order with regard to the microcapsule concentration. The breakage kinetic constant was ob served to be dependent on the temperature and the particle size, and proportional to the average shear rate and the third power of the turbine angular velocity. Decrease of the breakage kinetic constant with temperature can be explained by a decrease of fluid viscosity and a change in nylon membrane properties. An increase in the breakage kinetic constant with the microcapsule diameter can be due to a lowering of internal pressure and a reduction of the membrane resistance with size. Proportionality between the breakage kinetic constant and the shear rate shows that shear is the main process which leads to microcapsule breakage. The additional intervention in the shear rate expression of the turbine angular speed in the form of the turbine and particle velocities, results in the dependence of the breakage kinetic constant on the third power of the angular velocity.
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  • 7
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    Biotechnology and Bioengineering 33 (1989), S. 563-569 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Purified cellobiase was coupled to periodate-oxidized dextran by reductive alkylation using sodium cyanoborohydride, sodium borohydride, and dimethylaminoborane for various reaction times. The thermal stability of the different conjugates obtained was studied and correlated to the number of links introduced between the enzyme and the soluble support. We observe that resistance to heat inactivation increases as a function of the number of modified lysines. Sodium cyanoborohydride was the most effective reducing agent. After 24 h reaction, the modification of 92% of the lysines gave a cellobiase-dextran conjugate that is a most stable enzyme. We conclude that the thermal stability observed for the chemically modified enzyme results from the rigidification of the three-dimensional structure of the protein. This rigidification increases with the number of links introduced between the enzyme and the polysaccharide. We also observe that chemical modification leads to a heterogeneous population of stabilized enzymes. Because of this heterogeneous population, it is necessary to develop a mathematical model of the kinetics of enzyme inactivation.
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  • 8
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    Biotechnology and Bioengineering 33 (1989), S. 584-591 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article presents a calculation procedure useful for the optimization and scale up of batch sterilization cycles in large-scale fermentors. This technique determines the sterilization temperature and hold-time necessary to minimize nutrient damage in a specific fermentor. The method can also be used for “scaledown” experiments to eliminate sterilization conditions as a scale up parameter. A method for the systematic evaluation of different sterilization conditions on product yield is also presented. This procedure is useful in determining if scale up of sterilization conditions is important for a given process. The validity of the techniques presented are supported by data showing significant yield improvements in a 1.2 × 105 L antibiotic fermentation.
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  • 9
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    Biotechnology and Bioengineering 33 (1989), S. 570-577 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The construction and use of an automatic on-line titration unit for routine or event- initiated monitoring of alkalinity, buffer capacity, and volatile fatty acid (VFA) levels is presented. Under computer control a sample of digester liquor is pumped into the titration vessel and weighed. A sequence of titration, sparging, and back-titration operations are then initiated during which the pH and weight are recorded continuously and a titration curve constructed. From the curve, estimates of the alkalinity, buffer capacity to any desired pH endpoint, and total VFA levels are computed. The data is stored to disk and output as hard copy together with the titration curve itself. Monitoring and control of the titration apparatus is effected by a microcomputer via two analog input lines and eight digital output lines, respectively. The system is suitable for downloading to a small, inexpensive dedicated microprocessor-based system. The apparatus is constructed from standard and widely available equipment and the titration sequence, being under software control, is fully adaptable to particular requirements. The use of this facility in the on-line monitoring, control and optimization of the anaerobic digestion process is discussed.
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  • 10
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    Biotechnology and Bioengineering 33 (1989), S. 173-182 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel purification technique is proposed which employs affinity-ligand-modified liposomes to specifically purify bioactive macromolecules from solution. This process is demonstrated with avidin as the model biomolecule and biotin as the affinity ligand. Biotin is covalently bound to the surface of small unilamellar vesicles composed of dimyristoyl phosphatidylcholine (DMPC) and dimyristoyl phosphatidylethanolamine (DMPE). The number of accessible binding sites on the liposomes is determined by titration with avidin, and the kinetics of binding are evaluated by monitoring the concentration of free avidin in solution after the addition of biotinylated liposomes. The specificity of the process is determined by following the affinity binding of avidin to biotinylated liposomes in the presence of model impurities (i.e., lysozyme and cytochrome C). Liposome-bound avidin is separated from the impurities by ultrafiltration through a membrane which retains the liposomes.
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  • 11
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    Biotechnology and Bioengineering 33 (1989), S. 657-660 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 12
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    Biotechnology and Bioengineering 33 (1989), S. 631-637 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Adsorption reversibility and competition between fractionated components of the Trichoderma reesei cellulase system were studied. Specific endoglucanase (EGI), nonspecific endoglucanases (EGII, EGIII), and cellobio-hydrolase (CBHI) were previously grouped according to their hydrolytic function. At 5°C, direct evidence of exchange between adsorbed and free enzyme was obtained for each component using [3H] and [14C] radiolabeled tracers. No release of bound enzymes was detected upon dilution of the free enzyme solution. In simultaneous adsorption of enzyme pairs, CBHI was shown to predominate adsorption. Endoglucanase EGI was preferentially adsorbed over EGII and EGIII. Sequential adsorption studies have shown that interaction between enzyme components largely determines the degree of their adsorption. Evidence suggests that both common and distinct adsorption sites exist and that their occupation depends on which components are involved. Predominance in adsorption by any one of the enzyme components is decreased at 50°C. Light microscopy and monitoring of sugar production during cellulose hydrolysis provided evidence that reduction in the ionic strength decreases the adsorption predominance of CBHI and enhances the synergism between the cellulase components.
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  • 13
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    Biotechnology and Bioengineering 33 (1989), S. 638-649 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new method for manipulating the steady-state behavior of a mixed culture is introduced. The method makes use of differences in adherence properties between competing populations to maintain a desired population ratio. The very specific nature of some ligand-to-cell interactions allows precise manipulation of even closely related populations. The control method is illustrated by analysis and simulations of models of a competitive mixed culture and a culture of an unstable recombinant organism. In both cases, retention of the disadvantaged population via cell adhesion results in creation of a stable coexistence steady state over a range of operating conditions.
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  • 14
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    Biotechnology and Bioengineering 33 (1989) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 15
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    Biotechnology and Bioengineering 33 (1989), S. 256-265 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The balance equations for carbon, reduction potential, and energy during cell growth and product formation are rederived in a general form. Cells are treated simply as a very complex product, and the YATP concept is extended to products. Limitations on the theoretical yield are discussed for different product types. Simple aerobic products cannot be energy limited unless the maintenance requirement is large, while complex products cannot be reduction limited. A maximum yield is defined for products much more oxidized than their substrate (carbon limited) because the theoretical yield conditions may violate the energy balance. For reduced complex products the yield on available electrons is related to YATP, the P/O ratio, and the product composition. Narrow bounds are established on the actual yields in simple anaerobic fermentations, and the significance of the yields in the linear growth equation is discussed.
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  • 16
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    Biotechnology and Bioengineering 33 (1989), S. 266-271 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Water activity of the substrate is an important and acute factor for growth as well as for metabolic production of microorganisms or for biocatalyst systems. A sensor has been designed in order to control this parameter on-line during submerged and solid-substrate fermentations. This sterilizable sensor allows the measurement of the relative humidity of the atmosphere in a small chamber by means of a capacitive element separated from the medium by a thin ethylenepolytetrafluoride membrane. For high aw values (〉0.90) a sequential circulation of a dried gas prevents the sensor saturation. Measurements are rapid and accurate, and control of the water activity of a fermentation medium has been carried out for 5 days using this sensor.
