Experimental and numerical investigations on the effects of cavitation and flow-related collisions on aggregate formation and loss of activity after cell disruption in the high-pressure homogeniser using the model systems lipase or beta-lactoglobulin as e

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Biotechnologically obtained enzymes or protein isolates from plant sources are often obtained by cell disruption. High pressure homogenisers are used for this purpose. In high-pressure homogenization, an extreme acceleration of the medium generates stresses, which are responsible for high cell disintegration rates. A side effect is often cavitation, which creates gas/liquid (bubbles) and/or solid/liquid (abrasion particles) interfaces. This research proposal concentrates on the loss of enzyme activity and the denaturation and aggregation of proteins, for which according to literature a boundary and/or shear-induced unfolding of the three-dimensional structure followed by aggregation in the flow is held responsible. The basic working hypothesis of this project is the assumption that structural losses of enzyme or protein activity can be reduced if cavitation in disruption units of high-pressure homogenisers is largely avoided and the collision frequency in the out-flow chamber is efficiently reduced. Methods for this are the application of back pressure and feeding of a diluting mixed stream directly into the outflow chamber behind the narrowest cross-section, so that high mixing efficiencies can be achieved locally. In the proposal, numerical flow simulations of such novel simultaneous homogenizing and mixing (SHM) units will be performed and evaluation methods for predicting cavitation and collision rates as a function of geometry and process parameters will be developed and verified by accompanying experiments. In cooperation with other subproject partners in the SPP, stress histories and expected aggregation rates are predicted. This leads to design strategies for the preservation of functionality of enzymes and proteins obtained by cell disruption in a high-pressure homogeniser.