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  • LUNAR AND PLANETARY EXPLORATION  (3,082)
  • Biochemistry and Biotechnology  (2,788)
  • 1985-1989  (5,870)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 171-176 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hemicellulosic sugars, predominantly D-xylose, comprise about one-half the total carbohydrate that can be obtained from hardwoods and agricultural residues through dilute acid hydrolysis. Because rates and yields in the xylose fermentation are low, economic utilization of these materials as fermentation feedstocks is difficult. Pachysolen tannophilus formed 5.5% ethanol from 12% glucose but only 2% ethanol from 12% xylcose. Aeration doubled the specific rate of D-glucose fermentation by P. tannophilus, as compared to anaerobic fermentation, but the specific rate of the xylose fermentation remained unchanged. Periodic additions of 0.5% D-glucose to aerobic fermentations of 3% xylose increased the yield of ethanol from 0.28 g/g xylose to greater than 0.41 g/g xylose utilized. The rate of xylose utilization remained unchanged, and radiotracer studies showed that addition of 0.5% glucose did not inhibit xylose utilization under aerobic or anaerobic conditions. No enhancement was observed anaerobically, nor was enhancement observed with acid hydrolysates, apparently because of the presence of acetic acid which inhibited growth and fermentation.
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  • 2
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 182-186 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Mathematical analyses of a diffusion-limited hollow fiber reactor for the measurement of effective substrate diffusivities are presented. An analytical solution to the mathematical model with a first order substrate consumption rate is used to show that the procedure of Webster and Shuler1 is incorrect. A rigorous analysis that requires numerical solution is also outlined for any form of the substrate consumption rate. These analyses allow for more accurate estimations of effective substrate diffusivities since they should be used in conjunction with integral reactor behavior.
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  • 3
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 177-181 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cellulose samples from cotton and wood pulps with varying low degrees of crystallinity (mechanically decrystallized) were studied. The influence of initial cellulose crystallinity on sugar yield after enzymatic hydrolysis was determined by two different methods. As expected, samples with low crystallinity were much more accessible to enzymatic attack and glucose yields were higher than were samples of high initial crystallinity. Hydrolysis of cellulose seems more dependent on cellulose crystallinity than on the source of cellulose. It is known that decrystallized or amorphous cellulose can recrystallize under proper conditions, e.g., during acid hydrolysis. The data reported here also reveal some recrystallization during enzymatic hydrolysis which probably occurs simulataneously with a selective enzymatic attack on the amorphous regions of cellulose. In all cases, the amorphous celluloses recrystallized in the original lattice form, that of native cellulose.
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  • 4
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 187-191 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Stable steady-state growth of Escherichia coli B limited by succinate, phosphate, or sulfate ion over the range of specific growth rates of 0.025-0.51 h-1 was achieved using pH-controlled auxostasis in the phauxostat. The concentration of the growth-limiting substrate in the growth vessel could be varied at will in the region of the Monod half-maximal saturation constants by adjusting the concentration of that substrate in the reservior (at constant buffering capacity) or by varying the population density of the culture through changing the buffering capacity of the medium in the reservoir.
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  • 5
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 208-213 
    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 27 (1985), S. 192-201 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Automatic constant-value control of mineral ions was attempted in semibatch culture of high cell mass concentration (more than 150 g dry cell/L) with ethanol and ammonia feeds. Equations were derived from the mass balance principle to calculate the required concentration of each mineral ion in the mineral feed solution, taking into account both the decrease in the volume of the culture supernatant as a proportion of the whole culture broth and the increase in the volume of the whole culture broth during the cultivation. The mineral solution was supplied automatically, linked either with ethanol feed or ammonia water feed. The actual concentrations of mineral ions could be kept within small variations. To adjust the supplementation in accordance with the culture change from oxygen sufficiency (early growth phase) to oxygen deficiency (later growth phase), the concentration of each mineral ion was altered stepwise when the dissolved oxygen concentration fell to zero. The mineral supplementation gave better results coupled with ethanol feed than with ammonia feed. The mineral ions studied were K+, Mg2+, Na+, Fe2+, Zn2+, Ca2+, Co2+, Cu2+, Mn2+, NH+4, PO43- and SO42-.
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  • 7
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A novel process for the production of extracellular carboxymethylcellulase (CMCase) and xylanase by fermentation under nonaseptic or nonsterile conditions is described. The fermentation process is carried out under very acidic conditions of pH 2.0 by using a acidophilic cellulolytic fungus. Microbial contamination is avoided or minimized to an insignificant level under this acid pH condition. The culture medium for this production consists of a carbon source from cellulosics or lignocellulosics, such as Na-CMC, xylan, Avicel cellulose, cellulose powder, α-cellulose, sawdust, etc., or a mixture of the forementioned together with simple ingredients such as (NH4)2SO4, K2HPO4, MgSO4 and NaNO3. The fermentation is carried out at room temperature (28-30°C), under aerobic conditions, and without controlling the pH. The CMCase and xylanase produced are stable under very simple storage conditions, such as in the fresh culture medium not containing the substrate for a period of 3 days, at any temperature from 0 to 30°C. These extracellular enzymes have an optimum pH around 3, with the best range of pH from 2.0 to 3.6, for any temperature between 15 and 60°C. The optimum temperatures are 55°C for CMCase activity and 25-50°C for xylanase activity, at any pH between 2.0 and 5.2. The apparent Michaelis constants Km are 2.6 and 1.5 mg/mL for CMCase and xylanase of the culture filtrate, respectively.
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  • 8
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 463-470 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The enzymatic hydrolysis of cellulose to glucose involves the formation of cellobiose as an intermediate. It has been found necessary1 to add cellobiase from Aspergillus niger (NOVO) to the cellobiase component of Trichoderma reesei mutant Rut C-30 (Natick) cellulase enzymes in order to obtain after 48 h complete conversion of the cellobiose formed in the enzymatic hydrolysis of biomass. This study of the cellobiase activity of these two enzyme sources was undertaken as a first step in the formation of a kinetic model for cellulose hydrolysis that can be used in process design. In order to cover the full range of cellobiose concentrations, it was necessary to develop separate kinetic parameters for high- and low-concentration ranges of cellobiose for the enzymes from each organism. Competitive glucose inhibition was observed with the enzymes from both organisms. Substrate inhibition was observed only with the A. niger enzymes.
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  • 9
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 471-481 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Three strains of Erwinia rhapontici especially suitable for use in the form of nongrowing immobilized cells were selected by screening strains of cells for high activity and operational stability in an immobilized form. Immobilization in calcium alginate gel pellets was easily the best method of immobilizing E. rhapontici. Much greater operational stabilities were obtained than when other immobilization methods were used. Conditions of operation which optimize the activity, stability, and yield and the ease of operation of the immobilized cell columns working in a steady state are described. These include the effects of substrate concentration, diffusional restrictions and water activity, the concentration of cells immobilized, and the type of reactor used. Thus, the immobilized cells produce about 1500 times their own weight of isomaltulose during one half-life of use (ca. 1 year). Loss of activity was most closely correlated with the volume of substrate processed and so presumably is due to the presence of low concentrations of a cummulative inhibitor in the substrate. Methods for regenerating the activity of the immobilized cells by the periodic administration of nutrients, of forming isomaltulose by continuously supplying nutrients to growing immobilized cells, and of crystallizing isomaltulose from the column eluate are also described.
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  • 10
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 490-497 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The multispecies biological treatment model including the consequent substrates consumption is suggested. The model describes the adaptation in the distribution of species that are included in the composition of activated sludge. It was shown that the effects of adaptation are similar for the consequent as well as simultaneous mechanisms of substrate oxidation.
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  • 11
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    Biotechnology and Bioengineering 27 (1985), S. 296-301 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous cultivation of Pelobacter acidigallici on gallic acid is accompanied by biofilm formation. Steady states can be obtained at dilution rates nearly twice the maximum growth rate. A two-compartment model is presented which allows us to determine rate constants of attachment and detachment. The model is based on the assumption that the biofilm is fully penetrated by the substrate. At high dilution rates the outcome of our experiments is mainly determined by the attachment rate. The influence of the thickness of the biofilm is discussed in order to demonstrate the limitations of the model.
