摘要:

AbstractProduction of 2,3‐butanediol byKlebsiella oxytocais influenced by the degree of oxygen limitation. During batch culture studies, two phases of growth are observed: energy‐coupled growth, during which cell growth and oxygen supply are coupled; and, energy‐uncoupled growth, which arises when the degree of oxygen limitation reaches a critical value. Optimal 2,3‐butanediol productivity occurs during the energy‐coupled growth phase. In this article, a control system which maintains the batch culture at a constant level of oxygen limitation in the energy‐coupled growth regime has been designed. Control, which involves feedback control on the oxygen transfer coefficient, is achieved by continually increasing the partial pressure of oxygen in the feed gas, which in turn continually increases the oxygen transfer rate. Control has resulted in a balanced state of growth, a repression of ethanol formation, and an increase in 2,3‐butanediol productivity of 18%. © 1993 John W

ISSN:0006-3592    

DOI:10.1002/bit.260421102

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

年代:1993

数据来源: WILEY

摘要:

AbstractMicrobial production of 2,3‐butanediol byKlebsiella oxytocaoccurs under conditions of an oxygen limitation. The extent to which substrate is oxidized to 2,3‐butanediol and its coproducts, (acetic acid, acetoin, and ethanol) and the relative flow rates of substrate to energetic and biosynthetic pathways are controlled by the degree of oxygen limitation. Two energetic relationships which describe the response to an oxygen limitation have been derived. The first relationship describes the coupling between growth and energy production observed under oxygen‐limited conditions. This allows calculation of energetic parameters and modeling of the cell mass and substrate profiles in terms of the degree of oxygen limitation only. The second relationship describes the average degree of oxidation and the rate of the end‐product flow. The model has been tested with both batch and continuous culture. During these kinetic studies, two phases of growth have been observed: energy‐coupled growth, which was described above; and, energy‐uncoupled growth, which arises when the degree of oxygen limitation reaches a critical value. Optimal culture performance with respect to 2,3‐butanediol productivity occurs during energy‐coupled growth. © 1993 John

ISSN:0006-3592    

DOI:10.1002/bit.260421103

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

年代:1993

数据来源: WILEY

摘要:

AbstractIn many natural environments, bacterial populations experience suboptimal growth due to the competition with other microorganisms for limited resources. The chemotactic response provides a mechanism by which bacterial populations can improve their situation by migrating toward more favorable growth conditions. For bacteria cultured under suboptimal growth conditions, evidence for an enhanced chemotactic response has been observed previously. In this article, for the first time, we have quantitatively characterized this behavior in terms of two macroscopic transport coefficients, the random motility and chemotactic sensitivity coefficients, measured in the stopped‐flow diffusion chamber assay.Escherichia colicultured over a range of growth rates in a chemostat exhibits a dramatic increase in the chemotactic sensitivity coefficient forD‐fucose at low growth rates, while the random motility coefficient remains relatively constant by comparison. The change in the chemotactic sensitivity coefficient is accounted for by an independently measured increase in the number of galactose‐binding proteins which mediate the chemotactic signal. This result is consistent with the relationship between macroscopic and microscopic parameters for chemotaxis, which was proposed in the mathematical model of Rivero and co‐workers. © 1993 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260421104

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

年代:1993

数据来源: WILEY

摘要:

AbstractA grating coupler was used for the on‐line determination of monoclonal antibodies produced in perfused animal cell bioreactor. The device was connected with the culture vessel via a flow‐injection analysis (FIA) system, which was controlled automatically. Specific antimouse lgG antibodies were immobilized on the surface of the sensor‐chip. After injection of the sample, the binding of mouse lgG was observed in real time. The regeneration of the binding sites of the immobilized antibodies using an acidic solution allowed the on‐line detection of produced monoclonal antibodies in the range of 10 to 150 μg/mL. In contrast to other techniques coupled to bioprocesses, the developed method represents a regenerable direct immunosensor. Results were compared with standard ELISA techniques (off‐line) and a competitive immunochemical assay using the grating coupler (off‐line). © 1993 John Wi

ISSN:0006-3592    

DOI:10.1002/bit.260421105

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

年代:1993

数据来源: WILEY

摘要:

AbstractA series ofBombyx morinuclear polyhedrosis virus (Bm‐NPV) transfer vectors has been developed containing various lengths of the polyhedrin promoter, including sequences 3′ of the initiation codon. The ATG initiation codon was mutated in some of these vectors to allow for the production of authentic nonfusion proteins. The ability of the various polyhedrin promoter constructs to direct expression of foreign gene sequences was assessed using two test genes, chloramphenicol acetyl transferase (cat), and human metallothionein II. Accumulation ofcatmRNA and nonfused protein was low when only polyhedrin promoter sequences to –8 (relative to the translational start site of polyhedrin mRNA) were included in the transfer vector, butcatexpression was comparable with that of the wild‐type polyhedrin gene when promoter sequences to +5 were present. Further addition of polyhedrin gene sequences to +26 or +94 resulted in no further increase in expression. Similar results were obtained for expression of human metallothionein II, where constructs encoding polyhedrin–metallothionein fusion proteins containing polyhedrin sequences to at least +5 resulted in high levels of mRNA and protein accumulation. The expression vectors containing the +5, +26, or +94 BmNPV polyhedrin promoter can thus be used to direct maximal levels of production of nonfused proteins (when the polyedrin ATG has been mutated) or of fusion proteins, depending on which is more suitable for a particular application. These new vectors are a useful addition to those presently available and should increase the utility of the BmNPV expression system for large‐scale protein production. © 1993 John Wil

