Disclosed herein is a unit for ultrafiltration and purification (1) of a product stream (3) containing a biological macromolecular product as well as a substance to be separated from the product stream, comprising at least one capillary ultrafiltration module (2), characterized in that - at least one pump (4) conveys the product stream into the capillaries of the at least one capillary ultrafiltration module, - at least one positive displacement pump (5) conveys the product stream from the capillaries and - at least one further pump (6) passes a washing fluid (9) over the outside of the capillaries, - the unit includes no measure for circulating the product stream and the washing fluid into the ultrafiltration module, as well as at least one guard filter(8), through which all fluid leaving the at least one capillary ultrafiltration module in the direction of the product stream is passed.
