Purification process based on magnetic beads

A process for the separation of molecules from a suspension comprising cells at a concentration of at least 56×106 cells/ml, comprising the steps of:

• growing the cells in a cell medium in a bioreactor, wherein a perfusion method is used, wherein spent cell medium depleted of nutrients and including cell waste products is removed and wherein fresh cell medium is provided to the cells in the bioreactor at the same rate as spent cell medium is removed, wherein molecules with a molecular weight over a determined cut off value are not removed together with the spent cell medium, and wherein the cells in the cell medium form the suspension comprising the cells, which suspension is used in the following steps without any filtration;
• providing magnetic particles having a specific interaction with said molecules to be separated;
• mixing the magnetic particles with the suspension containing the molecules;
• bringing the suspension in contact with a magnetic field provided by a magnetic separation device to collect the magnetic particles;
• decreasing or removing said magnetic field and collecting said magnetic particles carrying said molecules;
• and
• removing said molecules from said magnetic particles, to provide a concentrated fraction of said molecules, and/or provide partial or complete removal of impurities and cells from the fraction containing the molecules.