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  • Biochemistry and Biotechnology  (524)
  • Engineering  (448)
  • 1985-1989  (972)
  • 1965-1969
  • 1950-1954
  • 1987  (972)
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  • 1985-1989  (972)
  • 1965-1969
  • 1950-1954
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 242-248 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The inhibitory effect of butanol on yeast growth has been studied for the strain Candida utilis ATCC 8205 growing aerobically on butanol under batch conditions. A mathematical expression was then proposed to fit the kinetic pattern of butanol inhibition on the specific growth rate: \documentclass{article}\pagestyle{empty}\begin{document}$$ \mu = \frac{{\mu _m S}}{{K_s + S}}\left[{1 - \frac{S}{{S_m }}} \right]^n $$\end{document}The maximum allowable butanol concentration above which cells do not grow was predicted to be 9.16g/L. The proposed model appears to accurately represent the experimental data obtained in this study and the literature data developed for a variety of batch culture systems at widely ranging substrate concentrations.
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  • 2
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    Biotechnology and Bioengineering 29 (1987), S. 269-278 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bisubstrate secondary utilization model is based on the concept that an individual substrate can be utilized not only by the biomass by its utilization but also by the biomass made from the utilization of the other substrate. When substrate concentrations are low, a key factor is having sufficient substrate to initiate biofilm growth. Modeling results for three characteristic cases demonstrate that satisfying a total Smin concentration for a bisubstrate system is the necessary condition for initiating biofilm growth and simultaneous utilization of both substrates. Because having more than one substrate supporting biofilm growth enhances the removal of each compound, the utilization rate of a specific compound can be increased by the concentration of other compounds, and the total Smin concentration can be less than the weighted average of individual Smin values.
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  • 3
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    Biotechnology and Bioengineering 29 (1987), S. 279-288 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Diffusion of gases through legume nodules is important for nitrogen fixation. A mathematical model is presented for diffusion and enzymatic reaction for legume nodules with a reactive core and an inert shell. The transient model is solved numerically for spherical geometry for acetylene reduction by nitrogenase enzyme. The results are used to estimate the diffusivities of acetylene and ethylene in the nodules by comparing predicted and experimental lag times. The experimental results are also analyzed using an effectiveness factor plot for spherical nodules with inert shells and reactive cores. The results show that the diffusivities are slightly higher than those for acetylene and ethylene in water because of some contribution of gas phase diffusion. Applications to oxygen diffusion through nodule tissue are suggested.
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  • 4
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 335-342 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A bisubstrate system having Ss1 〉 Smin 1 was tested with phenol and acetate as model compounds in completely mixed biofilm reactors. Two series of experiments compared the kinetics of phenol removal as a single substrate and as part of a bisubstrate system having a fixed total feed COD. Experimental results showed that, although the rate of utilization of either substrate was almost the same in a bisubstrate system as in a single substrate system, the utilization rate of either compound always was slightly greater in a bisubstrate system than in a single-substrate system. This slight enhanced removal of an individual compound in a bisubstrate system was attributed to the extra biomass accumulated from the utilization of the other substrate. As the fraction of the feed COD contributed by an individual compound decreased in a bisubstrate system, the effluent concentration of that compound decreased and its fractional removal efficiency increased. The bisubstrate secondary-utilization model successfully described the experimental results and explained the differences that occurred as phenol became a smaller fraction of the fixed total feed COD.
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  • 5
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    Biotechnology and Bioengineering 29 (1987), S. 388-391 
    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 29 (1987) 
    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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  • 7
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    Biotechnology and Bioengineering 29 (1987), S. 171-175 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Higher activity of ethanol production due to higher density of yeast cells was observed in yeast cells immobilized with artificial polymer carriers of higher water content based on methoxypolyethyleneglycol methacrylate and 2-hydroxyethylacrylate. These polymer carriers were prepared by radiation-induced polymerization below 0°C. Yeast cells were immobilized with these carriers by adsorption method during multiplication. Two possible reasons for higher activity were discussed.
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  • 8
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The suitability of using annually grown, carrot-sized buffalo gourd (Cucurbita foetidissima) roots as a feedstock for alcoholic fermentation was explored. Roots grown in 1982 and 1983 were slurried, dextrinized and saccharified using Takatherm™ and Diazyme™ (commercial enzymes manufactured by Miles Laboratories), and fermented by the action of Saccharomyces cerevisiae. These processes were monitored in detail and results were compared with those displayed by controls formulated using potato tubers. The preparation of gourd root slurries with suitable viscosity characteristics for enzymatic digestion required the addition of water (at least 50% by weight) which reduced the proportion of fermentable sugars in the resulting saccharified suspensions. The resulting slurries were well-suited to enzymatic conversion of starch to sugar. Estimates of enzymatic efficiency in gourd root suspensions did not suggest the presence of naturally occurring amylase or glucosidase inhibitors in these plant materials. Saccharified gourd root mashes supported yeast growth well and produced ethanol yields at 82.2-86.5% of the theoretically maximum efficiency.
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  • 9
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    Biotechnology and Bioengineering 29 (1987), S. 476-481 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Available electron methods are presented and used to estimate theoretical energetic growth yields for photoautotrophic, mixotrophic, and photoheterotrophic growth of algae and photosynthetic bacteria. The theoretical yields are compared to experimental values reported previously. For photoautotrophic and mixotrophic growth of algae experimental values that approach and even exceed the theoretical values have been reported in the literature. For photosynthetic bacteria experimental yields are much smaller than thetheoretical maximum values.
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  • 10
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    Biotechnology and Bioengineering 29 (1987), S. 488-492 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We describe a first-principles analysis of a system for the continuous culture of the green alga Scenedesmus obliquus under light-limiting conditions. According to this analysis, the productivity of the algal culture is given by the relation Y = EmI0AK(1 - e-αcl) - GRcV, where Y = yield (g cells/h), Em = 0.20 (the maximum attainable photosynthetic conversion on an energy basis), A = illuminated area (m2), K = 0.156[(g cells/h/W), the energy equivalent of the algae], I0 = light intensity (W/m2), α = extinction coefficient (L/cm/g),c = cell concentration (g/L), I = light path (cm), R = respiration rate (g carbon/g cells/h), V = culture volume (L), and G = ratio of g cells to g carbon (2.04). This formula is completely determined and has no free adjustable parameters. Using parameter values determined independently, the model accurately predicted the relationship of productivity to cell density in the culture system.
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  • 11
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    Biotechnology and Bioengineering 29 (1987), S. 513-519 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Temperature shifting was investigated as a means of improving cloned-gene product yields form a recombinant Escherichia coli containing the temperature-sensitive plasmid, pOU 140. In a series of shaker flask fermentations recombinant cells were thermally induced for different time periods. The growth, stability, and plasmid product levels were followed, and the results indicate the existence of an induction time period that maximizes product yield. A sustained thermal induction results in recombinant cell death and instability, while exposure to a runaway temperature for minimal time periods does not give sufficiently high product yields. At intermediate cycling times, however, the recombinant cells remain stable, and the plasmid replication region is activated, resulting in higher product yields.
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  • 12
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    Biotechnology and Bioengineering 29 (1987), S. 545-551 
    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 is presented to determine (1) the rate constant for the main reaction, (2) the rate constant for deactivation, (3) the effective diffusivity, and (4) the active enzyme distribution within a porous solid support by utilizing data of bulk substrate concentration versus time in a continuous stirred basket reactor. The method relies on an assumption of parallel deactivation mechanism with strong pore diffusional resistance with respect to substrate species. The data of hydrogen peroxide-immobilized catalase published in the literature are used to demonstrate the theory. A parameter determination procedure is also presented.