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  • 12
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    Biotechnology and Bioengineering 27 (1985), S. 308-315 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High-level yeast inocula was investigated as a means of overcoming the toxicity problem in ethanol fermentation of acid hydrolyzate of wood cellulose. When the inoculum level exceeded 108 initial cells/mL, 50% of the yeast cells survived the initial cell death period during which furfural and HMF were depleted. The fermentation thus proceeded to completion by virtue of cell regrowth. The specific ethanol productivity in batch fermentation on the basis of viable cells was comparable to that of pure glucose fermentation. Continuous fermentation with cell recycle was superior to batch fermentation in that there was no overall cell decline and the ethanol yield was substantially higher. The maximum ethanol productivity in continuous fermentation was 4.9 g/L h and it occurred at a dilution rate of 0.24 hr-1.
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  • 13
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    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 27 (1985), S. 519-524 
    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 deals with the effect of P-control and Plcontrol on the dynamic behavior of a continuous stirred tank fermentor (CSTF). Several conditions concerning the stability of steady states and the existence of limit cycles of the closed-loop system are derived. The application is made to the substrate inhibition model with variable yield coefficient. It is shown how the unfavorable phase-plane trajectories of the uncontrolled CSTF can be altered to favorable ones by the appropriate choice of control parameters based on the conditions derived.
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  • 14
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two endo-xylanases (1,4-β-D-xylan xylanohydrolase, EC 3.2.1.8) were purified to homogeneity from a crude Aspergillus niger pentosanase preparation by Ultrogel AcA 54 gel permeation chromatography, SP-Sephadex C-25 cation exchange chromatography at pH 4.5, Sephadex G-50 gel permeation chromatography, and a second SP-Sephadex C-25 step, this one at pH 5.8. The two xylanases hydrolyzed soluble xylan more rapidly than insoluble branched xylan, but attacked each substance to an equal extent. Their low activity on a linear xylooligosaccharide mixture and absence of activity on insoluble xylan freed of branches suggest that the xylanases require a branch point nearby for significant attack. No xylose or L-arabinose was produced, the major products of low molecular weight being tri- and pentasaccharides and smaller amounts of di-, tetra-, and hexasaccharides. There was low activity on untreated and crystalline cellulose and on carboxymethylcellulose and no activity on other polysaccharides tested. These two xylanases had molecular weights of ca. 1.3 × 104 and similar amino acid profiles, high in acidic and low in sulfur-containing residues. Isoelectric points were 8.6 for I and 9.0 for II. Optimum pH values for activity were 6.0 and 5.5, respectively. In a 20-min assay at pH 5.5, each was most active at 45°C, with activation energies up to 40°C of 30.4 and 38.8 kJ/ mol, respectively. Optimum pH levels for stability were 5.0 and 6.0, with half-lives at 60°C and those pHs of 20 and 75 min, respectively.
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  • 15
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    Biotechnology and Bioengineering 27 (1985), S. 334-344 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Wheat straw was treated with NaOH and anaerobically digested for methane production. Alkaline treatment resulted in a greater than 100% increase in biodegradability of wheat straw. The potential of a process flow scheme employing high alkali concentration at ambient temperature with solids separation and recycle of filtrate containing residual alkali was explored. The effect of NaOH on the solubilization of cell wall constituents and potential problems of toxicity are discussed. A solubilization model was developed which is used to predict biodegradability of whole samples based on solids and filtrate biodegradabilities. Energy requirements and chemical costs are also addressed.
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  • 16
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    Biotechnology and Bioengineering 27 (1985), S. 327-333 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cell growth and lincomycin production were measured in batch cultures of Streptomyces lincolnensis in chemically defined media. In these fermentations the specific rate of antibiotic production was maximal during growth and always declined at the end of the growth phase. It was found that both phosphate and ammonium salts, while required for cell growth, had negative effects on antibiotic production. By increasing the concentration of magnesium sulfate, it was possible to increase both the production rates and final titers of lincomycin. The mechanism for this effect was found to be the reduction of soluble phosphate in the medium through the precipitation of ammonium magnesium phosphate. Lincomycin production rates were not inhibited by glucose at concentrations of up to 30 g/L.
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  • 17
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    Biotechnology and Bioengineering 27 (1985), S. 345-354 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The alkali consumption during alkaline treatment of wheat straw at ambient temperature was measured as a function of time, solids concentration, and alkali concentration. The maximum measured alkali consumption was 5.5 g NaOH/100 g TS over a period of 30 days of treatment. Chemical functional groups (e.g., acyl and carboxyl groups) were measured and compared with the observed alkali consumption. The kinetics of alkali consumption were studied and a model was developed which predicts alkali consumption reasonably well. Use of this model was made to predict biodegradability of alkali-treated wheat straw, since a strong correlation was found to exist between alkali consumption and observed biodegradability. The method of bioconversion used was anaerobic digestion for methane production.
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  • 18
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    Biotechnology and Bioengineering 27 (1985), S. 792-799 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The balances of reductivity and high-energy bonds (HEB) during microbial growth on glucose (a standard substrate), methanol, and ethanol are reported. Also, numerical values for the quantities of HEB formation in the respiratory metabolism, HEB consumption in the constructive metabolism, as well as in a number of the other intracellular processes are evaluated. Estimations of maximum cell yields by mass and energy are made during growth on methanol and ethanol with regard to peculiar features of different microbe metabolism.
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  • 19
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    Biotechnology and Bioengineering 27 (1985), S. 800-806 
    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 hybrid reactor, the upflow blanket filter (UBF), which combined on open volume in the bottom two-thirds of the reactor for a sludge blanket and submerged plastic rings (Flexiring, Koch Inc., 235 m2/m3) in the upper one-third of the reactor volume, was studied. This UBF reactor was operated at 27°C at loading rates varying from 5 to 51 g chemical oxygen demand (COD)/L d with soluble sugar wastewater (2500 mg COD/L). Maximum removal rates of 34 g COD/L d and CH4 production rates of 7 vol/vol d [standard temperature and pressure (STP)] were obtained. The biomass activity was about 1.2 g COD/g volatile suspended solids per day. Conversion (based on effluent soluble COD) was over 93% with loading rates up to 26 g COD/L d. At higher loading rates conversion decreased rapidly. The packing was very efficient in retaining biomass.
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  • 20
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    Biotechnology and Bioengineering 27 (1985), S. 786-791 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The properties of two isozymes of β-glucosidase of Penicillium funiculosum (part I of this series) are described. The molecular weights of isozyme 1 was 2.3 × 105 by gel filtration and 1.2 × 105 by SDS gel electrophoresis, indicating two subunits. The molecular weight of isozyme 2 was unusually low for a fungal β-glucosidase: 1.6 × 104 by gel filtration and 3.7 × 104 in the presence of isopropanol. The two enzymes differed from other fungal β-glucosidases in their substrate specificities. They showed high activity with pNPG, cellobiose, cellotriose, cellotetraose, cellopentaose, gentiobiose, and laminarin, but were inactive with filter paper, CM cellulose, or derivatives or stabilized by bovine serum albumin and several alcohols such as butanol and propanol. It was inhibited by glucono-δ-lactone (Ki = 0.67μM) and glucose (Ki = 0.92mM).The enzyme was quantitatively adsorbed by P. funiculosum mycelium at pH 4 and the immobilized enzyme was as enzymically active as the free enzyme, but more heat stable. The binding efficiency was very high (5000 IU enzyme/g mycelium). It could be quantitatively eluted with buffers at pH 7 or by 0.02M Ca, Mg, or Al chlorides. The binding was selective, since mycelium grown on lactose could produce and also bind only β-glucosidase isozyme 1, whereas mycelium grown on cellulose could produce as well as bind both β-glucosidase isozymes as well as cellulases. Mycelial binding was unaffected by washing with EDTA or trypsinization, but was totally lost by washing with dilute KOH, HCl, or ethylenediamine.
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  • 21
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    Biotechnology and Bioengineering 27 (1985), S. 1005-1011 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A newly designed batch calorimeter was used to investigate the degradability of some celluloses having varying degrees of crystallinity. The PTC of an aerobic culture of Cellulomonas uda ATCC 21399 obtained revealed a diauxic growth which is attributed to the presence of hemicellulose contaminating Avicel and MN300 cellulose. The microcrystalline celluloses used were not completely utilized, whereas amorphous cellulose was easily metabolized, indicating that under the growth conditions used here, the physical structure of cellulose strongly influenced its microbial degradability. An equivalent growth yield of ca. 0.44 g/g was found with all the substrates used. The heat evolved by metabolism of 1 g cellulose was -5.86 kJ/g, a value similar to that obtained with glucose culture. The growth rate was the only variable parameter. The data obtained showed as expected that the hydrolysis product of cellulose was consumed in the same way as that of glucose and that the only limiting factor to the biodegradability of cellulose was the breakdown of the polymeric substrate. It is concluded that data obtained with glucose metabolism can be used to evaluate the extent of cellulose degradation.
