Problems emerging during the scale up As the size of the equipment is increased, the surface- volume ratio changes Large fermentor has much more volume for a given surface area, it is obviously more difficult to mix the big tank than the small flask · In scale up studies on aerobic fermentations, oxygen rate in the fermentor is best kept constant as the size of the fermentor is increased How to keep do constant? Increase stirring rate Increase air pressure Use pure oxygen Increase air inletProblems emerging during the scale up • As the size of the equipment is increased, the surface￾volume ratio changes • Large fermentor has much more volume for a given surface area, it is obviously more difficult to mix the big tank than the small flask • In scale up studies on aerobic fermentations, oxygen rate in the fermentor is best kept constant as the size of the fermentor is increased. – How to keep DO constant? • Increase stirring rate • Increase air pressure • Use pure oxygen • Increase air inlet