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  • 13
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    Biotechnology and Bioengineering 29 (1987), S. 558-565 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Host-plasmid interactions were studied for the broad-host range plasmid, pTJS26, a derivative of RK2. To isolate host and plasmid contributions to the growth dynamics and plasmid stability, separate experiments were performed with host and recombinant cells for two different gram-negative hosts, Pseudomonas putida and Escherichia coli, at two different temperatures, 30 and 37°C. At the lower temperature (30°C) the growth kinetics were not affected by the plasmid, but plasmid instability was observed. At the higher temperature (37°C) growth rates and yields were lower than that for the hosts, but the plasmid was stable. This behavior can be explained by a combination of two phenomena. First, the copy number control mechanism may be temperature sensitive and, second, plasmid segregation may be inefficient. For both E. coli and P. putida the growth dynamics of the recombinant system was dictated by the presence of the plasmid.
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  • 14
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    Biotechnology and Bioengineering 29 (1987), S. 625-632 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study deals with the behavior of a heterogeneous multisubstrate enzymatic system under enzyme inactivation in a reaction. Electronic computer modeling data have been obtained for its macrokinetics at different modes: (1) under mixed inflow of the substrates and (2) under their spatial separation. The enzymatic membrane exhibits low sensitivity to a change in the external conditions as the substrates are intermixed on the boundary. Quite the contrary, in the case of spatial separation of the substrates, the product flow from the membrane has displayed abrupt fluctuations at different boundary conditions. This work also looks into the arrangement of the reaction zones in the membrane and their transitions under different conditions.
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  • 15
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    Biotechnology and Bioengineering 29 (1987), S. 601-611 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A step function model of milk micelle agglomeration is proposed to explain the observed kinetics of milk clotting following rennet addition. The model ties together the primary and secondary phases of coagulation. The basis of the model is that no micelle flocculation takes place until ca. 75% of the κ-casein in the milk is hydrolyzed, at which time flocculation occurs rapidly and the rate limiting step for the clotting process shifts to the κ-casein hydrolysis reaction. Using such a model, it is possible to explain the clotting kinetics for both rapidly denaturing enzymes and stable enzyme systems. The average rate of the flocculation reaction can be obtained from clotting time-versus-reciprocal-enzyme-concentration data by extrapolating the data to infinite enzyme concentration. The critical conversion required for imminent flocculation can be found by extrapolating the enzyme concentration to zero. This approach indicates that the critical conversion necessary for gelation is temperature dependent changing from a limiting value of essentially 100% hydrolysis at temperatures below 15°C to only 60% conversion at temperatures above 30°C.
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  • 16
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    Biotechnology and Bioengineering 29 (1987), S. 652-655 
    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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  • 17
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    Biotechnology and Bioengineering 29 (1987), S. 648-651 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: β-D(+)-Glucose pentaacetate was hydrolyzed both chemically and enzymatically. In contrast to the alkaline hydrolysis, esterase-catalyzed deacetylations afforded significant accumulation of intermediate glucose esters at different degrees of substrate conversion. Aspergillus niger lipase, the most suitable of the four enzymes tested, was used for preparative hydrolysis of glucose pentaacetate. As a result, gram quantities of pure glucose-2,3,4,6-tetraacetate, glucose triacetate (a mixture of two positional isomers, 2,4,6- and 3,4,6-), and glucose-4,6-diacetate were prepared.
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  • 18
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    Biotechnology and Bioengineering 29 (1987), S. 705-713 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Homogeneous membranes containing immobilized glucose oxidase and catalase were stored in buffered solutions at 37°C to determine the mechanisms and rates of catalyst inactivation. The experiments were designed so that inactivation occurred homogeneously throughout the membrane, thereby simplifying the analysis. The mechanism of inactivation is consistent with the reaction of hydrogen peroxide and certain catalytic intermediates of both enzymes. Based on this information, numerical simulations were developed that incorporate spatially heterogeneous catalytic and inactivation processes.
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  • 19
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    Biotechnology and Bioengineering 29 (1987), S. 572-581 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Corn stover was pretreated for compositional fractionation and structural modification for maximum conversion of carbohydrate to soluble sugars. The process scheme consisted of three steps: (1) mild prehydrolysis in dilute sulfuric acid, (2) delignification with various organosolv solvents, and (3) enzymatic hydrolysis in an agitated bead reactor. Prehydrolysis of corn stover can be achieved at temperatures ranging from 95 to 120°C, which is a much milder condition than must be applied to wood. Various organosolv solvents, including several alcohols with acid as catalyst, ethylene glycol, and its derivatives, and amines were used for delignification of the prehydrolyzed corn stover. Aromatic alcohols were found to be more effective in solubilizing the prehydrolyzed corn stover than were the aliphatic alcohols. Butanol was the most effective among the aliphatic alcohols; on the other hand, phenol was the best among the aromatic alcohols. Ethylene glycol, methylcellosolv, and ethylcellosolv were effective in solubilizing the prehydrolyzed corn stover but not for enhancing the enzymatic hydrolysis. Various amines achieved delignification at the mild temperature of 95°C, but they tended to solubilize substantial amounts of carbohydrate in addition to lignin. n-Butylamine was effective in enhancing the conversion during enzymatic hydrolysis; it was a good delignifying agent as well as one that achieved a concomitant swelling of the cellulose structure. The low enzymic conversion (20-37%) of prehydrolyzed and solvent-extracted corn stover that was achieved implies that lignin is not the only major barrier for enzymatic hydrolysis. Modification of cellulose structure also should be accomplished to achieve a high degree of conversion. Enzymatic hydrolysis in the agitated bead system increased the rate and extent of conversion of corn stover substantially compared to systems without beads.
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  • 20
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    Biotechnology and Bioengineering 29 (1987), S. 679-689 
    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 29 (1987), S. 690-695 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: It has been demonstrated that Thiobacillus denitrificans may be readily cultured aerobically in batch and continuous flow reactors on H2S(g) under sulfide limiting conditions. Under these conditions sulfide concentrations in the culture medium were less than 1μM resulting in very low concentrations of H2S in the reactor outlet gas. Biomass yield under aerobic conditions was much lower than previously reported for anaerobic conditions, presumably because of oxygen inhibition of growth. However, biomass yield was not affected by steady state oxygen concentration in the range of 45μM-150μM. Biomass yield was also observed to be essentially independent of specific growth rate in the range of 0.030-0.053 h-1. Indicators of reactor upset were determined and recovery from upset conditions demonstrated. Maximum loading of the biomass for H2S oxidation under aerobic conditions was observed to be 15.1-20.9 mmol/h/g biomass which is much higher than previously reported for aerobic conditions. Other aspects of the stoichiometry of aerobic H2S oxidation are also reported.
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  • 22
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    Biotechnology and Bioengineering 29 (1987), S. 759-761 
    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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  • 23
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    Biotechnology and Bioengineering 29 (1987), S. 767-769 
    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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  • 24
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    Biotechnology and Bioengineering 29 (1987), S. 770-772 
    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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  • 25
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    Biotechnology and Bioengineering 29 (1987), S. 775-777 
    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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  • 26
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    Biotechnology and Bioengineering 29 (1987), S. 783-785 
    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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  • 27
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    Biotechnology and Bioengineering 29 (1987), S. 793-795 
    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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  • 28
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    Biotechnology and Bioengineering 29 (1987), S. 789-792 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reliable dynamic descriptions of cellular growth are important for many practical applications including bioreactor design and control. A chemically structured growth model of Escherichia coli has been formulated and herein we focus on finding the essential dynamic order of the metabolic part of this model. Standard linear analysis is applied and the main finding is that the model contains three essential modes of motion over the time scale of growth. The doubling time is successfully predicted from an unstable growth motion and the metabolite composition of the three modes of motion suggests that only a three pool metabolic model is necessary. The three pools correspond to important groups of macromolecules; protein, nucleic acids and cell wall constituents.
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  • 29
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    Biotechnology and Bioengineering 29 (1987), S. 832-843 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Blue-green algae, Spirulina platensis, is cultivated under photoautotrophic growth conditions designed to have nearly uniform growth rate throughout the fermentor by illumination both sides of a rectangular vessel. The results show that growth rate and bioenergetic yield are a function of light intensity. Several kinetic models are considered to express the relationship between growth rate and light intensity.
