NOVELTY - A separation apparatus comprises a filtration reservoir adapted to be in fluid communication with a bioreactor; inlet(s) adapted to receive liquid cell culture from the bioreactor; a rotatable filter located within the filtration reservoir; a first outlet adapted to be in fluid communication with the bioreactor; and a second outlet adapted to be in fluid communication with a harvest reservoir.    USE - For separating an expressed protein from cell retentate in liquid cell culture media produced in a bioreactor (claimed).    ADVANTAGE - The invention allows for the production of proteins in cell culture with an increase in yield and a reduction in production cost. It avoids the problems associated with internal filter clogging, in which clogging may prematurely terminate a culture batch.    DETAILED DESCRIPTION - A separation apparatus comprises a filtration reservoir (300) adapted to be in fluid communication with a bioreactor (200); inlet(s) (340, 350) into the reservoir adapted to be in fluid communication with the bioreactor and adapted to receive a liquid cell culture from the bioreactor; a rotatable filter located within the filtration reservoir and separating liquid culture media containing expressed protein from retentate in the filtration reservoir; a first outlet from the filtration reservoir adapted to be in fluid communication with the bioreactor and adapted to transfer the separated retentate to the bioreactor through the first outlet from the filtration reservoir; and a second outlet from the filtration reservoir in fluid communication with a harvest reservoir (400) and adapted to transfer the separated media containing the expressed protein from the filtration reservoir to the harvest reservoir.    An INDEPENDENT CLAIM is also included for a method for separating an expressed protein from cell retentate in liquid cell culture media comprising providing cells expressing the protein in liquid cell culture media; separating the cell culture media into cell culture media containing the expressed protein and cell retentate using a rotatable filter; returning the separated cell retentate from the rotatable filter to a bioreactor; and removing the separated cell culture media containing the expressed protein from the rotatable filter.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic diagram of a bioreactor and filtration apparatus system.    Fresh media (10)    First reservoir (100)    Valve (110, 210, 345, 360)    First conduit (120)    First reservoir outlet (130)    Bioreactor (200)    Second conduit (220)    Pump (230)    Third conduit (240)    Bioreactor inlets (250, 255, 260)    Bioreactor outlet (270)    Agitator (290)    Filtration reservoir (300)    Lid (311)    Rotator (315)    Inlet (340, 350, 370)    Steam supply source (341)    Harvest conduit (371)    Harvest pump (375)    Harvest reservoir (400)