Patent ID: 7628528

Claim:
A pneumatic bioreactor comprising: a containment vessel, said vessel having a top, a closed bottom, a surrounding wall and being of sufficient size to contain a fluid to be mixed and a mixing apparatus, said mixing apparatus comprising: at least one gas supply line, said supply line terminating at an orifice adjacent said bottom of said vessel; and at least one buoyancy-driven mixing device comprising: a cylindrical chamber, said chamber having an inner surface, an outer surface, a first end, a second end and a central axis and being mounted within said containment vessel so as to be rotatable about its central axis and with its central axis oriented substantially horizontally; a plurality of gas holding members extending between said first end and said second end of said cylindrical chamber along said outer surface of said cylindrical chamber and being sized and shaped to entrap gas bubbles from said at least one gas supply line, wherein said gas supply line terminates adjacent said cylindrical chamber on a first side of said chamber below said gas holding members; whereby gas introduced into said containment vessel through said gas supply line will rise in said fluid, and gas bubbles will be entrapped by said gas holding members, thereby causing said cylindrical chamber to rotate about said central axis in a first direction to agitate said fluid; and at least one mixing plate disposed radially inwardly from said gas holding members and extending axially with respect to said cylindrical chamber so as to be configured to agitate fluid contained in said containment vessel as said cylindrical chamber rotates about said central axis.