point of gas in the pneumatic motor where the sparging from one source of the sparger is not sufficient a situation that is more likely to arise when fermenting bacteria the sparging surface can be made from stainless steel perforated plastic a membrane or aluminum oxide or any other hard or soft surface capable diffusing gas out as fine bubbles in this capacity the source of energy utilized to turn the pneumatic motor is also utilized to provide aeration of the fluid making the salient features of the instant invention most energy optimized the fluid agitating element 8 is affixed to a hard surface 18 which in turn is attached to the interior surface of the bottom sheet of the bag 3 this allows the fluid agitating element 8 to stay upright during operation once use of the bag 3 is complete it may then simply be discarded along with the sparger 10 and fluid agitation device 8 and the pneumatic motor 6 besides a sparger 17 and or a pneumatic fluid agitating element 8 it may also be desirable to provide disposable means in the bag 3 to facilitate sensing characteristics of the fluid such as the ph oxygen content temperature etc preferably these sensors 7 fig1 are of disposable type and embedded in the bag 3 and remote receivers monitor the response to the sensors fig3 shows a topical view of the bioreactor wherein the round shape of the bag 3 and the location of the.