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  • 22
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    Biotechnology and Bioengineering 27 (1985), S. 1012-1020 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Streptomyces aureofaciens (ATCC 12416c) was grown in the interstitial region formed by a parallel arrangement of three hollow silicone tubules contained within a microporous polypropylene hollow fiber. Liquid-soluble nutrients were supplied by diffusion across the polypropylene fiber to the interstitial cell-containing region whereas air or oxygen was provided by diffusion from the silicone tubule lumina to the cell mass. In this bioreactor, S. aureofaciens grew to high cell densities (greater than 1011 cells/cm3) and the culture so-obtained continously synthesized the secondary metabolite tetracycline. The volumetric productivity of tetracycline based on the interstitial volume was 90 μg/ml/h and based on the total reactor volume was 5.5 μg/mL/h. The high surface area-to-volume ratio afforded by the cylindrical configuration together with spatially distinct conduits to continuously transport liquids and gases, each of which may be nutrients or products of biosynthesis, to or from a tissuelike cell mass provides an alternative to the conventional air- or oxygen-sparged fermentation vessel. High volumetric reactor productivities may be achieved by virute of the concentrated stationary cell mass and by the appropriate selection of fiber sizes and materials so as to ensure adequate supplies of liquid and gaseous substrates to, as well as removal of metabolites from, most cells in the culture. This reactor topology is quite general and may be adapted to most microbial as well as mammalian and plant cell systems.
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  • 23
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    Biotechnology and Bioengineering 27 (1985), S. 1021-1026 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Human embryonic kidney cells grown as an attached, confluent monolayer on a flat substrate were subjected to steady, uniform laminar flow of medium in a specially designed chamber in which flow patterns and shear stress are accurately defined and controlled. Experiments were performed for shear stress levels ranging from 0.2 to 6.0 N/m2 with times of exposure to the shear stress ranging from 2 to 24 h. The influence of the shear field was slight at low shear stress (0.26 N/m2). Higher stress levels (0.65 N/m2 and higher) had significant effects on cell morphology, and on the post-shear release of urokinase enzyme. Still higher stress levels (2.6 N/m2 and higher) caused marked reduction in cell viability. These results may be of interest in addressing practical problems in developing commercial biosynthesis reactors.
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  • 24
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    Biotechnology and Bioengineering 27 (1985), S. 41-49 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: More than 90% of initial pyritic sulfur was removed from bituminous coal samples (containing 2.1% pyritic sulfur) using the thermophilic organism Sulfolobus acidocaldarius. Microbial desulfurization rate was improved nearly ten fold by adjusting the N/P and N/Mg ratios in the nutrient medium. Environmental conditions were optimized. The optimal values of temperature and pH were 70°C and 1.5, respectively. The influence of certain process variables (such as coal pulp density, particle size, and initial cell number density) on the rate of pyritic sulfur removal were determined. A pulp density of 20%, particle size of D¯p 〈 48 μm, and an initial cell number density of 1012 cells/g pyrite in coal were found to be optimal. The carbon dioxide enriched air did not improve the rate of pyritic sulfur removal compared to pure air at 10% pulp density of coal samples containing 2.1% pyritic sulfur. The kinetics of microbial leaching of pyritic sulfur from coal was investigated. The rate of leaching was found to be first order with respect to pyritic sulfur concentration in the reaction medium.
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  • 25
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    Biotechnology and Bioengineering 27 (1985), S. 1036-1043 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The partitioning of endo-β-glucanase, exo-β-glucanase, and β-glucosidase from Trichoderma reesei QM 9414 in aqueous two-phase systems has been studied with the object of designing a phase system for continuous bioconversion of cellulose. The partitioning of the enzymes in two-phase systems composed of various water soluble polymeric compounds were studied. Systems based on dextran and polyethylene glycol (PEG) were optimal for one-sidedly partitioning the enzymes to the bottom phase. The influence of polymer molecular weights, polymer concentration, ionic composition of the medium, pH, temperature, and adsorption of the enzymes to cellulose on the enzyme partition coefficients (K) were studied. By combining the effects of polymer molecular weight and adsorption to cellulose, K values could be reduced for endo-β-glucanase to 0.02 and for β-glucosidase to 0.005 at 20°C in a phase system of Dextran 40-PEG 40000 in the presence of excess cellulose, At 50°C, K values were increased by a factor of two. In a phase system based on inexpensive crude dextran and PEG, the partition coefficient for endo-β-glucanase was 0.16 and for β-glucosidase was 0.14 at 20°C with excess cellulose present.
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  • 26
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model substrate, Solka Floc BW 200, was semicontinuously hydrolyzed in an aqueous two-phase system based on crude dextran and polyethylene glycol over a period of more than 450 h. With an initial concentration of 75 g/L and intermittent addition of cellulose an average concentration of 50 g/L sugar was semicontinuously produced at dilution rates of 0.006-0.012 h-1. The conversion of substrate varied between 49 and 66%. The enzyme consumption measured as FPU/g reducing sugar (RS) produced could be reduced by a factor two when compared to a batch process since, in the aqueous two phase system investigated, the enzyme could be recycled two times.
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  • 27
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    Biotechnology and Bioengineering 27 (1985), S. 861-869 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two rate equations have been developed to model the hydrolysis of ground lean meat protein by Alcalase. The first equation was based on classical Michaelis-Menten kinetics and the second on the adsorption of enzyme to the protein prior to reaction. It was assumed that this adsorption could be modelled by a Langmuir-type adsorption isotherm. Each equation considered the enzyme to be competitively inhibited by reaction product, and considered enzyme inactivation to be first order. Both rate equations have been fitted to experimental data obtained from the hydrolysis of meat protein by Alcalase. Initial rate data indicated that the adsorption model was more appropriate. However, both equations gave satisfactory fits to 11 reaction progress curves determined over a wide range of enzyme and substrate concentrations.
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  • 28
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    Biotechnology and Bioengineering 27 (1985), S. 883-886 
    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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  • 29
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    Biotechnology and Bioengineering 27 (1985), S. 128-131 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The aqueous effluent generated by the Fischer--Tropsch process, containing a total of 13 g/L C2-C5 monocarboxylic acids, was investigated as a potential substrate for the production of single-cell protein (SCP). A bacterial isolate, Acinetobacter calcoaceticus, could utilize all the acids in the effluent simultaneously in chemostat cultures, and no residual acids were detected in the culture below a dilution rate of 0.78 h-1. The critical dilution rate was 1.04 h-1. The maintenance energy requirement of the cells growing on the monocarboxylic acid mixture was considerably lower than that of cells growing on acetate as the sole carbon source. Enrichment of the effluent with ethanol to increase the biomass concentration was successful and still allowed the simultaneous and efficient utilization of all the carbon sources, but resulted in a decrease of the critical dilution rate by ca. 20%.
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  • 30
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    Biotechnology and Bioengineering 27 (1985), S. 137-145 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dried spheres made from an alginate solution containing magnetite particles have excellent potential as a support for enzyme immobilization and chromatographic applications. The beads were found to be much stronger than gels such as polyacrylamide and dextran, indicating that high flow rates and pressures could be used in column separations. The support withstood not only temperatures of up to 120°C, but also most pH values and common solvents. While some solutions, such as phosphate buffers, dissolved the spheres, stabilization with Tyzor TE® eliminated this problem. The physical properties of the beads include a glasslike density of 2.2 g/mL, excellent sphericity, low porosity, and a narrow size distribution. The magnetite present in the support allows the beads to be used for magnetic separations such as high gradient magnetic filtration. Their high degree of microroughness provides a large exposed surface area for enzyme and ligand binding. Mixed Actinomyces fradiae proteases and Aspergillus niger α-amylase, two enzymes representative of classes which attack large substrates, were immobilized on the bead's surface with high activity and stability. A cyanuric dye which can be used in chromatographic applications (Cibacron Blue F3GA®) was also readily coupled to the surface of this support with good yield. The support should have a wide range of applications in bioseparation and immobilized biochemical technology.
