The effects of varying the levels of cell disruption achieved by high-pressure homogenization upon subsequent centrifugal separation of cell debris have been defined by measuring sedimentation velocity distributions of the cell debris. Using this data together with particle size distributions, a computer-based model of a disk stack centrifuge has been used to predict the efficiency of centrifugal separation. These predictions have been compared with both laboratory scale and pilot plant scale experimental results. A similar sedimentation velocity technique has been used to characterize the properties of the flocs formed by addition of poly(ethylene imine) to a borax-clarified homogenate supernatant. The variations of floc settling properties with respect to polymer concentration are defined.

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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. List of symbols

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