New developments in solid-state fermentation II. Rational approaches to the design, operation and scale-up of bioreactors

Over the last decade there has been a significant improvement in understand ing how to design, operate and scale-up solid-state fermentation bioreactor s. The key to these advances has been the application of mathematical model ing techniques to describe the biological and transport phenomena within th e system. This review focuses on the advances in understanding that have co me from this modeling work, and the insights it has given us into bioreacto r design, operation and scale-up. It also highlights two promising bioreact or designs that have emerged over the last decade or so. For processes in w hich the substrate bed must remain static throughout the fermentation, the most promising design is the Zymotis design of ORSTOM at Montpellier, Franc e, which involves closely spaced internal heat transfer plates within a pac ked-bed bioreactor. For those processes in which mixing can be tolerated, t he stirred bioreactor developed at INRA, in Dijon, France, has been success fully demonstrated at scales of 1-25 t of substrate. Theoretical work sugge sts that mathematical models will be useful tools in the scale-up process, however, there are no reports that they have been used in the development o f any current large-scale process. Rather, the models have been validated a gainst data obtained from laboratory-scale bioreactors. There is an urgent need to test the accuracy and robustness of the models by applying them wit hin real process development. (C) 2000 Elsevier Science Ltd. All rights res erved.