Abstract: A stainless steel column housing is capped with an O-ring sealed cover to form a sealed autoclavable sterile chamber. A pair of stainless steel mesh circular cylindrical concentric inner and outer columns are within the chamber. A bed of porous glass spherical beads are packed in the region between the inner and outer mesh columns. The pH and DO are monitored and controlled while culture medium is continuously supplied to and from the sterile chamber. The outer mesh column forms an outer bulk medium chamber with the housing and the inner mesh column forms an inner bulk medium chamber. A ring sparger bubbles air and CO.sub.2 mixture into the outer bulk medium chamber, the bubbles creating pressure differentials in the bulk medium chambers. These differentials cause radially bulk medium flow through the packed bead bed without pressure gradients in the bed and axial bulk medium recirculation flow in and between the inner and outer bulk medium chambers at their axial ends.