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  • 11
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 20 (1978), S. 1487-1492 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 832-836 
    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 characterizing the extracellular xylanases produced by a strain of the thermophilic bacterial genus Thermomonospora. Supernatant from centrifuged fermentation broth was used as a crude enzyme preparation. From pH 5.5 to pH 7.7 the temperature optimum based on a 10-min assay of activity was 80°C. The crude enzyme had a half-life of approximately 1 month when stored at 55°C at pH 6.5. The enzyme produced a mixture of xylose oligomers from xylan, with xylobiose occuring in greatest quantity on a molar basis. Only trace quantities of xylose were produced by this hydrolysis.
    Additional Material: 5 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 909-913 
    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 is concerned with characterizing cell-bound inducible β-xylosidase produced by a strain of the thermophilic bacterial genus Thermomonospora. A crude preparation of this enzyme recovered from sonicated cells of this organism displayed high activity against paranitrophenyl-β-xylopyranoside over a pH range of 5.5-7.7. The temperature optimum, based on a 30-min assay of activity, at pH 6.5 was 70°C. The crude enzyme had a thermal half-life of approximately 1 week at 55°C and pH 6.5. Xylose inhibited the enzyme. Values of Km and Vmax are estimated from the reaction rate data as 0.82 mM and 8 U/L, respectively.
    Additional Material: 9 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 11 (1969), S. 945-966 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A multistage tower laboratory fermentor has been constructed consisting of eight compartments separated by sieve plates. Flow of substrate and air is concurrent from the bottom to the top of the column. It, was hoped that this system could be used to reproduce, simultaneously on a continuous basis, eight distinct phases of a batch growth curve. It was believed that the extent of batch curve simulation would depend upon the character of hydraulic mean residence time of broth in the column and in the individual compartments. The expected relationship did not occur. Rather it was found that growth in the column involved residence time characteristics not only for the fluid but also for the microorganisms, and for the growth limiting substrate. Depending upon the column operation, these could be distinct and different.The purpose of this investigation was to study the residence time distribution (RTD) of the continous (fluid) and dispersed (microorganisms) phases for model systems as well as for a yeast fermentation. Various degrees of flow nonideality, i.e., fluid blackflow and dispersed phase sedimentation, were noticed. The former seems to be due to interaction of the concurrent gas and liquid flow; it is particularly dependent upon void area of the sieve plate holes. Sedimentation is probably a function of plate design as well as cell size and density. It wa concluded that for a particular plate design the gas hold-up wass controlled by superficial air velocity and was the main parameter governing the differences between dispersed and continous phase(Rt1). This conclusion was supported by a computeraided styudy utilizing a mathematical model of fluid flow to fit the growth kinetics and cell distribution observed experimentally throughout the fermentor.Some advantages of foam control in the tower fermentor by surface active compounds are mentioned. Also, suggestions are made for carrying out fermentations that have two liquid phases, such as a hydrocarbon fermentation. The possibility of closely approximating plug-flow conditions in the multistage tower fermentor, a necessary condition for batch growth simulation, is discussed from a practical point of view.
    Additional Material: 17 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 20 (1978), S. 141-144 
    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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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 8 (1966), S. 85-96 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previously, the degree of mixing was not felt to be an important consideration in fermentor design. In this study on the continuous propagation of Baker's yeast, it was found that at low dilution rates, i.e., 0.02hr-1, the degree of mixing achieved does effect the cell yield. At low dilution rates, appreciable quantities of sugar can be utilized for endogenous respiration in comparison to that utilized for making cell mass. Poor distribution of the sugar aggravates the balance of sugar utilized for each process. Yields at these low dilution rates can be improved to a limited extent by using a multiple feed-distribution system and better mixing.
    Additional Material: 10 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 9 (1967), S. 375-386 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper deals with a theoretical study on the dynamic, character of the chemostat system. It. is primarily based on the Monod model for growth limitation, although certain more complex models are considered. Since the Monod model is described in terms of two variables, an analysis by use of a phase plane plot will show the various possible types of behavior theoretically expected for transient conditions of the system. In this paper it will be shown that the chemostat system might show an overshoot (or an underswing) with respect to changes in cell and substrate concentrations, depending on the extent to which the system might be disturbed from steady-slate conditions. Other types of transient behavior ran also be expected when one of the system parameters such as dilution rate or input substrate concentration is disturbed in a stepwise manner. The simple Monod chemostat model was found never to oscillate in either a damped or a sustained manner as has been experimentally reported. Discussion is included about the transient behavior of other chemostat models such as that involving a variable yield coefficient, i.e., including the effect of cell maintenance requirements.
    Additional Material: 5 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 11 (1969), S. 449-466 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mathematical models which can be used to describe batch growth in fermentations with two liquid phases are developed for systems in which the growth limiting substrate is dissolved the dispersed liquid phase. In the models, the possibilities of growth occurring at the surface of the dispersed phase and in the continuous phase are considered. It is assumed that the composition of the dispersed phase is such that substrate utilization from it causes little of no change, in interfacial area. Three special cases are examined. In the first, it is assumed that all growth occurs at the surface of the dispersed phase. In the second and third, it is assumed that growth occurs both at the interface and in the continuous phase. The second case assumes that substrate equilibrium is continuously established between the two phases while the third assumes substrate consumption in the continuous phase is limited by rate of transport of substrate to that phase. Comparison of the first model with available experimental data shows good agreement between model and data.
    Additional Material: 5 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 17 (1975), S. 85-98 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pectin esterase (E.C. 3.1.1.11) was covalently immobilized to porous glass particles by reaction of the native protein with pendant, benzoyl azide groups of the carrier. Enzyme loading on the carrier was 0.5 unit per ml as measured by pH stat, assay. Decreasing the size of the immobilized enzyme particles by grinding produced a 12-fold increase in activity suggesting severe internal mass transport restrictions on turnover kinetics, Gross fractionation of the citrus pectin substrate into high and low molecular weight categories and their subsequent use in kinetic characterization shows no effect of molecular weight upon the kinetic behavior of the native enzyme. In contrast the immobilized enzyme displayed a 5-fold increase in the apparent. Km for the high molecular weight fraction relative to that of the low molecular weight fraction. A striking difference exists in the low pH profile of immobilized pectin esterase relative to the native enzyme. Carrier matrix interactions with the polyelectrolyte substrate are invoked to explain this difference. The thermal stability of the immobilized enzyme is relatively low and displays a half-life of approximately 2 weeks at 25°C.
    Additional Material: 5 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 18 (1976), S. 987-1000 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An analysis of the pore diffusion model involving a two-substrate enzymatic reaction is presented. The resulting equations have been applied to the case of galactose oxidase catalyzed oxidation of galactose when the enzyme is immobilized on porous glass particles. The physical constants of the system were obtained by theoretical predictions and the enzyme concentration in the porous medium was derived from the experimental results. The calculations were performed with the assumption that the kinetic parameters of the enzyme remain unchanged upon immobilization. The theoretically calculated effectiveness factors were compared with the experimental effectiveness factors determined from the batch kinetic experiments and were found to be in agreement. The results are presented as effectiveness factor plots graphed as functions of bulk galactose and oxygen concentrations. The model was extended in order to study the effect of external mass transfer coefficients and pore enzyme concentrations on the effectiveness factors.
    Additional Material: 4 Ill.
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