Regime analysis and scale-down: Tools to investigate the performance of bioreactors

Scale-up and optimization of biotechnological processes on a large scale tend to be more methodically approached than the application of rules of thumb, experience, and trial and error. Methods frequently used in chemical engineering are adopted in biochemical engineering and are employed with great effect. A summary is given of methods and rules of thumb used in scaling up chemical processes. A procedure to scale up and optimize bioreactors is presented. It is based on the so-called scale-down approach. Some elements of this procedure, viz. theoretical regime analysis and small-scale investigations, are extensively demonstrated by examples. It is shown that a regime analysis based on characteristic times can give a quick estimation of the performance of bioreactors. Small-scale experiments based on the result of such analysis or on the results of a dimensional analysis can give valuable information for scale-up or optimization fermentation processes.