摘要:

AbstractThe specific uptake rate of phenol by washed cells ofPseudomonas putidagrown on phenol in steady‐state continuous culture at various dilution rates was studied. The Monod‐Haldane‐type equation was applied to fit the data and the best kinetic parameters were determined by nonlinear least‐squares techniques. The values of the kinetic parameters were found to increase monotonically with the phenol concentration in the original chemostat. The relations between the values of kinetic parameters and phenol concentration in the chemostat were described by empirical equations. Then the equation governing the instant uptake of phenol by microorganisms in chemostat in the high conversion range of phenol was proposed. This equation together with the mass balance equations can be used to determine the stability range of continuous stirred tank biochemical reactors (CSTBR) utilizing

ISSN:0006-3592    

DOI:10.1002/bit.260300802

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

年代:1987

数据来源: WILEY

摘要:

AbstractExperimental investigations on α‐amylase and glucoamylase bound to porous polystyrene show that the activity of immobilized enzymes can be raised in the presence of an ultrasonic field. The maximum activity increase in a flow cuvette at 7.6 MHz and a sound intensity of 5 kW/m2amounts to more than 200% under the given experimental conditions. A mathematical model based on the differential equation for the interior and exterior substrate transport is set up and solved numerically. From the theoretical considerations and the experiments it is evident that the mechanism of the ultrasonic effect can be explained in terms of a reduction of the unstirred diffusion layer around the matrix particl

ISSN:0006-3592    

DOI:10.1002/bit.260300803

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

年代:1987

数据来源: WILEY

摘要:

AbstractA novel technique has been developed for measuring effective solute diffusivities in entrapment matrices used for cell immobilization. In this technique radiotracers were used to measure effective diffusivities and equilibrium partition coefficients of the solute between the liquid and solid matrix. Ca‐alginate was used in this study, because it is one of the most commonly employed matrices for the immobilization of microbial, plant and mammalian cells. The experimental apparatus consisted of a single spherical Ca‐alginate bead which was attached to a rotating rod and immersed in water containing C14‐glucose. The rotational speed of the spherical bead was controlled and resulted in excellent mixing, and negligible external film mass transfer resistance, which allowed the measurement of true effective solute diffusivity within the solid matrix. The rates of C14‐glucose diffusion within the Ca‐alginate sphere were measured using a scintillation spectrometer. A mathematical model of unsteady‐state diffusion in a sphere was used with appropriate boundary conditions, and the effective diffusivity of glucose was found from the best fit of the experimental data using a computer regression analysis method. Using 2% (w/v) Ca‐alginate beads in this new radiotracer technique the effective diffusivity and partition coefficient of glucose were found to be 6.62 × 10−10m2/s and 0.98, respectively. The accuracy, advantages, and simplicity of this new method for diffusivity measurements are also compared to other

ISSN:0006-3592    

DOI:10.1002/bit.260300804

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

年代:1987

数据来源: WILEY

摘要:

AbstractCost estimates have been prepared for commercial‐scale production of ajmalicine‐richCatnaranthus roseusbiomass using plant cell culture. At the current state of the technology the cost would be approximately $7.30/lb dry biomass ($3215/kg ajmalicine). Naturally‐grownC. roseusroots have a 50% lower ajmalicine concentration but would cost only ca. $0.70/lb ($619/kg ajmalicine). The principal reason for the high cost of the plant cell culture route is not the slow specific growth rate (0.35 day−1), but rather the slow specific product accumulation rate (0.26 mg/g day). This rate will have to be increased by a factor of 40 to make the process comp

ISSN:0006-3592    

DOI:10.1002/bit.260300805

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

年代:1987

数据来源: WILEY

摘要:

