Fine Bubbles for Biocatalytic Processes: Microscale Phenomena and Novel Applications (DFG Project Number 501131738)
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 .
In the current project, a rotating bed reactor (SpinChem®, Sweden) aerated with fine bubbles is characterized with respect to fluid dynamics as well as the biocatalytic performance of glucose oxidase (GOX) enzymes immobilized in the rotating bed. Furthermore, to unveil the mechanisms behind the enhanced mass transfer and reaction yields, the local mass transfer phenomena from fine bubbles are studied in the scope of the current project. For this purpose, novel studies on single bubbles on a microscale are conducted, from which deep insights into the interactions of enzymes and fine bubbles are expected. A specifically for this purpose developed Lightsheet Fluorescence Microscope (LSFM, Rapp OptoElectronic GmbH) with a sufficiently thin laser sheet width of w =5 μm and an excitation wavelength of λ=488 nm is used to capture the mass transfer at the interfaces and the concentration boundary layers of single bubbles.
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