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  • 31
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    Biotechnology and Bioengineering 27 (1985), S. 146-150 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An improved membrane has been developed for the microencapsulation of islets of Langerhans which protects these cells from the immune system. These requirements were accomplished through the optimization of important microencapsulation parameters and through the improved biocompatibility of a new alginate-poly-l-lysine (PLL)-alginate capsule membrane. Spherical and smooth microcapsules could be formed by utilizing a purer sodium alginate and by keeping the viscosity of the sodium alginate solution above 30 cps. The strength of the capsule membrane was enhanced by increasing the alginate-PLL reaction time as well as the PLL concentration. The permeability of the membrane [4 μm thick, 93% (w/w) water] was a function of the viscosity average molecular weight (Mv) of the PLL (Mv = 4000-4 × 105) used in the encapsulation procedure. Microcapsules prepared with PLL with Mv = 1.7 × 104 were the least permeable, being impermeable to normal serum immunoglobulin, albumin, and haemoglobin. The microencapsulation procedure, by protecting transplanted tissue from the components of the immune system, has great clinical potential as a new form of treatment for diseases such as diabetes and liver disease.
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  • 32
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    Biotechnology and Bioengineering 27 (1985), S. 555-561 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two photosynthetic algal cultures, one Chlorella vulgaris, and the other a Chlorogonium sp., were cultured under light limitations in chemostats. The effects of growth temperature on their energy yield and maintenance energy requirement were studied. It was observed that a lowering in temperature resulted in a lower maximum growth yield from the light energy, YG. This was attributed to two reasons. First, at low temperatures there was a change in the algal cell composition with more energy being expended to synthesize a higher biomass protein content. Secondly, at low temperatures, a cyanide-resistant respiratory pathway became operative which led to a decrease in the number of ATP being generated. The maintenance energy coefficient was a function of temperature increasing with decreasing temperature. This might reflect energy wastage by the cell at low temperatures. The maximum specific growth rate dropped with decreasing temperature, and can be described by an Arrhenius type rate-temperature model up to the optimal temperature for growth; i.e., activation energy remained constant.
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  • 33
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    Biotechnology and Bioengineering 27 (1985), S. 1102-1107 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Glucose oxidase, invertase, and amyloglucosidase were entrapped in calcium alginate gels as concanavalin A complexes in order to prevent the leaching out of the enzymes from the porous matrix. The free as well as the gel-entrapped concanavalin A-glycoenzyme complexes exhibited a relatively high effectiveness factor, η, indicating good accessibility to the substrates. Concanavalin A-invertase complex exhibited marked broadening of pH-activity and temperature-activity profiles and was highly resistant to temperature inactivation even after entrapment in the alginate beads. It was possible to entrap considerable quantities of invertase as concanavalin A complex in the beads without a marked decrease in η. A column containing crosslinked concanavalin A-invertase complex entrapped in alginate beads retained the ability to completely hydrolyze 1M sucrose even after continuous operation for over four months.
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  • 34
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    Biotechnology and Bioengineering 27 (1985), S. 953-960 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In enzymatic synthesis of cephalexin from D-α-phenylglycine methyl ester (PGM) and 7-amino-3-deacetoxy-cephalosporanic acid (7-ADCA) using α-acylamino-β-lactam acylhydrolase from Xanthomonas citri, it was found that this enzyme catalyzes all three reactions including PGM hydrolysis, cephalexin synthesis, and cephalexin hydrolysis. Based on our experimental results, a mechanistic kinetic model for cephalexin synthesizing enzyme system having acyl-enzyme intermediate was proposed. From this kinetic model, the reaction rate equations for three reactions were derived, and the kinetic parameters were evaluated. A good agreement between the simulation results and the experimental results was found.
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    Biotechnology and Bioengineering 27 (1985), S. 1146-1151 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A classical quantitative (analytical and/or statistical) analysis is not appropriate for some ill-defined and/or very complex bioengineering problems. Therefore, a new form of analysis using fuzzy mathematics has been developed. The fuzzy model can utilize semiqualitative and linguistic data which are to a certain level inconsistent. Bioengineering interpretation of the basic concept of fuzzy mathematics is given together with a numerical algorithm for a fuzzy evaluation of a model. A simple fuzzy model of a fermentor is studied in detail.
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    Biotechnology and Bioengineering 27 (1985), S. 1136-1145 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An analytical model for dissolved oxygen concentration in an algal minipond was used to develop a new method for estimating, on-line, the net O2 production rate (OPR) of the biological process. The method was tested experimentally and was found to provide crucial information on the vitality of the biological process and to provide an early warning of a possible forthcoming collapse of the ecosystern. It is suggested that the newly developed model and measurement method could provide investigators with useful tools for optimization of algal cultivation in the laboratory and plant.
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    Biotechnology and Bioengineering 27 (1985), S. 943-952 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The simultaneous separation of volatile fermentation products from product-inhibited fermentations can greatly increase the productivity of a bioreactor by reducing the product concentration in the bioreactor, as well as concentrating the product in an output stream free of cells, substrate, or other feed impurities. The Immobilized Cell Reactor-Separator (ICRS) consists of two column reactors: a cocurrent gas-liquid “enricher” followed by a countercurrent “stripper” The columns are four-phase tubular reactors consisting of (1) an inert gas phase, (2) the liquid fermentation broth, (3) the solid column internal packing, and (4) the immobilized biological catalyst or cells. The application of the ICRS to the ethanol-from-whey-lactose fermentation system has been investigated. Operation in the liquid continuous or bubble flow regime allows a high liquid holdup in the reactor and consequent long and controllable liquid residence time but results in a high gas phase pressure drop over the length of the reactor and low gas flow rates. Operation in the gas continuous regime gives high gas flow rates and low pressure drop but also results in short liquid residence time and incomplete column wetting at low liquid loading rates using conventional gas-liquid column packings. Using cells absorbed to conventional ceramic column packing (0.25-in. Intalox saddles), it was found that a good reaction could be obtained in the liquid continuous mode, but little separation, while in the gas continuous mode there was little reaction but good separation. Using cells sorbed to an absorbant matrix allowed operation in the gas continuous regime with a liquid holdup of up to 30% of the total reactor volume. Good reaction rates and product separation were obtained using this matrix. High reaction rates were obtained due to high density cell loading in the reactor. A dry cell density of up to 92 g/L reactor was obtained in the enricher. The enricher ethanol productivity ranged from 50 to 160 g/L h while the stripper productivity varied from 0 to 32 g/L h at different feed rates and concentrations. A separation efficiency of as high as 98% was obtained from the system.
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  • 38
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    Biotechnology and Bioengineering 27 (1985), S. 1173-1184 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The leaching of a zinc sulfide concentrate by Thiobacillus ferrooxidans was investigated in continuous stirred tank reactors. A mathematical model for the growth of T. ferrooxidans on this solid substrate is presented and tested. Experimental leaching studies were done using two reactors in series with and without recycle of solids from the outlet of the first reactor back to its inlet. The proposed model fits the authors' experimental data well. However, comparison of the parameters calculated with those calculated from the data of others showed that a wide variation can exist; thus, the parameters seem to depend on the nature of the substrate. The area occupied on the sulfide surface by a bacterium was found to be 5.4 μm2. The calculated maximum specific growth rates ranged from 0.20 to 0.31 h-1, and these values were dependent on whether they were observed in the first or second of the two reactors in series.
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  • 39
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    Biotechnology and Bioengineering 27 (1985), S. 1185-1191 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hollow fiber enzyme reactor with pulsation developed by Kim and Chang (1983) was operated in a differential mode by recycling a substrate solution, in order to assess the efficiency of ultrafiltration swing. The rates of lactose conversion by β-galactosidase contained in the shell side of the reactor were measured to determine the effects of recirculation rate, pulsation period, and amplitude. The conversion increased with the increase of recirculation flow rate and the amplitude while variation in period affected the conversion relatively little. The maximum increase of 113% in the activity was observed in the reactor with pulsation as compared to that without pulsation. The two-compartment model well described the experimental data obtained in this study. Square-wave pulsation was theoretically more effective in increasing conversion than sine wave pulsation. However, in experimental operation the damping effect of the hollow fiber wall narrowed the difference between these two wave forms.
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    Biotechnology and Bioengineering 27 (1985), S. 638-649 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Anaerobic digestion of biological organic particulates to methane has been described by a structured mathematical model based on multiple-reaction stoichiometry, conventional material balances, and liquid phase equilibrium chemistry. A general stoichiometric treatment for any set of multiple biological reactions is derived based on a unit mass of oxggen equivalents of the reactions limiting substrate. The model agrees well with two existing experimental studies of anaerobic digestion of biomass particulates. Hypothetical computer simulations are presented to illustrate possible instabilities of the anaerobic process under various operating scenarios.