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  • 30
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    Biotechnology and Bioengineering 29 (1987), S. 924-933 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: For a reversible one-substrate reaction system that follows the Haldane reaction mechanism, a new and effective method has been proposed to extract true or intrinsic kinetic parameters of immobilized enzymes from diffusion limited rate data. The method utilizes the effectiveness factors correlated in terms of the general modulus defined by Aris and Bischoff, and a new modulus defined in the present study. It requires a trial-and-error calculation, but only a few data points. Furthermore, it provides a saving of materials such as substrates and enzymes, and takes less time for experiments compared to the initial rate methods. The usefulness of the method is demonstrated by determining the kinetic parameters for membrane bound fumarase which catalyzes the reaction of the conversion of fumarate to L-malate, for which the equilibrium constant is ca. 4.
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  • 31
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    Biotechnology and Bioengineering 29 (1987), S. 941-949 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Process control of different reactor models for continuous production of ethanol from sucrose with immobilized yeast has been studied. An enzyme thermistor with immobilized invertase recorded the concentration of sucrose continuously. Ethanol was recorded by a membrane gas sensor with a SnO2 semiconductor used as detector. A process computer controlled the substrate feed to keep substrate as well as ethanol concentration at preset values by using algorithms of varying complexity. It was thereby demonstrated that PID regulators as well as more advanced algorithms (Otto-Smith regulator, state feedback from a Kalman filter, and cascade control) are useful alternatives to maintain a constant concentration in the fermentor effluents. The time required for the system to return to predetermined conditions after various kinds of disturbances has been especially studied. It was shown that the more advanced regulator used the shorter time.
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  • 32
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    Biotechnology and Bioengineering 29 (1987), S. 950-961 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The steady-state behavior of a continuous bioreactor containing antibiotic-resistant recombinant cells has been investigated. Only the plasmid-free cell is susceptible to and killed by antibiotics. A Monod form of specific death rate was found to simulate quite well the experimental death rates of various cells due to antibiotics. The stability characteristics, including bifurcation of the possible steady states, are examined. Appropriate numerical illustrations for the steady-state characteristics have been provided. Theoretically, two coexistence steady states (CO), three partial washout steady states (PW), and one total washout steady state (TW) are feasible, but only one CO, one PW, and one TW were realized. When antibiotic consumption is not extremely significant the CO can exist over one or two ranges of dilution rates depending upon the antibiotic concentration in the feed. The CO is globally stable. Whenever the PW and/or the TW exist(s) together with the CO they are unstable. Sensitivity analyses for several key kinetic parameters have been made. The rate at which the plasmid-bearing cells revert to the plasmid-free cells has the most significant effect on the antibiotic susceptibility of the system. Some simplified optimization calculations for maximum profit have been carried out.
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  • 33
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    Biotechnology and Bioengineering 29 (1987), S. 976-981 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Solute exclusion was used to determine the pore volume and micropore size distribution of wet cellulosic materials. Glucose, cellobiose, and polyethylene glycol (PEG) (8 to 130 Å in diameter) were used as molecular probes. Four replicates of cellulosic samples, with each sample being analyzed 4 to 8 times, gave the concentrations of each molecular probe before and after contact with cellulose. Sugar concentrations were determined by the DNS method and PEG concentrations by a differential refractometer. Deviations arising from sample-to-sample variability result in variations of solute uptake from which the pore size distribution was determined. The need for replicate samples and a statistical approach to data analysis is indicated. Consequently, the data were fitted to an empirical logistic model function based on the minimum of the residual sum of squares using the finite-difference, Levenberg-Marquardt algorithm. A smooth increasing function resulted. We report experimental methodology employing a differential refractometer, common in many laboratories having a liquid chromato-graph instrument, combined with statistical treatment of the data. This method may also find application in determining pore size distribution in wet, hydrophilic polymers used in some types of membranes, chromatographic supports, and gel-type resins.
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  • 34
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    Biotechnology and Bioengineering 29 (1987), S. 1003-1014 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Expression of the lactose (lac) operon in the Escherichia coli chromosome has been studied in mixed-sugar chemostat cultures under steady-state and transient conditions. A unified model has been formulated which involves regulation of active inducer (lactose) transport, promoter-operator regulated expression of the lac operon, glucose-mediated inducer exclusion, and catabolite repression. The model of the lac operon control system focuses on the molecular interactions among the regulatory species and the genetic control elements for the initiation of transcription. The role of catabolite modulator factor (CMF) in the regulation of transcription is described. The modeling of glucose-mediated regulation of intracellular cyclic adenosine monophosphate (cAMP) and inducer exclusion is based on the recently elucidated mechanisms of the involvement of the PTS (phosphoen-olpyruvate dependent sugar transport system) enzymes, in the presence of glucose, in regulation of adenylate cyclase and non-PTS sugar transport proteins (i.e. per-meases). The adequacy of the unified model was verified with experimental data.
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  • 35
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    Biotechnology and Bioengineering 30 (1987), S. 164-168 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Zooplankton was successfully used for the biological control of unicellular algal contaminants in Spirulina mass cultures even under conditions adverse to the growth of Spirulina (maximal winter daily temperature of approximately 10°C and very low bicarbonate concentration). Brachionus plicatilis (Rotifera) was the most successful species of zooplankton used. The interrelationships between Spirulina, green unicellular contaminant, and B. plicatilis were studied under various conditions. Two species of unicellular contaminant were used; Monoraphidium minutum was isolated from local cultures and Chlorella vulgaris, obtained from contaminated Spirulina cultures in Israel. The rotifer B. plicatilis successfully controlled the population size of both contaminants whether they were introduced in a single addition or as a daily dose. The biological control of the unicellular contaminants allows Spirulina to be cultured in a medium low in bicarbonate, thereby reducing the cost of the medium and increasing the quantity of CO2 that may be freely absorbed from the atmosphere at the optimal pH for Spirulina cultivation.
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  • 36
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    Biotechnology and Bioengineering 30 (1987), S. 187-195 
    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 behavior of continuous fermentation is studied concentrating on the time scale intrinsic to the system. The time scale is the time required for the fermentorto reach a stable steady state after the disturbance of cell mass is introduced. When the cell concentration is disturbed from the steady-state value, in particular, at the dilution rate near washout, the transient period becomes extended significantly, and the steady state is resumed sluggishly. This sluggish transient behavior could be turned to an advantage for enhancing the cell mass output rate. The proposed transient operation is a continuous fermentation whereby a positive disturbance in the cell mass is introduced, so that the cell concentration is higher than the steady-state value for an extended transient period. It is shown that a significantly higher cell mass production than that from the steady-state continuous fermentation can be achieved. Simple experiments were performed to demonstrate the improvement of cell (Candida utilis) productivity.
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  • 37
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    Biotechnology and Bioengineering 30 (1987), S. 216-224 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Irreversible adsorption of bovine serum albumin onto porous polymer resins is examined by a pulse injection method. The experimental results are theoretically analyzed by a model based on the assumption that there exist three kinds of binding sites with different binding rates, which are considered to exist in the vicinity of the outer periphery surface, the inner surface of macropore, and the micropore, or center part, of particles. The three kinds of adsorption rates are also evaluated by a batch method and are nearly equal to the corresponding kinetic parameters by this method. The amount of BSA bound irreversibly to the resins is independent of the protein concentration and the flow rate examined, which suggests that protein molecules penetrate into pores of resins and occupy almost all the effective binding sites in the resins. The total amount of bound BSA shows a pH dependence with a maximum near the isoelectric point of BSA, and the amount of BSA bound at the slowest rate is most largely influenced by pH.
