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1.
Accurate and reliable models are required for a range of unit operations if simulations are to be used for accelerating the design and optimisation of bioprocesses. This paper presents results of pilot-plant studies that have been used to verify process simulations for a sequence of operations comprising of cell disruption, fractional protein precipitation and centrifugal separation. These have been tested using the purification of the enzyme alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae as being representative of the recovery of a labile intracellular enzyme. Comparison of pilot-plant against simulated data highlights where improvements to the models are required and has resulted in increased confidence in the simulations for a wide range of conditions including the operational scale and the nature of the starting material. Results demonstrate the effectiveness of the verification approach for the development of reliable predictive models to assess the feasibility of process designs and performance of a train of bioprocess operations. UCL is the Biotechnology and Biological Sciences Research Council's sponsored Advanced Centre for Biochemical Engineering and the Council's support is gratefully acknowledged. The authors would like to thank I Ms. N. Abidi for technical assistance.  相似文献   
2.
The use of a continuous, low-frequency conditioning process to alter the structure of protein precipitate aggregates is examined. An increase in the density of aggregates is correlated with the levels of fluid acceleration and hence hydrodynamic stress to which the aggregates are exposed during conditioning. A combination of low-frequency conditioning followed by shear break-up (as in the feed zone to a high-speed disk-stack centrifuge) is shown to result in a precipitate suspension of increased particle size at the fine end of the distribution, and having a greater sedimentation velocity. The resistance of large aggregates to shear disruption is increased by low-frequency conditioning.List of Symbols CR conditioning ratio - CRS conditioning ratio after shearing - d m amplitude of displacement - D m particle size - D c m critical size for centrifuge recovery - f s–1 frequency of vibration - G s–1 mean velocity gradient - Q m3/s volumetric throughput - SR shear ratio - t s ageing time Greek Symbols s–1 mass-average shear rate - K sedimentation shape factor - a kg/m3 aggregate density - f kg/m3 fluid density - s kg/m3 solids density - kg/m3 aggregate-suspension density difference - Ns/m2 kinematic viscosity - amplitude of pulse ratio (ref. 23, 9) - s mean residence time - s solids volume fraction  相似文献   
3.
The biocontrol properties of Trichoderma species are well documented, but their effectiveness in antagonism of the problematic Sclerotium cepivorum, the causal agent of white rot in Allium species, appears limited with reports of significant control only relating to deliberately-mutated strains of Trichoderma. Our previous studies have indicated the possibility of using selected naturally-occurring strains of the antagonist in the suppression of other diseases; now in vitro and controlled environment in vivo studies have indicated that a degree of control of Onion White Rot is possible, and that the selected antagonist strains can be used in integrated treatments with Iprodione to good effect. The possible value of such treatments is considered in light of other approaches to the suppression of this continuing problem.  相似文献   
4.
The refolding of recombinant protein from inclusion bodies expressed in Escherichia coli can present a process bottleneck. Yields at industrially relevant concentrations are restricted by aggregation of protein upon dilution of the denatured form. This article studies the effect of five factors upon the dilution refolding of protein in a twin impeller fed-batch system using refold buffer containing only the oxidized form of the redox reagent. Such a buffer is easier to prepare and more stable than a buffer containing both reduced and oxidized forms. The five factors chosen were: bulk impeller Reynolds number, mini-impeller Reynolds number, injection rate of denatured protein, redox ratio, and guanidine hydrochloride (GdHCl) concentration. A 2(5) factorial experiment was conducted at an industrially relevant protein concentration using lysozyme as the test system. The study identified that in the system used, the guanidine hydrochloride concentration, redox ratio, and injection rate were the most important factors in determining refolding yields. Two interactions were found to be important: redox ratio/guanidine hydrochloride concentration and guanidine hydrochloride concentration/injection rate. Conditions were also found at which high refolding yields could be achieved even with rapid injection and poor mixing efficiency. Therefore, a comparative assessment was carried out with minimal mixing in a simple batch-refolding mode of operation, which revealed different behavior to that of fed-batch. A graphical (windows of operation) analysis of the batch data suggested that optimal yields and productivity are obtained at high guanidine hydrochloride concentrations (1.2 M) and redox ratios of unity or greater.  相似文献   
5.
