Modeling, Simulation and Experimental Characterization of Mechanical and Surface-Induced Stresses on Pellets of the Filamentous Microorganism Lentzea aerocolonigenes

Filamentous microorganisms, such as Actinomycetes spp. and Aspergillus spp., are vital in industrial biotechnology for the production of pharmaceuticals and enzymes. Their growth morphology, ranging from dispersed mycelium to pellets, is influenced by cultivation conditions. This review, part of the DispBiotech priority program, examines the impact of particle suppplementation on these microorganisms using both experimental and simulative methods. For Lentzea aerocolonigenes, glass and ceramic beads in shaking flask cultivations were utilized to enhance the production of the antibiotic rebeccamycin. By adjusting bead size, concentration, density, and shaking rates, mechanical stresses were modulated, resulting in increased product concentrations. Computational fluid dynamics (CFD) coupled with the discrete element method (DEM) was employed to quantify these stresses, identifying optimal conditions for maximizing yields. Additionally, the supplementation of glass microparticles and lecithin was characterized, leading to further increases in rebeccamycin production. For advanced pellet investigations, oxygen measurements inside pellets were conducted, and the micromechanical behavior was examined using DEM-simulations of pellet compression. These methodologies advance our understanding of the interplay between cultivation processes, cellular morphology, and product formation, thereby enhancing the optimization of industrial applications involving filamentous microorganisms.