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    Biotechnology and Bioengineering 27 (1985), S. 660-674 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    Biotechnology and Bioengineering 27 (1985), S. 1591-1595 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 27 (1985), S. 1603-1607 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Biotechnology and Bioengineering 27 (1985), S. 1634-1639 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A formate-selective biocatalytic potentiometric electrode system based on whole cells Pseudomonas oxalaticus has been developed. Permeation of the Gram-negative Pseudomonas oxalaticus microbial cells by EDTA is shown to improve the response slope from 38 mV/decade to 49 mV/decade, resulting in increased sensitivity. Out of 13 possibly interfering compounds tested, only pyruvate and lactate showed moderate response.
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  • 45
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    Biotechnology and Bioengineering 27 (1985), S. 1623-1633 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A technique using C-14 isotope tracers to probe the branching of carbon flow in methylotrophic bacteria has been devised and applied to continuous steady-state cultures. Methylomonas L3, a strain which utilizes the KDPG/TA variant of the ribulose monophosphate cycle for carbon fixation, was employed in the experimental studies. The actual in vivo rates of substrate-carbon incorporation into biomass, both direct and via CO2, and of the two carbon oxidation schemes were determined in three different steady-state cultures. The results show that the carbon substrate is oxidized predominantly via formate (the linear oxidation scheme), and that the cyclic scheme of oxidation is minimally, if at all, utilized. The carbon incorporation and oxidation patterns appear to vary considerably with the dilution rate and the inoculum history. The experimental accuracy of the new technique is discussed in detail.
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    Biotechnology and Bioengineering 27 (1985), S. 1229-1235 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: During the steady-state continuous culture of Saccharomyces cerevisiae on sugar cane blackstrap molasses under different experimental conditions, oscillatory variations of the invertase activity of the intact yeast cells were observed. The continuous morphological changes of the cells wall and of the periplasmic space affecting the interaction between invertase and sucrose molecules could be responsible by the observed oscillatory phenomena. The average invertase activity at the steady state is linearly correlated to the cell's growth rate.
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  • 47
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    Biotechnology and Bioengineering 27 (1985), S. 1246-1257 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A fermentation system has been designed to demonstrate the use of gas chromatography (GC) for on-line monitoring of the butanol-acetone and other complex saccharolytic fermentations. Tangential flow ultrafiltration was used to sterilely and continuously obtain a cell-free filtrate from the fermentation broth for on-line GC analysis of butanol, butyrate, acetate, acetone, ethanol, and acetoin. The liquid injection system consists of a phosphoric acid contactor, a slider-type injection valve, and a heater to address the difficulties (ghosting) encountered in the analysis of carboxylic acids. The fermentation headspace gas was also analyzed by on-line GC for nitrogen and carbon dioxide, while hydrogen was measured by difference. Raw chromatographic data were analyzed by a chromatography data system. Both raw and processed data were transmitted to a VAX 11/750 computer for further processing (using the fermentation equation) and archiving. The fermentation equation, which has recently been derived and tested on completed fermentation data, was also found to be valid during transient fermentations and thus useful as a gateway sensor for calculating various fermentation parameters on-line. Such parameters include glucose concentration and gas composition, as well as a number of unobservable parameters (such as YATP, excess ATP, and NAD reduced by FdH2), which characterize the state of the fermentation.
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    Biotechnology and Bioengineering 27 (1985), S. 1258-1269 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The microbial epoxidation of propene and 1-butene was used to study some fundamental aspects of two-liquid-phase biocatalytic conversions. Introduction of a water-immiscible organic solvent phase in a free-cell suspension gave rise to a series of undesired phenomena, e.g., inactivation by the solvent, clotting of biomass, and aggregation of cells at the liquid-liquid interface. Immobilization of the cells in hydrophilic gels, e.g., calcium alginate, prevented direct cell-organic solvent contact and the related clotting and aggregation of biomass. However, the gel entrapment did not seem to provide additional protection against the organic solvent. The influence of various organic solvents on the retention of immobilized-cell activity was related to solvent properties like the polarity (as expressed by the Hildebrand solubility parameter) and the molecular size (as expressed by the molecular weight or molar volume). High activity retention was favored by a low polarity in combination with a high molecular weight. The solubility parameter also proved useful to describe the capacity of various organic solvents for oxygen and alkene oxides. This facilitated the optimization of the solvent polarity.
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    Biotechnology and Bioengineering 27 (1985), S. 1721-1725 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The advant of a new range of high-protein capacity cellulosic ion exchangers suitable for use on an industrial scale made it worthwhile investigating the conditions necessary to remove the contaminating enzyme glucosyltransferase from a commercial preparation of crude glucoamylase. The potential of the SP derivative, SP Indion®, for achieving this separation is shown. At pH 2.5 the glucosyltransferase was selectively adsorbed by the ion exchanger, and 99% of the glucoamylase was recovered in the eluate from the column. Purification of an Aspergillus culture filtrate by this method will require careful control of the ionic strength of the culture medium if it is to be used without the additional step of cation exchange to lower than pH to 2.5.
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    Biotechnology and Bioengineering 27 (1985), S. 1276-1276 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 27 (1985), S. 1274-1275 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The study of the effect of glucose addition to the kinetics of maltodextrin hydrolysis catalyzed with free and immobilized Aspergillus niger glucoamylase does not show any significant glucose inhibitory effect. This result is in contradiction with data previously reported in the literature. On the contrary, a slight glucose-activating effect was observed. This effect was greater in the case of the immobilized enzyme. The glucose inhibitory effect may thus not be involved in the case of practical saccharification conditions catalyzed with glucoamylase when maltodextrins are used as substrate.
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    Biotechnology and Bioengineering 27 (1985) 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 28 (1986) 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
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  • 54
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    Biotechnology and Bioengineering 28 (1986), S. 16-20 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A method is described using fast protein liquid chromatography (FPLC) for the monitoring of protein formation during fermentation. The procedure consists of centrifugation to recover the cells, sonication of the cells, centrifugation to remove cell debris, and analysis of supernatant on a column of Mono Q (a strong anion exchanger). Analysis of peak areas provides quantitative determination of product concentration. Maintenance and life of the Mono Q column is discussed. We find that FPLC is a convenient method for measuring products in cell homogenates because it gives rapid, highly resolved separations.
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  • 55
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    Biotechnology and Bioengineering 28 (1986), S. 21-28 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Biosorption of uranium and lead by lyophilized cells of Streptomyces longwoodensis was examined as a function of metal concentration, pH, cell concentration, and culture age. Cells harvested from the stationary growth phase exhibited an exceptionally high capacity for uranium (0.44 g U/g dry weight) at pH 5. Calculated values of the distribution coefficient and separation factor indicated a strong preference of the cell mass for uranyl ions over lead ions. The specific uranium uptake was similar for the cell wall and the cytoplasmic fraction. Uranium uptake was associated with an increase in hydrogen ion concentration, and phosphorus analysis of whole cells indicated a simple stoichiometric ratio between uranium uptake and phosphorus content. It is proposed that metal ions are bound to phosphodiester residues present both in the cell wall and cytoplasmic fractions. Based on this model, it was shown that uranium accumulation exhibits a maximum at pH 4.6 that is supported by experimental data from previous investigations.
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  • 56
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    Biotechnology and Bioengineering 28 (1986), S. 41-50 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous cellulase production by Trichoderma viride QM 9123, immobilized in 6 mm diameter, spherical, stainless steel biomass support particles, has been achieved using a medium containing glucose as the main carbon source. Experiments were carried out in a 10-L spouted bed fermentor. In this type of reactor-recycled broth is used to create a jet at the base of a bed of particles, causing the particles to spout and circulate. During the circulation, particles pass through a region of high shear near the jet inlet. This effectively prevents a buildup of excess biomass and thus enables steady-state conditions to be achieved during continuous operation. Continuous production of cellulase was achieved at significantly higher yield and productivity than in conventional systems. At a dilution rate of 0.15 h-1 (nominal washout rate for freely suspended cells is 0.012 h-1), the yield of cellulase on glucose was 31% higher than that measured during batch operation, while the volumetric productivity (31.5 FPA U/L· h) was 53% greater than in the batch system. The specific cellulase productivity of the immobilized cells was more than 3 times that of freely suspended cells, showing that diffusional limitations can be beneficial. This offers significant opportunity for the further development of biomass support particles and associated bioreactors.
