摘要:

AbstractThis article reports on the reaction of urease immobilization through its covalent bonding on carboxymethylcellulose. The reaction is activated by dicyclohexylcarbodiimide. The coupling reaction is influenced by the enzyme–support and activator–support ratios, as well as by duration. Starting from a rotating, composed experimental program of the second order, the function correlating the activity of the immobilized enzyme with the reaction parameters is established. Immobilized urease exhibits thermal stability higher than that of free enzyme, regarding both pH and the inhibiting action of some metal ions or organic substances. The stability over time of the immobilized urease is high, its enzymatic activity being maintained at over 85% of the initial value three months after synthe

ISSN:0006-3592    

DOI:10.1002/bit.260340302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe desorption ofTrichoderma reeseicellulase from Avicel by a wide range of desorbents was measured. Emphasis was placed on desorption at alkaline pH. A maximum desorption of 65–68% Avicelase activity was achieved by contact with NaOH, pH 10.0, at 40°C for 5 min in the presence of 0.005% Triton X‐100 or Tween 80. The design of a suitable desorption process using these conditions is discussed. Glycerol was also effective as a desorbent either alone or in combination with alkali and detergent. However, relatively high concentrations of glycerol were needed and the maximum desorption achieved, 68%, was not significantly greater than that with only alkali and deter

ISSN:0006-3592    

DOI:10.1002/bit.260340303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractAn improved method is presented for producing high maltose conversion syrups from liquefied and raw starch. It comprises saccharifying the starch at higher temperatures than presently used with environmentally compatible thermostable β‐amylase and other thermostable enzym

ISSN:0006-3592    

DOI:10.1002/bit.260340304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractIsooctane–AOT–H2O is a suitable system for studying enzyme behavior in organic solvents. Tyrosinase was able to catalyze a well‐known reaction in aqueous medium: oxidation of 4‐methylcatechol to yield 4‐methyl‐o‐benzoquinone. This reaction was studied using the preceding ternary system with adequate amounts of each component to make up reverse micelles. 4‐Methyl‐o‐benzoquinone stability was demonstrated in isooctane even at alkaline pH values. ApparentKmandVmaxwere similar to those in water, but substrate inhibition was more evident. The pH and temperature appear to be shifted toward high and low values, respectively. Characteristic parameters of reverse micelles, ω0(= H2O/AOT) and percentage of H2O (v/v), were investigated. The results obtained showed that the steady‐state rate varies either with ω0or with percentage of H2O. The variation observed with ω0showed an optimal value while an increase in percentage of H2O can lead to decreased or increased activity depending on

ISSN:0006-3592    

DOI:10.1002/bit.260340305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe characteristics of growth and synthesis of plasmid‐encoded protein were studied for strains of recombinantE. coliJM103 which carried the β‐lactamase gene on plasmids of different sizes. The plasmids used included the vector pUC8 and its recombinant derivatives containing varying‐sized inserts ofDrosophilaDNA (not expressed inE. coli). Luria broth (LB) and a minimal medium (M9) supplemented in some cases with additional inorganic phosphate were used as growth media. There was no evidence of segregational instability in these experiments, where no antibiotic selection pressure was employed. Responses of the recombinant strains to variations in environmental parameters including pH, phosphate concentration in the medium, and aeration rate were examined. While the cell growth rate in LB decreased with pH in the range 7.0–8.0, the bulk β‐lactamase activity was maximized at an intermediate pH. The recombinant cell growth rate decreases with increasing plasmid size in the minimal medium, while such decrease is not significant when a rich medium such as LB is used. There is an intermediate plasmid size in the range studied (2.7–8.7 kb), at which β‐lactamase activity is maximum. While reduction in aeration rate (which determines the dissolved oxygen level) is detrimental for cell growth, it is beneficial for β‐lactamase synthesis. The bulk β‐lactamase activity therefore exhibits a maximum with respect to aeration rate. Cell growth and β‐lactamase production are affected in a similar manner by phosphate concentration in the minimal medium and therefore both are maximized at the same phosphate concentration. This investigation demonstrates clearly how the production of a recombinant plasmid‐encoded protein can be maximized by proper manipulation of culture conditions and how it

ISSN:0006-3592    

DOI:10.1002/bit.260340306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractPseudomonas putidacells were grown in confined volumes in dual‐membrane immobilized cell reactors constructed from microporous polyethylene hollow fibers and silicone rubber tubules as a model system for the study of mass transport in microbial aggregates. Local cell concentrations in the reactors reached 300 g dry mass/L. Pulse‐chase radioisotope labeling with35SO42−was used to estimate the rates of cell mass synthesis and degradation. Sulfur incorporation consistently exceeded sulfur release, implying that the cell mass concentration continually increases. The location and size of the cell growth region was determined using liquid emulsion autoradiography of thin sections prepared from labeled reactors. Cell growth occurs in a region less than 25 μm in depth adjacent to the oxygen supply, and the expansion of the cells caused by cell growth promotes convection of the cell mass into regions of the reactor where starving cells accumulate. The combination of mass‐balance and spatial distribution measurements that can be made using radioisotope tracers provides a versatile method for determining metabolic rates and limitations caused by mass transfer in immobilized cell

