摘要:

AbstractA perfusion culture system was developed to investigate the oxygenation of high‐density hybridoma cell cultures. The culture system was composed of a stirred‐tank bioreactor and an external microfiltration hollow fiber cartridge for medium perfusion. Cell growth and antibody production were examined with large bubble (≈5 mm in diameter), micron‐sized bubble (≈ 80 μm in diameter), and silicone tubing oxygenation techniques. Comparable cell growth and monoclonal antibody (MAb) production were found for both the micron‐sized and large oxygenation methods, provided that large bubbles were enriched with pure oxygen. Relatively low cell growth and MAb production were attained with the bubble‐free silicone tubing oxygenation. It is concluded that direct bubble oxygenation can be applied successfully in high‐density animal cell cultures, provided that the culture medium is supplemented with Pluronic F‐68. The accumulation of ammonia in the culture medium rather than oxygen limitation was found to be one of the possible problems that eventually inhibited cell growth. This and the fouling of the filtration cartridge during long‐term cultivation were found to be more problematic than simple bubble oxygenation of high‐density cell culture. The micron‐sized bubble oxygenation method is highly recommended for high‐density animal cell cultures, provided that Pluronic F‐68 is supplemented into the culture medium.

ISSN:0006-3592    

DOI:10.1002/bit.260410702

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe purpose of this study is to investigate the feasibility of biologically removing phenol from waste gases by means of a biofilter using aPseudomonas putidastrain. Two series of both batch and continuous tests have been performed in order to ascertain the microbial degradation of phenol. For the preliminary batch tests, carried out in order to test the effective feasibility of the process and to investigate their kinetic behavior, two different microbial cultures belonging to thePseudomonasgenus have been employed, a heterogeneous culture and a pure strain ofP. putida. The results of these comparative investigation showed that the pure culture is more efficient than the mixed one, even when the latter has undergone three successive acclimatization tests. The continuous experiments have been conducted during a period of about 1 year in a laboratory‐scale column, packed with a mixture of peat and glass beads, and utilizing the pure culture ofP. putidaas microflora and varying the inlet phenol concentration from 50 up to 2000 mg m−3. The results obtained show that high degrees of conversion can be obtained (0.93/0.996) operating at a residence time of 54 s. © 1993 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410703

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe anaerobic digestion of cheese whey was studied in a UASB reactor. The profiles of the reactor, i.e., the distributions of the substrate concentration and pH under different operating conditions were developed. From the concentrations of substrates measured at various levels above the bottom of the reactor, two reaction stages, namely acidogenesis and methanogenesis, were distinguished. The instability caused by high influent concentration was interpreted as the accumulation of VFAs in the acidogenic stage beyond the assimilative capacity of the methanogenic stage. A range of stable operating conditions was predicted from the results of the profile measurements. The optimal influent concentration was found to be between 25 and 30 g COD/L at an HRT of 5 days for system stability. Other options fro stability control were discussed. © 1993 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260410704

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

年代:1993

数据来源: WILEY

摘要:

AbstractA genetically structured mathematical model of thetrpoperon based on known molecular interactions of aporepressor, corepressor, and inducer is proposed. The model simulates, both qualitatively and quantitatively, the influence of these regulatory species on the extent of repression and expression of cloned gene products. It shows that at low aporepressor concentration, full repression is not possible even with high tryptophan levels, resulting in leaky expression. Calculations based on the model enabled predictions of optimum levels of aporepressor and tryptophan for effective repression and, concurrently, the β‐indoleacrylic acid concentrations required for induction for both low and high plasmid copy number clones. Using the model we attempted to provide explanations for seemingly anomalous and sometimes contradictory observations by researchers when working with thetrppromoter. © 1993 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410705

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

年代:1993

数据来源: WILEY

摘要:

AbstractBased on the reported mechanisms for filamentous growth, a simple morphologically structured growth model is set up. The model may describe the growth of filamentous microorganisms both on a solid medium and in a submerged culture. For description of a submerged culture the model is combined with a simple population model, which is derived from a balance for the distribution function for the hyphal elements. The model is compared with experimental data for three species of filamentous microorganisms:Geotrichum candidum, Streptomyces hygroscopicus, and Penicillium chrysogenum. © 1993 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260410706

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

年代:1993

数据来源: WILEY

摘要:

