Staphylococcal Protein A (SPA), a cell wall protein of Staphylococcus aureus, is 
in high demand because of its ability to bind immunoglobulins. Much of the SPA 
that we use today is recombinant SPA (rSPA), which is produced in Escherichia 
coli. As rSPA is obtained by expressing SPA as an intracellular protein, its 
purification is tedious and time consuming. In order to obtain a large amount of 
highly purified rSPA with relative ease, we expressed SPA as a secretory form in 
the yeast Pichia pastoris. To increase the expression level of SPA and repress 
its proteolysis during fermentation, the cell density (OD600), temperature and 
pH at which SPA expression was induced as well as the induction time were 
optimized. The final yield of SPA obtained was about 8.8 g per liter of culture, 
which under the optimized fermentation condition, accounted for 80% of the total 
protein in the culture supernatant. The expressed SPA was purified from the 
culture supernatant by DEAE ion-exchange chromatography (IEC) after the 
supernatant was subjected to a desalting step. The purified SPA was resolved as 
a single band by SDS-PAGE and as a single peak by HPLC. Its identity was 
confirmed by MALDI-TOF MS and western-blot. Moreover, the protein also exhibited 
excellent affinity for IgG when tested with human IgG. The production and 
purification of SPA described in this study offers a new method for obtaining 
high level of SPA in relatively pure form that is suitable for practical 
application.