Abstract: Method and apparatus for carrying out biochemical reactions in particular for cell-free polypeptide biosynthesis. A bioreactor has, within a housing, a reaction chamber containing a producing system as well as a supply chamber separated from the reaction chamber by means of a semi-permeable membrane and containing a liquid serving as supply medium for the producing system. The supply chamber is subdivided within the bioreactor into a first partial chamber and a second partial chamber which are each connected to the reaction chamber via a semi-permeable supply membrane and which are connected to each other by means of a connection conduit.