When these tests are successful, the process is scaledup to the pilot plant stage, usually in fermentors of 300- to 3000-liter capacity. Here the conditions more closely approach those of the actual commercial fermentor, but cost is not yet an issue.
Finally, the process moves to the commercial fermentor itself, 10,000–500,000 liters in volume. In all stages of scale-up, aeration is the key variable that is closely monitored; as scale-up proceeds, oxygen dynamics are
carefully measured to determine how increases in volume affect oxygen demand in the fermentation.