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  • 17
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    Biotechnology and Bioengineering 33 (1989), S. 780-785 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 18
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    Biotechnology and Bioengineering 33 (1989), S. 786-790 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 19
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model of hydrocortisone transformation was developed in studies of the kinetics of biochemical systems. The regulatory bases of the model are the biosynthesis of steroid-transforming enzymes and their activity, the level of endogenous substrates, the respiratory chain activity, and the initial concentrations of reagents. When compared, the experimental data completely coincide with the results of the computer modeling, the coincidence being not only qualitative but also quantitative. It indicates that the model suggested can be used for further studies of other transformations of steroid compounds, as well as for transformation of steroid compounds under close-to-biotechnological conditions. The results obtained by means of this model permit one to trace in dynamics the behavior of a number of parameters characterizing the process which is very difficult or not feasible to do in a biochemical experiment. The following was shown: (1) the behavior of the respiratory chain (the reversible transition of its oxidized and reduced forms); (2) the change of the transmembrane potential of hydrogen ions within a far larger stretch of time than is feasible to register in a biochemical experiment; (3) the regulation of the activity of 20β-hydroxysteroid dehydrogenase and 1, 2-reductase not only by the change in the level of endogenous substrates, but also by means of their biosynthesis; and (4) the regulatory role of 3-ketosteroid-1-en-dehydrogenase.
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  • 20
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    Biotechnology and Bioengineering 33 (1989) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 21
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    Biotechnology and Bioengineering 33 (1989), S. 809-814 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 22
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to better understand the high plasmid stability in immobilized recombinant E. coli cells, the effects of dilution rate on the pTG201 plasmid stability, the copy number, and the catechol 2,3-dioxygenase (encoded by XyIE gene) production were, at first, studied in free E. coli W3101 continuous cultures in minimal media. It was found that decreasing specific growth rate increased the plasmid copy number and the catechol 2,3-dioxygenase activity but the stability decreased. In continuous culture with immobilized cells, an increase was shown in plasmid copy number and catechol 2,3-dioxygenase activity probably due to the distribution of growth in the gel beads. Besides mechanical properties of gel beads which may allow limited cell divisions, the increase in plasmid copy number is involved in enhanced plasmid stability in immobilized cells. In the same way, an experiment conducted in LB medium dealing with competition between pTG201-free and pTG201-containing E. coli B cells was described. It was shown that the competition was not more pronounced in gel bead compared to a free system. The effects of nutritional limitations on pTG201 plasmid stability and catechol 2,3-dioxygenase activity during chemostat cultivations in free and immobilized E. coli B cells were also investigated. It was found that immobilization of cells increased the stability of pTG201 even under glucose, nitrogen, or phosphate limited cultures. However in the case of magnesium depleted culture, pTG201 was shown to be relatively instable and a decrease in viable cell number during the immobilized continuous culture was observed. By contrast to the free system, the catechol 2,3-dioxygenase activity increased in immobilized cells under all culture conditions used.
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  • 23
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    Biotechnology and Bioengineering 33 (1989), S. 699-705 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The system described is a modified Hospodka's turbidostat. This device helps to measure the maximum growth rate of fungi in steady-state aerobic conditions with defined and independent concentration of dissolved oxygen, biomass, and substrate even unlimited. The principle consists of a turbidostat controlled by the dissolved oxygen concentration. The inlet medium pump operates when the dissolved oxygen concentration falls below the set point value. This method allows us to study independently effects of different physical and chemical variables on the maximum specific growth rate of microorganisms. A fungus, Fusarium oxysporum 47 isolated from soil, does not show a depressive effect on growth when dissolved oxygen concentration decreases to 5% and osmotic potential to -25 bars. Increasing biomass concentration in the range 0.1-1.0 g/L appears to depress markedly the maximum growth rate.
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  • 24
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    Biotechnology and Bioengineering 33 (1989), S. 706-715 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An extensive in vivo study of the electrokinetic properties of six strains of the brewing yeast S. cerevisiae has been carried out. The yeasts were cultured under laboratory conditions. They were electrokinetically characterized by the electro-osmotic dipped cell technique, and data are presented as zeta-potentials. The effects of pH, fermentation time, successive fermentation cycles, and initial wort density have been established. The electrokinetic properties of an ale yeast which did not function correctly during commercial fermentation have also been examined. The results are discussed in the context of two controversial topics concerning the mechanism of yeast flocculation, the relative importance of yeast cell wall carboxyl and phosphate groups and the influence of wort components.
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  • 25
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    Biotechnology and Bioengineering 33 (1989), S. 832-838 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two strains of Pseudomonas able to grow on phenol or p-nitrophenol (PNP) were isolated from sewage. Pseudomonas sp. PN101 mineralized and formed nitrite from PNP but did not mineralize phenol, and Pseudomonas sp. PH111 mineralized phenol but not PNP. Phenol increased the lag period before Pseudomonas sp. PN101 grew on and mineralized PNP, but this toxicity was reduced by inoculation of the medium with Pseudomonas sp. PH111. PNP inhibited growth of Pseudomonas sp. PH111 and slightly increased the length of the acclimation period for the mineralization of phenol by the bacterium. Inoculation of Pseudomonas sp. PN101 into solutions containing PNP and phenol increased the lag period prior to growth of Pseudomonas sp. PH111 on phenol and markedly lengthened the lag period for its mineralization of phenol. Coinciding with this delay in the onset of phenol degradation was the accumulation of an organic compound formed from PNP by Pseudomonas sp. PN101. This compound was not mineralized by the phenol-degrading bacterium. The data suggest that bacteria may interact during the decomposition of chemical mixtures by destroying or by forming toxins that affect the biodegradation of individual components of those mixtures.
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  • 26
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    Biotechnology and Bioengineering 33 (1989), S. 845-855 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The stability of immobilized maltotetraose (G4)-forming amylase (1,4-α-D-glucan maltoteraohydrolase, EC 3.2.1.60) from Pseudomonas stutzeri was investigated in both batch and continous processes. The inactivation process of the immobilized enzyme seemed to obey first-order kinetics, and the immobilized enzyme became more stable when coexisting with 20-30 wt % substrate and calcium ions. From intensive studies on the operational stability in the continuous process, the apparent half-life of G4 productivity in a constant-flow system was mainly affected by the reaction temperature, substrate concentration, and initial immobilized enzyme activity. A new factor, immobilized enzyme stability factor fs, was proposed to evaluate the half-life of the immobilized enzyme system.
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  • 27
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    Biotechnology and Bioengineering 33 (1989), S. 856-861 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A forced-flow enzyme membrane reactor system for sucrose inversion was investigated using three ceramic membranes having different pore sizes. Invertase was immobilized chemically to the inner surface of a ceramic membrane activated by a silane - glutaraldehyde technique. With the cross-flow filtration of sucrose solution, the reaction rate was a function of the permeate flux, easily controlled by pressure. Using 0.5 μm support pore size of membrane, the volumetric productivity obtained was 10 times higher than that in a reported immobilized enzyme column reactor, with a short residence time of 5 s and 100% conversion of the sucrose inversion.
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  • 28
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    Biotechnology and Bioengineering 33 (1989), S. 839-844 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of hydrogen acceptors on the kinetic parameters of D-xylose fermentation under anaerobic conditions was studied in a transient culture of immobilized Pachysolen tannophilus cells. Addition of oxygen to a steady-state culture resulted in a rapid increase (up to fivefold) in the rates of ethanol production and D-xylose uptake, but the rate of xylitol production was unaffected. Furthermore, the molar ethanol yield increased from 0.97 to 1.43 in the presence of oxygen. The moles of ethanol produced per moles of oxygen utilized were considerably greater than would be predicted from the stoichiometry of D-xylose fermentation, which suggests that the organism required oxygen for other functions in addition to its role as a hydrogen acceptor in D-xylose metabolism. When the artificial hydrogen acceptors acetone, acetaldehyde, and acetoin were added to the culture, the rate of ethanol production increased while the xylitol production rate decreased but the rate of xylose uptake was unaffected. The molar ethanol yields increased from 1.03 to 1.63, 1.43, and 1.24 upon addition of acetaldehyde, acetone, and acetoin, respectively, at the expense of the molar xylitol yields. The hydrogen acceptors sodium acetate, methylene blue, benzyl viologen, phenazine methosulfate, indigo carmine, and tetrazolium chloride had no effect on ethanol production.
