Lauri Hoffmann

Filamentous fungi are cultivated in bioprocess engineering in bioreactors, especially in stirring reactors, to obtain pharmaceutically interesting substances. In addition to the cultivation conditions provided by the configuration of the cultivation liquid, the reactor components such as stirrers and sensors also have an influence on the cultivation process. My exercise is to investigate the influence of different geometries and set-ups of reactor internals inside the culitvation vessel. Especially the observation of shear stresses as a consequence of stirring has a special relevance, as shear stress has a major impact on the morphology of fungi. 

In a first step I digitalized the conventional used bioreactor and exported him into a software for fluid simulation. This software allows the evaluation of shear stresses and mixing times of substances in fluid. I use this mixing time evaluations for the comparison with real mixing time experiments and as a consequence for the validation of software. The simulation of the actual state allows me to identify potentials for optimization inside the reactor. In specific, the aim is to investigate the effects of particular geometric changes and to apply these in an iterative optimization process for an improved reactor configuration. After designing new components , these can then be additively manufactured from plastic or metal, depending on the application. In addition to the iterative optimization work, material studies are also carried out to examine the various 3D-printing processes and available material options in terms of their suitability for use in bioprocess-engineering. These include testings for material strength or tightness. 

Summarized, the aim of my work is the optimization of the reactor internals using simulation based design, additive manufacturing and validation of the optimization by testing the internals in use. As a perspective, recommendations for industrial use can then be determined from the internals developed.

A typical work day begins with the configuration of a new simulation. While calculating the simulation I do some literature work or I design new simulation setups. In addition I operate several 3D-printers, which is a good variation from working on the computer.