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In steam sterilizable, or conventional fermentors, we have had the ability to deliver more horsepower to the agitation system and oxygen to the sparging system than was sometimes needed; an overabundance of capacity, at times. With single-use fermentors, efficiency, especially in the process is the premium. Single-use fermentors are capable of controlling dissolved oxygen with the typical cascade control elements: air & oxygen gas flow, agitation and substrate feed. Pressure is all that is missing. Gas flow rates between 1 and 2 vessel volumes per minute are available. And, with agitation systems equipped with one or more Rushton impellers capable of supporting oxygen transfer rates in the 500-1100 range, single-use fermentor performance is comparable to conventional fermentors. Ensuring sufficient cooling to handle metabolic heat loads while overcoming the insulative properties of the bag film has been achieved. Like the application of technology in any area, there are boundaries. Within those boundaries, or design space, the user obtains the associated benefits. Necessity will help push and expand current boundaries.