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  • 57
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    Biotechnology and Bioengineering 28 (1986), S. 64-72 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Urokinase was immobilized by entrapment to fibrocollagenous tubes in order to develop a small-caliber fibrinolytic vascular prosthesis. Several parameters associated with the immobilization process were studied in order to optimize bound urokinase activity and stability. A total of 37% of the absorbing enzyme was attached to the collagen tube and 38% of the attached enzyme retained esterolytic activity, under optimal conditions. In the crosslink step of the entrapment process, the glutaraldehyde concentration was varied from 0.01 to 5.00% (i.e., 0.01, 0.1, 1.0, 3.0, and 5.0%). Urokinase activity was optimized at a 1.0% glutaraldehyde crosslink concentration. Urokinase-bound fibrocollagenous tubes (UK-FCT) prepared at the above glutaraldehyde concentrations were tested for their activity with time. The UK-FCT's with 0.1, 1.0, and 3.0% glutaraldehyde retained constant activity for at least 75 h operation time. The UK-FCT's with 0.1, 1.0, and 3.0% glutaraldehyde retained constant activity for at least 75 h operation time. The UK-FCT's with 5.0 and 0.01% glutaraldehyde remained stable for the first 50 h operation time, but begandeactivating beyond 50 h. UK-FCT'S Crosslinked with 0.01, 0.1, 1.0, and 5.0% glutaraldehyde were recrosslinked with 0.02% glutaraldehyde for 24 h, after they have been operating for 50 h, and the effect of reexposing the crosslink agent on the stability of the UK-FCT's was studied. The results showed that 0.02% glutaraldehyde reexposure had no effect on 0.1, 1.0, and 5.0% glutaraldehyde crosslinked UK-FCT's but exerted an inhibitory effect on a 0.01% crosslink density UK-FCT. Several fibrocollagenous tubes were exposed to various glutaraldehyde concentrations prior to immobilizing urokinase. The subsequent immobilization process occurred under optimal conditions. The effect of the precrosslink step on the activity of the UK-FCT was studied. Results indicated that UK-FCT activity decreases as the precrosslink density increases. The UK-FCT's made under optimal conditions remained stable for at least 75 h operation time, corresponding to ca.1 year of storage time. Ex vivo exposure of UK-FCT's to whole canine blood did not affect catalytic activity. Implantation of a UK-FCT by carotid arterial interposition via an end-to-end anastomosis and subsequent excision after 60 days resulted in an enhanced esterolytic activity which decreased with time to a level close to preoperative levels.
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    Biotechnology and Bioengineering 27 (1985), S. 1710-1716 
    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 applying the UASB concept for the anaerobic treatment of stillage of distilleries in the sugar producing area of Argentina was subject to study. Results obtained in a 100-L UASB reactor treating stillages with COD values between 35 and 100 g COD/L are presented. Loading rates of up to 24 g COD/L/day were applied with an average COD removal of 75% and a biogas production of more than 9 L/L/day, with an average methane content of 58%. The settling velocity distribution of sludge particles would indicate a good formation of biomass pellets. System interruptions of months without feed and at ambient temperature (20-24°C) were well tolerated.
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    Biotechnology and Bioengineering 27 (1985), S. 1726-1729 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 28 (1986), S. 101-106 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 28 (1986), S. 110-111 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 28 (1986), S. 115-118 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 28 (1986), S. 119-121 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No Absract.
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    Biotechnology and Bioengineering 28 (1986), S. 129-132 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 28 (1986), S. 29-40 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A separate role for water activity in the conversion of sugars to ethanol by two strains of yeast is identified. During fermentation of both single and mixed sugar substrates, the water activity was shown to remain constant during the logarithmic growth phase. This is despite the changes in concentration of substrates and product, the constancy reflecting the fact that the greater influence of ethanol on the solution activity is counterbalanced, in the early stages of the fermentation, by its low yield. The end of the log phase of growth coincides with the start of a period of gradually decreasing water activity. For the more ethanol-tolerant strain UQM66Y, growth was found to cease at a constant value of water activity while that for the less tolerant strain UQM70Y depended on both ethanol concentration and water activity. It is argued that water activity is a more appropriate variable than ethanol concentration for describing some of the nonspecific inhibitory effects apparent in ethanol fermentations. A straightforward method for the calculation of water activity during such fermentations based on the use of solution osmolality is presented.
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  • 66
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Notes: Poly(maleic anhydride styrene) graft copolymers of cellulose, pectin polygalacturonic acid salt, calcium polygalacturonate, and starch were prepared and used to immobilize proteins. The cellulose grafts coupled quite appreciable quantities of acid phosphatase, glucose oxidase, and trypsin. However, the general retention of activity was somewhat disappointing. Further investigation with acid phosphatase showed that the amount of enzyme immobilized increased as the amount of anhydride in the graft copolymer increased but no such relationship existed for the enzymic activity. The cellulose graft copolymers were hydrolyzed and it appeared that the carboxyl group aided adsorption of the enzyme. Attempts to couple acid phosphatase using CMC through the free carboxyl groups, created by hydrolysis, gave only a small increase in the extent of protein coupling. However, the unhydrolyzed system gave a useful degree of immobilization of cells of Bacillus stearothermophilus, as did a poly(maleic anhydride/styrene)-cocellulose system. Attempts to improve the activity by using grafts based on other polysaccharide supports met with mixed success. Pectin products were soluble. Polygalacturonic acid products were partially soluble and extremely high levels of enzymic activity were obtained. This was probably due in part to the hydrophilic nature of the system, which also encouraged absorption of the enzyme. Attempts were made to reduce the solubility by using the calcium pectinate salt. Immobilization of acid phosphatase and trypsin resulted in inceased protein coupling but relatively poor activities were attained. A starch based system gave similar results. Calcium polygalacturonate was used to prepare an insoluble graft copolymeric system containing acrylonitrile-comaleic anhydride. The resulting gels gave excellent coupling with acid phosphatase which had a very good retention of activity.
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    Biotechnology and Bioengineering 28 (1986), S. 107-109 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 27 (1985), S. 1403-1410 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 28 (1986), S. 603-604 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 28 (1986), S. 585-602 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comprehensive review of the microbial kinetics, energetics, and substrate specificities of anaerobic waste-water treatment systems is presented with descriptions of three different state-of-the-art reactor configurations. Each of these reactor systems is intended to enrich different populations of anaerobic acidogens and methan-ogens as a result of design and operational strategies for control of hydrogen and volatile acids. Imposition of these strategies results in different substrate utilization patterns, conversion kinetics, and operational stabilities as are currently being demonstrated in laboratory-scale investigations.
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    Biotechnology and Bioengineering 27 (1985), S. 1411-1417 
    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 the upflow anaerobic sludge bed (UASB) process for the treatment of potato starch wastewater at low ambient temperatures was demonstrated by operating two 5.65-L reactors at 14°C and 20°C, respectively. The organic space loading rates achieved in these laboratory-scale reactors were 3 kg COD/m3/day at 14°C and 4-5 kg COD/m3/day at 20°C. The corresponding sludge loading rates were 0.12 kg COD/kg VSS/day at 14°C and 0.16-0.18 kg COD/kg VSS/day at 20°C.These findings are of considerable practical importance because application of anaerobic treatment at low ambient temperatures will lead to considerable savings in energy needed for operating the process. As compared with various other anaerobic wastewater treatment processes, a granular sludge upflow process represents one of the best options developed so far. Although the overall sludge yield under psychrophilic conditions is slightly higher than under optimal mesophilic conditions, this doesn't seriously hamper the operation of the process. The extra sludge yield, due to accumulation of slowly hydrolyzing substrate ingredients, was 4.75% of the COD input at 14°C and 1.22% of the COD input at 20°C.
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    Biotechnology and Bioengineering 27 (1985), S. 1418-1426 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Assessment was made to evaluate the effect of hydrogen peroxide pretreatment on the change of the structural features and the enzymatic hydrolysis of rice straw. Changes in the lignin content, weight loss, accessibility for Cadoxen, water holding capacity, and crystallinity of straw were measured during pretreatment to express the modification of the lignocellulosic structure of straw. The rates and the extents of enzymatic hydrolysis, cellulase adsorption, and cellobiose accumulation in the initial stage of hydrolysis were determined to study the pretreatment effect on hydrolysis. Pretreatment at 60°C for 5 h in a solution with 1% (w/w) H2O2 and NaOH resulted in 60% delignification, 40% weight loss, a fivefold increase in the accessibility for Cadoxen, an one times increase in the water-holding capacity, and only a slight decrease in crystallinity as compared with that of the untreated straw. Improvement on the pretreatment effect could be made by increasing the initial alkalinity and the pretreatment temperature of hydrogen peroxide solution. A saturated improvement on the structural features was found when the weight ratio of hydrogen peroxide to straw was above 0.25 g H2O2/g straw in an alkaline H2O2 solution with 1% (w/w) NaOH at 32°C. The initial rates and extents of hydrolysis, cellulase adsorption, and cellobiose accumulation in hydrolysis were enhanced in accordance with the improved structural features of straw pretreated. A four times increase in the extent of the enzymatic hydrolysis of straw for 24 h was attributed to the alkaline hydrogen peroxide pretreatment.