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  • 29
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    Biotechnology and Bioengineering 33 (1989), S. 999-1009 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Several on-line optimizing control strategies were proposed and tested by computer simulation for the efficient operation of bioreactors. The control task was divided into two, one of which was to search for the optimal operating point and passed the set point to the lower layer of which task was to make the process output follow the set point as soon as possible. It was shown to be effective for the upper layer to express the objective function as a polynomial with respect to the measurement variable and to make use of it for finding the optimum point. Noting that the major dynamic characteristics of bioreactor system is the time-varying and nonlinear nature, the adaptive type control system is in evitable. It was shown to be quite effective to use discrete type self-tuning PID controller and the optimal controller compensated for the interaction between the control loops.Application was made to the cell recycle system for the production of lactic acid and baker's yeast cultivation. I was found from the former application that the control quality can be significantly improved by incorporating the decoupling strategy into the lower layer closed-loop system. It was also found from the latter application that the initial startup period can be significantly reduced by making use of the rough mathematical model.
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    Biotechnology and Bioengineering 33 (1989), S. 1010-1020 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cell growth and enzyme (α-amylase) production characteristics of Bacillus subtilis TN106 containing the recombinant plasmid pAT5 are investigated in batch and continuous cultures using a defined medium with glucose as the limiting nutrient. The batch culture studies demonstrate that the recombinant plasmid, reported earlier1 to be stably maintained in the host, suffers from segregational and structural instabilities. The structural instability of this strain occurred during culture storage and can be eliminated in bioreactor experiments by using a modified inoculum preparation procedure. Such elimination allows an unbiased investigation of segregational instability via continuous culture studies. Such studies conducted with this fast growing microorganism, in the absence of antibiotic selection pressure, indicate a very efficient glucose utilization (very low residual glucose concentrations) over a wide range of dilution rates (0.16 h-1 - 0.94 h-1). The nearly time-invariant and low residual glucose concentrations at each such dilution rate enable convenient estimation of growth parameters of the host and recombinant cells and frequency of segregational instability from transients in the resulting mixed cultures. The specific α-amylase activity exhibits an inverse relationship to the specific growth rate of recombinant cells. The growth of recombinant cells is not affected by the presence of antibiotic (kanamycin). The growth advantage of host cells over recombinant cells diminishes with increasing dilution rate.
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    Biotechnology and Bioengineering 33 (1989), S. 886-895 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An important factor complicating the recovery of recombinant proteins from Escherichia coli is their intracellular location. An alternative to the commonly used method of releasing these proteins by mechanical disruption is to chemically permeabilize the cells. The objective of this research was to characterize the protein release kinetics of a permeabilization process using guanidine-HCl and Triton X100. The protein release rate and yield were determined as a function of the guanidine and Triton concentrations. The initial release rate increased monotonically with increasing concentrations of Triton and guanidine whereas the release yield varied in a complex manner. Electron microscopy indicated that the permeabilization process involves a solubilization of the inner membrane and molecular alteration of the outer wall. Some advantages of this process over mechanical disruption include avoiding extensive fragmentation of the cells and retainment of nucleic acids inside the cell structure.
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    Biotechnology and Bioengineering 33 (1989), S. 896-905 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Substrate regulation patterns were changed by covalent binding of bovine liver glutamate dehydrogenase via primary amino groups to CNBr- and CH-activated Sepharose 4B. Lineweaver-Burk plots show that the NAD activation region changed from being abrupt to elongated when the enzyme was immobilized to either support. The elongated region contains two inflection points and resembles substrate activation of several other allosteric oligomers. Glutamate induced varying degrees of abrupt activation in immobilized glutamate dehydrogenase and inhibited the native enzyme. This activation is characterized by an activation threshold, an increase in the apparent dissociation constant, and a correlation between the apparent rate constant and the degree of activation. These three features characterize other glutamate dehydrogenase systems.
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    Biotechnology and Bioengineering 33 (1989), S. 912-914 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 33 (1989), S. 915-917 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 33 (1989), S. 924-926 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 36
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Integrating the properties of synthetic membranes with biological catalysts such as cells and enzymes forms the basis of an exciting new technology called membrane bioreactors. The impetus behind this marriage comes from the recent spectacular advances in recombinant DMA and cell fusion technologies and the need to develop competitive bioprocessing schemes to produce complex and active biological molecules. The advantages and limitations of using membrane bioreactors for entrapping whole cells and enzymes are reviewed. Various membrane configurations such as microcapsules, hollow fibers, and flat sheets are compared. Several different entrapped membrane bioreactors, including single, laminated and microporous, for the conversion of optically active enantiomers are described. As with new and exciting technologies, the future of membrane bioreactors in biotechnology will depend on their ability to produce desired molecules at competitive costs.
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    Biotechnology and Bioengineering 33 (1989), S. 932-937 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 33 (1989), S. 1072-1076 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 34 (1989), S. 207-213 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effect of one and two four-flat-bladed turbine impellers on the surface aeration intensity in a laboratory tormentor was investigated at different agitation speeds and sparge rates. The surface aeration was found to be generally more intensive with two impellers for the same other operating conditions because of higher power consumption and the position of the upper impeller closer to the free liquid surface. The surface aeration intensity was successfully correlated in terms of power consumption and sparge rate. The aeration number alone cannot be used for general predicting surface aeration intensities.
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    Biotechnology and Bioengineering 34 (1989), S. 30-38 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The synthesis of 2-heptanone from octanoic acid by Caalginate/Eudragit RL entrapped spores of Penicillium roquefortii is performed in batch and continuous reactions. The measurement of the HCI solution needed to overcome the pH increase during the course of a reaction allows continuous monitoring of the reaction progress of batch as well as continuous processes without any aliquot sampling. The hydration of the biocatalyst prior to a bioconversion performance is of major importance to achieve reproducible results. A continuous reaction carried out at pH 6.5 for one month demonstrates the feasibility of such a process and shows that the reaction occurs with a Michaelian behavior, with KM = 1.82 mmol/L and rsm = 0.82 mmol/L h, and no intraparticle diffusion limitation is found. The complex behavior of the spores during batch reactions makes this kind of operation unsuitable for kinetic studies.
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    Biotechnology and Bioengineering 34 (1989), S. 39-54 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Energetic and reaction-rate interactions between hydrogenic (hydrogen-producing) and hydrogenotrophic (hydrogen-consuming) bacteria were investigated in five perturbation experiments performed on steady-state, mixed-culture methanogenic CSTRs receiving ethanol, propionate, or both hydrogenic substrates. When a large quantity of propionate was suddenly added to a propionatefed CSTR, PH2 increased to 10-4 atm and propionate oxidation remained energetically favorable. When ethanol was added to a CSTR receiving ethanol, PH2 rose to 6.3 × 10-3 atm within 5 h. In both perturbations, PH2 remained at levels such that oxidation of the hydrogenic substrate remained energetically favorable throughout the transient. Sudden increase in ethanol concentration in the ethanol- and propionate-fed CSTR resulted in an increase in PH2 such that propionate oxidation became energetically unfavorable and was blocked. Propionate utilization resumed when the added ethanol was depleted and PH2 returned to its previous steady-state levels. Ethanol perturbation of ethanol- and propionate-fed CSTRs led to the formation of reduced products, including n-propanol and four-through seven-carbon n-carboxylic acids, when PH2 was elevated; these products disappeared after PH2 returned to previous, steady-state levels. The transformations were consistent with reaction energetics. Reduced product formation may have been a sink for reducing equivalents, as an alternative to oxidation for propionate utilization, as indicated by an electron equivalents balance over the time course of experiments.
