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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical considerations of membrane fouling and its treatment with immobilized enzymes for protein ultrafiltration (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 21-32 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The ultrafiltration process was modelled in three separate stages with distinctive time constants. It was shown that in the first stage lasting less than 5 s a quasi-steady-state concentration profile is reached on the membrane/solution interface. In the second stage of 1-10-min solute adsorption on the membrane surface including the pores controls the permeation rate. The third stage is governed by a reaction mechanism which produces a surface gel causing flux decline at a slower rate than in the previous adsorption step. This polymerization of the protein to a gel on the membrane was shown to be second order in the interface protein concentrations. A reproducible and inexpensive method has been developed to attach food-grade proteases onto UF membranes by producing a primary adsorbed layer of enzyme which then retards the rate of gel formation on the ultrafilter. This resulted in 25-78% improvement in cumulative permeate yield in a standard 22-h run when processing 0.5% albumin or hemoglobin. The enhanced fluxes with self-cleaning membranes were modelled by incorporating an enzyme activity term to counteract the deposition of gel on the membrane surface and altering the apparent order of the gelation reaction.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1982.070270103
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  • 2
    Electronic Resource
    Electronic Resource
    Mixed culture biooxidation of phenol. I. Determination of kinetic parameters (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 889-896 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mixed culture derived from soil and activated sludge organisms was used to degrade phenol which was inhibitory to microorganisms at higher concentrations. The purpose of the experiments was to determine the kinetic parameters governing growth of the organisms by measuring growth rates in batch culture. To maintain a constant inoculum for the experiments inoculum was taken from a continuously operating continuous culture. Two populations were studied corresponding to two separate residence times in the continuous culture apparatus. One contained predominantly filamentous organisms, the other nonfilamentous. Five kinetic models were applied to the data and the best kinetic parameters for each model were determined by nonlinear least squares techniques. The models were then evaluated for best relative fit to the data. No significant differences were found between the models on the basis of fit and so a choice was made on the grounds of simplicity. A model proposed by Haldane was chosen as the best. No function however gave a satisfactory fit at the highest growth rates obtained. This experimental maximum in the plot of growth rate against substrate concentration was very sharp.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260150506
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  • 3
    Electronic Resource
    Electronic Resource
    Mixed culture biooxidation of phenol. III. Existence of multiple steady states in continuous culture with wall growth (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 15 (1973), S. 905-916 
    Details
    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 shown that two steady states exist in certain regions of operation of a 2-liter continuous stirred tank biological reactor. Transition was made from one steady state to another by applying shock loads of either phenol substrate which is inhibitory to the culture at high concentrations or by adding large additional amounts of concentrated organisms. The existence of the multiple steady states is ascribed to the existence of wall growth, and their position is determined by the amount of wall growth. Transient behavior of the system did not follow the predictions of the simple wall growth model but the culture appeared to undergo a lag period immediately after applying the shock load to the system. It is concluded that the stability of a continuous culture utilizing an inhibitory substrate is improved by increasing the degree of wall growth and decreasing the substrate feed concentration. It is also concluded that small scale experiments can usually not be interpreted correctly unless the effect of wall growth is taken into account.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260150508
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetics of solka floc cellulose hydrolysis by trichoderma viride cellulase (1975)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 17 (1975), S. 873-893 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A product inhibition model is developed to describe the hydrolysis of cellulose by the Trichoderma viride enzyme system. It is assumed that noncompetitive inhibition by cellobiose dominates the reaction kinetics. Experiments show that this is indeed a reasonable assumption for initial cellulose concentrations of up to 15 g/liter and at hydrolysis extents up to 65′. Kinetic parameters were determined for the noncompetitive inhibitionmodel in batch experiments with durations of up to 1.5 hr. These parameterswere then used in predicting reaction progress for up to 10 hr. Cellobiose was added to the reaction mixture at the onset of some runs and againreliable predictions were obtained for up to 8 hr of hydrolysis. Finally reaction was carried out in a membrane reactor whereby the product cellobiose was being continuously removed and again reasonable predictability was obtained with a higher net reaction rate.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260170608
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  • 5
    Electronic Resource
    Electronic Resource
