the present invention is a disposable bioreactor formed of molded plastic . the bioreactor is presterilized and has a top and body sealed to each other . one or more ports are formed in the top and side of the housing . preferably at least one port is below the liquid / air level for the housing . the one or more ports that are below the liquid / air interface level may be used as sampling ports or access ports for probes or drains or supply ports for liquids or gases . the bioreactor provides a direct retrofit for the existing glass or steel assembly that utilizes the existing support structures and controls . the molded design overcomes issues of discontinuity , dead spots and the like due to its fixed dimensions that are built in by the molding process . reproducible probe and other equipment location is also guaranteed through the use of the molded port features . the molded plastic allows for greater flexibility in material selection to reduce or eliminate lipid or cholesterol binding .