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    Biotechnology and Bioengineering 34 (1989), S. 59-64 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cellulomonas sp. ATCC 21399 produced extracellular enzyme activities against Avicel, H3PO4-swollen Avicel, carboxymethylcellulose, (1-3, 1-4)-β-D-heteroglucan, xylan, galactomannan, and amylose drying growth on microcrystalline cellulose. No extracellular cellobiase activity was produced. Crossed immunoelectrophoresis of the crude extracellular enzyme system revealed 15 immunologically distinct immunoprecipitates. The immunoprecipitates of endoglucanase A, endoglucanase B and the xylanase appeared heterogeneous with several optima, whereas the immunoprecipitates of endoglucanase C and the amylase appeared homogeneous. The heterogeneity of endoglucanase A, endoglucanase B and xylanase was also visualized using electrofocusing-immunoelectrophoresis. Electro-focusing could resolve the activity against carboxymethylcellulose into six peaks, whereas only one peak of activity against Avicel was observed. The later peak coincided with the major peak of activity against carboxymethylcellulose with isoelectric point between pH 4.0-5.0.
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    Biotechnology and Bioengineering 33 (1989), S. 251-255 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The estimation of the size of each reactor of a series of CSTR's performing a Michaelis-Menten reaction in the liquid phase can be obtained to advantage via an optimization technique leading to the minimum overall capital cost. The cost scaleup is assumed to be described by a power rule on the equipment capacity. Various contributions are lumped into the exponent, thus leading to values above unity. The analytical development leading to the optimal intermediate concentrations of substrate according to the foregoing criterion is presented. A short-cut method based on an empirical expression that approximates the numerical solution is reported. This correlation is found to be exact at the asymptotic behaviors, and to give accurate results within an acceptable error level for the range with physical interest. Therefore, it is particularly useful during the predesign steps of equipment for the biochemical industry.
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    Biotechnology and Bioengineering 33 (1989), S. 272-281 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model describing the dynamics of foreign protein secretion from yeast cells is developed. The secretion events, which are a series of complicated enzymatic reactions and carrier-involved transport, are lumped to a practically applicable model structure, based on the major interactions between the heterologous polypeptides and the host cell's secretory machinery through the pathway. The developed model structure predicts that the secretion rate constant is represented as a saturated form with respect to the host cell's specific growth rate. The validity of the proposed model structure is tested by generating dynamic response data to a step input of cycloheximide. The model system used in the experiment is SEY2102-s21, which has an integrated copy of a yeast secretion-mutant invertase that simulates well typical gene cassettes designed to secrete mature foreign proteins utilizing the yeast cell's secretion signals. Protein quantification is done by gel electrophoresis followed by immuno-blot on nitrocellulose filters and subsequent scanning with a reflectance densitometer. Experimental data confirm the proposed model structure.
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    Biotechnology and Bioengineering 33 (1989), S. 282-292 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The control of the continuous, competitive mixed culture of the yeast Candida utilis (ATCC 8205) and the bacterium Escherichia coli B/r (ATCC 12407) was examined. A modified version of the dynamic matrix control (DMC) algorithm was tested in simulation and then was successfully implemented. This represents the first report of the location and stabilization of a competitive mixed culture at a metastable equilibrium point using automatic control.
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    Biotechnology and Bioengineering 33 (1989), S. 293-299 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel technique has been developed to immobilize plant cells. The cells are deposited on a surface of manmade fibrous material that provides for strong binding of the plant tissue biomass growing in the submerged culture. The immobilized plant cells remain fully viable. Relatively uniform biomass loadings of up to 20 mg d.w. plant cells/cm2 support material have been attained. All plant cells from the inoculum suspension became attached within the first 24-48 h depending on the support matrix configuration and hydraulic culture conditions. The advantages and scale-up potential of this technique are discussed and compared to other culturing modes.
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    Biotechnology and Bioengineering 33 (1989), S. 300-305 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model of contact-inhibited growth of cells on flat and spherical surfaces is presented. It shows that contact inhibition does not significantly affect the calculated growth rate of cells unless they are allowed to multiply a large amount from the original seeding density. Microcarriers seeded at low densities require long times to reach confluence because contact inhibition becomes important. In systems with both growth and separate cell death, the equilibrium fraction of holes in the confluent monolayer is below 8% if the death rate is less than half the growth rate, but increases rapidly as the death rate increases from that value.
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    Biotechnology and Bioengineering 33 (1989), S. 306-312 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Immobilization of Aureobasidium pullulans by adsorption on solid supports and entrapment in open pore polyurethane foam were attempted. By adsorption, the highest cell loading of 0.012-0.018 g dry wt/cm2 support was obtained in pH 2.0 medium. Under this acidic condition, the net surface charges (zeta potentials) of both the cells and supports were close to zero and no pullulan was synthesized. Cationic coatings of Cytodex and polyethylenimine were not efficient in enhancing the binding strength between the cells and the supports. Surface immobilized cells and polyurethane foam entrapped cells exhibited a similar fermentation characteristics resulting in ca. 18 g/L pullulan and ca. 5 g/L leaked cells. However, cells entrapped in the polyurethane foam were more shear resistant. The immobilized cells thus could be repeatedly used for pullulan biosynthesis.
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    Biotechnology and Bioengineering 34 (1989), S. 131-136 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 34 (1989) 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 34 (1989), S. 153-159 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The low substrate specificity of alcohol oxidase from Pichia pastoris makes this enzyme system of potential biotechnological interest. Whole cells of Pichia pastoris are able to oxidize benzyl alcohol to benzaldehyde in aqueous reaction media. The low water solubility of the reactant and product of this bioconversion, combined with the ability of both to strongly inhibit the reaction, favor the use of nonaqueous reaction fluids. Purified alcohol oxidase was shown to function in a number of 2-phase reaction systems of varied aqueous to organic phase ratios (0.01-0.05 v/v). The apparent Vmax and Km were 5.26 g/Lh and 7.41 g/L respectively, for the oxidation of benzyl alcohol to benzaldehyde in hexane containing 3% aqueous phase. The volume of the aqueous phase had a strong effect on the reaction, with an aqueous: organic ratio of 3-5% found to be optimum. The enzyme could be firmly immobilized on DEAE-Biogel (Biorad) to enhance stability and biocatalyst recovery.
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    Biotechnology and Bioengineering 34 (1989), S. 196-206 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aiming to satisfy the need for the formalization of semiquantitative reasoning in the analysis of biochemical systems, the O[M] formalism for reasoning with orders of magnitude and approximate relations has been developed. It is based on seven primitive relations among quantities and compound relations which are formed as implicit disjunctions of primitives. O[M] can perform inferences by using formal approximate relations, algebraic equations, inequalities, if-then rules, assumptions, and goals. The applications discussed include Michaelis-Menten kinetics, different modes of inhibition of an enzymatic reaction, analysis of fluxes in biochemical networks, and identification of rate-limiting steps of biochemical pathways. In these applications, O[M] provides a medium for acquisition and formalization of previously informal concepts, analysis of systems at the order-of-magnitude level of detail, and automation of commonsense reasoning.
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    Biotechnology and Bioengineering 34 (1989), S. 223-233 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The economic feasibility of preconcentrating dilute sugar solutions prior to fermentation is investigated. Two methods, evaporation and reverse osmosis, are compared. A computer program to determine the optimal preconcentration conditions for glucose solutions of 1.5-16 wt% has been developed. It was used to compute the fractional cost for labor and maintenance, preconcentration, fermentation, and distillation. Preconcentration with evaporation resulted in a higher total cost, compared with no preconcentration, for all cases studied, although a six-effect unit was used. Reverse osmosis was found to be economically feasible for preconcentration to about 5-10 wt % depending on the concentration of the feed.
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    Biotechnology and Bioengineering 34 (1989), S. 252-261 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The cybernetic framework developed by Ramkrishna and co-workers has been expanded to include the effects of cellular maintenance energy requirements on biomass levels in slow-growing, carbon-substrate-limited cultures. A simple structured model, based on the existence of distinct key enzymes for growth and maintenance functions, is presented. Comparisons of the model with experimental data for the growth of Klebsiella oxytoca in constant fed-batch culture on glucose, fructose, arabinose, and xylose show good agreement. In addition, perturbed fed-batch culture experiments indicate that slow-growing cultures respond less rapidly to a removal of the growth limitation than do faster-growing ones. The possibility of a growth-rate dependent “critical resource” is discussed.
