Engineering downstream processing

It is not a bad idea for the process engineer to familiarize himself with compressor surge controls. The interaction of the compressor surge controls with downstream process control valves can become a problem area later, and this study phase is not too early to put such items on a checklist. An LNG plant example comes to mind where such an operating problem existed. 

Jones, A.G., 1985b. Crystallization and downstream processing interactions. In POW-TECH 85, Institution of Chemical Engineers. Sympos. Ser. No. 91. Rugby Institution of Chemical Engineers, pp. 1-11. 

Biocatalysts in nature tend to be optimized to perform best in aqueous environments, at neutral pH, temperatures below 40 °C, and at low osmotic pressure. These conditions are sometimes in conflict with the need of the chemist or process engineer to optimize a reaction with respect to space-time yield or high product concentration in order to facilitate downstream processing. Furthermore, enzymes and whole cells are often inhibited by products or substrates. This might be overcome by the use of continuously operated stirred tank reactors, fed-batch reactors, or reactors with in situ product removal [14, 15]. The addition of organic solvents to increase the solubility of substrates and/or products is a common practice [16]. 

As much as a quarter of a flexible foam block can be wasted in downstream processing into flnished products. Thanks to the efforts of process technologists and engineers, this scrap material can be recycled by at least 17 basic methods. However, only a few have found significant practical applications. Most other PU scrap ends up as uncollectable domestic waste with perhaps one key exception, materials from end-of-life vehicles. WESTERN EUROPE-GENERAL Accession no. 709465... 

Before the details of a particular reactor are specified, the biochemical engineer must develop a process strategy that suits the biokinetic requirements of the particular organisms in use and that integrates the bioreactor into the entire process. Reactor costs, raw material costs, downstream processing requirements, and the need for auxiliary equipment will all influence the final process design. A complete discussion of this topic is beyond the scope of this chapter, but a few comments on reactor choice for particular bioprocesses is appropriate. 

TMPase acts to dephosphorylate both TMP and its precursor dUMP, forming a mixture of TdR and 2 -deoxyuridine (UdR). As a starting material for zidovudine synthesis, TdR must be essentially free of this impurity, which would pass through the manufacturing process to form a demethylated analogue of zidovudine. Separation of TdR and UdR requires difficult and costly downstream processing hence, the key to a commercial process is metabolic engineering to minimize biosynthetic UdR. 

The chemical route to orlistat was ultimately favoured over the biosynthetic route as the latter required complex downstream processing that eliminated the benefits gained from the biotransformation itself. More recent advances in metabolic engineering and drownstream processing might have resulted in the development of a more competitive process. 

Two of the more recent such approvals are that of Ovitrelle and Luveris. Ovitrelle is the trade name given by Serono to its recombinant hCG-based product. The producer is an engineered CHO cell line that has been co-transfected with the genes coding for both the hCG a- and P-subunits. Downstream processing entails a combination of several chromatographic and ultrafiltration steps and the final product is presented in freeze-dried form. Each vial of product contains 285 fig of active substance (hCG) and the product has been assigned a 2 year shelf-life. It is reconstituted with water for injections (WFI) immediately before use. 

Bell, D. J., Hoare, M. and Duimill, P. (1983) The formation of Protein Precipitates and Their Centrifugal Recovery. Downstream Processing. nAdv. Biochemical Engineering, edited by A.Fiechter, pp. 1-72. Berhn Springer-Verlag. 

Disparate elements, which affect economic decisions for bioprocesses, can be combined into a logical approach. An attempt must be made to combine fundamentals of bioreactor design, downstream processing, and properties of biomolecules in the context of process evaluation. The ability to set technical priorities based on economic assessment is essential, and requires communication betv/een researchers, process engineers, technical managers, and marketing managers. 

Cliffe, K., "Downstream Processing," in Biotechnology for Engineers, ed. A. Scragg. Chichester, England Ellis Horwood Ltd., 1988. pp. 302-321. 

H. P. Meyer, Continuous cell-recyde process for L-camitine production performance, engineering and downstream processing aspects compared with discontinuous processes, J. Biotechnol. 

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