摘要:

AbstractAn automated analysis system for on‐line fermentation monitoring is presented. The modular system consists of an in‐line sterilizeable crossflow microfilter, a selection valve that allows injection of sample or standards, a degassing unit, a dilution module, and a FIA manifold with a spectrophotometric UV/VIS detector. In the dilution module samples are conditioned and diluted depending upon concentration of analyte and the working range of the analyzer. Methods for the monitoring of glucose, ethanol, ammonia and phosphate are described. Results from the monitoring of glucose and their use in fermentation control are presented. The maximal analysis frequency is 30 samples per hour including the dilution of 1 : 200. Detection limits are 5 mg/L for ethanol and glucose, 1 mg/L for phosphate and 50 mg/L for ammo

ISSN:0006-3592    

DOI:10.1002/bit.260340402

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of temperature on the hydrolysis of lactose by immobilized beta‐galactosidase were studied in a continuous flow capillary bed reactor. Temperature affects the rates of enzymatic reactions in two ways. Higher temperatures increase the rate of the hydrolysis reaction, but also increase the rate of thermal deactivation of the enzyme. The effect of temperature on the kinetic parameters was studied by performing lactose hydrolysis experiments at 15, 20, 25, 30, and 40°C. The kinetic parameters were observed to follow an Arrhenius‐type temperature dependence. Galactose mutarotation has a significant impact on the overall rate of lactose hydrolysis. The temperature dependence of the mutarotation of galactose was effectively modelled by first‐order reversible kinetics. The thermal deactivation characteristics of the immobilized enzyme reactor were investigated by performing lactose hydrolysis experiments at 52, 56, 60, and 64°C. The thermal deactivation was modelled effectively as a first order decay process. Based on the estimated thermal deactivation rate constants, at an operating temperature of 40°C, 10% of the enzyme activity would be lost in

ISSN:0006-3592    

DOI:10.1002/bit.260340403

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe hydrolysis of lactose by immobilized β‐galactosidase was studied in a continuous‐flow capillary bed reactor operating at 30°C. Solutions containing 50, 100, and 150 g lactose and 0.5 g sodium acetate/L were fed to the reactor. Lactose conversions ranging from 24% to greater than 99% were achieved at reactor space times ranging from 0.06 to 6.3 min. These conversion data were successfully modeled in terms of a plug flow reactor model and a form of Michaelis–Menten kinetics which included competitive inhibition by both the alpha and beta forms of ga

ISSN:0006-3592    

DOI:10.1002/bit.260340404

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

年代:1989

数据来源: WILEY

摘要:

AbstractAlthough cross‐flow membrane filtration is a very attractive option for harvesting cells and recovering enzymes from cell homogenates, the process is not without its problems. Foremost of these is the deposit of dissolved and suspended solutes onto the membrane surface during operation. The formation of these dense and sometimes compressive sublayers (often called cakes) offers additional resistance to axial and permeate flows and often affects the retention characteristics of the process. In view of the complex nature of the sublayer formation process and its sensitivity to cross‐flow velocity, this investigation was undertaken to determine the main factors responsible for the decline in performance during the harvesting ofB. polymyxabroth by membrane microfiltration. System parameters varied include axial flow rate, concentration of cells, proteins and other components in the feed, membrane materials (ceramic, polypropylene, and stainless steel), and cleaning methods. To help explain the observed results, a new mass transport model—the solids flux model—based on the assumptions that back migration of particles from the sublayer or membrane surface is negligible and that particles that reach the solid–solution interface attach (stick) completely, is tested. Using a variety of diagnostic methods, magnesium ammonium phosphate precipitate is formed during steam sterilization of the medium and is implicated as the major foulant in t

ISSN:0006-3592    

DOI:10.1002/bit.260340405

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

年代:1989

数据来源: WILEY

摘要:

