One-way separator for retaining and recirculating cells

A solids separator for retaining and recirculating solids from a reactor mixture, comprising a flow-bearing sterilizable plastic bag or plastic bottle and, within the plastic bag or plastic bottle:

• in the upper region, one or more passages/internals for withdrawing from a harvest stream collection region a harvest stream that is separated from the solids,
• in the upper segment of a central region, a separation region having a separation area, which, during operation, is inclined at an angle of 0° to 80° to the horizontal,
• in the lower segment of the central region, one or more passages or internals for a uniform horizontal flow distribution of the reactor mixture over an introduction surface, wherein the separation area is situated above the introduction surface,
• in the lower region a solids collection region that is tapered at the bottom for collecting the solids using gravity.