This paper evaluates a prototype agarose-based affinity adsorbent utilizing a bound synthetic ligand designed to replace Protein A as an IgG-affinity capture resin and compares its purification characteristics with four commercially available matrices for the recovery of polyclonal antibodies from crude hyperimmune ovine serum. The novel adsorbent was found to show the highest dynamic capacity (29.2 mg/mL) of all matrices under evaluation--30% higher than the other commercial adsorbents evaluated. When using a post-load caprylic acid wash, IgG yields of over 85% and purities of over 90% were achieved consistently over multiple loading cycles. To evaluate bead diffusion, inverted confocal microscopy was used to visualise fluorescent antibody binding on to individual adsorbent beads in real time. The results indicate that the binding characteristics of the prototype adsorbent are similar to those obtained with Protein G Sepharose. This study indicates that the high-capacity prototype matrix is a feasible and potentially cost-effective alternative for the direct capture of antibodies from crude ovine serum and may therefore also be applicable to the purification of other complex industrial feedstocks such as transgenic milk or monoclonal antibodies expressed using recombinant technologies.  相似文献   
6.
This article describes the rapid prediction of recovery process performance for a new recombinant enzyme product on the basis of a broad portfolio of computer models and highly targeted experimentation. A process model for the recombinant system was generated by linking unit operation models in an integrated fashion, with required parameter estimation and physical property determination accomplished using data from scale-down studies. This enabled the generic modeling framework established for processing of a natural enzyme from bakers' yeast to be applied. An experimental study of the same operations at the pilot scale showed that the process model gave a conservative prediction of recombinant enzyme recovery. The model successfully captured interactions leading to a low overall product yield and indicated the need for further study of precipitate breakage in the feed zone of a disc stack centrifuge in order to improve performance. The utility of scale-down units as an aid to fast model generation and the advantage of integrating computer modeling and scale-down studies to accelerate bioprocess development are highlighted.  相似文献   
7.
A rapid method for designing integrated bioprocesses, using a combination of a windows of operation and a Pareto optimisation approach, is described in this paper. Within bioprocesses, multiple objectives are common, and achieving a satisfactory trade-off amongst the design objectives is crucial. Conventional optimisation results in the identification of the best operating policy for a given desired performance but gives little insight into how the process performance changes in the vicinity of the solution. In this paper, we explore the use of a Pareto optimisation technique to locate the optimal conditions for an integrated bioprocessing sequence and the benefits of first reducing the feasible space by the development of a series of windows of operation to provide a smaller search area for the optimisation. The final results are then presented in performance trade-off graphs and look-up tables, which give the design engineer an easily manageable solution set to work with. In this way, the decision-making procedure for design is made faster and more transparent. Two case studies illustrate the results from this integrated design methodology, some of which are counter-intuitive compared with the general design experience.  相似文献   
8.
Summary : FT is a tool written in C++, which implements the Fourier analysis method to locate periodicities in aminoacid or DNA sequences. It is provided for free public use on a WWW server with a Java interface. Availability : The server address is http://o2.db. uoa.gr/FT Contact : shamodr@atlas.uoa.gr   相似文献   
9.
This paper reports how financial and operational results from bioprocess simulations can be combined with other criteria pertinent to decision-making predictions to provide a more holistic approach to the evaluation of biomanufacturing alternatives. The classical additive weighting method, which is a multiattribute decision-making technique that can account for both the quantitative and qualitative parameters that ultimately need to be considered, is used. Its application is demonstrated through a case study that addresses whether start-up companies should invest in a stainless steel pilot plant or use disposable equipment for the production of early phase clinical trial material. The technique is extended to allow for uncertainty in parameters. An illustration of its use to compare alternatives based on cumulative frequency curves of the aggregate scores is provided. For cases where it is difficult to discriminate between the options, plots of risk versus reward are shown to be useful for identifying the best alternative based on the risk preference of the company's management.  相似文献   
10.
This paper presents the application of a decision-support tool, SIMBIOPHARMA, for assessing different manufacturing strategies under uncertainty for the production of biopharmaceuticals. SIMBIOPHARMA captures both the technical and business aspects of biopharmaceutical manufacture within a single tool that permits manufacturing alternatives to be evaluated in terms of cost, time, yield, project throughput, resource utilization, and risk. Its use for risk analysis is demonstrated through a hypothetical case study that uses the Monte Carlo simulation technique to imitate the randomness inherent in manufacturing subject to technical and market uncertainties. The case study addresses whether start-up companies should invest in a stainless steel pilot plant or use disposable equipment for the production of early phase clinical trial material. The effects of fluctuating product demands and titers on the performance of a biopharmaceutical company manufacturing clinical trial material are analyzed. The analysis highlights the impact of different manufacturing options on the range in possible outcomes for the project throughput and cost of goods and the likelihood that these metrics exceed a critical threshold. The simulation studies highlight the benefits of incorporating uncertainties when evaluating manufacturing strategies. Methods of presenting and analyzing information generated by the simulations are suggested. These are used to help determine the ranking of alternatives under different scenarios. The example illustrates the benefits to companies of using such a tool to improve management of their R&D portfolios so as to control the cost of goods.  相似文献   
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