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  • 38
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    Biotechnology and Bioengineering 30 (1987), S. 239-250 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Heparinase immobilized to agarose has previously been shown to be useful in degrading heparin and thereby preventing thromboembolytic complications when this anticoagulant has been used in extracorporeal perfusions. The current study examined the kinetics of this immobilized enzyme. When heparinase is covalently bound to 8% agarose, the partition coefficient of heparin in the catalytic particle is 0.36 ± 0.048 (N = 10). The immobilized enzyme has a Km of 0.15 ± 0.03 mg/mL and an activation energy of 10.3 ± 0.57 kcal/gmol (N = 5). These values are statistically indistinguishable from the values for the free enzyme. The immobilized enzyme showed a pH activity optimum between 7.0 and 7.4, compared to the optimum pH of 6.5 for the soluble enzyme. The activity optimum of immobilized heparinase with respect to salt concentration was between 0 and 0.1M. A reactor containing immobilized heparinase recirculating internally at 1300 mL/min behaved as a continuously stirred tank reactor (CSTR) when solutions at a flow rate of 120 mL/min were passed through the device. The residence time distribution was determined using blue dextran (molecular weight 2 × 106 daltons), which is sterically excluded from the agarose catalyst. A model of the heparinase reactor based on ideal CSTR behavior and the immobilized enzyme kinetic parameters was developed. It accurately predicted experimental conversions over a range of catalyst volumes, enzyme loadings, and substrate concentrations to within 7% in most cases and with a maximum deviation of 13%.
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  • 39
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    Biotechnology and Bioengineering 30 (1987), 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: An acetic-acid-based synthetic wastewater of different organic concentrations was successfully treated at 35°C in anaerobic downflow fixed-film reactors operated at high organic loading rates and short hydraulic retention times (HRTs). Substrate removal and methane production rates close to theoretical values of complete volumetric chemical oxygen demand (COD) removal and maximum methane conversion were obtained. A high concentration of biofilm biomass was retained in the reactor. Steady-state biofilm concentration increased with increased organic loading rate and decreased HRTs, reaching a maximum of 8.3 kg VFS/m3 at a loading rate of 17 kg COD/m3 day. Biofilm substrate utilization rates of up to 1.6 kg COD/kg VFS day were achieved. Soluble COD utilization rates at various COD concentrations can be described by half-order reaction kinetics.
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  • 40
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    Biotechnology and Bioengineering 30 (1987), S. 66-73 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Polyacrylamide gel-immobilized cells of a Citrobacter sp. removed cadmium from flows supplemented with glycerol 2-phosphate, the metal uptake mechanism being mediated by the activity of a cell-bound phosphatase that precipitates liberated inorganic phosphate with heavy metals at the cell surface. The constraints of elevated flow rate and temperature were investigated and the results discussed in terms of the kinetics of immobilized enzymes. Loss in activity with respect to cadmium accumulation but not inorganic phosphate liberation was observed at acid pH and was attributed to the pH-dependent solubility of cadmium photsphate. Similarly high concentrations of chloride ions, and traces of cyanide inhibited cadmium uptake and this was attributed to the ability of these anions to complex heavy metals, especially the ability of CN- to form complex anions with Cd2+. The data are discussed in terms of the known chemistry of chloride and cyanide-cadmium complexes and the relevance of these factors in the treatment of metal-containing liquid wastes is discussed. The cells immobilized in polyacrylamide provided a convenient small-scale laboratory model system. It was found that the Citrobacter sp. could be immobilized on glass supports with no chemical treatment or modification necessary. Such cells were also effective in metal accumulation and a prototype system more applicable to the treatment of metal-containing streams on a larger scale is described.
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    Biotechnology and Bioengineering 30 (1987), S. 101-107 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The metabolic control theory developed by Kacser, Burns, Heinrich, and Rapoport is briefly outlined, extended, and transformed so as optimally to address some biotechnological questions. The extensions include (i) a new theorem that relates the control of metabolite concentrations by enzyme activities to flux ratios at branches in metabolic pathways; (ii) a new theorem that does the same for the control of the distribution of the flux over two branches; (iii) a method that expresses these controls into properties (the so-called elasticity coefficients) of the enzymes in the pathway; and (iv) a theorem that relates the effects of changes in metabolite concentrations on reaction rates to the effects of changes in enzyme properties on the same rates. Matrix equations relating the flux control and concentration control coefficients to the elasticity coefficients of enzymes in simple linear and branched pathways incorporating feedback are given, together with their general solutions and a numerical example. These equations allow one to develop rigorous criteria by which to decide the optimal strategy for the improvement of a microbial process. We show how this could be used in deciding which property of which enzyme should be changed in order to obtain the maximal concentration of a metabolite or the maximal metabolic flux.
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  • 42
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    Biotechnology and Bioengineering 30 (1987), S. 123-137 
    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 describes a model for forced-flow electrophoresis (FFE), considering the desired species fraction removal, other fraction removals, and outlet concentrations of all species in the system. The model predicts the necessary inlet flow rate of the retentate chamber and the rate of filtration and the voltage gradient and also provides an appropriate heat balance permitting consideration of possible heat denaturation of the species. The equipment consists of two membranes and a filter, the electric field being imposed by means of external electrodes, and two fractions are obtainable. The main discriminating factor is not the pore sizes of the filter but the relative solute ionization, which depends on the pH and the ionic strength of the buffer solution. Serum proteins (albumin, γ-globulin) and bacteriophages (M13, MS2, φX174) have been used to characterize the separation process.
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    Biotechnology and Bioengineering 30 (1987), S. 157-159 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An actual yield of 99.97% (i.e., 3000 potential regenerating cycles) has been obtained for the electrochemical regeneration of NAD+. The deactivation of the coenzyme is not related to the number of cycles; it is only time dependent. For biotechnological applications, these results show that electrochemical regeneration can compete with enzymatic regeneration for selective oxidation by dehydrogenases.
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    Biotechnology and Bioengineering 30 (1987), S. 153-156 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The feasibility of using two fertilizers (urea plus superphosphate) in tap water as a medium for the mass culture of green algae (Scenedesmus and Ankistrodesmus) in outdoor plastic-enclosed minipond systems was investigated. Experiments in which the basic fertilizer-tap water medium was enriched with micro- and/or macronutrients revealed no nutrient deficiency symptoms in the algal biomass produced. Biomass production was found to be quantitatively related to the concentration of fertilizer added and maximal production (〉 15 g/m2 day) was achieved following the addition of 30 mg N/L (1.89 g N/m2 day) and 4.5 mg P/L (0.28 g P/m2/day).
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    Biotechnology and Bioengineering 30 (1987), S. 498-504 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biological phenol degradation in a draft tube gas-liquid-solid fluidized bed (DTFB) bioreactor containing a mixed culture immobilized on spherical activated carbon particles was investigated. The characteristics of biofilms including the biofilm dry density and thickness, the volumetric oxygen mass transfer coefficient, and the phenol removal rates under different operating conditions in the DTFB were evaluated. A phenol degradation rate as high as 18 kg/m3-day with an effluent phenol concentration less than 1 g/m3 was achieved, signifying the high treatment efficiency of using a DTFB.
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    Biotechnology and Bioengineering 30 (1987), S. 541-547 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A deterministic approximation of the thermal deactivation process is undertaken by structuring growth kinetics of cell populations on the activity level. Growth data of the green microalga Scenedesmus obliquus under forced periodic conditions of light intensity have been used for model verification. The model considers a straightforward extension of normal growth kinetics in such a way that different growth activities can be adjusted in the context of a thermal damage and repair mechanism. The nonlinear fitting of the measured response renders parameter values as a function of the light availability per unit biomass.
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  • 47
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    Biotechnology and Bioengineering 30 (1987), S. 565-570 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The feasibility of using specific enzyme and transport inhibitors to minimize the glutamine response of a potentiometric microbial sensor is demonstrated. The glutamine response of a bacterial electrode prepared with Escherichia coli as the biocatalyst in conjunction with an ammonia gas-sensing electrode was greatly reduced by treating the electrode with the enzyme inhibitor 6-diazo-5-oxo-L-norleucine (DONL) and the transport inhibitor γ-L-glutamylhydrazide. Each inhibitor effectively decreased glutamine response to a level sufficiently low to be considered negligible in clinical studies. Although the sensor ultimately recovered from the effects of a single exposure to an inhibitor, continuous exposure at an optimum concentration maintained a low response to glutamine. Furthermore, the treatment of the sensor with both inhibitors simultaneously resulted in a negligible response to glutamine of 〈1 mV, indicating that both inhibitors are necessary for optimum inhibition of glutamine response. This approach is promising as a means of enhancing the selectivity of microbial sensors.
