Bioprocess design problems are frequentlymultivariate and complex. However, they may be visualised by a graphical representation of the design constraints and correlations governing both the process and system under consideration, namely windows of operation. Windows of operation exist at all stages of process design and find use both in the identification of key constraints from limited information, and also, with more detailed knowledge, the sensitivity of a process to design or operating changes. In this way windows of operation may be used to help understand and optimise a bioprocess design. In this paper the formulation, development and application of windows of operation is discussed for a range of biological processes including fermentation, protein recovery and biotransformation.
1 introduction
Many of the process design problems tackled by biochemical engineers are complex in nature. In some instances design decisions are made on the basis of rules of thumb or heuristics, whilst in others design information exists so that a unique design solution may be obtained. Often the design solution will represent a compromise, based for example on a target selling price where a trade-off between yield and purity must be sought. Identifying the best design, and also determining the relative sensitivity of the solution to the variables governing a system is not a trivial task. Recently several attempts at making the bioprocess design activity more structured have been presented including the use of heuristics for protein recovery sequences [1] and intelligent-knowledge based systems (IKBS) for both protein recovery sequences [2] and biotransformation processes [3,4]. However, while these techniques enable initial design decisions to be made the interaction of operating variables and of each operation with the subsequent one in the process require a more detailed examination of the effect of operating variables on design