Quantification and modeling of macroparticle-induced mechanical stress for varying shake flask cultivation conditions

Marcel Schrader; Kathrin Schrinner; Laura Polomsky; Dimitri Ivanov; Ingo Kampen; Carsten Schilde; Rainer Krull; Arno Kwade

doi:10.3389/fbioe.2023.1254136

Quantification and modeling of macroparticle-induced mechanical stress for varying shake flask cultivation conditions

Front Bioeng Biotechnol. 2023 Sep 4:11:1254136. doi: 10.3389/fbioe.2023.1254136. eCollection 2023.

Authors

Marcel Schrader^#^{1

2}, Kathrin Schrinner^{2

3}, Laura Polomsky^{1

2}, Dimitri Ivanov^{1

2}, Ingo Kampen^{1

2}, Carsten Schilde^{1

2}, Rainer Krull^{2

3}, Arno Kwade^{1

2}

Affiliations

¹ Institute for Particle Technology, Technische Universität Braunschweig, Braunschweig, Germany.
² Center of Pharmaceutical Engineering, Technische Universität Braunschweig, Braunschweig, Germany.
³ Institute of Biochemical Engineering, Technische Universität Braunschweig, Braunschweig, Germany.

^# Contributed equally.

Abstract

In biotechnological processes, filamentous microorganisms are known for their broad product spectrum and complex cellular morphology. Product formation and cellular morphology are often closely linked, requiring a well-defined level of mechanical stress to achieve high product concentrations. Macroparticles were added to shake flask cultures of the filamentous actinomycete Lentzea aerocolonigenes to find these optimal cultivation conditions. However, there is currently no model concept for the dependence of the strength and frequency of the bead-induced stress on the process parameters. Therefore, shake flask simulations were performed for combinations of bead size, bead concentration, bead density and shaking frequency. Contact analysis showed that the highest shear stresses were caused by bead-bottom contacts. Based on this, a newly generated characteristic parameter, the stress area ratio (SAR), was defined, which relates the bead wall shear and normal stresses to the total shear area. Comparison of the SAR with previous cultivation results revealed an optimum pattern for product concentration and mean product-to-biomass related yield coefficient. Thus, this model is a suitable tool for future optimization, comparison and scaling up of shear-sensitive microorganism cultivation. Finally, the simulation results were validated using high-speed recordings of the bead motion on the bottom of the shake flask.

Keywords: CFD-DEM simulation; filamentous microorganism; macroparticle-enhanced cultivation; mechanical stress; rebeccamycin; shake flask.

Grants and funding

The authors gratefully acknowledge the financial support provided by the German Research Foundation (DFG) in the priority programmes “DiSPBiotech–Dispersity, structural and phase modifications of proteins and biological agglomerates in biotechnological” processes (SPP 1934, project number 315457657) and “Opus Fluidum Futurum–Rheology of reactive, multiscale, multiphase construction materials” (SPP 2005, project number 313773090). The authors acknowledge support from the Open Access Publication Funds of Technische Universität Braunschweig.