On a new approach to describing soft pellets of filamentous cultivated in shake flasks under turbulent flow conditions

When cultivating filamentous pellets, the mechanical behaviour during cultivation is of particular interest for high process productivity under turbulent hydrodynamic flow conditions. However, the exact mechanical interactions between the pellets or between the pellets and the reactor walls are still not fully understood and can hardly be resolved using experimental methods. This study therefore presents a combined numerical approach to investigating the mechanical behaviour of soft biological pellets in highly turbulent flows. Unlike conventional models, which focus on rigid particles, this approach captures the complex interactions between culture fluid and pellet, pellet and pellet, and pellet and reactor wall. The developed model efficiently calculates the conditions in shake flask cultivations while providing a realistic representation of them by modelling the motion of particles on a large scale and capturing the free surface. By incorporating turbulence-induced mechanical effects, the model sheds light on the impact of fluid and contact forces on changes in pellet morphology. These findings contribute to the optimisation of large-scale biotechnological processes, increasing productivity and operating efficiency in microbial cultivation systems.