Purification of non-glycosylated proteins

The current invention reports a method for the purification of a not-glycosylated, heterologous polypeptide, which has been recombinantly produced in a prokaryotic cell, wherein the method comprises three chromatography steps of which the first chromatography step selected from i) hydrophobic charge induction chromatography, or ii) hydrophobic interaction chromatography, or iii) affinity chromatography, or iv) ion exchange chromatography, the second chromatography step is selected from i) anion exchange chromatography, or ii) cation exchange chromatography, or iii) hydroxylapatite chromatography, or iv) hydrophobic interaction chromatography, and the a third chromatography step is selected from i) hydrophobic charge induction chromatography, or ii) anion exchange chromatography, or iii) cation exchange chromatography, or iv) hydrophobic interaction chromatography, whereby the first chromatography step is an affinity chromatography in case of polypeptides capable of interacting with metal ligands, the second chromatography step is not a hydroxylapatite chromatography step in case of polypeptides with an isoelectric point below 6.0, and the third chromatography step can be performed in flow-through mode with polypeptides having a low or high isoelectric point.