ISSN:0006-3592    

DOI:10.1002/bit.260421106

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

年代:1993

数据来源: WILEY

摘要:

AbstractA new method (named a “jumping spider”) is introduced for the optimization of slow biotechnological processes. The more traditional sequential experimentation (i.e., gradient search, simplex, etc.) is not well suited for slow dynamic processes, e.g., plant cell culture and differentiation. Therefore, a more simultaneous approach is proposed. A large number of initial experiments are performed, on the basis of which several of the initial experiments are selected as starting points. A search is then performed simultaneously from several gradient directions and the optimum is estimated by a quadratic approximation. In simulations, the spider generally climbs up the slopes quickly and the final estimator yields good maximum point estimates even on a complex topography. The spider may even approach more than one local maximum point simultaneously. As a model application, the average xylitol conversion rate ofCandida guilliermondiiwas optimized in relation to cultivation volume (oxygen availability) and the concentration of nitrogen and phosphorus in the medium. A threefold increase in xylitol production was obtained with three experimental steps. © 1993 John Wiley&Sons,

ISSN:0006-3592    

DOI:10.1002/bit.260421107

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis article presents an industrial case study, examining the application of a novel adaptive biomass estimator to an industrial microfungi production process. It is our intention that this contribution should focus upon the implementation issues of the algorithm, in preference to a rigorous theoretical development. The novel algorithm adopted is developed from Adaptive Inferential Estimation studies of Guilandoust and co‐workers. The technique utilizes input–output process measurements obtained at different frequencies, thereby providing more frequent estimates of biomass concentration than are otherwise available from off‐line laboratory analyses. The algorithm is particularly suited to the biotechnology industry, as it is capable of utilizing irregular assay measurements with varying delays.Although this article demonstrates the encouraging industrial implications of the adaptive algorithm, like all adaptive techniques currently developed, it is restricted by the inability to perform robust on‐line system identification. The ultimate selection of a “suboptimal” “fixed parameter” algorithm for on‐line implementation, is therefore directly attributable to these inadequacies. Aspects of data acquisition, data pretreatment, and data quality are critical for real process applications, and while some practical approaches are adopted here, many important implementation problems remain unresolved. © 1993 Jo

ISSN:0006-3592    

DOI:10.1002/bit.260421108

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

年代:1993

数据来源: WILEY

摘要:

AbstractSeveral experimental data on continuous cultures of hybridoma cells show that monoclonal antibody productivity is a decreasing function of dilution rate. It has been suggested that this unusual behavior may be due to the arrest of a fraction of cycling cells at a critical point of Phase G1. Although this hypothesis has been recently investigated by using population balance models, mathematical analysis has been performed without accounting for the dynamics of the arrested cells properly. In this article, a more general and accurate approach is presented and new specific assumptions are introduced to characterize the arrest and the later progress through the cycle. Two different models (stochastic and deterministic) and two different critical points for the arrest (at the beginning and at the end of G1) are considered. The cell cycle parameters are estimated so that data predicted by the model fit those reported in the literature. In particular, the fraction of arrested cells, the cell arrest probability, and the mean cell generation time are computed as functions of the dilution rate. Results so far obtained predict that there is an optimal value of dilution rate for maximizing specific production rate of monoclonal antibody. © 1993 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260421109

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

年代:1993

数据来源: WILEY

摘要:

AbstractA rapid two‐step procedure has been developed for the purification of Despro(2)‐Val15‐Leu17‐aprotinin from the culture supernatant of a recombinant yeast by affinity and ion‐exchange chromatography. DesPro(2)‐Val15‐Leu17‐aprotinin was purified to homogeneity, as demonstrated by dodecylsulfate gel electrophoresis and analysis of the N‐terminal amino acid sequence. © 1993 Jo

ISSN:0006-3592    

DOI:10.1002/bit.260421110

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis work describes investigations into the viability of cells growing on 3,4‐dichloroaniline (34DCA). Two bioreactors are employed for microbial growth, a continuous stirred tank (CST) bioreactor with a 2‐L working volume, and a three‐phase air lift (TPAL) bioreactor with a 3‐L working volume. Experiments have been performed at several dilution rates between 0.027 and 0.115 h−1in the CST bioreactor and between 0.111 and 0.500 h−1in the TPAL bioreactor. The specific ATP concentration was calculated at each dilution rate in the suspended biomass in both bioreactors as well as in the immobilized biomass in the TPAL bioreactor. The ATP was extracted from the cells using boiling tris‐EDTA buffer (pH 7.75), and the quantity determined using a firefly (bioluminescence) technique. The cultures were inspected under an electron microscope to monitor compositional changes. Results from the CST bioreactor showed that the biomass‐specific ATP concentration increases from 0.44 to 1.86 mg ATP g−1dry weight (dw) as dilution rate increases from 0.027 to 0.115 h−1. At this upper dilution rate the cells were washed out. The specific ATP concentration reached a limiting average value of 1.73 mg ATP g−1dw, which is assumed to be the quantity of ATP in 100% viable biomass. In the TPAL bioreactor, the ATP level increased with dilution rate in both the immobilized and suspended biomass. The specific ATP concentration in the immobilized biomass increased from approximately 0.051 mg ATP g−1dw at dilution rates between 0.111 and 0.200 h−1to approximately 0.119 mg ATP g−1dw at dilution rates between 0.300 and 0.500 h−1. This indicates that the immobilized biomass contained a viable cell fraction of around 5%. Based on these results, kinetic data for freely suspended cells should not be applied to the modeling of immobilized cell systems on the assumption that immobilized biomass is 100% viable

ISSN:0006-3592    

DOI:10.1002/bit.260421111

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

年代:1993

数据来源: WILEY