Polypeptides are useful in a variety of diagnostic, therapeutic, agricultural, nutritional, and research applications. Although polypeptides can be isolated from natural sources, the isolation of large quantities of a specific polypeptide from natural sources may be expensive. Also, the polypeptide may not be of uniform quality due to variation in the source material. Recombinant DNA technology allows more uniform and cost-effective large-scale production of specific polypeptides.
One goal of recombinant polypeptide production is the optimization of culture conditions so as to obtain the greatest possible productivity. Incremental increases in productivity can be economically significant. Some of the methods to increase productivity in cell culture include using enriched medium, monitoring osmolarity during production, decreasing temperatures during specific phases of a cell culture, and/or the addition of sodium butyrate (see, e.g., U.S. Pat. No. 5,705,364).
However, as more polypeptide-based drugs demonstrate clinical effectiveness and increased commercial quantities are needed, available culture facilities become limited. Accordingly, there remains a need in the art to continually improve yields of recombinant polypeptides from each cell culture run.