External-loop perfusion air-lift bioreactor

A bioreactor for cell culture comprising:

• (a) a riser conduit having a generally cylindrical shape, an upper portion and a lower portion, a cell culture medium inlet, and an oxygen-containing gas inlet in said lower portion, a centerline of said riser conduit between said lower and upper portions of said riser conduit defining a substantially vertical axis;
• (b) a downcomer conduit having an upper portion and a lower portion, a centerline of said downcomer conduit between said upper and lower portions defining a substantially vertical axis, said upper portion of said downcomer conduit having the shape of a truncated cone, and said upper portion of said downcomer conduit including a spent medium outlet, said spent medium outlet defining a liquid level surface;
• (c) an upper transfer conduit connecting said upper portion of said riser conduit and said upper portion of said downcomer conduit, a centerline of said upper transfer conduit defining a substantially horizontal fluid flow path therebetween;
• (d) a lower transfer conduit connecting said lower portion of said downcomer conduit and said lower portion of said riser conduit, and a centerline of said lower transfer conduit defining a substantially horizontal fluid flow path therebetween;
• wherein said upper transfer conduit extends into said upper portion of said downcomer and has two outlet conduits, a first one of said outlet conduits extending in a direction generally parallel to said vertical axis, and forming an outlet port above said liquid level surface, a second one of said outlet conduits extending in a direction generally parallel to said vertical axis and in a direction opposite said direction in which said first outlet conduit extends, and said second outlet conduit forming an outlet port in a lower portion of said truncated cone.