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    Biotechnology and Bioengineering 34 (1989), S. 262-264 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 34 (1989), S. 273-277 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 34 (1989), S. 283-290 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article reports on the reaction of urease immobilization through its covalent bonding on carboxymethylcellulose. The reaction is activated by dicyclohexylcarbodiimide. The coupling reaction is influenced by the enzyme-support and activator-support ratios, as well as by duration. Starting from a rotating, composed experimental program of the second order, the function correlating the activity of the immobilized enzyme with the reaction parameters is established. Immobilized urease exhibits thermal stability higher than that of free enzyme, regarding both pH and the inhibiting action of some metal ions or organic substances. The stability over time of the immobilized urease is high, its enzymatic activity being maintained at over 85% of the initial value three months after synthesis.
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    Biotechnology and Bioengineering 34 (1989), S. 304-308 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Isooctane-AOT-H2O is a suitable system for studying enzyme behavior in organic solvents. Tyrosinase was able to catalyze a well-known reaction in aqueous medium: oxidation of 4-methylcatechol to yield 4-methyl-o-benzoquinone. This reaction was studied using the preceding ternary system with adequate amounts of each component to make up reverse micelles. 4-Methyl-o-benzoquinone stability was demonstrated in isooctane even at alkaline pH values. Apparent Km and Vmax were similar to those in water, but substrate inhibition was more evident. The pH and temperature appear to be shifted toward high and low values, respectively. Characteristic parameters of reverse micelles, ω0 (= H2O/AOT) and percentage of H2O (v/v), were investigated. The results obtained showed that the steady-state rate varies either with ω0 or with percentage of H2O. The variation observed with ω0 showed an optimal value while an increase in percentage of H2O can lead to decreased or increased activity depending on substrate concentration.
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    Biotechnology and Bioengineering 34 (1989), S. 337-356 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Escherichia coli K-12 cells were grown in a confined volume using microporous hollow fiber membranes. The local cell concentrations in the reactors were above 400 g dry mass/L, in excess of the predicted limit based on the specific volume of free cells determined by tracer exclusion. Cell mass synthesis and degradation rates in these reactors were measured using radioisotope labeling with 35S. Net accumulation of cell material persisted at these high cell densities. The rates of substrate uptake and cell growth were predicted from the theory of reaction and diffusion assuming that kinetics of cell metabolism are identical for free-living and immobilized cells. This theory was tested by comparison of overall rates and by the size of the region in which cell growth occurred, measured by autoradiography. A yield coefficient of 4 ± 1 mol sulfur/mol glucose was measured, in agreement with the value determined for free-living cells in similar conditions. Cell growth occurs in a thin layer (10-30 μm), at a rate similar to the growth rate for free cells. Volume expansion by the cells as a consequence of proliferation induces convection of cell mass out of the growth region into a region of the reactor filled with starving cells, which then accumulate in the reactor. The combination of mass-balance and spatial distribution measurements made possible by the use of radioisotope labeling enables a direct test for mass transfer limitations, the determination of the intrinsic cell kinetics, and noninvasive measurements of cell growth in immobilized cell reactors.
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  • 60
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    Biotechnology and Bioengineering 34 (1989), S. 357-368 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The performance of an ultrafiltration hollow-fiber reactor, in which the enzymatic synthesis of glucose 6-phosphate from glucose and cofactor ATP and the enzymatic regeneration of ATP from ADP and acetyl phosphate are performed simultaneously, was analyzed theoretically. A simple analytical model in which the liquid flowing in the fiber tubes is assumed to be plug flow, and the radial concentration gradients in the tube and shell sides are both neglected, could simulate the reactor performance with satisfactory accuracy. The simulation elucidated the effects of the reactor configurations and various operational conditions on glucose conversion, ATP recycle number, and space-time yield. If the fiber tubes, through which the permeability of the relevant components such as substrates is high, were packed as much as possible in the reactor, good reactor performance could be expected. Furthermore, with a sufficiently high enzyme concentration, low ATP concentration in the feed solution, and appropriate space velocity, good space-time yield with high glucose conversion and with very high ATP recycle number is theoretically possible.
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  • 61
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enzymatic synthesis of glucose 6-phosphate from glucose and ATP catalyzed by glucokinase from B. stearothermophilus and enzymatic regeneration of ATP from ADP and acetyl phosphate catalyzed by acetatekinase from B. stearothermophilus were simultaneously performed in an Ultrafiltration hollow-fiber reactor of the multitubular heat-exchanger type. Experimental results of space-time yield, the conversion, and ATP recycle number were in good agreement with the theoretical predictions based on the simple analytical model developed in the preceding article. The best results for space-time yield and conversion were Ys = 1.97 mol/m3 h and X = 92.8%, respectively, under the same conditions, and the best result for the ATP recycle number was NR = 2130 under conditions different from those above. However, Ys = 1.72 mol/m3 h, X = 81.2%, and NR = 1620 were the results when the space-time yield, conversion, and recycle number were at the highest in combination under the same conditions. Results of long-term operation showed that the apparent remaining activity of the enzyme system was ca. 55% after continuous operation for 16 days, the decrease in the enzyme activity being faster than that expected from their half-life times determined individually in the homogeneous system.
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  • 62
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    Biotechnology and Bioengineering 33 (1989), S. 415-421 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transient response method is introduced to elucidate the mechanism of reaction over immobilized enzyme. Glucose oxidation over the glucose oxidase that was immobilized on ion-exchange resin using glutaraldehyde as a linking agent is selected as an example here. The transient responses of a fixed-bed reactor to step increases and decreases in glucose, oxygen, and gluconolactone feed concentrations have been monitored and interpreted. From some responses, we have found that gluconolactone is formed in the reaction of glucose with adsorbed oxygen, while hydrogen peroxide is formed in the reaction of oxygen with adsorbed glucose. Combining all information from interpreting the responses with the literature, a mechanistic picture can be obtained as follows: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {E_{{\rm ox}} + G \to E_{{\rm red}} GL} \\ {E_{{\rm red}} GL \to E_{{\rm red}} + GL} \\ {E_{{\rm red}} + {\rm O}_2 \to E_{{\rm ox}} {\rm H}_2 {\rm O}_2 } \\ {E_{{\rm ox}} {\rm H}_2 {\rm O}_2 \to E_{{\rm ox}} + {\rm H}_2 {\rm O}_2 } \\ \end{array} $$\end{document}.
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  • 63
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    Biotechnology and Bioengineering 33 (1989), S. 422-427 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The saccharification of the polysaccharides of barley, oat, and wheat straws and Solka Floc was studied using the extracellular enzyme system synthesized by mutant strain NTG III/6 of the fungus Penicillium pinophilum 87160iii. The enzymes obtained in cultures containing Solka Floc or barley straw as the carbon source were compared. Solka Floc at 10% (w/v) concentration was hydrolyzed to the extent of 70% in 72 h at 50°C using a reaction mixture containing 7 filter paper units/mL of cellulase induced on Solka Floc, but hydrolysis was increased to 90% when the enzyme induced on barley straw was used. Under the same conditions, the polysaccharides in barley, oat, and wheat straws were hydrolyzed, respectively, in 72 h, to the extent of 42-48%, 62%, and 52%, but hydrolysis was increased to 93%, 100%, and 92%, respectively, after treatment of the substrates with alkaline-H2O2 reagent at room temperature.