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    Biotechnology and Bioengineering 30 (1987), S. 598-606 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The competition between flocculating and nonflocculating microorganisms was investigated in a continuous reactor-settler system (e.g. activated sludge). Co existence states were found to be possible, over a certain domain of operating conditions, even with simple monotonic kinetics and simple competition. Multiple solutions exist when coexistence states are unstable. Coexistence solutions are stable when the flocculating bacteria grow faster at feed conditions as in the activated sludge problem. The analysis applies to one or several mixed or plug flow reactors. Other effects, such as enrichment of the recycle stream by the flocculating microorganism or substrate adsorption and storage, may change the structure of solution.
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    Biotechnology and Bioengineering 30 (1987), S. 621-627 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effectiveness of a new immobilized cationic triazine dye was investigated alongside two new amphoteric triazine dyes and two well known anionic triazine dyes, Procion Red H-3B and Procion Blue H-B, as chromatographic media for binding four familiar proteases-trypsin, chymotrypsin, thrombin and carboxypeptidase-B-as well as a typical oxidoreductase, lactate dehydrogenase, and human serum albumin. The new affinity adsorbent, CL-Sepharose-immobilized Cationic Dye, specifically binds trypsin-like proteases such as trypsin, thrombin, and carboxypeptidase-B, but none of the other proteins tested. In contrast, the amphoteric and anionic immobilized dyes bind all the other proteins tested in a similar fashion. The specificity of the cationic dye was exploited in the resolution of trypsin and chymotrypsin from a crude activated bovine pancreatic extract. The procedure described here affords trypsin with specific activity of 7400 units/mg with a 79% overall yield in a single step. The immobilized cationic dye, unlike previously reported adsorbents for trypsin, is inexpensive, readily synthesized, and displays a workable capacity of 4000 trypsin units or 0.55 mg protein/g moist weight gel (1.2 μmol dye/g moist weight gel) from a crude bovine pancreatic extract and, thus, is potentially amenable to process-scale operations.
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    Biotechnology and Bioengineering 30 (1987), S. 661-667 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Kinetics of methanogenesis from acetate was studied using pure cultures of Methanosarcina barkeri and Methanosarcina mazei. Methane formation was found to be associated with cell growth. Nearly equimolar methane was produced from acetate during the methanogenic growth, and about 1.94 g of cells were formed from each mole of acetate consumed. Cell growth can be estimated from methane production. Significant substrate inhibition was found when acetate concentration was higher than 0.12 M. Among the three methanogenic strains studied, M. mazei strain S6 had the highest specific growth rate at all acetate concentrations studied and was least sensitive to environmental factors investigated (e.g., acetate concentration). The maximum specific growth rate found for strain S6 was 0.022 hr-1 at acetic acid concentration around 7 g/L. The other two strains studied were M. barkeri strain 227 and strain MS. Growth of M. barkeri was completely inhibited at sodium acetate concentrations higher than 0.24 M. The maximum specific growth rate found for strains 227 and MS was 0.019 and 0.021 h-1 at acetic acid concentrations of 3.6 and 6.8 g/L, respectively. A kinetic model with substrate inhibition was developed and can be used to simulate the methane formation from M. mazei strain S6 grown on acetate at 35°C, pH 7.
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    Biotechnology and Bioengineering 30 (1987), S. 685-691 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 30 (1987), S. 697-702 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Immobilized Sporotrichum cellulophilum with nonwoven materials was cultured continuously by a rotating-disk fermentor to supply cellulase into the saccharification system. The filter paper activity (5.0) was retained after 696 h under conditions of 250 rpm stirring and 0.014 h-1 dilution rate. The product of the culture was supplied continuously to the saccharification reactor and used for the saccharification of bagasse. A glucose solution of ca. 0.9% was obtained continuously from 5% bagasse slurry during 610 h saccharification by this method.
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    Biotechnology and Bioengineering 30 (1987), S. 724-735 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Determination of glucose concentrations in fluids frequently requires the application of immobilized glucose oxidase. An accurate description of the immobilized enzyme kinetics is critical for such applications. In this study, the overall rate of reaction of immobilized glucose oxidase is investigated theoretically. A novel steady-state model based on a ping-pong kinetic mechanism for glucose oxidase is developed. Numerical studies are used to examine the parameter sensitivity of this model. The enzyme loading, matrix thickness and geometric con figuration are found to have a significant influence on substrate uptake by insolubilized glucose oxidase.Aditionally, this new model is compared with a previously developed model based on an alternative ping-pong kinetic mechanism. Under steady-state conditions, no significant difference between the two models is apparent when appropriate kinetic parameters are applied to each of the models. The model developed herein is also compared with models utilizing the simplifying assumption of Michaelis-Mented kinetics for substrate reaction. Numerical studies indicate that under most realizable biological conditions, a model based on ping-pong kinetics should be applied to accurately describe substrate uptake by immobilized glucose oxidase.
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    Biotechnology and Bioengineering 30 (1987), S. 794-797 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 30 (1987), S. 805-808 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 30 (1987), S. 836-843 
    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 a continuous vertical packed-bed reactor with yeast immobilized in carrageenan gel beads is reported. The study focuses on the mathematical modelling of the steady-state fermentor behavior by means of a tanks-in-series model which includes the intrinsic kinetic model and the external mass transfer and internal diffusion-reaction conditions in the beads.
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    Biotechnology and Bioengineering 30 (1987), S. 852-859 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Autoflocculation and bioflocculation are considered to be the most promising means for the economical harvesting of microalgae. We have therefore studied these phenomena with cultures of Scenedesmus obliquus produced during biological tertiary wastewater treatment. The quantity of extracellular polymers produced during ageing of the cultures proved insufficient to initiate bio-flocculation while the concentration of Ca2+ and PO43- of the treated effluent were too low to induce autoflocculation. It has been shown, however, that the algae sediment more readily upon ageing, possibly as a result of increased ceil density. The use of density gradients made with Percoll (a colloidal solution of silica particles) allowed measurement of the true cell density and showed that this increases when cultures enter the declining growth phase. The quality of the biomass thus harvested is, however, considerably impaired, protein content decreasing from 62.7% (dry wt) during the exponential growth phase (day 5) to 14% at the end of cultures (day 21).
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    Biotechnology and Bioengineering 30 (1987), S. 882-886 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The presence of anions in solution was found to inhibit the uptake of La3+, Cd2+, Pb2+, UO2+2, and Ag+ by Rhizopus arrhizus biomass. The effects ranged from total inhibition of Cd2+ and Pb2+ uptake at equimolar concentrations of EDTA to no change in uptake of La3+ or UO2+2 at 12-fold molar excesses of Cl- or CO2-3. No anion was found to enhance metal uptake levels, and the degree of inhibition generally followed the series: \documentclass{article}\pagestyle{empty}\begin{document}$${\rm EDTA } \ge \ge {\rm SO}_{^{^{^{\rm 4} } } }^{{\rm 2} - } \ge {\rm Cl}^ - \ge {\rm PO}_{^{^{^{\rm 4} } } }^{{\rm 3} - } \ge {\rm glutamate} \ge {\rm CO}_{^{^{\rm 3} } }^{{\rm 2} - } $$\end{document} The chemical equilibrium model REDEQL2 was adapted to treat metal uptake by R. arrhizus biomass and used to predict the effects of anions in solution. Comparisons with the experimental results are made and discussed in light of the assumptions underlying the model.