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    Biotechnology and Bioengineering 28 (1986), S. 167-175 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The kinetics in fed-batch cultures of acetone butanol fermentation by Clostridium acetobutylicum is compared on glucose, xylose, and mixtures of both sugars. The final conversion yield of sugars into solvents always increases with the sugar feeding rate. At low feeding rates, the sugar concentration in the medium becomes limiting, which results in a slower cellular growth, a slower metabolic transition from an acid to a solvent fermentation and, thus, a higher accumulation of acids. It is only at sufficiently high feeding rates that fed-batch fermentations yield kinetic results comparable to those of batch fermentations. With mixtures of glucose and xylose, because of a maintained low glucose level, both sugars are taken up at the same rate during a first fermentation period. An earlier accumulation of xylose when the fermentation becomes inhibited suggest that xylose utilization is inhibited when the catabolic flux of glucose alone can satisfy the metabolic activity of the cell. Kinetic results with batch and fed-batch fermentations indicate several important features of the regulation of C. acetobutylicum metabolism: an early inhibition by the produced acids; an initiation of solvent formation between 4 and 6 g/L acetic and butyric acid depending on the metabolic activity of the cell; a metabolic transition from acids to solvents production at a rate closely related to the rate of sugar uptake; during solvent production, a reassimilation of acids above a minimal rate of sugar consumption of 0.2 h-1; a final inhibition of the fermentation at a total butanol and acids concentration of ca. 20 g/L.
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    Biotechnology and Bioengineering 28 (1986), S. 631-645 
    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 applying an adaptive control technique to a fermentation process is investigated. The nonlinear, time-variant parameters of a fermentation process were estimated on-line as a series of linearized describing matrices. The matrices were used to update a suboptimal feedback law which controlled the process in real time over the linear region. Experiments were performed on a small-scale fully instrumented fermenter with the online, real-time adaptive control package. Results are presented for both single- and multivariable control, and indicate successful control of yeast cell growth.
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    Biotechnology and Bioengineering 28 (1986), S. 659-662 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A nitrate control system has been devised for the maintenance of stable nitrate concentrations throughout fed-batch fermentations of Corynebacterium glutamicum. The feedback control system was based on the use of a nitrate-ion-selective electrode to directly monitor the nitrate levels in the fermentor and an automatic controller to activate a nitrate feed pump. The electrode which was used for controlling the nitrate level was stable through-out the fermentation period. The apparent maximum specific growth rate, biomass production, protein production, biomass yields on glucose and nitrate, and amino acid production were all optimal at approximately 50mM nitrate.
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    Biotechnology and Bioengineering 28 (1986), S. 646-658 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Growth of a hybridoma culture, along with production of monoclonal antibody, was demonstrated over extended periods in polysulfone hollow fiber membrane modules. The molecular weight cutoffs of the membranes were 70,000, 50,000, and 100,000 daltons. The hybridoma cell line, designated 65/26, produced IgG (2b/κ) directed at mouse thymus cell surface antigen, TL.1. Cell growth occurred in the shell space of the reactor, using supplemented RPMI 1640 (20% fetal bovine serum) supplied from a separate reservoir vessel through the hollow fiber lumen. The reservoir contained 125 mL media, which was changed every 4 days. Concentrations of immunoglobulin were determined by an enzyme immunoassay (using protein A and alkaline phosphatase-labeled antibody conjugate). For the 10K, 50K, and 100K hollow fiber membrane modules, the maximum IgG concentrations detected in the 2.5-mL shell space were 47.5-80, 510, and 740 μg/mL, respectively. In the 125-mL reservoir for the 100K hollow fiber membrane module, the IgG concentration was measured at 260 μg/mL These values compare with an IgG concentration of 1 μg/mL when grown in a standard tissue culture flask and 3.2-7.6 μg/mL when grown in 100 ml media in a spinner flask. In addition, 10K and 50K hollow fiber membrane modules were run in a mode that decreased the fetal bovine serum supplement with time. Differences between these systems suggest that it is possible to obtain high IgG accumulation rates, both during and after the exponential growth phase of the hybridoma population.
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    Biotechnology and Bioengineering 27 (1985), S. 1477-1481 
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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 semicontinuous operation of affinity chromatography columns charged and eluted alternately is studied mathematically. A strongly nonlinear adsorption equilibrium relation is utilized to examine the periodic mode of adsorption and desorption. The governing differential equations are solved by the method of characteristics. The time interval between desorption and adsorption periods is estimated, and implications for separations are discussed to show the advantages of semicontinuous cyclic operation.
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    Biotechnology and Bioengineering 28 (1986), S. 1056-1063 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Isoelectric fractionation of the two major proteins of soy is characterized. Fractions are acid precipitated and cen-trifugally collected at pH 6.0 (glycinin) and pH 4.8 (β-conglycinin). Two extremes in the speed of acid addition (rapid, with no mixing, and slow, via acid dialysis, with complete mixing) are compared to determine their effects on the properties of the precipitate. Total protein yield, fraction composition, and aggregate microstructure do not depend significantly on the method of acid addition. Particle size distribution and hindered settling behavior do differ and are explained using a model of aggregate strength. The rapid acid addition produces larger primary particles, because of higher supersaturation, and yields larger aggregates, because of higher interparticle potential and stronger aggregates. Further aggregation in low-shear hindered settling is faster for the slowly precipitated aggregate because few of these bonding sites could survive the high-shear precipitator, whereas more can contribute to aggregation during hindered settling.
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    Biotechnology and Bioengineering 28 (1986), S. 1080-1085 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Dehydrogenase activity assay of activated sludge using the redox dye 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride (INT) was investigated. INT-dehydrogenase activity (INT-DHA) was directly proportional to INT dosage and inversely proportional to bio-mass concentration over limited ranges. INT dosages exceeding 2.5m/M were toxic to dilute activated sludge suspensions. INT-DHA was greatest near pH 9, whereas the peak oxygen uptake rate (OUR) occurred at pH 8. Both INT-DHA and OUR varied inversely with sludge age, but INT-DHA was the more sensitive of the two parameters to this variable. Consistently good and highly significant correlations between INT-DHA and OUR of chlorine stressed activated sludge were found at sludge ages ranging 2.2-7.0 days.
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    Biotechnology and Bioengineering 27 (1985), S. 1500-1506 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 27 (1985), S. 1512-1515 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 27 (1985), S. 1507-1511 
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    Keywords: Chemistry ; Biochemistry and Biotechnology
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    Biotechnology and Bioengineering 27 (1985), S. 1516-1519 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    Biotechnology and Bioengineering 27 (1985), S. 1520-1523 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    Biotechnology and Bioengineering 27 (1985) 
    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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  • 86
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    Biotechnology and Bioengineering 27 (1985), S. 1525-1532 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Under certain simplifying hypotheses, a chemostat in which one microbial population feeds on another can be described by a system of three ordinary differential equations. A study is conducted to find which features of the equations are the most important to the dynamics of the system; it is found that the main influence comes from the from the particular form of the specific growth rate of the feeding population. Some conditions are derived that relate the form of the specific growth rate of the feeding population to the dynamic behaviour of the system.
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  • 87
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    Biotechnology and Bioengineering 28 (1986), S. 1127-1137 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two microorganisms, E. coli and S. cerevisiae, competing for glucose were maintained in a stable cycle of coexistence by alternating the growth advantage between the two organisms by oscillating the pH in a Chemostat. Pure culture experiments found S. cerevisiae to be insensitive to pH between 5 and 4.3 with a maximum specific growth rate (μmax) of 0.4/hr; while μmax of E. coli decreased from 0.6 h-1 at pH 5 to 0.1 h-1 at pH 4.3. Steady-state and cross-inoculation chemostat runs at a dilution rate of 0.17 h-1 confirmed the expectation that the mixed culture system is unstable at constant pH with E. coli dominating at pH 5 and S. cerevisiae dominating at pH 4.3. Three pH oscillation experiments were performed at D =0.17 h-1 with 1 g per liter glucose feed. The 16 h/16 h cycle was stable for six periods with a stable alternating cycle of E. coli and S. cerevisiae being quickly established. A 18 h pH 5/14 h pH 4.3 cycle was found to be stable with smaller yeast concentrations. A 6 h/6 h cycle was found unstable with yeast washout. Simulation results were compared with these runs and were used to predict the onset of instability. Oscillations of pH can force stable persistence of a competing mixed culture that is otherwise unstable. Thus, varying conditions are experimentally demonstrated to be one explanation for competitive coexistence.
