Design and Operation of Fixed-Bed Bioreactors for Immobilized Bacterial Culture

Fixed-bed processes operated in perfusion, where cells are immobilized within macroporous carriers, are a promising alternative to processes with suspended microbial or mammalian cells. Their potential has been demonstrated for many purposes. Nevertheless, the number of industrial fixed-bed processes is quite small. To some extent, this is due to the lack of process development tools for fixed-bed processes. To fill this gap, a strategy was developed for the design and evaluation of relevant process parameters of fixed-bed processes. A scale-up concept is presented in order to evaluate the performance as part of process design of fixed-bed processes. This comprises fixed-bed reactors on three different scales, the smallest being the downscaled Multiferm with 10 mL fixed-bed units, the second a 100 mL fixed-bed reactor, and the third a pilot-scale reactor with 1 L fixed-bed volume. The performance of this concept will be discussed for fixed-bed cultures of lactic acid bacteria. Furthermore, a reaction kinetic model for the design of fixed-bed reactors will be presented.