AbstractIt is very important to understand the equilibrium and dynamic characteristics of biospecific adsorption (affinity chromatography) for both scientific and application purposes. Experimental equilibrium and dynamic column data are presented on the adsorption of lysozyme onto antibody immobilized on nonporous silica particles. The Langmuir model is found to represent the equilibrium experimental data satisfactorily, and the equilibrium association constants and heats of adsorption have been estimated for two systems with different ligand densities. The effects of nonspecific interactions are more pronounced in the system with low‐density ligand. The dynamic interaction kinetic parameters are estimated by matching the predictions of a fixed‐bed model with the experimental breakthrough curves. The agreement between theory and experiment is good for the initial phases of breakthrough, where the mechanism of biospecific adsorption is dominant. In the later phase (saturation neighborhood) of breakthrough, the effects of nonspecific interactions appear to be greater in the low‐density ligand system. The kinetics of the nonspecific interactions were estimated from the data of the later phase of breakthrough and were found to be considerably slower than those attributed to biospecific adsor

ISSN:0006-3592    

DOI:10.1002/bit.260340406

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

年代:1989

数据来源: WILEY

摘要:

AbstractSimple models are of great value in order to simulate cell dynamics, and a class of potentially useful models are the so‐called compartment models, which are a simple extension of the unstructured approach. Compartment models have earlier been used with great success to describe cell dynamics. In this article the authors present a 4‐compartment model that is able to describe a majority of the observations that have been made through fermentations with recombinant microorganisms. The compartment model is especially suited for description of dynamic changes in plasmid copy number, e.g., runaway replication. Simulation of batch fermentation with runaway conditions corresponds very well with experimental results. Finally the model is used in the design of an optimal fermentation strategy in a C

ISSN:0006-3592    

DOI:10.1002/bit.260340407

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

年代:1989

数据来源: WILEY

摘要:

AbstractA shrinking‐core mathematical model describing bioleaching of lead sulfide is developed considering the deposition of insoluble bio‐oxidation products on metal sulfide particle surfaces. Variations in particle size are considered as it affects diffusion limitati

ISSN:0006-3592    

DOI:10.1002/bit.260340408

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

年代:1989

数据来源: WILEY

摘要:

AbstractA framework using material balances in metabolic pathways to study cellular metabolism is examined and the results are discussed. Rate measurements on extracellular compounds alone were found to be not always sufficient to validate proposed unique intracellular mechanisms. The conditions to delineate among candidate mechanisms based solely on extracellular measurements are established. The number of half reactions comprising the reaction network is found to be an important parameter.

ISSN:0006-3592    

DOI:10.1002/bit.260340409

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

年代:1989

数据来源: WILEY

摘要:

AbstractSelectedDigitalis lanatacell lines cultivated in 1‐L shake flasks or 20‐L airlift bioreactors converted β‐methyldigitoxin into β‐methyldigoxin with almost no side reactions. This biotransformation process was optimized with regard to substrate supply and culture medium composition, and was then scaled up to a volume of 210 L using a 300‐L airlift bioreactor. A semicontinuous process was developed in which 513.3 g β‐methyldigoxin were produced after 89 days

ISSN:0006-3592    

DOI:10.1002/bit.260340410

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

年代:1989

数据来源: WILEY

摘要:

AbstractKinetic studies are presented for the growth and fermentation of the yeastPichia stipitiswith xylose as the carbon source. Ethanol is produced from xylose under anaerobic as well as under oxygen‐limiting conditions but only at dissolved oxygen concentrations up to 3 μmol/L Maximum yields and production rates were obtained under oxygen‐limiting conditions, where the xylose metabolism may be considered to be consisted of three different components (assimilation, respiration, fermentation). The contribution of each pathway is determined by the availability of oxygen and the energy yield of each pathway. In order to describe the course of oxygen‐limited fermentations, a mathematical model has been developed with the assumption that growth is coupled to the energy production. The resulting model requires only four independent parameters (Y x/O 2, Y ATPmax,mATP, andP/O). These parameters were estimated on the basis of eight separate batch f

ISSN:0006-3592    

DOI:10.1002/bit.260340411

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

年代:1989

数据来源: WILEY