{HEAD ~ A process} 1, in which, in {TAIL ~ the vessel}, the stirrer blades further comprise a material to which the biological material does not substantially adhere 
{ HEAD ~ A process } 1 , in which , in { TAIL ~ the vessel } , the stirrer blades further comprise a material to which the biological material does not substantially adhere
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH