By Tom Fletcher, Scott D Storms, and Jenny Y Bang, Irvine Scientific
The challenge of effective cell culture process development often involves how to simultaneously meet two competing needs: the need to maximize improvement of process performance and the need to minimize time spent on process development. This case study describes how applying a rational approach to culture media optimization produced results that alone led to a seven-fold increase in recombinant protein production in less than the available six months time. Employing a previously developed approach, the project involved conducting just nine cell culture experiments to complete six overlapping development phases. The project resulted in an optimized basal medium, an optimized feed medium and an optimized feeding strategy, each tailored to the specific metabolic requirements of a previously established recombinant Chinese Hamster Ovary (CHO) cell line.
The goal of this project was to improve the cell culture process yield from the initial level of approximately 200 mg/L to at least 500 mg/L. An important first step was to characterize the behavior of the cell line in batch culture by acquiring data describing both its growth kinetics and, through chemical analysis, a metabolic profile. Analysis of these data provided enough guidance to establish a preliminary fed-batch process based on the simple replacement of potentially limiting components at rates approximately matching their calculated cell specific depletion rates. The project proceeded to focus on feed optimization; hydrolysate selection, blending and optimization; basal medium optimization; feed volume and timing; and finally, the combination of results from each phase into a practical process. Although incremental improvements were achieved at each phase of development, the complete value of those individual discoveries was not apparent until they were combined into a final verification experiment. The resulting fed-batch process produced over 1,500 mg/L recombinant protein in less than two weeks.