The production of food, such as cheese, often gives rise to byproducts, such as whey. It would be good if the proteins and other valuable substances contained in whey could be extracted and sold instead of being disposed of with the whey. Extraction techniques removing a substance from a solution as quickly and selectively as possible are indispensable parts also of cleaning processes in the chemical and pharmaceutical industries. Many known extraction techniques are based on two-phase systems, with the target substance better soluble in one of the two phases. Among the drawbacks encountered are frequently insufficient selectivity and high expense of time. Moreover, the solutions prepared for extraction can only partly be recycled (re-used). KIT scientists of the Institute of Functional Interfaces (IFG) have developed a procedure allowing fast and exact separation of a target substance. In this process, the solution is treated with functionalized magnetic nanoparticles able to bind to their surface the target substance, such as a protein. In addition, a phase forming agent (tenside) is added which causes the solution to be present in one phase or two phases, depending on temperature. The impact of a magnet causes the nanoparticles to move, for instance, into the upper phase, taking the bound target protein along. After separation of the lower phase, a buffer is added which separates the target substance from the magnetic particle. In this way, both the tenside and the functionalized magnetic particles can be recycled almost completely. Another advantage is the formation of chains by the magnetic particles whose mutual attraction causes faster phase production and, consequently, faster extraction. The functionalized magnetic particles also can be modified in such a way as to bind enzymes which then act as re-usable biocatalysts. The KIT is looking for partners interested in employing the procedure on an industrial scale.