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  • 64
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    Biotechnology and Bioengineering 33 (1989), S. 428-439 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidation of Fe2+ with oxygen in sulfate solutions was studied in the presence of T. ferrooxidans. To measure the chemical activity of bacteria, and the oxidation rate of iron, the redox potentials of solutions were continuously monitored during the experiments. The redox potentials were simultaneously monitored on the platinum and pyrite indicator electrodes. The redox potential versus time curves were further used to calculate the basic kinetic parameters, such as the reaction orders, the activation energy, and the frequency factor. It was found that under atmospheric conditions, and at Fe2+ 〈 0.001M, T 〈 25°C, and at pH above 2.2, the oxidation of iron is governed by the following rate expression: \documentclass{article}\pagestyle{empty}\begin{document}$$ - \frac{{d[{\rm Fe}^{2 + }]}}{{dt}} = 1.62 \times 10^{11} C_{{\rm bact}} [{\rm H}^ + ][{\rm Fe}^{2 + }]p{\rm O}_2 e^{ - (58.77/RT)} $$\end{document} Below pH = 2.2, the oxidation rate is independent of H+ Concentration.
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  • 65
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    Biotechnology and Bioengineering 33 (1989), S. 440-450 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth rate of the hybridoma cell line ATCC-CRL-1606 in low serum medium declines rapidly with time after inoculation. To characterize this phenomenon, the stability of the growth-promoting activity of serum was investigated. The activity of serum was found to de grade with time, and was stabilized by alterations in the medium formulation that acted to lower the oxidation/reduction potential. This included both the addition of thiols and the elimination of disulfides from the medium. Additionally, cysteine and other thiols were shown to stimulate growth in low serum, low cell density cultures, suggesting that thiols may be rate-limiting in low serum medium. Stimulation of growth by thiol addition was less significant at high cell levels, implying that the cells themselves may be acting to reduce their environment. A hypothesis is presented based on these results which suggests that the actual rate-limiting moieties in low serum cultures may be dithiols.
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  • 66
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    Biotechnology and Bioengineering 33 (1989), S. 451-459 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A simple procedure is developed to process experimental data from plasmid maintenance studies of recombinant cells in a chemostat with nonselective medium. This procedure, based on the model proposed by Imanaka and Aiba, provides quantitative information on the rate of plasmid loss and the difference in the specific growth rate between the plasmid-carrying and plasmid-free cells. The performance of the proposed method is evaluated through simulation studies. In addition, the method is applied to a set of previously reported experimental data. The two-parameter model, together with the estimated parameter values, provides an excellent fit to the experimental data.
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    Biotechnology and Bioengineering 33 (1989), S. 460-470 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It is well established that pure and simple microbial competitors cannot coexist at a steady state if their environment is homogeneous. For the case of two microbial populations competing purely and simply in two interconnected chemostats having time-invariant input(s), it is known from the literature that a stable steady state of coexistence arises in domains of the operating parameters space and is attributed to the spatial heterogeneities of the system, which allow a different species to have the competitive advantage in each one of the two sub-environments. This article investigates whether the aforementioned result can be extended to the case of three species competing in three interconnected vessels. By studying all possible alternate configurations of the three-chemostat system, it is shown that coexistence of the three species is impossible, except possibly for some discrete values of the operating parameters. Some potential explanations for the results are discussed.
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    Biotechnology and Bioengineering 33 (1989), S. 471-476 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Recently more and more interest is manifested in the utilization of high-pressure extraction using supercritical gases for the purification of products in biochemical processes. Some researchers have examined the possibility of circulating continuously a supercritical gas through the fermentor, under hyperbaric pressure, to recover the desired product while the fermentation is taking place. However, an earlier study has demonstrated that fermentation with baker's yeast was inhibited by a long exposure under hyperbaric pressure. This article is concerned with the improvement of ethanol production under hyperbaric pressure in view of the development of an integrated fermentation-extraction process where supercritical carbon dioxide would be used for the in situ recovery of ethanol. The selection of the best yeast strain and operation under cyclic pressures are considered.
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    Biotechnology and Bioengineering 33 (1989), S. 477-486 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucose and glutamine are the main nutrients used by mammalian cells in culture. Each provides unique biosynthetic precursors but are complementary for production of other metabolites and energy. The transient and steady-state responses of hybridoma growth and metabolism to glucose pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The glucose consumption rate increased by 100-200% immediately after glucose was added to the reactor, and the increased glycolytic ATP production appears to be responsible for the concurrent rapid decrease in the oxygen consumption rate. The effects on glutamine consumption were delayed, probably due to buffering by the TCA cycle and interrelated pathways. A period of increased biosynthetic activity, as evidenced by an increase in the estimated specific ATP production rate and lower by-product yields from glutamine, preceded the increase in cell concentration after the glucose step change. The biosynthetic yield of cells from ATP was calculated, and it was estimated that maintenance accounted for about 60% of the energy used by the cells at a specific growth rate of 0.66 day-1. The estimated 22% ATP production due to glycoysis was twice as great as that before the step change.
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    Biotechnology and Bioengineering 33 (1989), S. 487-499 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transient and steady-state responses of hybridoma growth and metabolism to glutamine pulse and step changes have been examined. Metabolic quotients are reported for oxygen, glucose, lactate, ammonia, glutamine, alanine, and other amino acids. The specific glutamine consumption rate increased rapidly after all glutamine additions, but the responses of the glucose and oxygen consumption rates and the cell concentration were found to depend on the intial feed glutamine concentration. The glucose consumption rate was 1.4-10.9 times that of glutamine, and serine and branched-chain amino acids were consumed in larger amounts at the higher glucose: glutamine uptake ratios. It was estimated that maintenance accounted for ca. 60% of the cellular ATP requirements at specific growth rates ranging from 0.57 to 0.68 day-1.
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    Biotechnology and Bioengineering 33 (1989), S. 1324-1329 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 33 (1989), S. 1330-1342 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The disruption of native and recombinant strains of Escherichia coli was studied using a high-pressure homogenizer (Microfluidizer). The cells were grown in both batch and continuous fermentations. Cell suspensions ranging from 4 to 175 g dry wt/L were investigated at disruption pressures ranging from 30-95 MPa and at up to five passes. For both types of cells, the fraction of cells disrupted was dependent on the growth rate and concentration of the cells, the disruption pressure, and the number of passes through the disrupter. A model is presented that correlates the fractional disruption with these operating variables. The recombinant strain disrupted more readily than the native strain; 95 to 98% disruption of the former was achieved in two to three passes at a pressure of 95 MPa.
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    Biotechnology and Bioengineering 33 (1989), S. 1343-1346 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 33 (1989), S. 1347-1349 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    Biotechnology and Bioengineering 33 (1989), S. 1358-1362 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 33 (1989) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 33 (1989), S. 1350-1352 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Acetic acid at concentrations as may occur during vinification and other alcoholic yeast fermentations induced death of glucose-grown cell populations of Saccharomyces cerevisiae IGC 4072 at temperatures at which thermal death was not detectable. The Arrhenius plots of specific death rates with various concentrations of acetic acid (0-2%, w/v) pH 3.3 were linear and could be decomposed into two distinct families of parallel straight lines, indicating that acetic acid induced two types of death: (1) High enthalpy death (HED) predominated at lower acetic acid concentrations (〉 0.5%, w/v) and higher temperatures; its enthalpy of activation (ΔH≠) approached that of thermal death (12.4 × 104 cal/mol); (2) Low enthalpy death (LED) predominated at higher acetic acid concentrations and lower temperatures with ΔH≠ of 3.9 × 104 cal/mol. While the ΔH≠ values for HED induced by acetic acid were similar with those reported earlier for HED induced by other fermentation endproducts, the values for the entropy coefficients were different: 127-168 entropy units mol-1L for acetic acid as compared with 3.6-5.1 entropy units mol-1L for ethanol, which agreed with experimental results indicating that acetic acid is over 30-times more toxic than ethanol with respect to yeast cell viability at high process temperatures.
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    Biotechnology and Bioengineering 34 (1989), S. 1398-1402 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 34 (1989), S. 1403-1408 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    Biotechnology and Bioengineering 34 (1989), S. 1277-1288 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This article reports the steady-state performance of two hybrid anaerobic digesters treating soluble synthetic sugar wastes of 1 and 0.5% strength and the assessment of the associated macroenergetic parameters (growth yield, so-called maintenance coefficient). A theoretical development shows a “nongrowth” parameter concept to be more appropriate than maintenance or decay. Combined energy and mass balances are used to develop a model for growth rate which compares well with experimental data. The COD removal efficiency had no significant effect on growth yield and the maintenance parameter, although a dual combined balance indicated the possibility of such an effect. Macroenergetic parameters did not vary significantly with the specific feeding rate of the system. We thus conclude that a single model may be used over a broad range of feeding and performance conditions.