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  • 88
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    Biotechnology and Bioengineering 28 (1986), S. 256-268 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of chemical modification on the initial specific activity, residual activity, and deactivation kinetics of various enzymes is analyzed using a series mechanism. This straightforward multistate sequential model presented is consistent with the enzyme deactivation data obtained from different fields. The enzymes are placed in five different categories depending on the effect of chemical modification on initial specific activity and residual activity or stability. Wherever possible, structure-function relationships are described for the enzymes in the different categories. The categorization provides one avenue that leads to further physical insights into enzyme deactivation processes and into the enzyme structure itself.
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  • 89
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    Biotechnology and Bioengineering 28 (1986), S. 283-287 
    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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  • 90
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    Biotechnology and Bioengineering 28 (1986), S. 288-293 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Wheat straw has been hydrolized with sulfuric acid at 34 and 90°C. The treatment at 90°C yields complete solubilization of hemicellulose to xylose and arabinose without significant amounts of furfural. The influence of acid concentration was studied and the kinetics of the acid-catalyzed hydrolysis has been modeled suggesting a two-consecutive reactions mechanism. This model is useful to explain the different behavior of the concentration of the two main sugars produced. The enhanced cellulose accessibility to enzymatic attack is also reported.
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  • 91
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    Biotechnology and Bioengineering 28 (1986), S. 269-282 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Within the framework of a program aiming to improve the existing extractive recovery technology of fermentation products, the state of the art is critically reviewed. The acids under consideration are propionic, lactic, pyruvic, succinic, fumaric, maleic, malic, itaconic, tartaric, citric, and isocitric, all obtained by the aerobic fermentation of glucose via the glycolytic pathway and glyoxylate bypass. With no exception, it is the undissociated monomeric acid that is extracted into carbon-bonded and phosphorus-bonded oxygen donor extractants. In the organic phase, the acids are usually dimerized. The extractive transfer process obeys the Nernst law, and the measured partition coefficients range from about 0.003 for aliphatic hydrocarbons to about 2 to 3 for aliphatic alcohols and ketones to about 10 or more for organophosphates. Equally high distribution ratios are measured when long-chain tertiary amines are employed as extractants, forming bulky salts preferentially soluble in the organic phase.
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  • 92
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    Biotechnology and Bioengineering 28 (1986), S. 678-683 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch and continuous fermentations with Clostridium thermoaceticum (ATCC 39073) using automatic pH control were conducted. The value of μmax obtained from batch fermentation was about 0.14 h-1; acetate yield, which was both growth and non-growth associated, was about 2 mole of acetic acid/mole of glucose, compared with a theoretical maximum value of 3. This low yield, compared with literature data, may be explained by glucose loss through a combination of degradation routes. Continuous fermentation could be sustained for 1600 h or more without contamination problems. Continuous fermentation at high dilution rates indicates that μmax may be well above 0.17 h-1 when fresh feed medium is used. Acetate yields in continuous fermentation were about 77% of theoretical or 2.3 mole of acetic acid/mole of glucose.
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  • 93
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Both the forward and backward reactions of xylose isomerase (Sweetzyme Q) with xylose and glucose as substrates have been studied in terms of kinetics and thermodynamics. The relationship between the two reactions can thus be determined. Much attention has been given to the reaction with xylose as substrate. The optimal conditions of the xylose reaction in terms of pH, buffer, metal ions, substrate concentration, temperature, and ionic strength have been determined. These findings did not differ much from those reported for the glucose reaction. Equilibrium constants for the aldose to ketose conversion were more favorable in the case of glucose. The results obtained with continuous isomerization of xylose in columns packed with either Sweetzyme Q or Taka-Sweet were very similar to those obtained from batch isomerization processes. Particle size had a definite effect on reaction rate, which indicates that diffusion limitations do occur with the immobilized enzyme particles. Heat stability of Sweetzyme Q was good with t1/2 of 118, 248, and 1200 h at 70, 55, and 40°C, respectively. A novel method for the separation of xylose-xylulose mixtures with water as eluant on a specially prepared Dowex 1 × 8 column was developed. This technique has the capability of producing pure xylulose for industrial or research applications. A writ for a patent regarding this technique is at present prepared.
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  • 94
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    Biotechnology and Bioengineering 28 (1986), S. 711-717 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Alcoholic fermentations of starch hydrolysate by two different yeast strains, Saccharomyces cerevisiae(var. Vinal) and Saccharomyces oviformis(IMAP 383), have been studied in batch runs. In order to evaluate the different inhibition phenomena due to both substrate and product, a new kinetic equation is suggested.
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    Biotechnology and Bioengineering 28 (1986), S. 700-710 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous cultures of Saccharomyces cerevisiae are known to exhibit oscillatory behavior in the oxidative region. Important findings of a series of experiments conducted to identify the causes for initiation of and the means for elimination of oscillations in these cultures are reported in this paper. These oscillations are seen to be connected to the growth kinetics of the microorganism and are induced at very low glucose concentrations and at dissolved oxygen (DO) levels that are neither high nor low (DO values between 20 and 78% air saturation at a dilution rate of 0.2 h-1 and pH of 5.5 at 30°C). The oscillatory behavior is encountered over a range of dilution rates (0.09-0.25 h-1 at 30°C for pH = 5.5 and DO = 50% air saturation). The oscillations can be eliminated by raising the DO level above a critical value or by lowering the DO level below a critical value.
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    Biotechnology and Bioengineering 28 (1986), S. 728-735 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comparison of the relative performance of production techniques using coenzyme or cofactor electrochemical regeneration demonstrates the superiority of those processes in which the enzymatic reaction and the regeneration are conducted in the same reactor as opposed to those in which the reaction and regeneration are separated. For the former type of reactor, a method of calculation is proposed. This method is based on the solution of equations which describe the phenomena in modules representing three areas: the surface of the electrode, a layer where occur simultaneously the transport of material and the enzymatic reaction, and the bulk of the solution. This method is suggested for three types of reactor: those in which an enzyme solution is held close to an electrode by a semipermeable membrane, those in which an enzyme-charged membrane is in contact with an electrode, and those in which the enzyme is in solution in the vessel into which the electrode is dipped.
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  • 97
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    Biotechnology and Bioengineering 28 (1986), S. 718-727 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The development of granular sludge in thermophilic (55°C) upflow anaerobic sludge blanket reactors was investigated. Acetate and a mixture of acetate and butyrate were used as substrates, serving as models for acidified waste-waters. Granular sludge with either Methanothrix or Methanosarcina as the predominant acetate utilizing methanogen was cultivated by allowing the loading rate to increase whenever the acetate concentration in the effluent dropped below 200 and 700 mg COD/L, respectively. The highest methane generation rates, up to 162 kg CH4-COD/m3 day, or 2.53 mole CH4/L day, were achieved at hydraulic retention times down to 21 min, with granules consisting of Methanothrix. The formation of Methanothrix granules did not depend on the type of seed material, nor on the addition of inert support particles. The growth of granules proceeded rapidly with adapted seed material, even when the reactors were inoculated with low concentrations. With mesophilic seed materials growth of granules took much longer. Thermophilic Methanothrix granules strongly resemble mesophilic granules of the “filamentous” type. Some factors governing the thermophilic granulation process are discussed.
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    Biotechnology and Bioengineering 28 (1986), S. 741-746 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
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    Biotechnology and Bioengineering 28 (1986), S. 736-740 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bovine trypsin was crosslinked to human serum albumin (HSA) with glutaraldehyde to form soluble and insoluble copolymers. The physical and kinetic properties of trypsin and trypsin-HSA polymers were compared. Trypsin was heat labile, retaining only 24% of its enzymic activity after heating for 5 min at 60°C. In contrast, under the same condition both the soluble and insoluble trypsin-HSA polymers showed enhanced resistance to heat in-activation, retaining 81 and 100% of their original activities, respectively. The trypsin-HSA polymers also showed shifts in pH optima, an increase in activation energy, and a broadening of their pH stability profiles.
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    Biotechnology and Bioengineering 28 (1986) 
    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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