Dialysis fermenter - biorector with dialysis device

The subject matter disclosed herein concerns the use of a semipermeable membrane having a molecular cut-off of 15 kDa to 50 kDa in a dialysis fermenter as a separation layer between (a) the cell-containing liquid culture medium and (b) the non-cell-containing dialysis medium (nutrient solution). Furthermore the disclosed subject matter concerns a dialysis fermenter with compartments for cell-containing culture medium, non-cell-containing nutrient solution as well as an exchange unit of a semipermeable membrane, wherein mass transfer takes place between the culture medium and the dialysis medium by means of diffusion and/or ultrafiltration. The dialysis fermenter includes a functional unit which is suitable for preventing precipitates formed in the dialysis medum from entering the hollow fibers of the exchange unit. Furthermore, a method for culturing cells is disclosed.