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 34 (1989), S. 1357-1365 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Monocrotaline, a pyrrolizidine alkaloid of chemotherapeutic interest, was successfully extracted from the crushed seeds of Crotalaria spectabilis using supercritical carbon dioxide and ethanol mixtures. Overall solubilities of the plant material in the supercritical fluid phase were as high as 1.1 mass percent, and monocrotaline solubilities were as high as 0.07 mass percent. The solubility of monocrotaline in the presence of other plant material was smaller by 50 to 98% compared with the solubility of pure monocrotaline in the supercritical fluid. Also, it was found that the extraction of the complex plant material was time-dependent after approximately one percent of the original mass of the material had been extracted.
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    Biotechnology and Bioengineering 34 (1989), S. 1391-1392 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 34 (1989), S. 1383-1390 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The initial testing of the safety of a cellulose-heparinase hollow fiber device was assessed with respect to physical properties and in vitro biocompatibility. The material cleared urea and creatinine without passing albumin, even at high flow rates. The clearance of urea and creatinine by cellulose-heparinase was equal or slightly reduced in comparision to the cellulose device. The cellulose-neparinase device tolerance to now rates was also unchanged. In addition, scanning electron microscopy of the lumen established the uniformity of the material. The analysis of clearance rates and the scanning electron micrographs show there to be no damage to the cellulose membrane after tresyl chloride activation and heparinase immobilization. The investigation of biocompatibility in an in vitro test system with whole human blood indicated that there were no significant changes in the biocompatibility of cellulose with bound heparinase. There was no change in the level of red blood cells, white blood cells, or platelets over the course of in vitro whole blood perfusion through cellulose or cellulose-heparinase hollow fiber devices. Low levels of plasma hemoglobin and complement activation were observed with cellulose and cellulose-heparinase devices. Thus, the cellulose hollow fibers can be functionalized without any changes in in vitro performance.
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    Biotechnology and Bioengineering 33 (1989), S. 1437-1444 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of various factors in culture medium on the phenolics production from cultured tobacco cells (free and immobilized) were studied. It was found that removing the growth hormone from the medium increased the productivities of phenolics for both free and immobilized cultures. Low initial sucrose concentration in the medium restricted growth and resulted in high cellular productivities of the phenolics for freely suspended cells, but not for the immobilized cells. Addition of 1.4% DMSO to standard culture medium greatly increased phenolics productivities without affecting cell viability in both free and immobilized cell cultures. Continuous operation of a packed-column reactor of the immobilized cells was achieved for 500 hours. Aeration was accomplished by diffusing pure oxygen through silicone tubing placed inside the reactor. It was found that prolonged cell viability was contingent upon initially operating the reactor with total recycle for several days, and then introducing fresh feed while maintaining a high recycle rate. Immobilized cells packed in a continuous column reactor achieved productivities more than twice that achieved in any batch run.
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    Biotechnology and Bioengineering 33 (1989), S. 1425-1436 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An experimental study was undertaken to identify and quantitate the effects of plasmid amplification and recombinant gene expression on Escherichia coli growth kinetics. Identification of these effects was possible because recombinant gene expression and plasmid copy number were controlled by different mechanisms on plasmid pVH106/172. Recombinant gene expression of the lactose operon structural genes was under the control of the lac promoter and was activated by the addition of the chemicals, IPTG and cyclic AMP, to the fermentation medium. Plasmid content was amplified in a separate fermentation by increasing culture temperature since the plasmid replicon was temperature-sensitive. A final fermentation was performed in which both plasmid content and recombinant gene expression were induced simultaneously by adding chemicals and raising the culture temperature. Recombinant growth rates were found to be reduced by the expression of high levels of recombinant lac proteins in the chemical induction experiments and by the amplification of plasmid levels in the temperature induction experiment. High expression of recombinant lac proteins following chemical induction was accompanied by a loss in recombinant cell viability. In the plasmid amplification experiment, the recombinant cells did not lose viability but the recombinant product yields were much lower than those achieved in the chemical induction experiments. Combining temperature and chemical induction increased the recombinant product yield by a factor of 4400 but also lowered cellular growth rates by 70%.
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    Biotechnology and Bioengineering 33 (1989), S. 1445-1460 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A previously isolated cellodextrin glucohydrolase (β-glucosidase) from Trichoderma reesei QM 9414 is characterized using β-1,4-glucose oligomers with defined degrees of polymerization as soluble substrates. The enzyme splits off glucose units from the nonreducing chain ends of cellooligomers. Besides this hydrolytic activity there is also evidence for transfer activity depending on the concentration and degree of polymerization of substrates. Concentration-time-course data have been gathered for the degradation of cellobiose, cellotriose, cellotetraose, cellopentaose, and cellohexaose covering a wide range of enzyme and substrate concentrations. A Michaelis-Menten type kinetic model has been developed, which is able to satisfactorily describe the complex system of parallel and series reactions during the conversion of oligomers to glucose. The only kind of inhibition considered is competitive inhibition by the final product glucose. The model takes into account the formation of multiple enzyme-substrate complexes and is limited to those conditions, in which no transglucosylation products are observed. Cellodextrins with higher degrees of polymerization are found to be better substrates for this enzyme than is the dimer cellobiose.
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  • 88
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    Biotechnology and Bioengineering 33 (1989), S. 1461-1468 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alginate-entrapped cells of Mucuna pruriens L. hydroxylate L-tyrosine, tyramine, para-hydroxyphenylpropionic acid, and para-hydroxyphenylacetic acid to their corresponding catechols, which were released into the incubation medium. Michaëlis-Menten kinetics was applied for each bioconversion. The apparent affinity constants were comparable with the affinity constants obtained with a homogenate directly prepared from the cells used for entrapment and with a derived partly purified phenoloxidase. The values found for the apparent maximum rates of bioconversion of the entrapped cells were ca. 50% of the values of the maximum rates of bioconversion of the cell homogenate, indicating that the entrapped cell system was not operating optimally. The effective diffusivities of the substrates and products were measured with alginate-entrapped, inactivated cells. From the five inactivation methods tested, glutaric aldehyde treatment was chosen as the general procedure. Calculated effective diffusivities for the monophenols and catechols demonstrated that these compounds could diffuse freely into and out of the beads. For each bioconversion, the observable modulus was calculated from the initial rate of bioconversion and the effective diffusivity of the substrate. The resulting values indicated that the diffusional supply rate of the substrates was not the limiting factor, except for the conversion of tyramine for which a modulus higher than one was obtained. Analogously, the observable moduli were calculated for oxygen, which was utilized for bioconversion and cell respiration, and these values pointed towards strong oxygen limitation in all cases. The bioconversion rates of the entrapped cells increased with decreasing cell aggregate size. Therefore, it was concluded that direct cell-matrix contact determined the amount of phenoloxidase involved in the bioconversions. The bioconversion rate on a protein basis was constant with enhancement of the bead charge and thus, in spite of limitations, the mixing conditions as such were relatively optimal. In conclusion, the nonoptimal efficiency of the plant cell system studied was caused by oxygen limitation and a partial phenoloxidase participation, but not by mass transfer limitations for substrates and products with the exception of the conversion of tyramine into dopamine.