AbstractOne of the least understood processes affecting biofilm accumulation is detachment. Detachment is the removal of cells and cell products from an established biofilm and subsequent entrainment in the bulk liquid. The goal of this research was to determine the effects of shear stress and substrate loading rate on the rate of biofilm detachment.MonopopulationPseudomonas aeruginosaand undefined mixed population biofilms were grown on glucose in a RotoTorque biofilm reactor. Three levels of shear stress and substrate loading rate were used to determine their effects on the rate of detachment. Suspended cell concentrations were monitored to determine detachment rates, while other variables were measured to determine their influence on the detachment rate. Results indicate that detachment rate is directly related to biofilm growth rate and that factors which limit growth rate will also limit detachment rate. No significant influence of shear on detachment rate was observed.A new kinetic expression that incorporates substrate utilization rate, yield, and biofilm thickness was compared to published detachment expressions and gives a better correlation of data obtained both in this research and from previous research projects, for both mono‐ and mixed‐population biofilms. © John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410707

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

年代:1993

数据来源: WILEY

摘要:

AbstractEffective diffusivity of lactose in active acidogenic biofilms was measured at 35°C and pH 4.6 with a specially designed diffusion cell. The diffusion cell was designed and operated in such a way that the lactose concentrations on the surface and at the center of a living bacterial aggregate could be measured at steady state. As a model parameter in a widely accepted reaction–diffusion equation which describes lactose distribution in living biofilms, the effective diffusivity of lactose in the biofilms was found to be about 65% of the lactose diffusivity in free solutions. It was experimentally determined that the active biofilms had about 66% void volume made up of channels through which the lactose molecules were transported into the bacterial aggregates. Therefore, the decrease in lactose diffusivity was mainly caused by the biofilm's solid biomass fraction rather than the tortuosity of the channels. © 1993 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260410708

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

年代:1993

数据来源: WILEY

摘要:

AbstractData on viscous (η′) and elastic (η″) components of the complex viscosity versus oscillatory angular frequency (0.01 to 4.0 rad/s) with increasing strains were obtained for hybridoma cell (62′D3) and HeLa cell (S3) suspensions in PBS at 0.9 (mL/mL) cell volume fraction using a Weissenberg rheogoniometer equipped with two parallel plate geometry at ambient temperature. Both cell suspensions exhibited shear thinning behavior. From the measured viscoelastic properties, the yield stress was calculated. Hybridoma cell suspension (15 μm as the mean diameter of cells) showed the yield stress at 550 dyne/cm2that was 1.8 times higher than the value of HeLa cell suspension (22 μm mean diameter) as measured at the oscillatory angular frequency, 4.0 rad/s. The apparent viscosities of HeLa cell suspension at four concentrations and varying steady shear rate were also determined using the Brookfield rotational viscometer. The yield stress to steady shear test was about 130 dyne/cm2for HeLa cell suspension at 0.9 (mL/mL) cell volume fraction. The apparent viscosity was in the range about 1 ∼ 1000 Poise depending on the cell concentration and shear rate applied. A modified semiempirical Mooney equation,\documentclass{article}\pagestyle{empty}\begin{document}$ \eta = \eta _0 \exp [K\dot \gamma ^{ - \beta } \phi /(1 - K''\sigma \phi _c /D)] $\end{document}was derived based on the cell concentration, the cell morphology, and the steady shear rate. The β, shear rate index, was estimated as 0.159 in the range of shear rate, 0.16 to 22.1 s−1, for the cell volume fractions from 0.6 to 0.9 (mL/mL). In this study, the methods of determining the shear sensitivity and the viscous and the elastic components of mammalian cell suspensions are described under the steady shear field. © 1993 John

ISSN:0006-3592    

DOI:10.1002/bit.260410709

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

年代:1993

数据来源: WILEY

摘要:

AbstractA linear absorption model (LAM) is used to describe the process of metal binding to spherically shaped biopolymers particles. The LAM was solved using a numerical algorithm which calculates diffusivities of metal ion in biopolymer gels. It assumes attainment of rapid metal‐biopolymer binding equilibrium accompanied by rate limiting diffusion of the metal ions through the gel. The model was tested using batch experiments in which copper (Cu2+) binding with calcium alginate beads was investigated. Biopolymer density in the beads was varied between 2% and 5%. The diffusion coefficient of Cu2+calculated from the LAM ranged from 1.19 × 10−9to 1.48 × 10−9m2s−1(average 1.31 ± 0.21 × 10−9m2s−1), independent of biopolymer density. The LAM has theoretical advantages over the shrinking core model (shell progressive model). The latter calculated an unreasonable exponential increase in the diffusion coefficient as density of alginate polymer in the bead increased. © 1993 John

ISSN:0006-3592    

DOI:10.1002/bit.260410710

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

年代:1993

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260410701

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

年代:1993

数据来源: WILEY