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    Biotechnology and Bioengineering 30 (1987), S. 896-908 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The anaerobic digestion of wood ethanol stillage in a UASB reactor was studied. At organic loading rates be low 16 kg COD/m3 day the reactor performed effectively, achieving soluble COD and BOD removals in excess of 86 and 93%, respectively. Removal of color averaged 40%. At a loading rate of 16 kg COD/m3 day the methane yield was 0.302 L CH4 (STP)/g COD removed, and the observed cell yield was 0.112 g VSS/g COD removed. Operation of the reactor at higher loading rates was unsuccessful. Nitrogen, phosphorus, and alkalinity were supplemented. No additions of the essential trace elements Fe, Co, and Ni were required.
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    Biotechnology and Bioengineering 30 (1987) 
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    Biotechnology and Bioengineering 30 (1987), S. 593-597 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The immobilization process of some biologically active proteins on acrylic ion exchange supports was studied. The cross-linking and swelling coefficient, as well as the molecular weight of the enzyme, were proved to influence the immobilization process. The kinetic data indicate mainly a binding process controlled by diffusion. The uptake coefficient values of different proteins ranged between 35.0 and 98.0%. The laboratory experiments per formed with some of the obtained enzymic preparation certify the preservation of the catalytic activity following the immobilization process.
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    Biotechnology and Bioengineering 30 (1987), S. 991-994 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 30 (1987), S. 1006-1018 
    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 known from the literature that two microbial populations competing purely and simply for a common substrate in a spatially inhomogeneous environment may under certain conditions coexist in a steady state. This paper studies pure and simple competition between two microbial species in three alternate configurations of two interconnected ideal chemostats and focuses on the effects of the operating parameters-dilution rate, substrate concentration in the feed to the vessels, recycle ratio, and volume ratio of the two vessels, splitting ratio of the external feed to the chemostats-on the coexistence of the two competitors. It is shown that the coexistence steady state is practically feasible in the sense that it occurs in a finite domain of the operating parameters space. Theoretical and numerical results are presented, some of them in the form of operating diagrams projected on the two-dimensional subspace. A comparison of the three possible configurations is offered.
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    Biotechnology and Bioengineering 30 (1987), S. 675-680 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 30 (1987) 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 30 (1987), S. 754-768 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Quantification of the degree of acclimation of a mixed culture is demonstrated. An industrial landfill leachate was used as a model mixed substrate. The biodegradable fraction, the specific rate of substrate uptake, and the apparent reaction order were measured. The method of acclimation did not appear to affect the biodegradable fraction. The apparent reaction order is shown to be related to the difference between the rates of uptake of the various leachate components. This difference is defined as the differential in the rate. The effects of a supple mental carbon source and different inocula were investigated. Addition of glucose tends to diminish the differential but also decreases the specific rate of substrate uptake. The outcome of an acclimation procedure is dependent on the quality of the inoculum; however, a poor inoculum does not preclude an acclimation that yields a superior culture. A normalized rate coefficient is shown to have merit as an indicator of the degree of acclimation. Two microorganisms were isolated, Acinetobacter calcoaceticus var. Iwoffi and Moraxella sp., that could grow axenically with the leachate as their sole source of carbon. Comparisons are made between pure and mixed cultures with regard to biodegradable fraction, specific rate of substrate uptake, and apparent reaction order.
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    Biotechnology and Bioengineering 30 (1987), S. 817-824 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using commercial immobilized glucose isomerase (SWETASE®, Nagase Co.), the effect of substrate protection on enzyme deactivation has been studied in a batch manner. The data analysis was carried out based on Briggs-Haldane kinetics in which enzyme deactivation accompanying the protection of substrates was also considered. The protection factor was proposed to elucidate the dependence of the degree of substrate protection. The existence of the protection of glucose isomerase by the substrates has been verified experimentally. Also, the enzyme-substrate complex deactivates with a decay constant which is one-half that of the free enzyme. Theoretical analysis of enzyme deactivation with substrate protection offers an effective understanding which is essential for enzyme replacement and process optimization.
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    Biotechnology and Bioengineering 29 (1987), S. 101-113 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A tube rheometer system has been constructed for aseptic study of the rheology and fundamental flow properties of mycelial fermentation fluids. The rheometer consists of a U-formed tube circuit starting and ending inside the fermentor. The mash is pumped through the tubes with a lobe rotor pump. The flow is measured by an electromagnetic flow meter. Pressure drops have been measured with a system of differential membrane transducers for different flow rates. The rheometer system was tested with Newtonian and non-Newtonian fluids.
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    Biotechnology and Bioengineering 29 (1987), S. 142-145 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 29 (1987), S. 160-164 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Cellulase (Cellulosin AC-8) was immobilized on poly-L-glutamic acid. This immobilized cellulase (IC) is water soluble in the neutral and alkaline solutions, where IC has the activity, while IC can be made insoluble by lowering the pH so that it can be recovered from the reaction mixture with its activity. The optimum pH and temperature were determined to be 5.5 and 55°C, respectively. The stability of IC against change in the pH and temperature was improved by the immobilization. Solvolysis of 3N-NaOH-treated cellulose, with IC under the optimum conditions found here, led to the production of low-molecular-weight compounds.
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    Biotechnology and Bioengineering 29 (1987), S. 151-159 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Biodehalogenation of 10-5 M concentrations of bromotrichloromethane (BTM) and 1,2-dibromo-3-chloropropane (DBCP) was studied in static cultures of Pseudomonas putida PpG-786. The experimental cultures were prepared by growing P. putida on camphor, which is known to induce the synthesis of high concentrations of cytochrome P-450 in this bacterium. Measurements of bromide ion release were found to be approximately consistent with the amounts of halocarbon degraded. Gas chromatography/elctron capture detection (GC/ECD) measurements of hydrocarbon degradation products as a function of incubation time showed the transitory appearance of chloroform and bromodichloromethane from BTM and the transitory appearance of lower boiling but unidentified products from DBCP. The degradation of BTM to trihalomethanes and the halide ion is consistent with the enzymatic reductive dehalogenation by cytochrome P-450 reported by others. The dependence of initial conversion rates on halocarbon concentration (0.1-2 ppm) and cell mass concentration (1-28 g cell/L) was determined by measuring the decline of parent halocarbon in stirred batch cell suspensions. The rate of DBCP conversion was up to 10-fold higher than the rate of BTM conversion. When the intracellular, enzyme-catalyzed conversion BTM is analyzed by the effectiveness factor of heterogeneous catalysis, the initial conversion rates measured suggest that intrinsic enzyme kinetics, rather than halocarbon permeation of the cell membrane or other diffusive processes, is rate limiting.
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    Biotechnology and Bioengineering 29 (1987), S. 180-186 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: There are many scaling formulas that predict the oxygen mass transfer coefficient as kL·a = constant·(Hp/V)αVsβ Exponents α and β frequently are scale dependent themselves. A general formula has been derived from the work of Calderbank,1 Miller,2 and Tilton,3 resulting in kL·a = C1 φ + C2 log (Pm/V) φ where φ equals the gas-holdup fraction and Pm/V equals the effective mechanical power input per unit of volume. This formula is consistent with the formula of Westerterp4 modified by Miller.2 Gas holdup can be predicted in several ways. Gas-sparged isothermal expansion power input, used for predicting φ, demonstrates that scaling can be done by using either superficial air velocity or volume per volume per minute for aeration.The importance of mixing in replenishing oxygen at the boundary layers of microorganisms will be assessed and compared with the kL·a as the oxygen transfer ratelimiting step.
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    Biotechnology and Bioengineering 30 (1987), S. 987-990 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 30 (1987), S. 1001-1005 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Since a stable alcohol oxidase with a high specific activity is not commercially available, we propose to produce and purify this enzyme from a strain of the yeast Hansenula polymorpha. This alcohol oxidase was immobilized into a gelatin matrix and its activity was estimated by a pO2 sensor. The enzyme electrode obtained was then used in a continuous flow system to measure methanol or ethanol concentrations. The sample oxygen content dependence of the signal was minimized by the support properties. Measuring time for each sample were less than two minutes including response data treatment and rinsing step. The enzyme electrode response was set for ethanol from 0.5mM to 15mM and for methanol from 10mM to 300mM. On repeated use, the electrode signal for 10mM of ethanol was stable for at least 500 assays. Analysis have been performed in different beverages such as wine and beer, and the results compared to those obtained with classical methods of analysis.
