Simulation and optimization of nutrient uptake and biomass formation using a multi-parameter Monod-type model of tobacco BY-2 cell suspension cultures in a stirred-tank bioreactor

Henrik Nausch; Marco Baldan; Katrin Teichert; Jannik Lutz; Carsten Claussen; Michael Bortz; Johannes Felix Buyel

doi:10.3389/fpls.2023.1183254

Simulation and optimization of nutrient uptake and biomass formation using a multi-parameter Monod-type model of tobacco BY-2 cell suspension cultures in a stirred-tank bioreactor

Front Plant Sci. 2023 Oct 31:14:1183254. doi: 10.3389/fpls.2023.1183254. eCollection 2023.

Authors

Henrik Nausch^#¹, Marco Baldan^#², Katrin Teichert², Jannik Lutz¹, Carsten Claussen³, Michael Bortz², Johannes Felix Buyel^{1

4

5}

Affiliations

¹ Department Bioprocess Engineering, Fraunhofer Institute for Molecular Biology and Applied Ecology IME, Aachen, Germany.
² Division Optimization, Fraunhofer Institute for Industrial Mathematics ITWM, Kaiserslautern, Germany.
³ Fraunhofer Institute for Translational Medicine and Pharmacology ITMP, Hamburg, Germany.
⁴ Institute for Molecular Biotechnology, RWTH Aachen University, Aachen, Germany.
⁵ Institute of Bioprocess Science and Engineering (IBSE), University of Natural Resources and Life Sciences, Vienna (BOKU), Vienna, Austria.

^# Contributed equally.

Abstract

Introduction: Tobacco (Nicotiana tabacum) cv Bright Yellow-2 (BY-2) cell suspension cultures enable the rapid production of complex protein-based biopharmaceuticals but currently achieve low volumetric productivity due to slow biomass formation. The biomass yield can be improved with tailored media, which can be designed either by laborious trial-and-error experiments or systematic, rational design using mechanistic models, linking nutrient consumption and biomass formation.

Methods: Here we developed an iterative experiment-modeling-optimization workflow to gradually refine such a model and its predictions, based on collected data concerning BY-2 cell macronutrient consumption (sucrose, ammonium, nitrate and phosphate) and biomass formation.

Results and discussion: The biomass formation was well predicted by an unstructured segregated mechanistic Monod-type model as long as the nutrient concentrations did not approach zero (we omitted phosphate, which was completely depleted). Multi-criteria optimization for sucrose and biomass formation indicated the best tradeoff (in a Paretian sense) between maximum biomass yield and minimum process time by reducing the initial sucrose concentration, whereas the inoculation biomass could be increased to maximize the biomass yield or minimize the process time, which we confirmed in calibration experiments. The model became inaccurate at biomass densities > 8 g L^-1 dry mass when sucrose was almost depleted. We compensated for this limitation by including glucose and fructose as sucrose hydrolysis products in the model. The remaining offset between the simulation and experimental data might be resolved by including intracellular pools of sucrose, ammonium, nitrate and phosphate. Overall, we demonstrated that iterative models can be used to systematically optimize conditions for bioreactor-based processes.

Keywords: biopharmaceuticals; cultivation medium; mechanistic model; multi-criteria optimization; upstream production.

Grants and funding

This work was funded in part by the Fraunhofer-Gesellschaft Internal Programs under grant no. Attract 125-600164 and the state of North-Rhine-Westphalia under the Leistungszentrum grant no. 423 “Networked, adaptive production” as well as the BMBF-funded Fraunhofer innovation program project number 800 093 (digitalization of bioprocesses – dibi).