Staphylococcal protein A (SpA) plays an important role in Staphylococcus aureus 
pathogenesis. The recombinant SpA is also widely used in biotechnology to purify 
polyclonal and monoclonal immunoglobulin G antibodies. In this study, expression 
and secretion of a truncated form of SpA containing five immunoglobulin-binding 
domains using its own native signal sequence were optimized in Escherichia coli. 
Optimization was carried out using response surface method (RSM), making use of 
the interaction between five variables. The initial results revealed that the 
signal peptide from S. aureus was recognized in E. coli and the resulting SpA 
was expressed and secreted into the medium. Compounds, such as glycine, affected 
the secretion of SpA into the culture medium. The central composite design 
experiment showed that the optimum conditions for the maximum expression of 
recombinant truncated SpA in E. coli included 10% (w/v) lactose, 1.77% (w/v) 
glycine, induction time of 11 H, an optical density (600) of 1.1, and a 
temperature of 33 °C. Optimization using RSM resulted in a fivefold increase in 
the secretion of SpA. To date, this is the first study of its kind regarding the 
definite influence of glycine concentration and duration of the cultivation 
period on the secretion of SpA.