This chapter discusses the challenges in the scale-up of perfusion bioreactors from the few litres laboratory scale to the thousands of litres clinical and commercial scale. We consider comparative studies between laboratory- and large-scale reactor systems, including multiphase reactor models, computational fluidynamic tools as well as omics studies to support solid and reliable scale-up procedures. Specific scale-up issues – such as the scalability of the cell retention device, long-term operation, and batch definition in the case of process failure – are discussed. Finally, we evaluate the potential of single-use technologies and close the chapter with economic, financial, and environmental considerations in the context of future developments in biomanufacturing.

In this introductory chapter, we discuss mammalian cell culture for the production of therapeutic proteins in the broader context of biotechnology and, in particular, of the biopharmaceutical industry. We begin with a short retrospect on the history of cell cultures for bioproduct manufacturing and eventually introduce recombinant technology, in order to appreciate how the present standards were established. An overview of the current market on recombinant therapeutic proteins provides some important understanding of the industry challenges to come and the contribution that continuous manufacturing can provide. We then introduce the various bioreactor types that can be used in this area and indicate the challenges to be faced for their development, design, and operation. The objective here is to put all these aspects in the right perspective and address the reader to the chapters where each of them is specifically treated in the monography.

In this chapter, we give an overview of the challenges and objectives in operating mammalian cell perfusion cultures and provide guidelines for the design and set-up of lab-scale bioreactor systems. Next, the control structure needed to maintain long-term stable and viable cultures is illustrated, followed by a section on the media design. In the last section, we discuss steady-state operation, reactor, and process dynamics, including product quality considerations. Comparisons with current technologies, particularly with respect to product quality, are also discussed.

This chapter provides a general introduction for the application of mechanistic and statistical models in bioreactor process development and optimisation. We first introduce the equations governing the behaviour of batch and continuous stirred tank reactors (CSTR) for a given chemical system. After presenting the criteria to generalise these concepts to biological systems and bioprocesses, we discuss the implementation of mechanistic models for the simulation and control of the bioreactor performance with particular emphasis on product quality attributes, such as N-linked glycosylation. In addition, we describe the implementation of statistical and hybrid models and their application in process development and reactor optimisation. Lastly, we compare the use of the various modelling techniques for process monitoring and control.

The design and development of perfusion cultures require extensive experiental campaigns in order to identify the most convenient conditions in terms of a very large number of operating parameters. There is a need for high-throughput technologies that allow for the simultaneous operation and monitoring of several cultures at different process conditions. This requires suitable scale-down models, which allow the reliable prediction of the behaviour at larger scale. Within this chapter, we describe systems allowing the operation at the µL and mL scale and enabling early process development, such as clone and media screening, as well as the design of suitable process operating conditions at the larger scale. Managing such a high number of experiments is not possible without a proper level of automation, including suitable sensors for process monitoring.

The state-of-the-art strategies for perfusion process design, development, and optimisation are discussed. We first introduce the essential steps and boundaries for the development of a perfusion process. Next, we evaluate clone and media screening for perfusion processes and compare various alternative scale-down systems. Once the expression system is selected, we proceed with the design of the reactor operating conditions to maximise volumetric productivity and yield while reducing medium consumption. The fundamental issue of product quality attributes for biologics and biosimilars, and the impact of perfusion operating mode are also discussed. Finally, we introduce the main objectives in the scale-up of the developed process to clinical and commercial productions.