Bioreactor for the cultivation of mammalian cells

A scalable bioreactor for the cultivation of mammalian cells, said bioreactor comprising:

• a biocompatible tank or vessel having at least one top impeller and at least one bottom impeller, wherein the top impeller is a hydrofoil impeller, wherein an impeller spacing (Ds) between the at least one top impeller and the at least one bottom impeller is between 1.229×the diameter of the bottom impeller (Dbottom) and 2×Dbottom, wherein the height of a liquid above the at least one top impeller (Do) is between 0.3×the diameter of the at least one top impeller (Dtop) and 2.5×Dtop, and wherein a bottom clearance (Dc) between the tank bottom and the center-line of the bottom impeller is at least 0.35×Dbottom, wherein the scalable bioreactor allows for performance and product quality independent of the size of the bioreactor.