The invention relates to a system and a method for cell separation via a filter, with a powder bag which can be arranged in a recirculation circuit and is partly filled with a pulverulent filter aid and to which a cell solution containing the cells to be separated can be delivered from a bioreactor via a pump arranged in the recirculation circuit, the bioreactor, which has an agitator, being arranged in the recirculation circuit, and, when the recirculation circuit is interrupted, the bioreactor being connectable to the filter.