Morphological and mechanical properties of filamentous pellets during the cultivation process

Abstract

Filamentous bacteria and fungi are attracting increasing attention due to their medicinal value. Among these microorganisms, Actinomadura namibiensis has attracted great interest due to its ability to produce Labyrinthopeptin A1 with antiviral activity. In order to increase productivity and shorten the development cycle, recent studies have shown that the production of Labyrinthopeptin A1 can be enhanced by optimising the cultivation processes of filamentous pellets with the help of morphology engineering techniques including the appropriate preparation of the culture medium and the flow conditions for agitation, as well as the contact mechanisms during the flow‐induced movements of the pellets. From a mechanical point of view, contact energy is positively correlated with productivity and is determined by the mechanical and morphological properties of the pellets, which have a string influence on the stresses, contact frequency and structure for mass transfer of nutrients. To gain a deeper understanding of the stress‐induced pellet growth mechanisms during cultivation, experimental characterisation of Actinomadura namibiensis pellets was performed using a micromechanical setup. Considering that filamentous pellets exhibit an irregular geometry with tightly intertwined and branched hyphal networks, the measured force responses of cyclic compression experiments were analysed in correlation with the morphological properties. In addition, the process‐dependent mechanical behaviour was investigated by comparing the mechanical behaviour at different cultivation times. The results obtained provide sufficient information to propose a contact model of the pellets and to derive the process‐dependent material parameters for further numerical simulations of the cultivation process.