AbstractViable human diploid fibroblasts have been micro‐encapsulated in EUDRAGIT RL, a commercially available water‐insoluble polyacrylate, by an interfacial precipitation technique. Cells in medium and polymer solution (in diethyl phthalate) were coextruded and formed into droplets by a coaxial air stream. The droplets fell into a corn‐oil/mineral‐oil mixture to extract the solvent to precipitate the polymer around the cells. Capsules were ca. 500 μm in diameter depending on the air flowrate with a ca. 10‐μm thick wall. When collagen (1 mg/mL) was added to the cell suspension prior to encapsulation and base‐washed corn oil was used, cell growth occurred with one doubling achieved after five to six days as the collagen gel contracted inside the capsule. In the absence of collagen, cells spread on the inner wall of the capsule but did not grow, presumably because the surface charge on the capsule was inadequate. In similar fashion fibroblasts spread but did not grow on films of EUDRAGIT RL but did grow on blends of EUDRAGIT RL and EUDRAGIT E containing 10–30% of the latter more highly aminated polyacrylate. Although not suitable for anchorage‐dependent cell growth by itself, EUDRAGIT RL has been suitable as a model polymer to demonstrate the feasibility of using water insoluble polyacrylates and organic solvents and nonsolvents for the micro‐encapsulation of fibroblasts. Such microcapsules are of potential interest as a mode of large scale tissue culture for the production of novel

ISSN:0006-3592    

DOI:10.1002/bit.260300806

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

年代:1987

数据来源: WILEY

摘要:

AbstractA theoretical study has been carried out on the evaluation of the apparent half‐life of immobilized enzyme activity during continuous reaction both in a plug‐flow reactor (PFR) and in a continuous‐flow stirred‐tank reactor (CSTR). Two apparent half‐lives have been defined: the elapsed time at which the feedrate becomes half of the initial one when the feedrate of the substrate solution is lowered to keep the conversion fixed (constant‐conversion policy), and the elapsed time at which the conversion becomes half of the initial one when the feedrate (or space velocity) is kept constant (constant‐feedrate policy or constant‐space‐velocity policy). Under no intraparticle diffusional limitation, the constant‐conversion policy of operation in the PFR and CSTR gives the same half‐life as that of the enzyme inactivation regardless of the formula of the reaction rate, and the constant‐feedrate policy of operation in the PFR and CSTR offers the same half‐life as that of the enzyme inactivation only when the reaction is zero‐order. Under intra‐particle diffusional limitation, apparent half‐lives are always greater than that of enzyme denaturation, depending on many factors such as order of reaction, feeding policy (constant‐conversion and constant‐feedrate policies), initial conversion, and bioreactor configuration. It is suggested to perform the continuous operation with changing feedrate to keep the conversion (or outlet substrate concentration) fixed under the domain of zero‐order kinetics so as to obtain an apparent half‐life as close

ISSN:0006-3592    

DOI:10.1002/bit.260300807

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

年代:1987

数据来源: WILEY

摘要:

AbstractActual laboratory data obtained from steady‐stateDunaliella tertiolectacultures grown under a wide range of photon flux densities were used in a simple model to calculate daily production in a conventional algal mass culture system. In spite of large physiological and biochemical variations between low‐light‐ (LL) and high light‐ (HL) adapted cultures, the overall calculated daily productivity is almost identical for both strains grown at optimal conditions. When production of fine biochemicals is considered, however, a hypothetical HL strain, which cannot shade adapt, is advantageous. Based on biochemical and biophysical analysis ofD. tertiolectaresponses to growth irradiance levels, specific targets are defined for genetic manipulation to enhance productivity in algal mass culture systems. The targets identified are (1) amplification of the carboxylation enzyme ribulose‐1,5‐bisphosphate carboxylase‐oxygenase relative to the electron transport complexes, which should increase photosynthetic capacity at light saturation, and (2) enlargement of the light‐harvesting complexes by varying their pigment composition in order to increase light harvesting at low photon

ISSN:0006-3592    

DOI:10.1002/bit.260300808

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

年代:1987

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260300809

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

年代:1987

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260300810

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

年代:1987

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260300811

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

年代:1987

数据来源: WILEY