Micromechanical Properties of Filamentous Fungi
In fermentation processes fluid dynamic greatly influences morphology and productivity of the growing organism. Within the SFB 578 the filamentous fungi Aspergillus niger as a model organism is used to investigate the production of antibodies and glycosyltransferases. In dependency on several process parameters two extreme types of the fungus morphology can appear during the fermentation, namely particle-like-pellets or freely dispersed filaments. The physical properties of spores and hyphae are investigated by different micromechanical experiments. These experiments are necessary to achieve a fundamental knowledge of the physical behaviour of spores and hyphae during the cultivation and to gain a deeper understanding of the morphologic development of the fungus. Therefore, adhesion forces of spores and the cellular spring constant of hyphae are measured by force distance experiments with an atomic force microscope (AFM). This requires a fixation of a single spore to an AFM cantilever (see figure 1).
One major focus of this project is to determine differences in adhesion and attraction of spores and hyphae as a function of different aqueous solutions. A significant influence is expected because of the well known effects of the pH-value and the ionic strength on the electrostatic surface charge density. Modelling of aggregation of spores and hyphae assuming equilibrium state between aggregation and desaggregation due to attractive long-range interactions and hydrodynamically induced shear stress shall complete these considerations.
The measurement of breaking forces and elastic modulus of single hyphae in liquid is another big focus of this project. Based on those data and additional data from cuette shear cell measurements we want to figure out breaking kinetics that describes the breaking of single hyphae and complete pellets under conditions of cultivation.
This project is a sub-project of the Collaborative Research Center 578 which is funded by the German Research Foundation (DFG).