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Published: Kem. Ind. 53 (1) (2004) 7–24
Paper reference number: KUI-19/2002
Paper type: Review
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Scale-up Criteria of Bioreactor

B. Šantek, S. Novak, P. Horvat and V. Marić+


Differences between transport and kinetics phenomena in different bioreactor volumes are related to the bioreactor scale-up problems. These phenomena, together with differences between great number of specific bioprocesses, are the main reasons for the fact that a general scale-up procedure is not established. In this work, the scale-up problems of bioreactor with pseudohomogeneous bioprocess (homogeneous distribution of microorganisms and suspended particles in medium) were considered. The criteria for the scale-up of bioreactor with pseudohomogeneous bioprocesses and their relations to the system and bioprocess parameters were studied. The most often used criteria for the scale-up of bioreactor with pseudohomogeneous bioprocesses are: geometrical similarity, mixing or circulation time, residence or circulation time distribution, specific power input, Reynolds rotation number or stirrer tip speed. Relations between these criteria and bioreactor process parameters for different experimental conditions and bioreactor constructions were presented and considered. Characteristic times of different processes during yeast biomass production were presented as examples to illustrate their range in industrial bioreactor (Table 1) and to show which process parameters could have significant influence on the scale-up of bioreactor. Industrial bioprocesses are mainly characterised by heterogeneous distribution of system components. Mass, heat or momentum balances have to be established for description of the system heterogeneity. Aerobic bioprocesses are the most numerous group of heterogeneous bioprocesses. The most often used criterion in the bioreactor scale-up procedure with žrobic bioprocesses, which are conducted in stirred tank bioreactor (Fig. 1), is volumetric oxygen transfer rate coefficient (kLa). Its relations to different bioprocess and system parameters were studied in details. In this work, criteria for the scale-up of bioreactors where mixing is performed by air (Fig. 2) or pump (Fig. 3) were also considered. Besides the geometrical and hydrodynamic similarity for successful bioreactor scale-up it is necessary to obtain the physiological similarity of the bioprocess in laboratory and industrial scale. Therefore, the bioprocesses with flocs, pellets and microbial biofilm were also studied. For these bioprocesses, mathematical relations between bioprocess and system parameters were also presented. For mathematical description of phenomena in heterogeneous systems structured models are most often used. These models are characterised by mass or heat balances which are most often established according to the physical mixing models with ideally mixed compartments – cascades (Fig. 4). Mass or heat balance equations usually define relations between bioprocess and system parameters. Obtained mathematical models are very often used with other criteria in the scale-up of bioreactor with heterogeneous systems.

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pseudohomogenuous and heterogeneous bioprocesses, bioreactors, structured models, scale-up criteria of bioreactor