    Enzyme deactivation during cellulose hydrolysis (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 20 (1978), S. 847-863 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrolysis of cellulose by Trichoderma viride cellulase reached a plateau after some 25 hr. If the initial enzyme-to-substrate ratio was low, resuspension of substrate in fresh enzyme or addition of enzyme resulted in further high rate hydrolysis. This did not occur if the initial ratio was high. Over 75% hydrolysis might be achieved in the former case, while less than 60% in the latter. A model postulating inactivation of adsorbed enzyme-substrate complex which blocked further hydrolysis was proposed, and it was found to fit the data well. The proposed model had five parameters, four of which could be checked by graphical methods, and all of which had physical meanings. The parameters were estimated by a nonlinear least-squares minimization FORTRAN computer program, using numerical integration and optimization of the parameters. The model was used to predict the resuspension data, powdered enzyme addition data, cellobiose addition data, and cellulose addition data; the deviations from the model are discussed. It was found that average values could be used for four out of the five parameters, while the fifth (initial enzyme concentration) did not correlate with independent measurements such as the filter paper activity or protein concentration.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260200607
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  • 6
    Electronic Resource
    Electronic Resource
    Self-cleaning membranes for ultrafiltration (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 23 (1981), S. 843-854 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to reduce the severe flux losses encountered during ultrafiltration of protein solutions, proteases were immobilized on Ultrafiltration membranes to hydrolyze the deposited solute molecules. Over a standard 22 hr run 25 to 78% improvement in cumulative permeate yield was obtained when processing 0.5% albumin or hemoglobin. It was also demonstrated that the flux enhancements were due to the biochemical action of the absorbed protease and not to its physical effect as a prefilter coat. with the aid of a model retardation of gel formation mechanism was demonstrated. Economics of the system were shown to be favorable, improving the rate of return on capital investment up to 50% by reduction of the total membrane area of the plant.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260230414
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  • 7
    Electronic Resource
    Electronic Resource
    Stratified mixed-culture biofilm model for anaerobic digestion (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 32 (1988), S. 348-355 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Development of a novel two-layer anaerobic biofilm model is based on substrate utilization kinetics and mass transport. The model is applied to steady-state conditions for a fixed-film anaerobic reactor. The microbial film is considered to consist of two distinct biofilm layers, one adjacent to the second, with an acidogenic bacteria biofilm forming the outer layer and a methanogenic film the inner one. The model assumes that sugars are only metabolized by the first layer and converted into volatile fatty acids (VFA), while fatty acids are taken up only by the inner layer. The model is able to predict both substrate flux net uptake and methane production for steady-state conditions. The results of modeling agree with methane production experimental data published elsewhere. Further, the model shows why layered fixed-film reactors can withstand high and inhibitory concentrations of volatile fatty acids as well as severe overloading without failure.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260320313
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  • 8
    Electronic Resource
    Electronic Resource
    Protease-coupled membranes for ultrafiltration (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 19 (1977), S. 1891-1894 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260191212
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  • 9
    Electronic Resource
    Electronic Resource
    Pulsatile flow filtration of yeast cell debris: Influence of preincubation on performance (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 41 (1993), S. 998-1002 
    Details
    ISSN: 0006-3592
    Keywords: microfiltration ; protein recovery ; pulsatile flow ; preincubation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The recovery of proteins from yeast cell debris suspension was investigated using a vortex mixing technique based on the combination of oscillatory flow and a baffled flat-sheet microfiltration system. For this system, increased protein transmission was obtained through the use of low transmembrane pressures and the preincubation of the yeast cell debris feed suspension at 30°C. Furthermore, a plateau in the flux-time curve was observed. In the absence of baffles and pulsations, preincubation had a little effect. © 1993 Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260411011
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of oxygen and substrate concentrations on the ideal film thickness and the maximum overall substrate uptake rate in microbial film fermenters (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 18 (1976), S. 15-35 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The criterion for the oxygen limitation of substrate uptake in microbial film fermenters is expressed in terms of diffusion coefficients, utilization coefficients, and the free solution concentrations of substrate and oxygen. It is proposed that the ideal film thickness in such fermenters is equal to the penetration depth of the limiting substrate. The ideal film thickness is calculated, in terms of the parameters contained in the criterion for oxygen limitation, for three separate kinetic rate expressions. It is found that for the air-glucose-microbe system a simplified kinetic rate expression can be used and the region of dependence on two substrates is shown to be very limited. This is not true for other systems. Maximum uptake rates are calculated for a range of concentrations. Finally, it is shown that the procedure used can be generalized to determine the limiting substrate in a multisubstrate system and to calculate ideal film thickness and uptake rates for any pair of substrates where the kinetics of substrate uptake are known for the individual microorganism.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260180103
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