A container system includes a collapsible bag having an interior surface at least partially bounding a chamber, the chamber being adapted to hold a fluid. A sparger is disposed within the chamber of the bag, the sparger bounding a compartment and having an inside edge that encircles an opening passing through the sparger. At least a portion of the sparger is gas permeable. A tubular member is coupled to the sparger and is in communication with the compartment. A shaft passes into the chamber of the bag and through the opening of the sparger. A mixing element is secured to the shaft and is disposed within the chamber of the bag.