This work focuses on the integration and intensification of ATPE in the downstream process of an Immunoglobulin G1 (IgG1). For the integration a pre-concentrating step prior to Protein A chromatography is suggested. To achieve an IgG1 concentration an aqueous two-phase system (ATPS) consisting of polyethylene glycol 2000 (PEG), phosphate salt and water is applied for the extraction. Applying extreme phase ratios to pure cell supernatant and cell culture, enables for a concentration of IgG1 by factor nine within a single extraction step. Moreover, an almost complete recovery in the product phase was achieved with an IgG1 concentration of 5000 mg/kg in the product phase. A successful scale up by factor 100 shows excellent reproducibility. To intensify ATPE, it is important to improve the IgG1 loading capacity of ATPS. PEG - phosphate ATPS may cause high IgG1 loss because of precipitation. By applying a hyperbranched polyglycerol-phosphate ATPS, the IgG1 loading capacity of ATPS was increased 30-fold in comparison to the PEG-phosphate salt ATPS which showed initial precipitation of IgG1 below a loading of 50 mg/kg. (C) 2015 Elsevier B.V. All rights reserved.