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    Biotechnology and Bioengineering 30 (1987), S. 1057-1062 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 29 (1987), S. 464-468 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: The soil yeast Trichosporon cutaneum was grown in continuous culture with phenol as the sole carbon source. The cultures were operated as carbon-limited chemostats or as steady-state continuous cultures without carbon limitation. Selected comparative runs were also conducted on glucose or acetate as carbon source. In addition to growth parameters, the activities of several intracellular enzymes were determined, comprising those directly involved in the degradation of phenol as well as auxiliary enzymes required for the generation of reducing power. All enzymes were assayed in detergent-permea-bilized cells. Phenol was found to serve as an excellent carbon source, comparable to glucose or acetate. The utilization of phenol in T. cutaneum is very efficient as indicated by a low maintenance requirement (0.01 g phenol/g cells·h). The cell yields obtained were on the order of 0.8 g cells/g phenol. Although the phenol-limited chemostats were run with fully phenol-induced cells, a further increase in the activities of isocitrate DH(NADP+), maleate DH and the phenol-degrading enzymes occurred after transition to nonlimiting condition. Enzyme activities increased in parallel with increasing phenol levels in the effluent, as well as with increasing toxicity. The significance of this phenomenon is discussed. The significance of this phenomenon is discussed. This elevation in enzyme activities in not related to an increase in specific growth rate.
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    Biotechnology and Bioengineering 30 (1987), S. 692-696 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 29 (1987), S. 1050-1058 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The development of Penicillium roqueforti on buckwheat seeds proceeds roughly into four steps, involving a lag phase and three growth phases. First, it appears as a spore germination and external colonization of the grains by the mycelium. Then, mainly external sporulation and internal colonization of the seeds occur and finally internal sporulation takes place. The Stoichiometry of the growth and the sporulation is established. Kinetic experiments performed in a fixed bed reactor show that the growth of the microorganism (biomass production) may be estimated by the protein content of the medium. This growth occurs with a very low μmax value close to 0.030 h-1. The chitin content of the medium is an indicator of the sporulation, just as the metabolic liquor (mainly water) produced during the course of a cultivation. The values of the observed respiratory quotient are close to those predicted by stoichiometry.
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    Biotechnology and Bioengineering 30 (1987), S. 809-816 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Rapid liquid-liquid extraction of lactate dehydrogenase from muscle by using a low-cost aqueous bipolymer two-phase system was achieved by using a centrifugal separator. Extraction of the target enzyme into the upper phase was enhanced by including the dye Procion yellow HE-3G (bound to polyethylene glycol). The dye acted as an affinity ligand for the enzyme. The isolation of the enzyme was carried out either by using a cell extract or by homogenizing the muscle directly in the system. The latter approach reduced the preparation time with a factor of 0.25. The two methods gave, respectively, 310 and 360 kU lactate dehydrogenase/kg muscle (measured at 22°C). By using a small centrifugal separator, Alfa Laval LAPX 202, 3-5 kg muscle could be processed/h in a 30-L, two-phase system.
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    Biotechnology and Bioengineering 30 (1987), S. 844-851 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this article, a two-phase system for the digestion of wastes with a high solid content is simulated. The solids are charged to the hydrolyzer and then leachate recirculation is activated until biodegradation is nearly complete. Several parameters are tested, namely moisture, leachate recirculation flow rate, and hydrolyzer-methanizer volume ratio. The results show that recirculation rate is an important parameter subject to optimization, with optimal values corresponding to hydrolyzer hydraulic retention times below 1 day. The quantity of recirculating water must be the highest possible. As a consequence, the organic load to the methanizer is reduced, making thus possible the use of a smaller methanizer volume.
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    Biotechnology and Bioengineering 30 (1987), S. 875-881 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: O-Acetylserine sulfhydrase in the form of a crude extract from Salmonella typhimurium LT2 was used for the production of L-cysteine from L-O-acetylserine and sodium hydrosulfide at pH 7.0 and 25°C. The two substrates have quite different pH stability relationships. O-Acetylserine readily rearranges to N-acetylserine and the rate of this O → N acyl transfer reaction increases at higher pH, temperature, and concentration of O-acetylserine. On the other hand, sodium hydrosulfide is more soluble at a higher pH. A stirred-tank bioreactor with a continuous substrate feed was employed to overcome this problem. The O-acetylserine feed was stored at its saturation level (2.05M) at pH 5.0, and the sodium hydrosulfide feed was dissolved at 2.05-2.3M without pH adjustment (pH ≥ 11.5). Both substrates were simultaneously introduced into the bioreactor. The performance of the bioreactor was optimized by employing an automatic feedback control system to regulate the concentration of O-acetylserine in the bioreactor. This feedback control system was based on the fact that as the bioconversion proceeds, protons are produced along with cysteine. A pH controller thus detected the decrease in pH and activated the substrate pumps. After mixing in the bioreactor, these two substrate solutions behaved as a base due to the high alkalinity of sodium hydrosulfide. Thus, substrate infusion started when the pH was lower than the set point, i.e., the reaction pH, and stopped when the pH was raised higher than the set point. The amount of substrate introduced was determined by the alkalinity of the mixture of the two substrates, which in turn was controlled by the concentration of sodium hydrosulfide. After optimizing the sodium hydrosulfide concentration and the substrate feed rate, the bioconversion gave a productivity of 3.6 g L-cysteine/h/g dry cell weight S. typhimurium, an L-cysteine titer of 83 g/L and a molar yield based on O-acetylserine of 94%.
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    Biotechnology and Bioengineering 29 (1987), S. 1164-1172 
    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 dynamics of Escherichia coli with the temperature-sensitive plasmid, pOU140, were examined. Recombinant cells exhibited nearly identical kinetic behavior to host cells at low culture temperatures and low copy numbers. However, at higher temperatures, in which the copy number was significantly increased, the recombinant cells showed decreased stability along with lower growth rates and substrate yields as compared to the host. Furthermore, the production of a constitutive cloned-gene protein was shown to increase with temperature in an Arrhenius fashion when culture temperature was varied between 38 and 42°C. These results suggest that temperature can be used to quantitatively control the production of a desirable plasmid-coded gene product.
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    Biotechnology and Bioengineering 30 (1987), S. 9-14 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During unsteady-state continuous culture of Saccharomyces cerevisiae on sugarcane blackstrap molasses, the invertase activity of the intact yeast cells oscillated. Disturbances were produced by changing medium composition, air rate, impeller speed, and dilution rate. The influence of the oxygen supply rate and of the dilution rate on the invertase activity depend on the medium composition. The highest invertase activity was obtained when, after a steady-state attained using unsupplemented culture medium, nutrients were added to the feeding mash. A Monod-like equation seems to be the best representation of the correlation between the specific rate of reducing sugars consumption and the specific rate of nonreducing sugar hydrolysis by the yeast cells.
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    Biotechnology and Bioengineering 30 (1987), S. 1084-1087 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 30 (1987), S. 117-122 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Reaction rates of hydrophobic enzymes, aminopeptidase, and alkaline phosphatase, in microsomes prepared from the porcine brush border membrane and in vesicles pre pared from microsomes and phospholipids were measured at various temperatures. Interactions between the hydrophobic enzymes and the phospholipid layers are discussed as well as the effects of fluidity change of phospholipid layers on enzyme activity. Further, reaction properties and stabilities of the immobilized vesicles containing microsomal enzymes were studied.
