A sterile enclosure contains a transfer module defining a window. A port covers the window to maintain the inside of the enclosure as a sealed and sterile environment. A sliding, heated cutting element mounted on the port serves to sterilize and sever a portion of a sterile transfer bag assembly attached to the port. Preferably, the excised portion of the sterile transfer bag assembly is affixed to the port when the port opens. The sliding cutting element remains extended and heated to prevent contamination when the port is open. Further, a heating element is mounted about the window in order to sterilize around the opening when the port is open.