title: Mechanism for multiplicity of steady states with distinct cell concentration in continuous culture of mammalian cells.
abstract: Continuous culture for the production of biopharmaceutical proteins offers the possibility of steady state operations and thus more consistent product quality and increased productivity. Under some conditions, multiplicity of steady states has been observed in continuous cultures of mammalian cells, wherein with the same dilution rate and feed nutrient composition, steady states with very different cell and product concentrations may be reached. At those different steady states, cells may exhibit a high glycolysis flux with high lactate production and low cell concentration, or a low glycolysis flux with low lactate and high cell concentration. These different steady states, with different cell concentration, also have different productivity. Developing a mechanistic understanding of the occurrence of steady state multiplicity and devising a strategy to steer the culture toward the desired steady state is critical. We establish a multi-scale kinetic model that integrates a mechanistic intracellular metabolic model and cell growth model in a continuous bioreactor. We show that steady state multiplicity exists in a range of dilution rate in continuous culture as a result of the bistable behavior in glycolysis. The insights from the model were used to devise strategies to guide the culture to the desired steady state in the multiple steady state region. The model provides a guideline principle in the design of continuous culture processes of mammalian cells.
authors: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota.
authors: Andrew
authors: A
authors: Yongky
authors: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota.
authors: Jongchan
authors: J
authors: Lee
authors: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota.
authors: Tung
authors: T
authors: Le
authors: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota.
authors: Bhanu Chandra
authors: BC
authors: Mulukutla
authors: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota.
authors: Prodromos
authors: P
authors: Daoutidis
authors: Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota. acre@umn.edu.
authors: Wei-Shou
authors: WS
authors: Hu
mesh_terms: D000818:Animals; D001688:Biological Products / Q000378:metabolism*; D001709:Biotechnology / Q000379:methods*; D002452:Cell Count; D018929:Cell Culture Techniques / Q000379:methods*; D002460:Cell Line; D053858:Metabolic Networks and Pathways; D051379:Mice; D015233:Models, Statistical; D011994:Recombinant Proteins / Q000378:metabolism; D013678:Technology, Pharmaceutical / Q000379:methods*
chemical_list: D001688:Biological Products; D011994:Recombinant Proteins
keywords: Continuous culture; bistability; glycolysis; metabolism; multi-scale model; multiple steady states