ISSN:0006-3592    

DOI:10.1002/bit.260340307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractEscherichia coliK‐12 cells were grown in a confined volume using microporous hollow fiber membranes. The local cell concentrations in the reactors were above 400 g dry mass/L, in excess of the predicted limit based on the specific volume of free cells determined by tracer exclusion. Cell mass synthesis and degradation rates in these reactors were measured using radioisotope labeling with35S. Net accumulation of cell material persisted at these high cell densities. The rates of substrate uptake and cell growth were predicted from the theory of reaction and diffusion assuming that kinetics of cell metabolism are identical for free‐living and immobilized cells. This theory was tested by comparison of overall rates and by the size of the region in which cell growth occurred, measured by autoradiography. A yield coefficient of 4 ± 1 mol sulfur/mol glucose was measured, in agreement with the value determined for free‐living cells in similar conditions. Cell growth occurs in a thin layer (10–30 μm), at a rate similar to the growth rate for free cells. Volume expansion by the cells as a consequence of proliferation induces convection of cell mass out of the growth region into a region of the reactor filled with starving cells, which then accumulate in the reactor. The combination of mass‐balance and spatial distribution measurements made possible by the use of radioisotope labeling enables a direct test for mass transfer limitations, the determination of the intrinsic cell kinetics, and noninvasive measurements of cell growth in immobilized ce

ISSN:0006-3592    

DOI:10.1002/bit.260340308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe performance of an ultrafiltration hollow‐fiber reactor, in which the enzymatic synthesis of glucose 6‐phosphate from glucose and cofactor ATP and the enzymatic regeneration of ATP from ADP and acetyl phosphate are performed simultaneously, was analyzed theoretically. A simple analytical model in which the liquid flowing in the fiber tubes is assumed to be plug flow, and the radial concentration gradients in the tube and shell sides are both neglected, could simulate the reactor performance with satisfactory accuracy. The simulation elucidated the effects of the reactor configurations and various operational conditions on glucose conversion, ATP recycle number, and space–time yield. If the fiber tubes, through which the permeability of the relevant components such as substrates is high, were packed as much as possible in the reactor, good reactor performance could be expected. Furthermore, with a sufficiently high enzyme concentration, low ATP concentration in the feed solution, and appropriate space velocity, good space–time yield with high glucose conversion and with very high ATP recycle number is theoretically p

ISSN:0006-3592    

DOI:10.1002/bit.260340309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractEnzymatic synthesis of glucose 6‐phosphate from glucose and ATP catalyzed by glucokinase fromB. stearothermophilusand enzymatic regeneration of ATP from ADP and acetyl phosphate catalyzed by acetatekinase fromB. stearothermophiluswere simultaneously performed in an Ultrafiltration hollow‐fiber reactor of the multitubular heat‐exchanger type. Experimental results of space–time yield, the conversion, and ATP recycle number were in good agreement with the theoretical predictions based on the simple analytical model developed in the preceding article. The best results for space–time yield and conversion were Ys= 1.97 mol/m3h andX= 92.8%, respectively, under the same conditions, and the best result for the ATP recycle number wasNR= 2130 under conditions different from those above. However,Ys= 1.72 mol/m3h,X= 81.2%, andNR= 1620 were the results when the space–time yield, conversion, and recycle number were at the highest in combination under the same conditions. Results of long‐term operation showed that the apparent remaining activity of the enzyme system was ca. 55% after continuous operation for 16 days, the decrease in the enzyme activity being faster than that expected from their half‐life times determined individually in the hom

ISSN:0006-3592    

DOI:10.1002/bit.260340310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractAcrylamide was produced from acrylonitrile using immobilizedBrevibacteriumCH1 cells that were isolated from soil and found to possess nitrile hydratase activity. The reaction conditions and stability of the enzyme activity were studied. The conversion yield was nearly 100%, including a trace amount of acrylic acid. This strain showed strong activity of nitrile hydratase toward acrylonitrile and extremely low activity of amidase toward acrylamide. A packed bed reactor was operated in a fed‐batch manner for acrylamide production of high concentration. The acrylonitrile concentration was maintained below 3% and the operating temperature at 4°C to minimize enzyme deactivati

ISSN:0006-3592    

DOI:10.1002/bit.260340311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY