The development of efficient recombinant protein production processes can be a critical factor in whether or not a pharmaceutical therapeutic protein can enter human clinical trials and ultimately the marketplace. This is especially true for therapeutic proteins that need to be administered on a daily basis for prolonged periods or if dosage requirements are very high. The use ofPichia pastorisas a recombinant expression host strain can be an excellent choice for such situations.P. pastorishas the potential for high expression levels (1 ,2 ), efficient secretion, and proper protein folding (3 –5 ), and is a robust fermentation organism capable of high cell density on inexpensive simple basal salts medium (6 ). The development of an insulin-like growth factor I (IGF-I) production process in whichP. pastorisis used as the recombinant host strain is discussed in this chapter.
