35 of the second filter 34 differ in shape in order to make sure that the correct side of the pump is connected to corresponding first tube 2 or second tube 3 in fig3 and fig4 an exploded view of the scaffold chamber 4 of the bioreactor 1 is shown in fact fig3 and fig4 show the scaffold chamber 4 in a disassembled or open position in which the bayonet mount structure 411 of the first part 41 of the casing is disengaged from the bayonet mount structure 421 of the second part 42 of the casing thereby a scaffold holder 7 and blocking adapters 8 are unloaded from the casing of the scaffold chamber 4 the blocking adapters 8 which both are made of silicone comprise a top first blocking adapter 81 and a bottom second blocking adapter 82 which both are made of silicone in order that the blocking adapters 8 can be conveniently mounted in a correct manner the first blocking adapter 81 is colored on its top side and the second blocking adapter is colored on its bottom side the scaffold holder 7 is essentially cylindrical and cup shaped at its outer surface the scaffold holder is provided with planar gripping surfaces 71 allowing for conveniently handling the scaffold holder 7 near its top and bottom end recesses 72 are circumferentially arranged about the outer surface of the scaffold holder 7 in each of the recesses 72 a sealing o ring 73 is arranged allowing for sealing a space between the scaffold holder 7 and the scaffold chamber 4 when the scaffold holder 7 is arranged inside the scaffold chamber 4 such that the scaffold holder 7 is held in the scaffold chamber 4 by friction.