Yeast protein expression system is a ideally suitable expression system for both secretion and intracellular expression as the yeast offer relatively easy genetic manipulation and rapid growth to high cell densities on inexpensive media. Common yeast protein expression systems are Pichia pastoris, Saccharomyces cerevisiae, Kluyveromyces lactis, Hansenula polymorpha, and Yarrowia lipolytica. TGpeptide use Pichia pastoris as our strain.