6.2 High Cell Density Cultivation Process

Abstract

Since human tissue plasminogen activator (tPA) became the first approved biotherapeutic obtained from mammalian cells using recombinant DNA technology in 1987 [1], the biopharmaceutical market rapidly expanded based on a development pipeline of several mammalian cell culture-derived drugs. Even more, mammalian cells are still the dominant recombinant protein production systems for clinical applications [2].In this scenario, high-throughput production processes of therapeutics, expressed in mammalian cells, are necessary to fulfil the market demands. The success of a process depends both on cell productivity (defined as the quantity of the interest protein produced by cell) and the viable cell density in the culture. Considering these parameters, one of the applied strategies to obtain a high recombinant protein yield is the development of culture systems that reach high cell densities and sustain cell viability, leading to an increment of the volumetric productivity.Animal cells can be grown using different modes of operation, and the maximum cell density that can be achieved will depend on that selection. The method of cultivation defines the environmental and nutritional conditions under which cells will proliferate and synthesize the protein of interest, determining the success of attaining high viable cell density and, consequently, high concentration of the desired product. A general classification distinguishes discontinuous modes (batch, repeated batch and fed-batch) and continuous ones (without cell retention or chemostat, or cell retention, also known as perfusion).Despite the fact that suspension cultures are by far the most common cell culture format for recombinant protein expression in mammalian cells [3], anchoragedependent cell lines are also used in the industry for the mentioned purpose. Consequently, the scaling up of a process where cells grow in adherence can be carried out by cultivating them as monolayer in static or gently agitated surfaces or by growing cells attached to polymers spheres that are introduced in bioreactors to maintain them in suspension at high density cultures.The present chapter comprehensively describes theapproaches for high cell density cultivation of animal cells taking into account strategies to grow them in suspension or immobilized into proper supports.

Dielectric Spectroscopy and Optical Density Measurement for the Online Monitoring and Control of Recombinant Protein Production in Stably Transformed Drosophila melanogaster S2 Cells

“…The commercial production of biologicals in animal cells is usually carried out as fed-batch or perfusion processes [ 62 ]. Perfusion is particularly attractive because it offers a high maximum cell density (>5 × 10 7 cells/mL) combined with superior volumetric productivity and long-term production cycles [ 63 , 64 ]. However, to be effective and robust, the corresponding processes require the appropriate reactor setup and the controlled adjustment of feed and bleed rates.…”