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    Biotechnology and Bioengineering 30 (1987), S. 297-305 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The relationship between cell mass and cell number dynamics for bacteria such as Escherichia coli depends on the cell cycle parameters C and D. Effects of plasmid copy number on these cell cycle parameters have been studied for Escherichia coli HB101 containing pMB1 plasmids propagated at different copy numbers ranging from 12 to 122. Determination of cell cycle and cell size parameters was accomplished using flow cytometry data on single-cell light scattering and DNA content frequency functions in conjunction with a mathematical model of cell population statistics. Two independent methods for estimating C and D intervals based on flow cytometry were developed and applied with essentially identical results. The presence of plasmids decreases the C and D periods, mean cell sizes, and initiation masses for chromosome replication by 14, 24, 38, and 18%, respectively, relative to corresponding values for plasmid-free host cells. Plasmid copy number has a negligible influence on these parameters, suggesting that host-plasmid inter actions which determine these properties are centered on the single plasmid selected for replication according to the random selection model established for ColE1-type plasmids.
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  • 88
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    Biotechnology and Bioengineering 30 (1987), S. 325-328 
    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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  • 89
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    Biotechnology and Bioengineering 30 (1987), S. 368-373 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Both kLa and kL measurements were carried out by an unsteady state technique at impeller speeds ranging from 1.6 to 5.8 s-1 in a mechanically agitated animal cell culture vessel of working volume 1.5 L. Checks were made that the time constant of the oxygen electrode was negligible compared to the time for aeration and that the oxygen electrode reading was not a function of agitator speed in the range employed. The kL values by surface aeration of (1.18-3.54) × 10-5 m/s and kLa values by sparged aeration of (2.8-8.5) × 10-4 s-1 were found. The former are in reasonable agreement with published experimental values and the latter in accord with values estimated from published correlations based on agitator power input and aeration rate. The fluids used were water, basal medium, and basal medium supplemented with 5% (v/v) foetal calf serum; for each of these, kL and kLa values were similar. However, the addition of silicone antifoam (6 PPM) reduced the kLa value by ca. 50%.
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  • 90
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    Biotechnology and Bioengineering 30 (1987), S. 413-419 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The equations of a chemostat in which one microbial population grows on multiple rate-limiting nutrients are formulated. The dynamics of a chemostat involving growth on complementary nutrients is studied through stability analysis of the system of equations. Some conditions are derived that relate the dynamic behavior of the chemostat to its operating conditions and can be applied to any model for the specific growth rate of the population. It is shown that, if maintenance of the population is neglected, the system exhibits no sustained or damped oscillations. If maintenance of the population is considered, damped oscillations are observed for some operating conditions.
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  • 91
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    Biotechnology and Bioengineering 30 (1987), S. 427-438 
    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 diffusion on a reaction taking place in a permeable catalyst are examined theoretically for the case where the reaction has two substrates supplied from opposite sides of a catalytic slab. The solutions of the reaction-diffusion equation for combinations of zeroth-and first-order kinetics are given in terms of an effectiveness factor and a parameter describing the position in the layer where the reaction occurs. In these terms, the results vary only weakly with reaction order. The use of the exact solutions for a reaction that is zeroth order in both sub strates is proposed as a general rule for estimating the reaction rate and the reaction position.
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  • 92
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    Biotechnology and Bioengineering 30 (1987), S. 995-999 
    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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  • 93
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    Biotechnology and Bioengineering 30 (1987), S. 1026-1031 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enzymatic lactose hydrolysis using two yeast and two fungal lactases that are of current technical interest was studied. The enzymes were compared regarding their oligosaccharide production. Parameters influencing oligosaccharide formation, together with the effect of immobilization were examined and conditions minimizing oligosaccharide content in the hydrolysis product were proposed. Enzymatic whey hydrolysis was also considered. A possibility of enzymatic lactose recombination from its hydrolysis products was shown.
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  • 94
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    Biotechnology and Bioengineering 29 (1987) 
    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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  • 95
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    Biotechnology and Bioengineering 29 (1987), S. 16-23 
    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 aims at deriving kinetic models for the RBS reactor operating with and without cell porous support. Since derivation of the kinetic equations from the Monod model is very complex, an empirical derivation from experimental data of continuous alcohol fermentations is used in this work.
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  • 96
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    Biotechnology and Bioengineering 29 (1987), S. 24-32 
    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 acoustic conditioning on the particle size distribution of isoelectric and calcium-ion-precipitated soya protein has been examined in low-residence-time chambers. In a previous study a beat frequency of 5 Hz obtained using a dual-source system of opposing vibrators was determined as giving optimal improvement in particle-settling characteristics for isoelectric soya protein precipitate. In this study the effect of amplitude of vibration, a measure of acoustic power input, and residence time of acoustic conditioning has been examined.Acoustic power input changed the flow pattern in the conditioning chamber from laminar streamline flow to a well-mixed, turbulent pattern. Such a mixing effect promoted the rapid aggregation of fine particles, a process that was modeled on the basis of orthokinetically controlled collisions. The rate of removal of fine particles due to acoustic conditioning was shown to be proportional to a mixing effect that was releated to the acoustic power dissipated per unit volume.The consequences of fine-particle aggregation on the centrifugal recovery of the precipitate are discussed.
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  • 97
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    Biotechnology and Bioengineering 29 (1987), S. 41-48 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Changes of pH and sulfate concentration in high-sulfur coal refuse slurries are used as measurements of microbial pyrite oxidation in the laboratory. Sodium lauryl sulfate (SLS), alkylbenzene sulfonate (ABS), benzoic acid (BZ) and combinations of SLS plus BZ and ABS plus BZ effectively inhibited formation of sulfate and acid when added in concentrations greater than 50 mg/L to inoculated 20 or 30% coal refuse slurries. Here 25 mg/L concentrations of SLS, ABS, and ABS + BZ stimulated acid production. Formic, hexanoic, oxalic, propionic, and pyruvic acids at 0.1% concentrations were also effective inhibitors. Four different lignin sulfonates were only slightly effective inhibitors at 0.1% concentrations. It was concluded that acid formation resulting from microbial oxidation in high-sulfur coal refuse can be inhibited.
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  • 98
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    Biotechnology and Bioengineering 29 (1987), S. 72-78 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Invertase from baker's yeast (Saccharomyces cerevisiae) was covalently bound via benzoquinone and glutaraldehyde to a macroporous polystyrene anion exchanger. The behavior of the invertase-polystyrene complexes in batch and packed-bed reactors was characterized kinetically. In addition to kinetic studies on sucrose hydrolysis at low initial substrate concentrations, the dependence of conversion degree on flow rate at high, industrially used substrate concentrations was determined. The described invertase-polystyrene complexes are suitable for technical application in the production of glucose-fructose mixtures because of their high specific and relative activities, as well as the good hydrodynamical and mechanical properties of the polystyrene matrix.
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  • 99
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    Biotechnology and Bioengineering 29 (1987), 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: High methanol concentrations have a negative effect on the growth rate and the biomass yield of growth transients induced by methanol pulses in continuous cultures of Methylomonas L3. The physiological basis of this effect is investigated by measuring the effect of the methanol pulse on the cell energy charge (EC) and ATP, ADP, and AMP concentrations, and by comparing the results of the pulse transients against an unstructured model. The methanol pulse is shown to lead to increased values of the cell EC and ATP concentration, and thus, inhibition and reduced availability of biosynthetic energy are excluded as causes of inhibition. When the biomass and methanol profiles of the transient experiments are compared in phase-plane diagrams against computer simulations based on the model, satisfactory agreement between experimental data and model predictions is found in single-substrate, high-dilution-rate experiments. Conversely, poor agreement between experimental data and simulation results indicates a more severe growth inhibition than the model predicts at low dilution rates and a less severe one in mixed-substrate experiments. Based on these findings and other relevant physiological information, we propose that the large variations in the negative effect of methanol on growth result from the fact that cells accumulate methanol to widely different concentrations depending on their physiological state. In their effort to detoxify from the high intracellular methanol and formaldehyde concentrations, cells oxidize considerably more methanol than they can incorporate into biomass. This leads to a useless ATP surplus, which the cells must hydrolyze without doing any useful biosynthetic work, and this results in lower biomass yields.
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  • 100
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrodynamic phenomena in microcarrier cultures are investigated with regard to the development of improved reactor designs for large-scale operations. New concepts and theoretical models that describe new data as well as previously published data are presented.
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