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  • 89
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    Biotechnology and Bioengineering 33 (1989), S. 1477-1481 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The water-in-oil microemulsion system bis(2 ethyl-hexyl-sodium-succinate (AOT)/isooctane/water is able to solubilize soybean nodules mitrochrondria. Transparent and thermodynamically stable hydrocarbon solutions are obtained, which can be assayed for mitochondrial activity just as aqueous solutions. Malate dehydrogenase (MDH) activity was measured in vivo and gave in reverse micelles very similar results as in water. However the kinetic behavior of this reaction in AOT/isooctane reverse micelles shows some differences with respect to water. Mitochondria in reverse AOT micelles are able to retain about 70% of their initial MDH activity after three days. Mitochondria can be back-transferred from reverse micelles to water and show respiratory activity almost identical to the native organelles. Electron microscopy studies show that the dimensions of mitochondria back-transferred into water from AOT micelles are comparable to the dimensions of the native organelles.
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  • 90
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    Biotechnology and Bioengineering 33 (1989), S. 1482-1488 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 91
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    Biotechnology and Bioengineering 34 (1989), S. 10-17 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The potential of uranium recovery from the dilute uranium ore bioleach solutions of the Elliot Lake district of Canada was examined using immobilized microbial biomass. Batch and continuous laboratory scale pilot plant experiments were carried out. The results have shown that the immobilized microbial biomass can successfully recover all of the uranium from dilute (less than 300 mg U/L) solutions. The uranium can subsequently be eluted producing a high uranium concentration eluate perhaps exceeding 5000 mg U/L. The biomass maintained its biosorption capacity of about 50 mg U/g over 12 examined successive adsorption-elution cycles with no apparent indication of failure.
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  • 92
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    Biotechnology and Bioengineering 34 (1989), S. 55-58 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effective diffusivity of oxygen, De, in Ca-alginate and PVA-SbQ gels was measured using a two-chamber vessel with a membrane between the two chambers. The effect of cell density, Cc, on De in Ca-alginate gels was studied. The effective diffusivity of oxygen decreased with increasing cell density, to Cc = 170 kg dry cells/m3 gel. The dependency of De on cell density was discussed in terms of a random-pore model. The model correlated well with experimental data, i.e., kDe/D0 = 0.86(1 - 1.47 × 10-3 Cc)2. Here, k is the partition coefficient, and D0 is diffusivity in water.
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  • 93
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    Biotechnology and Bioengineering 34 (1989), S. 65-71 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two endoglucanases (endoglucanase B and endoglucanase C) without affinity for cellulose were purified from the culture broth of Cellulomonas sp. ATCC 21399 using gelfiltration and ion exchange chromatography. Fused rocket immunoelectrophoresis was used to select the fractions with the highest content of endoglucanase and lowest content of contaminating proteins. The endoglucanases were purified to immunological homogeneity. In addition both endoglucanases were homogeneous when analyzed by sodium dodecyl sulfate - polyacrylamide gel electrophoresis (molecular weights of endoglucanase B and endoglucanase C were 67000 and 25000, respectively). Endoglucanase B was homogeneous when studied by isoelectric focusing showing one protein band at pl 4.3. Both endoglucanases lacked activity against microcrystalline cellulose (Avicel) and showed similar endo action on carboxymethylcellulose (CMC). Endoglucanase B had a high specific activity against CMC, H3PO4-swollen Avicel and xylan, but showed no activity against galactomannan. In contrast, endoglucanase C showed activity against both CMC, xylan, and galactomannan all being polysaccharide substrates linked with β-1-4-D-glucoside bonds. The specific activity of endoglucanase C against H3PO4-swollen Avicel was low.
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  • 94
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    Biotechnology and Bioengineering 34 (1989), S. 79-85 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Action pattern of endopolygalacturonase (E.C.3.2.1.15) immobilized by adsorption on porous powdered poly(ethyleneterephthalate) and covalently bound via amino groups on poly(2, 6-dimethyl-p-phenyleneoxide) and poly(6-caprolactame), respectively, were investigated in suspension and packed columns using polymeric and oligomeric D-galactosiduronates as substrates. The covalent binding invariably led to a lowering of randomness of degradation of high-molecular substrates and loss of specificity of (3 + 1) splitting of tetra(galactosiduronic acid), typical of the free enzyme. In the adsorbed endopolygalacturonase the degree of randomness of degradation of D-galacturonan and Km,app value were dependent on the substrate transfer; the former parameter increased, the later decreased with increasing flow-rate of the substrate through the immobilized enzyme bed. The action pattern on low-molecular substrates was not altered. The changes in action pattern of the covalently immobilized endopolygalacturonase are ascribed to sterical limitations resulting from a binding of the enzyme molecule in the proximity of its active site. In endopolygalacturonase bound to the support by hydrophobic interactions external diffusion effects are regarded the factors governing the enzyme action.
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  • 95
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    Biotechnology and Bioengineering 34 (1989), S. 126-130 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 96
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    Biotechnology and Bioengineering 34 (1989), S. 617-628 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Aerated and unaerated power consumption and flow patterns in a 0.56 m diameter agitated vessel containing water with dual Rushton turbines have been studied. Under unaerated conditions with a liquid height-to-diameter ratio of 2, an impeller spacing of 2 to 3 times the impeller is required for each to draw an amount of power equal to a single impeller. For aerated conditions, if a similar spacing is used, equations for the flooding-loading transition and for power consumption for a single Rushton impeller can be extended relatively easily to dual systems. All results for this spacing are explained by reference to bulk flow patterns and gassed-filled cavity structures and the proportion of sparged gas flowing through the upper impeller is also estimated. Such a spacing is generally recommended since it maximizes the power draw and hence the potential for oxygen mass transfer. Data are presented for other spacings but the results do not fit in easily with single agitator studies because strong impeller-impeller flow pattern interactions occur.
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  • 97
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    Biotechnology and Bioengineering 34 (1989), S. 647-659 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An algorithm is presented for detecting the appearance of contaminants during batch or fed-batch fermentations, using only presently available on-line measurements. Its adaptive nature enables it to rely on almost no prior knowledge of the real process. The necessary on-line measurements are total biomass and its production rate; it is also shown how a physical variable such as oxygen uptake can be used alone instead. The algorithm's properties are studied theoretically and through simulations. These were confirmed by on-line experimental results, obtained with a Yeast culture, both pure and contaminated by a Bacteria. The algorithm does not detect contaminants when none are there, and it also provides a convergent estimate of a pure culture's specific growth rate. Contaminated cultures are recognized by the algorithm, and this detection can be made more or less conservative. After detection, the various estimates may diverge, due to general observability difficulties, though this divergence can itself be monitored. Moreover, the algorithm is easy to tune and its qualitative behavior is quite insensitive to its adjustable parameters. A practical criterion and scheme for implementation are proposed. The generality of the approach, which far exceeds the experimental system used, is finally discussed.
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  • 98
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    Biotechnology and Bioengineering 34 (1989), S. 838-843 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In view of the biochemical reaction catalyzed by enzyme powder suspended in a water-insoluble organic solvent, an equation was derived to estimate the amount of water bound to the enzyme powder. With this equation, an apparent adsorption isotherm between free water (water freely dissolved in benzene) and bound water (water bound to crude lipase powder of Pseudomonas fluorescens) was obtained. A direct lactonization reaction (synthesis of cyclopentadenolide from 15-hydroxypen-tadecanoic acid) catalyzed by crude lipase powder of Pseudomonas fluorescens was carried out batchwise in microaqueous benzene at 40oC. A kinetic model of the enzymatic reversible lactonization reaction was derived, from which the effect of moisture content on the initial reaction rate with a fully hydrated enzyme was mathematically expressed. The observed initial reaction rate first increased, then decreased with increasing moisture content, giving rise to the maximum rate at a certain level of the moisture content. The drop in the reaction rate at lower moisture content was due to a lesser hydration of the enzyme molecule (hydration-limited) and the decrease in the reaction rate at higher moisture content was attributed to the dependence of the true initial rate of the reversible reaction on the moisture content (true reversible reaction limited), and could be simulated by the kinetic model. The equilibrium yield approached 100% at a lower moisture content.
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  • 99
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    Biotechnology and Bioengineering 34 (1989), S. 872-874 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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  • 100
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    Biotechnology and Bioengineering 34 (1989), S. 875-881 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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