In biocatalytic multiphase processes, the required oxygen is often supplied via aeration with bubbles of the liquid phase. In case of insufficient oxygen mass transfer into the liquid phase, kinetic limitations may occur. An aeration using fine bubbles with a large volume specific interfacial surface area enables significantly enlarged contact areas between both phases and improved volumetric mass transfer coefficients.
In stirred tank reactors (STR), higher volumetric mass transfer coefficients as well as reaction rates of biocatalytic reactions can be achieved by fine bubble aeration compared to macroscopic aeration. However, the recyclability of enzymes is a common challenge . In a new approach, a rotating bed reactor (RBR) is expected to provide a suitable environment for enzymes. In such a set-up, the enzymes can be immobilized on a packing material inside a rotating bed. The immobilization ensures the recyclability of enzymes and maintains their stability during the process . Moreover, higher yields from biocatalytic reactions are expected compared to an STR, as already shown for liquid-liquid systems .