A U.S. Patent Application for a “Reversible Liquid Filtration System” was published by Sartorius Stedim on August 8th, 2019. The present invention is a reversible liquid filtration system for cell culture perfusion comprises: a bioreactor vessel (B4), for storing the cell culture (L4); a perfusion pump (P7), comprising a reciprocable element (P71) which is movable in opposing first and second pumping directions (dF, dR); a filter (F4); and first and second bi-directional valves (BV1, BV2), each selectively controllable between open and closed positions. The perfusion pump (P7), the filter (F4), and the first and second bi-directional valves…  Learn More