The Scaling Up of Fermentation and Primary Recovery Processes of Soluble Protein Antigens
As a process is scaled up, there are several considerations that must be employed both during fermentation and the recovery of the product. The goal of scaling up a process is to identify the parameter or the combination of parameters, which affect the performance of antigen expression. It has been found that the mass-transfer coefficient of oxygen during fermentation and the physiological metabolism such as the feeding rate of nutrients are important factors to be maintained in improving antigen yields upon scale-up. Part I in this chapter will cover the calculations of some key empirical formulas such as power/volume ratios, mass-transfer coefficient (KLa) and mixing time at the bench-scale. The KLa value is kept constant upon scale-up to maintain similar mass-transfer of oxygen at the larger production scale. One way of keeping the same KLa value as the small scale is to improve the power input by increasing the number of Rushton impellers within the large-scale reactor. Part II in this chapter covers several recovery techniques used in the recovery of intracellular proteins. A number of filtration technologies (micro-filtration, static filtration and ultra-filtration) for harvesting the culture are discussed. A process consisting of cross-flow micro-filtration, homogenization and batch clarification using ion-exchange resins has been effective in recovering the protein.
About the Author
Timothy S. Lee, Ph.D.
Bacterial Development, Sanofi Pasteur, Ontario, Canada
Dr. Timothy Lee received his Ph.D. in Biochemical Engineering at the University College of London, UK. The area of research was focused on the mechanical and catalytic stability of immobilized enzymes. He then did a post-doctoral fellowship at sanofi pasteur, Canada, where he was involved in the optimization of primary recovery processes for bacterial systems, mainly focusing on micro-filtration, centrifugal and chromatographic separations. As a senior development scientist within Sanofi Pasteur, Dr. Lee has played a key role in the development of different bacterial media, fermentation and clarification optimization and scale-up as well as the transfer of proceses to Industrial operations for manufacturing. He has also published several patents and presented extensively at ACS meetings over the last several years, outlining the work performed in the industry. He continues to interact extensively with vendors to find new technologies to improve and simplify the clarification step within Process Development.