Method periplasmic proteins extraction of prokaryotic microorganisms in the presence of arginine

The invention relates to a periplasmic proteins extraction process of prokaryotic microorganisms which comprises: 1 / suspending the pellet of cells originating from the culture of a prokaryotic microorganism transformed with the aid of an expression vector containing a gene encoding said protein and means for its expression in the periplasm thereof in a buffer solution containing arginine; 2 / recovering the protein of interest in the supernatant of the bacterial suspension thus obtained . Application: extraction of proteins of interest produced by a prokaryotic microorganism such as for example interleukins or HGH