The invention refers to a new process for the production of purification of high purity plasmid DNA. The process comprehends: a) the production of cells containing plasmid DNA, b) the disruption of the cells in order to obtain a lysate containing plasmid DNA, c) a concentration step by precipitation with isopropanol, d) a pre-purification and conditioning step by the addition of ammonium sulphate, e) a purification step using hydrophobic interaction chromatography, f) a final concentration and/or buffer exchange step. The process is scaleable, it does not use enzymes or mutagenic agents and it enables the preparation of plasmid DNA with pharmaceutical grade, which complies with the requirements of regulatory agencies. The invention belongs to the technical domain of Biochemical Engineering/Biotechnology.