Optimization of extracellular truncated staphylococcal protein A expression in Escherichia coliBL21 (DE3)

Abstract S taphylococcal protein A ( S p A ) plays an important role in S taphylococcus aureus pathogenesis. The recombinant S p A 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 S p A containing five immunoglobulin‐binding domains using its own native signal sequence were optimized in E scherichia 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 S p A was expressed and secreted into the medium. Compounds, such as glycine, affected the secretion of S p A into the culture medium. The central composite design experiment showed that the optimum conditions for the maximum expression of recombinant truncated S p A 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 S p A . 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 S p A .