A bioreactor for the growth and cultivation of cells and enzymes, made of alloy steel, must be sterilised by steam under pressure at 121 deg.C. The sealed vessel has a valve housing which passes through its wall and has a hollow slider. The section of the housing joint inside the wall has an opening which can be closed by lowering the slider to a seat. When the slider is raised, the lower part of the bore (in which the slider moves) and the bore of the slider are accessible to the sterilising steam.
