Abstract: The invention relates to apparatus for cultivating microbiological substances. The fermenter comprises a container (1) accommodating an aerator (4) and a stirring unit (5) having the form of a circulation tube (6) and membrane (7). A partition (9) having a through hole (10) offset relative to the center thereof is disposed between the membrane (7) and the end of the tube (6) to define with the membrane (7) a closed volume (11). The aerator (4) and the stirring unit (5) are integrated into a single assembly secured on the partition (9) and having a chamber (12) for distributing liquid and gas flows.The fermenter is intended for intermittent cultivation of various substances of biological origin feeding on liquid, solid or mixed nutrient substrates.